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Salvage logging is a controversial tool for post-wildfire management that removes fire-killed trees. We use a generalized randomized experimental design to fulfill two main objectives: (1) quantify the immediate (1-year post-harvest) effects of salvage logging on stand structure, fine and coarse woody fuel loadings; and (2) use pre- and post-empirical field data and the Fire and Fuels Extension to the Forest Vegetation Simulator (Reinhardt and Crookston 2003) to simulate post- wildfire dead woody fuel succession and snag dynamics. We compared the effects on woody fuel loadings of two salvage logging prescriptions: (1) seed tree harvest, thin to 3.4 [m.sup.2] * [ha.sup.-1]; and (2) full salvage of all merchantable timber, relative to unlogged controls. There was substantial block-level variability in the implementation of the treatments and in their immediate effects on fine fuel loading, complicating comparison of the two prescriptions. Overall, salvage logging did reduce snag basal area and, relative to unlogged controls, significantly increased measured fine woody fuel loading (10 and 100 h). Simulated snag fall was rapid, with a mean predicted snag basal area loss of 61% within 10 years. Future long-term monitoring of permanent field plots will supplement model predictions and provide valuable data to inform post-wildfire management decisions. Key words: post-wildfire logging, salvage logging, salvage harvest, coarse woody debris, fine woody debris, Forest Vegetation Simulator, post-wildfire restoration, snags, post-wildfire management, fuel succession, Introduction In western United States dry-coniferous forests, large stand-replacing wildfires have increased in frequency and extent (McKenzie et al. 2004; Stevens et al. 2017). These wildfires are interacting with high [...]

In northeastern North America, group selection is frequently used in northern hardwood forests to maintain uneven-aged stand structure and promote regeneration of tree species spanning a range of shade tolerances. For this study, long-term application of group selection at the Bartlett Experimental Forest, New Hampshire, USA, provided a unique opportunity to address cohort- and stand-level progression after 80 years of treatment. Cohort-level evolution reflected successional and developmental dynamics associated with even-aged forest systems, whereas aggregate stand-level conditions were consistent with expectations for uneven-aged systems. As cohorts aged, diameter distributions progressed towards descending monotonic forms and species composition transitioned from shade-intolerant species to shade-tolerant species. Standing deadwood and downed woody material in cohorts followed trajectories of aging even-aged stands through time. Although American beech (Fagus grandifolia Ehrh.) was a primary species across cohorts and at the stand level, stand-level regeneration included a mixture of ecologically and commercially valuable species. These long-term results offer important insights into emergent cohort- and stand-level conditions and processes that may affect continued recruitment of desirable compositional and structural conditions in stands managed using group selection over numerous cutting cycles. Key words: group selection, uneven-age management, northern hardwood, silviculture. Dans le nord-est de l'Amerique du Nord, le jardinage par groupe est frequemment utilise dans les forets de feuillus nordiques pour maintenir la structure inequienne des peuplements et favoriser la regeneration d'especes d'arbres couvrant une gamme de tolerances a l'ombre. Dans cette etude, l'application a long terme du jardinage par groupe a la foret experimentale de Bartlett, situee au New Hampshire, Etats-Unis, a fourni une occasion unique de documenter la progression arborescente aux echelles de la cohorte et du peuplement apres 80 ans de traitement. Les changements temporels a l'echelle de la cohorte refletaient la dynamique de succession et de developpement associee aux systemes forestiers equiennes, tandis que les conditions globales a l'echelle du peuplement etaient coherentes avec les attentes reliees aux systemes inequiennes. Avec le vieillissement des cohortes, la distribution des diametres progressait vers des formes monotones descendantes alors que la composition des especes passait d'especes intolerantes a l'ombre a des especes tolerantes a l'ombre. Les arbres morts sur pied et les debris ligneux au sol dans les cohortes ont suivi les trajectoires de peuplements vieillissants de structure equienne au fil du temps. Bien que le hetre a grandes feuilles (Fagus grandifolia Ehrh.) soit une espece primaire dans toutes les cohortes et a l'echelle du peuplement, la regeneration a l'echelle du peuplement comprenait un melange d'especes desirees des points de vue ecologique et commercial. Ces resultats de longue duree fournissent des renseignements importants sur les conditions et les processus aux echelles de la cohorte emergente et du peuplement qui peuvent affecter le recrutement continu des conditions souhaitables de composition et de structure dans les peuplements amenages a l'aide du jardinage par groupe applique sur plusieurs rotations. Mots-cles: jardinage par groupe, amenagement inequienne, feuillus nordiques, sylviculture., Introduction Uneven-aged silvicultural systems have long been applied to a great range of forest types and ownerships throughout temperate regions of the globe (Meyer 1952; O'Hara 2002; Kerr 2014). Early [...]

Long-term studies of vegetation succession can inform restoration of degraded forests. We examined resilience of a boreal mixedwood vegetation community, asking whether treatments employed to restore wood production in a degraded ecosystem could also restore diversity and composition of vegetation communities. The Inga Lake trial, established in 1987 in northeastern British Columbia, used mechanical, fire, and chemical and manual treatments, encompassing a gradient of restoration effort, and tree planting to restore a shrubland to white spruce (Picea glauca (Moench) Voss) forest. We monitored vascular plant, bryophyte, and macrolichen composition five times over 31 years on five to seven treatments replicated five times. We used mixed-effects models and nonmetric multidimensional scaling to compare diversity and composition among treatments and with mature reference forests. Low- to high-effort restoration created a gradient from broadleaf- to spruce-dominated overstories. Diversity increased with restoration effort. Four of 253 taxa occurred in mature forests only. There was no evidence that lower versus higher effort treatments followed divergent successional pathways toward broadleaved versus spruce reference communities. Our results suggest that these mixedwood vegetation communities lie within a broad domain of successional attraction that confers high ecological resilience to disturbance. Gap cuttings to stimulate understory re-initiation and provide woody debris are recommended to complete the restoration. Key words: silviculture, biodiversity, ecological disturbance, restoration, Picea glauca, longitudinal study. Les etudes de longue duree sur la succession vegetale peuvent apporter de l'information sur la restauration des forets degradees. Nous avons etudie la resilience d'une communaute vegetale de la foret boreale mixte en se demandant si les traitements utilises pour restaurer la production de bois dans un ecosysteme degrade pourraient aussi restaurer la diversite et la composition des communautes vegetales. Le dispositif d'Inga Lake, etabli en 1987 dans le nord-est de la Colombie-Britannique, a permis de tester des traitements mecaniques, le feu et une combinaison de traitements chimiques et manuels, incluant un gradient d'efforts de restauration, ainsi que la plantation d'arbres pour restaurer une lande arbustive en foret d'epinette blanche (Picea glauca (Moench) Voss). Nous avons inventorie la composition des plantes vasculaires, des bryophytes et des macrolichens a cinq reprises sur une periode de 31 ans pour cinq a sept traitements repetes cinq fois. Nous avons utilise des modeles a effets mixtes et l'analyse multidimensionnelle non metrique pour comparer la diversite et la composition entre les traitements et des forets matures de reference. Les efforts de restauration faibles a eleves ont produit un couvert dominant dont la composition couvrait un gradient d'especes feuillues jusqu'a l'epinette. La diversite a augmente avec l'effort de restauration. Quatre des 253 taxons se retrouvaient uniquement dans les forets matures. Il n'y avait aucune indication que les traitements impliquant un effort de restauration plus faible comparativement a plus eleve etaient associes a des trajectoires de succession divergentes, en route vers les communautes de reference dominees par des feuillus plutot que par l'epinette. Nos resultats indiquent que ces communautes vegetales de foret mixte se situent dans une vaste zone d'attraction de succession vegetale qui leur confere une grande resilience ecologique face aux perturbations. Pour completer cette restauration, nous recommandons des coupes par trouees visant a stimuler la reinitialisation du sous-etage et a fournir des debris ligneux. Mots-cles: sylviculture, biodiversite, perturbation ecologique, restauration, Picea glauca, etude longitudinale., Introduction Forest succession remains a major theme in plant ecology, providing insights into important topics of ecosystem management and environmental change such as biodiversity loss, climate change, invasive species, and [...]

Precommercial thinning (PCT) is used to increase tree size and shorten harvest rotation time. Short-term results from PCT studies often show a trade-off between individual-tree growth and net stand yield, while longer-term effects of PCT on tree growth and stand yield are less well documented. We used a 54-year-old PCT study to test long-term effects of forest density and thinning schedules on stand yield and tree-level characteristics in even-aged western larch (Larix occidentalis Nutt.) stands. The study has three target densities (494, 890, and 1680 trees * [ha.sup.-1]) crossed with three thinning schedules (target density achieved through one, two, or four entries). Analysis of variance (ANOVA) and linear contrasts were used to test the effects of density and number of entries on tree-and stand-level attributes. Thinning before stand age 10 years leads to long-term constant yield (219.0-269.5 [m.sup.3] * [ha.sup.-1]; P > 0.05) across the tested densities. We also found constant volume growth across stand densities during the most recent measurement interval (5.42-6.41 [m.sup.3] * [ha.sup.-1] * [year.sup.-1]; P > 0.05). Number of entries did not affect any tree- or stand-level attribute. The primary effect of early PCT is to control whether wood volume and growth are concentrated on few large, stable trees or spread over many small, unstable trees. Key words: density management, stand density, competition, stand dynamics, growth and yield. L'eclaircie precommerciale (EPC) est utilisee pour augmenter la taille des arbres et devancer l'age de la recolte du peuplement. A court terme, les resultats de l'EPC montrent souvent un compromis entre la croissance des arbres individuels et la production nette du peuplement, alors que les effets a long terme de l'EPC sur la croissance des arbres et la production des peuplements sont moins bien documentes. Nous avons utilise une etude sur l'EPC, vieille de 54 ans, pour evaluer les effets a long terme de la densite des peuplements et du calendrier des eclaircies sur la production des peuplements et les caracteristiques des arbres dans des peuplements equiennes de meleze occidental (Larix occidentalis Nutt.). L'etude comprenait trois densites cibles du peuplement (494, 890 et 1680 arbres-ha-1) et trois calendriers des eclaircies (densite cible atteinte apres un, deux ou quatre interventions). Nous avons utilise des analyses de variance et des contrastes lineaires pour tester les effets de la densite du peuplement et du nombre d'interventions sur les caracteristiques des arbres et des peuplements. Une eclaircie realisee avant l'age de 10 ans a mene a une production constante a long terme (de 219,0 a 269,5 [m.sup.3] * [ha.sup.-1]; P > 0,05) pour l'ensemble des densites testees. Nous avons aussi trouve une croissance en volume constante entre les densites de peuplement au cours du plus recent intervalle de mesures (5,42 a 6,41 [m.sup.3] * [ha.sup.-1] * [an.sup.-1]; P > 0,05). Le nombre d'interventions n'a influence aucune caracteristique des arbres et des peuplements. L'effet principal d'une EPC precoce est de determiner si le volume et la croissance du bois sont concentres sur un nombre limite de gros arbres stables ou repartis sur de nombreux petits arbres instables. [Traduit par la Redaction] Mots-cles : gestion de la densite, densite du peuplement, competition, dynamique du peuplement, croissance et production., 1. Introduction Forest stand density affects the timing and intensity of competitive interactions between neighboring trees (Oliver and Larson 1996; Long et al. 2004; Harrington et al. 2009). In high-density [...]

Relationships between soil C and N stocks and soil formation, climate, and vegetation were investigated in a gridded database connected to the National Forest Inventory in Norway. For mineral soil orders, C and N stocks were estimated to be 11.1-19.3 kg C x [m.sup.-2] and 0.41-0.78 kg N x [m.sup.-2], respectively, declining in the following order: Gleysols > Podzols > Brunisols > Regosols. Organic peat-type soils stored, on average, 31.3 kg C x [m.sup.-2] and 1.10 kg N x [m.sup.-2], whereas shallow Organic folisols stored, on average, 10.2 kg C x [m.sup.-2] and 0.34 kg N x [m.sup.-2]. For Norway's 120 000 [km.sup.2] of forest, the total of soil C stocks was estimated to be 1.83 Gt C, with a 95% CI of 1.71-1.95 Gt C. Podzolic soils comprise the largest soil group and store approximately 50% of the forest soil C. Sixty percent of the soil C stock in Podzolic soils was stored in the mineral soil, increasing with temperature and precipitation. Poorly drained soil types store approximately 47% of the total forest soil C in Norway. Soils with water saturation have large C stocks mainly in the forest floor, suggesting that they are more susceptible to forest management and environmental change. Soil C stocks under pine and spruce forests were similar, although pine forests had larger C stocks in the forest floor, while spruce forests had the highest C stocks in the mineral soil compartment. C stocks in the forest floor increase from dry to moist ground vegetation, while ground vegetation nutrient classes reflect better the C and N stocks in the mineral soil. Key words: forest soil, carbon, soil formation, pedology, Norway, boreal forest. Resume: Les relations entre les stocks de C et de N du sol et la pedogenese, le climat et la vegetation ont ete etudiees a l'aide d'une base de donnees rectangulaires (1040 profils de sol) reliee a l'Inventaire forestier national en Norvege. Considerant les ordres de sol mineral, les stocks de C et N ont ete estimes a 11,1 a 19,3 kg C x [m.sup.-2] et de 0,41 a 0,78 kg N x [m.sup.-2] en declin dans l'ordre suivant: sols gleysoliques > podzoliques > brunisoliques > regosoliques. Les sols tourbeux de type organique emmagasinaient en moyenne 31,3 kg C x [m.sup.-2] et 1,10 kg N x [m.sup.-2], tandis que les folisols organiques minces emmagasinaient en moyenne 10,2 kg C x [m.sup.-2] et 0,34 kg N x [m.sup.-2]. En assumant que la foret norvegienne couvre une superficie de 120 000 [km.sup.2], les stocks totaux de C dans le sol ont ete estimes a 1,83 Gt C (IC 95 : 1,71-1,95). Les sols podzoliques constituent le groupe de sols le plus important et nous estimons qu'ils emmagasinent 50% du C total present dans les sols forestiers. Soixante pourcent du stock total de C dans les sols podzoliques est emmagasine dans le sol mineral et augmente avec la temperature et la precipitation. Les conditions locales de la station qui determinent l'humidite et la profondeur du sol ont une grande influence sur les stocks de C et de N. Les types de sol mal draines emmagasinent approximativement 47% du C total present dans les sols forestiers en Norvege. Les sols satures en eau contiennent d'importants stocks de C, principalement dans la couche holorganique, ce qui indique qu'ils sont plus sensibles aux pratiques d'amenagement forestier et aux changements environnementaux. Il n'y avait pas de differences dans les stocks de C du sol entre les forets de pin et les forets d'epicea. Par contre, dans les forets de pin les stocks de C etaient plus eleves dans la couche holorganique tandis que dans les forets d'epicea les stocks de C etaient plus eleves dans la couche minerale du sol. Les stocks de C du sol augmentent lorsqu'on passe d'une vegetation au sol xerophile a hygrophile, surtout en lien avec l'augmentation des stocks de C dans la couche holorganique, tandis que les classes de nutriments de la vegetation au sol refletent mieux les stocks de C et de N dans le sol mineral. [Traduit par la Redaction] Mots-cles: sol forestier, carbone, pedogenese, pedologie, Norvege, foret boreale., Introduction Boreal forests are an important part of the global carbon (C) cycle and are considered to be moderate to strong sinks for atmospheric C, depending on forest management, forest [...]

Hair lichens are strongly influenced by forest structure at local scales, but their broad-scale distributions are less understood. We compared the occurrence and length of Alectoria sarmentosa (Ach.) Ach., Bryoria spp., and Usnea spp. in the lower canopy of > 5000 Picea abies (L.) Karst. trees within the National Forest Inventory across all productive forest in Sweden. We used logistic regression to analyse how climate, nitrogen deposition, and forest variables influence lichen occurrence. Distributions overlapped, but the distribution of Bryoria was more northern and that of Usnea was more southern, with Alectoria's distribution being intermediate. Lichen length increased towards northern regions, indicating better conditions for biomass accumulation. Logistic regression models had the highest pseudo [R.sup.2] value for Bryoria, followed by Alectoria. Temperature and nitrogen deposition had higher explanatory power than precipitation and forest variables. Multiple logistic regressions suggest that lichen genera respond differently to increases in several variables. Warming decreased the odds for Bryoria occurrence at all temperatures. Corresponding odds for Alectoria and Usnea decreased in warmer climates, but in colder climates, they increased. Nitrogen addition decreased the odds for Alectoria and Usnea occurrence under high deposition, but under low deposition, the odds increased. Our analyses suggest major shifts in the broad-scale distribution of hair lichens with changes in climate, nitrogen deposition, and forest management. Key words: climate change, epiphytic lichens, forest structure, nitrogen deposition, temperature. Les lichens fruticuleux sont fortement influences localement par la structure de la foret mais on a une moins bonne comprehension concernant leur vaste distribution. Nous avons compare l'occurrence et la longueur d'Alectoria sarmentosa (Ach.) Ach., de Bryoria spp. et d'Usnea spp. en sous-etage de plus de 5000 tiges de Picea abies (L.) Karst repertoriees dans l'Inventaire forestier national dans toutes les forets productives de la Suede. Nous avons utilise la regression logistique pour analyser de quelle facon le climat, les depots d'azote et les variables forestieres influencent l'occurrence des lichens. Les distributions se chevauchent mais Bryoria est plus septentrional et Usnea plus meridional alors qu'Alectoria occupe une position intermediaire. La longueur des lichens augmente vers les regions nordiques vraisemblablement parce que les conditions sont plus favorables a l'accumulation de biomasse. Les modeles de regression logistiques ont un pseudo [R.sup.2] plus eleve dans le cas de Bryoria suivi d'Alectoria. La temperature et les depots d'azote ont un plus grand pouvoir explicatif que la precipitation et les variables forestieres. Des regressions logistiques multiples indiquent que les genres de lichens repondent differemment a l'augmentation de plusieurs variables. Le rechauffement reduit les probabilites d'occurrence de Bryoria peu importe la temperature. Les probabilites correspondantes pour Alectoria et Usnea diminuent sous des climats plus chauds mais augmentent sous des climats plus froids. L'apport d'azote diminue les probabilites d'occurrence d'Alectoria et d'Usnea en presence de depots eleves mais les probabilites augmentent lorsque les depots sont faibles. Nos analyses indiquent qu'il y a des changements dans la distribution a grande echelle des lichens fruticuleux en lien avec les changements climatiques, les depots d'azote et l'amenagement des forets. [Traduit par la Redaction] Mots-cles : changement climatique, lichens epiphytes, structure forestiere, depot d'azote, temperature., Introduction Filamentous 'hair' lichens in the genera Alectoria, Bryoria, and Usnea often dominate forest canopies throughout the boreal zone, as well as some temperate forests. Globally, Alectoria and Bryoria mainly [...]

Complex old-growth forests with large emergent trees may support more basal area than those without these trees. The so-called additive basal area phenomenon occurs when the presence of these emergent trees does not affect the basal area of the canopy trees, i.e., the basal areas of emergent and canopy trees add up. We studied two old-growth forests in south-central Chile with similar species composition and structure but contrasting soil quality. We sampled fifty-seven 1000 [m.sup.2] plots in a relatively high-quality site (Quillaipe) and sixty-five 1000 [m.sup.2] plots in a relatively low-quality site (Yaldad) and evaluated total stand basal area, basal area of emergent trees, basal area of canopy trees, and the influence of the basal area of emergent trees on total and canopy basal areas. On average, Quillaipe accumulated 50% higher basal area than Yaldad. The additive basal area effect only occurred on the high-quality site, Quillaipe. A more detailed analysis showed that canopy associates were differentially affected in terms of basal area depression with increasing basal area of emergent trees in each site. The relative competitive ability of canopy species, as affected by their ecological traits and geographical distribution, presumably explain if the basal area of individual species or functional groups are depressed by the basal area of emergents. Above--and below-ground resource partitioning may be decisive mechanisms affecting the occurrence of additive basal area accumulation in forest stands. Key words: canopy stratification, competition, emergent trees, Nothofagus, resource use complementarity. Les vieilles forets complexes avec de gros arbres emergents peuvent maintenir une plus grande surface terriere (ST) que les autres forets. Le phenomene que l'on appelle la surface terriere additive se produit lorsque la presence de ces arbres emergents n'influence pas la ST des arbres du couvert dominant, c'est-a-dire que la ST des arbres emergents et celle du couvert dominant s'additionnent. Nous avons etudie deux vieilles forets dans le centre-sud du Chili qui avaient une composition en especes et une structure similaires, mais dont la qualite du sol etait differente. Nous avons echantillonne 57 placettes de 1000 [m.sup.2] sur une station de qualite relativement bonne (Quillaipe) et 65 sur une station de qualite relativement faible (Yaldad), et nous avons evalue la ST totale des peuplements, la ST des arbres emergents, la ST des arbres du couvert dominant et l'influence de la ST des arbres emergents sur la ST totale et celle du couvert dominant. En moyenne, la station Quillaipe a accumule une ST 50 % plus grande que celle de Yaldad. L'effet de la ST additive a seulement ete observe sur la station Quillaipe de bonne qualite. Une analyse plus detaillee a montre que la diminution de la ST en fonction de l'augmentation de la ST des arbres emergents a influence differemment les elements du couvert dominant dans chaque station. Nous presumons que la capacite competitive relative des especes du couvert dominant, qui est influencee par leurs caracteristiques ecologiques et leur distribution geographique, explique si la ST des arbres emergents fait diminuer la ST des especes individuelles ou des groupes fonctionnels. Le partitionnement des ressources entre les parties aerienne et souterraine est un mecanisme qui peut avoir une influence decisive sur l'accumulation de la ST additive dans les peuplements forestiers. [Traduit par la Redaction] Mots-cles : stratification du couvert, competition, arbres emergents, Nothofagus, complementarite de l'utilisation des ressources., Introduction Several studies have demonstrated that multistratified old-growth forest stands can develop more biomass or basal area than pure stands when species occupy different canopy strata, i.e., in stands with [...]

In Ohio Euro-American setdement in the late 18th and early 19th centuries subjected forests to large scale disturbances, including widespread clearance. In the subsequent two centuries, some of this land has reforested. To describe changes in forest composition since setdement, we used archival maps of U.S. Public Land Survey records to characterize forest composition just before large scale Euro-American settlement in 27 Ohio counties. We then compared this with modern composition patterns from the U.S. Forest Service's Forest Inventory Analysis. Presetdement forests displayed strong spatial structure and regional differentiation. Counties in northwest Ohio were dominated by beech (Fagus grandifolia; mean relative abundance: 26.9%), whereas southeast Ohio counties were dominated by oaks (Qiiercus spp.; 50.1%). Modern forests, however, had weaker spatial structure and were dominated by oak species in both regions (24.0% and 22.4%, respectively). Overall, we found a decrease in previously dominant species and homogenization across the state. Partial Mantel tests indicated modern forest composition is more closely correlated with modern land use variation than environmental variables, suggesting that forest composition now is driven primarily by land use. Understanding factors influencing forest composition can inform projections of forest response to modern global change, including climate change and land use conversions., INTRODUCTION Modern day forests are products of complex climatic, ecological, and anthropogenic interactions over time. Anthropogenic influences and legacies increasingly are recognized as important factors affecting species assemblages in forests. [...]

In the southeastern United States, many forest managers are interested in restoring longleaf pine (Pinus palustris Mill.) to upland sites that currently support loblolly pine (Pinus taeda L.). We quantified the effects of four canopy treatments (uncut Control; MedBA, harvest to 9 [m.sup.2] x [ha.sup.-1]; LowBA, harvest to 5 [m.sup.2] x [ha.sup.-1]; and Clearcut) and three cultural treatments (NT, no treatment; H, herbicide release of longleaf pine seedlings; and H+F, herbicide release plus fertilization) on resource availability and growing conditions in relation to longleaf pine seedling response for 3 years. Harvesting treatments reduced competition from canopy trees but resulted in greater abundance of understory vegetation. Harvesting shifted the interception of light from the canopy to the subcanopy vegetation layer; however, total light availability at the forest floor increased with the intensity of canopy removal. Soil moisture was not affected by harvesting or by the cultural treatments. Foliar nutrient concentrations (N, P, and K) of longleaf pine seedlings generally increased with the intensity of the harvest treatment. Of the plant resources measured, we found that light was most strongly correlated with longleaf pine seedling growth and that incorporating the interception of light by subcanopy vegetation improved the relationship over that of canopy light transmittance alone. Key words: foliar nutrients, gap light index, longleaf pine restoration, resource availability, underplanting. Dans le sud-est des Etats-Unis, plusieurs amenagistes forestiers sont interesses a restaurer le pin des marais (Pinus palustris Mill.) sur des stations bien drainees presentement occupees par le pin a encens (Pinus taeda L.). Nous avons quantifie les effets de quatre traitements d'eclaircie du couvert dominant (temoin non traite; surface terriere residuelle de 9 [m.sup.2] x [ha.sup.- 1], MedBA; surface terriere residuelle de 5 [m.sup.2] x [ha.sup.-1], LowBA; et coupe a blanc) et de trois traitements culturaux (temoin non traite, TEM; application d'un herbicide autour des semis de pin des marais, H; et application d'un herbicide et d'une fertilisation, H+F) sur la disponibilite des ressources et sur les conditions de croissance en relation avec la reaction des semis de pin des marais pendant trois ans. Les traitements de coupe ont reduit la competition des arbres du couvert dominant, mais ont entrame une plus grande abondance de la vegetation sous couvert. La coupe a fait passer l'interception de la lumiere du couvert dominant a la strate de vegetation sous le couvert, mais la disponibilite totale de la lumiere au sol a augmente avec l'intensite de l'eclaircie du couvert dominant. L'humidite du sol n'a pas ete influencee par la coupe ou par les traitements culturaux. La concentration foliaire en nutriments (N, P et K) des semis de pin des marais a generalement augmente avec l'intensite des traitements de coupe. Parmi les ressources necessaires a la croissance des plantes que nous avons mesurees, la lumiere etait la plus etroitement correlee a la croissance des semis de pin des marais et cette relation etait amelioree en tenant compte de l'interception de la lumiere par la strate de vegetation sous le couvert dominant en plus de la transmission de la lumiere par le couvert dominant. [Traduit par la Redaction] Mots-cles: nutriments foliaires, coefficient de trouees lumineuses, restauration du pin des marais, disponibilite des ressources, plantation sous couvert., Introduction In forested ecosystems, the combination of abiotic conditions and biotic interactions at the growing site largely controls the establishment success (i.e., growth and survival rates) of individual tree seedlings [...]

We examined the dynamics of aboveground forest woody carbon pools--live trees, standing dead trees, and down wood--during the first 6 years following wildfire across a wide range of conditions, which are characteristic of California forest fires. From repeated measurements of the same plots, we estimated change in woody carbon pools as a function of crown fire severity as indicated by a post-fire index, years since fire, pre-fire woody carbon, forest type group (hardwood vs. softwood), elevation, and climate attributes. Our analysis relied on 130 U.S. national forest inventory plots measured before and 1 year after fire, with one additional remeasurement within 6 years after fire. There was no evidence of net change in total wood carbon, defined for this study as the wood in standing trees larger than 12.7 cm diameter at breast height and down wood larger than 7.6 cm in diameter, over the post-fire period in any of the three severity classes. Stands that burned at low severity exhibited considerable shifts from live to standing dead and down wood pools. In stands that burned at moderate severity, live wood decreased significantly whereas no net change was detected in standing dead or down wood. High severity fire burning resulted in movement from standing dead to down wood pools. Our results suggest that the carbon trajectories for stand-replacing fires may not be appropriate for the majority of California's forest area that burned at low to moderate severities. Key words: longitudinal analysis, post-fire dynamics, forest stand recovery, disturbance, Forest Inventory and Analysis. Nous avons etudie la dynamique des reservoirs de carbone ligneux de la partie aerienne des forets (les arbres vivants, les arbres morts sur pied et au sol) au cours des six premieres annees apres un feu pour une large gamme de conditions caracteristiques des feux de foret de la Californie. A partir de mesures repetees des memes placettes, nous avons estime les changements dans les reservoirs de carbone ligneux en fonction de la severite des dommages a la cime des arbres selon un indice apres feu, du nombre d'annees apres le feu, du carbone ligneux avant le feu, du groupe de types forestiers (feuillus ou resineux), de l'altitude et des caracteristiques du climat. Nos analyses ont porte sur 130 placettes de l'inventaire national etats-unien (FIA) mesurees avant et un an apres le feu de meme qu'une autre fois au cours des six premieres annees apres le feu. Il n'y a pas eu d'indices de changement net du carbone ligneux total apres feu, correspondant dans cette etude au bois des arbres sur pied ayant un diametre a hauteur de poitrine plus grand que 12,7 cm et des arbres au sol ayant un diametre superieur a 7,6 cm, dans aucune des trois classes de severite du feu. Les peuplements ayant subi un feu de severite faible ont connu des changements considerables dans les reservoirs de carbone ligneux, passant d'une dominance d'arbres vivants a une dominance d'arbres morts sur pied et au sol. Dans les peuplements brules par un feu de severite moderee, les arbres vivants ont diminue significativement alors qu'aucun changement net n'a ete detecte chez les arbres morts sur pied ou au sol. Le feu de severite elevee a provoque un deplacement de reservoir ligneux des arbres morts sur pied vers les arbres au sol. Nos resultats indiquent que les trajectoires de carbone typiques des feux qui entrainent le remplacement des peuplements peuvent ne pas etre appropriees pour les cas plus communs de peuplements subissant des feux d'intensites faible a moderee. [Traduit par la Redaction] Mots-cles: analyse longitudinale, dynamique apres feu, retablissement des peuplements forestiers, perturbation, programme d'analyse et d'inventaire forestiers (FIA)., Introduction Natural disturbances such as wildfire are increasing in frequency, severity, and extent across forested ecosystems of the western U.S. (Westerling et al. 2006; Miller et al. 2009; Stephens 2005; [...]

Alterations to forest canopy structure directly affect the hydrology and biogeochemistry of wooded ecosystems. Epiphytes alter canopy structure, thereby intercepting rainwater, reducing penetration of rain to the surface (as throughfall), modifying throughfall chemistry, and changing throughfall responses to storm conditions. These processes are well established for epiphyte presence versus absence; yet, it is unknown how epiphyte-throughfall interactions change across an epiphyte cover continuum (important information for prediction of ecological changes with epiphyte establishment or decline from disturbance). To fill this gap, we monitored throughfall water and dissolved ions ([Na.sup.+], N[H.sub.4.sup.+], [K.sup.+], [Mg.sup.2+], [Ca.sup.2+], [Cl.sup.-], N[O.sub.3.sup.-], P[O.sub.4.sup.3-], S[O.sub.4.sup.2-]) beneath a common epiphyte (Tillandsia usneoides L.) across cover percentages (0%-20%, 21%-40%, 41%-60%, 61%-80%, 81%-100%) for 47 storms. Throughfall amount inversely responded to epiphyte cover while increasing salt wash-off and intracellular leaching. Greater epiphyte cover released N[H.sub.4.sup.+] and decreased N[O.sub.3.sup.-] from throughfall. Storm conditions (high vapor pressure deficit, moderate wind speeds, and low intensity) strengthened throughfall responses as T. usneoides cover increased. Factorial MANOVA results revealed significant trends for throughfall ion enrichment or depletion via wash-off, leaching, and uptake. These data suggest that inclusion of epiphyte alterations to rainwater and solute inputs in ecosystem nutrient budgeting studies should consider the full continuum of epiphyte cover represented at that site. Key words: barrier island forest, biogeochemistry, epiphyte, hydrological cycling, meteorological conditions. Les alterations de la structure du couvert forestier ont un impact direct sur l'hydrologie et la biogeochimie des ecosystemes forestiers. Les epiphytes alterent la structure du couvert forestier, interceptant ainsi l'eau de pluie, reduisant la penetration de la pluie vers la surface (pluie au sol), modifiant les caracteristiques chimiques de la pluie au sol, et changeant les reponses de la pluie au sol lors des tempetes. Ces processus sont bien etablis en presence ou en l'absence d'epiphytes. Cependant, on ne sait pas comment les interactions entre les epiphytes et la pluie au sol changent en lien avec un continuum de couverture d'epiphytes (il s'agit d'une information importante pour predire les changements ecologiques a la suite de l'etablissement des epiphytes ou de leur declin apres une perturbation). Pour combler cette lacune, nous avons surveille la pluie au sol et les ions dissouts ([Na.sup.+], N[H.sub.4.sup.+], [K.sup.+], [Mg.sup.2+], [Ca.sup.2+], [Cl.sup.-], N[O.sub.3.sup.-], P[O.sub.4.sup.3-], S[O.sub.4.sup.2-]) sous un epiphyte commun (Tillandsia usneoides L.) dont le pourcentage de couverture variait de 0-20 %, 21-40 %, 41-60 %, 61-80 %, et 81-100 % lors de 47 tempetes. La quantite de pluie au sol reagissait negativement a la couverture d'epiphytes tout en augmentant l'elimination des sels et le lessivage intracellulaire. Une plus grande couverture d'epiphytes a libere NH4+ et reduit N[O.sub.3.sup.-] dans la pluie au sol. Les caracteristiques d'une tempete (deficit de saturation eleve, vitesses du vent moderees et faible intensite) ont renforce les reponses de la pluie au sol a mesure que la couverture de T. usneoides augmentait. Les resultats d'une analyse factorielle MANOVA ont revele des tendances significatives d'enrichissement ou d'epuisement des ions dans la pluie au sol par delavage, lessivage et absorption. Ces donnees indiquent que l'inclusion dans les etudes de bilan nutritif des ecosystemes des modifications a l'eau de pluie et aux apports de solutes dues aux epiphytes devrait tenir compte de la gamme complete de couverture des epiphytes representee dans un site donne. [Traduit par la Redaction] Mots-cles: foret d'iles barrieres, biogeochimie, epiphyte, cycle hydrologique, conditions meteorologiques., 1. Introduction The first biogeochemical process affecting rainfall as it enters forest ecosystems is the cycling and redistribution of solutes by tree canopies. Canopy surfaces intercept rainwater and then divert [...]

Increasing wild ungulate populations in the northern hemisphere led to extensive research on their influence on forest regeneration. According to the results of different studies, high ungulate densities may alter forest structure and composition, as well as inhibit forest regeneration. However, little is known about the long-term impact of large herbivores on forest dynamics at the landscape scale. Therefore, we studied forest regeneration in conifer forests of the highly protected Swiss National Park. We assessed sapling densities and apical shoot loss by repeated systematic sampling in 2003 and in 2011-2012 in two valleys featuring exceptionally high densities of wild ungulates of up to 86 individuals per vegetation-covered square kilometre during summer and 28 individuals per vegetation-covered square kilometre during winter. Mean apical shoot loss ranged between 2.9% and 10.6% depending on study site and assessment year. In addition to the increasing sapling densities, these results suggest that ungulates had little impact on tree establishment in the studied subalpine conifer forests. Additionally, sapling diversity was higher on plots repeatedly influenced by ungulates (apical shoot loss), suggesting rather positive effects of ungulates on sapling diversity. Habitat containing a mixture of forest and grassland without livestock or human disturbance provides a high-quality environment for ungulates, which likely explains the low impact of ungulates on forest regeneration in our study area. Key words: mountain forest, sapling density, sapling diversity, herbivory, red deer (Cervus elaphus), chamois (Rupicapra rupicapra), ibex (Capra ibex). L'augmentation des populations d'ongules sauvages dans l'hemisphere nord est a l'origine de recherches approfondies visant a determiner leur influence sur la regeneration forestiere. Selon les resultats de differentes etudes, de fortes densites d'ongules peuvent modifier la structure et la composition forestiere et inhiber la regeneration forestiere. Cependant, les impacts a long terme des gros herbivores sur la dynamique forestiere a l'echelle du paysage sont peu documentes. Ainsi, nous avons etudie la regeneration de forets resineuses du Parc national suisse qui est sous haute protection. Nous avons estime la densite des gaules et la perte de pousses apicales a l'aide d'un echantillonnage systematique realise en 2003 et repete en 2011-2012 dans deux vallees abritant des densites exceptionnellement elevees d'ongules sauvages atteignant jusqu'a 86 individus par [km.sup.2] de territoire couvert de vegetation pendant l'ete et 28 individus par [km.sup.2] pendant l'hiver. La perte moyenne de pousses apicales variait de 2,9 a 10,6 % selon la station etudiee et l'annee d'inventaire. Nos resultats associes a des densites croissantes de gaules indiquent que les ongules ont eu peu d'impact sur l'etablissement des arbres dans les forets subalpines de coniferes a l'etude. De plus, la diversite des gaules etait plus grande dans les parcelles influencees de facon repetee par les ongules (perte de pousses apicales), ce qui indique que les ongules auraient un effet plutot positif sur la diversite des gaules. Les habitats composes d'un melange de forets et de prairies sans betail ni perturbation humaine offrent un environnement de haute qualite pour les ongules, ce qui explique probablement le faible impact des ongules sur la regeneration forestiere dans notre aire d'etude. [Traduit par la Redaction] Mots-cles: foret montagnarde, densite des gaules, diversite des gaules, herbivorisme, cerf elaphe (Cervus elaphus), chamois (Rupicapra rupicapra), bouquetin des Alpes (Capra ibex)., Introduction Natural regeneration of temperate and boreal forests is influenced by several exogenous abiotic and biotic factors. Among the former, light and water availability, soil temperatures (degree days), and soil [...]

Trees form the terrestrial interface with the atmosphere in forested regions. The electrical properties of trees may influence their response to atmospheric conditions and potentially lethal phenomena (e.g., lightning). We review the literature describing electrical properties of trees and provide a tabular summary of the methods and goals of each study. We hypothesized that electrical resistivity varies consistently among species and between growth forms. We surveyed resistivity of eight tree and three vine species in Michigan and Kentucky, and we quantified resistivity over a moisture gradient for wood blocks of four tree species. Resistivity varied predictably with stem diameter and differed among species and growth forms. Specifically, resistivity of trees was approximately 200% higher than resistivity of vines, and resistivity of conifers was 135% higher than that of hardwoods. The regional comparison showed no difference in resistivity of red maple (Acer rubrum L.) and sugar maple (Acer saccharum Marsh.) between Michigan and Kentucky. These results, in combination with interspecific differences observed among wood blocks, suggest that there is a phylogenetic basis for variation in resistivity that reflects differences in anatomy and physiology. Our review and empirical survey provide a framework for studying the ecological effects of lightning in the context of the electrical properties of trees. Key words: lightning, Michigan, resistivity, Kentucky, moisture. Dans les regions forestieres les arbres constituent l'interface terrestre avec l'atmosphere. Les proprietes electriques des arbres peuvent influencer leur reaction aux conditions atmospheriques et aux phenomenes potentiellement letaux (p. ex. la foudre). Nous avons fait une revue de la litterature qui porte sur les proprietes electriques des arbres et nous presentons un tableau sommaire des methodes et objectifs de chaque etude. Nous formulons l'hypothese que la resistivite electrique varie uniformement parmi les especes et que des facteurs physiologiques ou anatomiques, autres que la teneur en humidite, font partie des mecanismes importants qui sous-tendent ces differences. Nous avons releve la resistivite de huit especes d'arbre et de trois especes de vigne au Michigan et au Kentucky et nous avons quantifie la resistivite de blocs de bois de quatre especes d'arbre en fonction d'un gradient d'humidite. La resistivite variait de facon significative selon l'espece et la forme de croissance. Plus particulierement, la resistivite des arbres etait environ 200 % plus elevee que celle de la vigne et la resistivite des coniferes etait 135 % plus elevee que celle des feuillus. La comparaison entre les regions n'a revele aucune difference de resistivite chez l'erable rouge (Acer rubrum L.) et l'erable a sucre (Acer saccharum Marsh.) entre le Michigan et le Kentucky. Ces resultats, combines aux differences interspecifiques observees parmi les blocs de bois, indiquent que la variation de la resistivite a un fondement phylogenetique qui reflete probablement des differences anatomiques et physiologiques. Notre revue de la litterature et notre releve empirique fournissent un cadre de travail pour etudier l'ecologie de la foudre dans le contexte des proprietes electriques des arbres. [Traduit par la Redaction] Mots-cles : foudre, Michigan, resistivite, Kentucky, humidite., Introduction Scientific interest in the electrical properties of plants spans more than a century (e.g., Stone 1903). We briefly summarize the literature concerning the biologically relevant electrical characteristics of plants [...]

Brown bears (Ursus arctos L., 1758) damage trees (mainly the cambium) during feeding and marking. It is thought that their stripping of bark and their subsequent foraging on sapwood can lead to substantial economic losses. However, the part played by this process in the ecosystem is still unknown. We hypothesize that brown bear foraging makes resources and habitats available to other species. We anticipated that wounds perpetrated by bears during foraging would attract saproxylic insects and consequently insectivorous birds. Bear wounds were searched for on trees in the Bieszczady Mountains (Polish Eastern Carpathians) from 2008 to 2011. We analyzed 278 wounds in silver firs (Abies alba Mill.) of different age classes: 43% of them had holes made by wood-boring insects and 33% had signs of woodpecker feeding. The presence of insect holes and woodpecker marks in the wound was found to depend on wound area, wound age, and tree circumference (insects only). In particular, the oldest wound age class (>5 years old) was associated with a high probability of occurrence of insects and woodpeckers. Insects were attracted by wounds of smaller area than woodpeckers. The density of insect holes (number of wood-boring insects) depended on the wound age and tree circumference. Insect densities in fresh wounds ( Key words: foraging behavior, Ursus arctos, brown bear, insects, woodpeckers. Les ours bruns (Ursus arctos L., 1758) endommagent les arbres (principalement le cambium) durant l'alimentation et le marquage. Le fait pour ces animaux d'arracher l'ecorce pour ensuite se nourrir de l'aubier pourrait causer d'importantes pertes economiques. Le role que joue ce processus dans l'ecosysteme demeure toutefois inconnu. Nous avons postule que la quete de nourriture par les ours bruns rend des ressources et des habitats disponibles a d'autres especes. Nous nous attendions a ce que les plaies laissees par les ours durant leur quete de nourriture attirent des insectes saproxyliques et, par consequent, des oiseaux insectivores. Nous avons cherche des plaies faites par des ours sur des arbres des montagnes Bieszczady (Carpates orientales polonaises) de 2008 a 2011. Nous avons analyse 278 plaies sur des sapins blancs (Abies alba Mill.) de differentes classes d'age : 43 % d'entre eux presentaient des trous faits par des insectes rongeurs de bois et 33 % presentaient des signes que des pics s'y etaient nourris. Nous avons constate que la presence de trous d'insecte et de marques de pic sur une plaie dependait de la superficie et de l'age de cette derniere, ainsi que de la circonference de l'arbre (pour les insectes seulement). Plus particulierement, la plus vieille classe d'age des plaies (>5 ans) etait associee a une forte probabilite de presence d'insectes et de pics. Les insectes etaient attires par des plaies de plus faible superficie que les pics. La densite des trous d'insectes (nombre d'insectes rongeurs de bois) dependait de l'age de la plaie et de la circonference de l'arbre. Les densites d'insectes dans les plaies fraiches ( Mots-cles: comportement de quete de nourriture, Ursus arctos, ours brun, insectes, pics., Introduction Ecosystem or ecological engineers are organisms that directly or indirectly modulate, modify, maintain, and (or) create the availability of resources to other species by causing physical state changes in [...]

Forest inventory estimates of tree volume for large areas are typically calculated by adding the model predictions of volumes for individual trees at the plot level, calculating the mean over plots, and expressing the result on a per unit area basis. The uncertainty in the model predictions is generally ignored, with the result that the precision of the large-area volume estimate is optimistic. The primary study objective was to assess the performance of a Monte Carlo based approach for estimating model prediction error that had been developed for boreal and temperate forest applications when used for a subtropical forest application. Monte Carlo simulation approaches were used because of the complexities associated with multiple sources of uncertainty, the nonlinear nature of the models, and heteroskedasticity. A related objective was to estimate the effects of model prediction uncertainty due to residual and parameter uncertainty on the large-area volume estimates for the Brazilian state of Santa Catarina. The primary conclusions were fourfold. First, the methodological approach worked well. Second, the effects of model residual and parameter uncertainty on large-area estimates of mean volume per unit area were negligible for the models and calibration datasets used for the study. Third, for the models currently in use in Santa Catarina, the effects of model residual and parameter uncertainty may be ignored when calculating large-area estimates of mean volume per unit area. Fourth, differences were negligible between estimates of the mean and standard error obtained using a single, nonspecific volume model and estimates obtained using both forest-type models and species-specific/species-group models. Key words: allometric model, residual uncertainty, parameter uncertainty, Monte Carlo simulation, Santa Catarina, Brazil. L'estimation du volume des arbres d'un inventaire forestier pour un grand territoire est typiquement calculee en additionnant les predictions, faites par un modele, du volume des arbres individuels a l'echelle de la placette, en calculant la moyenne des placettes et en exprimant le resultat par unite de surface. L'incertitude de la prediction du modele est generalement ignoree avec pour resultat que la precision du volume de ce grand territoire est optimiste. Un des premiers objectifs de cette etude etait d'evaluer la performance d'une approche utilisant la methode Monte-Carlo pour estimer l'erreur de prediction d'un modele, developpe pour etre utilise dans des forets boreales et temperees, lorsqu'il est utilise en foret subtropicale. L'approche des simulations Monte-Carlo a ete utilisee en raison de la complexite associee a des sources d'incertitudes multiples, de la nature non-lineaire des modeles et de l'heteroscedasticite. Un objectif connexe etait d'estimer les effets sur l'estimation du volume pour un grand territoire, de l'Etat bresilien de Santa Catarina, de l'incertitude associee a la prediction du modele causee par l'erreur des parametres et l'erreur residuelle. Les principales conclusions ont ete au nombre de quatre. Premierement, l'approche methodologique a bien fonctionne. Deuxiemement, les effets de l'erreur des parametres et de l'erreur residuelle sur l'estimation du volume moyen par unite de surface pour un grand territoire se sont averes negligeables pour les modeles et les ensembles de donnees d'etalonnage utilisees dans cette etude. Troisiemement, pour les modeles actuellement en usage dans l'Etat de Santa Catarina, les effets de l'erreur residuelle et de l'erreur des parametres du modele peuvent etre ignores lorsque l'on estime le volume moyen par unite de surface pour ce grand territoire. Quatriemement, les differences etaient negligeables entre les estimations de la moyenne et de l'erreur standard obtenues en utilisant un seul modele de volume, non specifique, et les estimations obtenues en utilisant a la fois des modeles de type forestier et des modeles d'especes individuelles ou de groupes d'especes. [Traduit par la Redaction] Mots-cles : modele allometrique, incertitude residuelle, incertitude des parametres, simulation Monte Carlo, Santa Catarina, Bresil., 1. Introduction Forest inventory and monitoring programs routinely use statistical models to predict the volume, biomass, or carbon content for individual trees using measurements of tree attributes such as species, [...]

Extensive urbanization of the Eastern Seaboard has meant that the forests of the eastern United States now reflect complex and highly dynamic patterns of change depending on the spatial and [...]

Soil fauna play a key role in litter decomposition as they influence the litter mass loss rate in terrestrial ecosystems. However, the interaction between decomposing litter and soil fauna has not been adequately addressed. We examine the interaction between different types of decomposing litter and soil fauna on the Betula ermanii Cham. (BE) forest floor of the Changbai Mountains, China, by measuring the mass loss of six litter species groups using litterbags with two sizes of mesh (4 mm and 0.01 mm) during a yearlong experiment. Soil fauna were identified at the order level. We found that soil fauna have a limited effect on litter mass loss at the initial stage of the experiment. Its positive effect became apparent at month 12 of the experiment. After 1 year, soil fauna increased the litter mass loss rate of the high-quality litter of Parasenecio komarovianus (Pojark.) Y.L. Chen (PK) by 7.02% and of the low-quality litter of Rhododendron aureum Georgi (RA) by 25.26%. BE + PK litter was associated with a significantly higher abundance of soil fauna at months 8 and 10 of the experiment and also with a significantly higher richness of soil fauna at month 10 of the experiment. At the end of the experiment, however, the Shannon-Wiener diversity index of soil fauna was not necessarily higher in mixed-species litter. Litter mixing did promote the abundance, richness, and diversity of soil fauna during the warm season in the high-quality litter substrate of BE + PK. Our results illustrate that the impact of soil fauna on the litter mass loss of both single- and mixed-species litterbags ranges from a limited impact to a positive impact as litter mass loss advances. The soil fauna contribute more to the litter mass loss of the low-quality litter with higher C to N ratios than to those with a low C to N ratio. The promoting effect of litter mixing on the soil faunal community composition is only short term and is dependent on substrate quality. Key words: litter mass loss, litterbags, soil fauna, Betula ermanii forest, Changbai Mountains. La faune edaphique joue un role cle dans la decomposition de la litiere en influencant le taux de perte de masse dans les ecosystemes terrestres. Cependant, l'interaction de la litiere en decomposition et de la faune edaphique n'a pas ete adequatement etudiee. Nous avons examine l'interaction de differents types de litiere en decomposition et de faune edaphique dans la couverture morte de Betula ermanii Cham. (BE) dans le massif du Changbai, en Chine, en mesurant la perte de masse de six groupes d'especes de litiere dans des sacs avec deux tailles de mailles (4 et 0,01 mm) au cours d'une experience d'une duree d'une annee. La faune edaphique a ete identifiee au niveau de l'ordre. Nous avons trouve que la faune edaphique avait un effet limite sur la perte de masse de la litiere au stade initial de l'experience. Son effet benefique est devenu apparent au 12ieme mois de l'experience. Apres un an, la faune edaphique a accelere la perte de masse de la litiere de bonne qualite de Parasenecio komarovianus (Pojark.) Y.L. Chen (PK) de 7,02 % et de la litiere de mauvaise qualite de Rhododendron aureum Georgi (RA) de 25,26 %. La litiere de BE + PK etait associee a une abondance significativement plus grande de la faune edaphique au 8ieme et 10ieme mois de l'experience. La litiere de BE + PK etait associee a une richesse de la faune edaphique significativement plus grande au 10ieme mois de l'experience. A la fin cependant, l'indice de Shannon-Wiener de la faune edaphique n'etait pas necessairement plus eleve dans la litiere plurispecifique. Le melange de litiere a favorise l'abondance, la richesse et la diversite de la faune edaphique durant la saison chaude avec la litiere de haute qualite de BE + PK. Nos resultats illustrent le fait que l'impact de la faune edaphique sur la perte de masse des sacs de litiere contenant une seule ou plusieurs especes va de limite a positif a mesure que la perte de masse de la litiere progresse. La faune edaphique contribue davantage a la perte de masse de la litiere de faible qualite avec un rapport C:N plus eleve qu'a la perte de masse de la litiere qui a un rapport C:N plus faible. L'effet benefique du melange de litiere sur la composition de la communaute faunique du sol est de courte duree et depend de la qualite du substrat. [Traduit par la Redaction] Mots-cles: perte de masse de la litiere, sacs de litiere, faune edaphique, foret de Betula ermanii, massif du Changbai., Introduction Litter decomposition is one of the most important pathways in energy transformation and material cycles of the terrestrial ecosystem (Berg and McClaugherty 2008; Liski et al. 2003; Melillo et [...]

Disturbances such as fire and harvesting shape forest dynamics and must be accounted for when modelling forest properties. However, acquiring timely disturbance information for all of Canada's large forest area has always been challenging. Therefore, we developed an approach to detect annual forest change resulting from fire, harvesting, or flooding using Moderate Resolution Imaging Spectroradiometer (MODIS) imagery at 250 m spatial resolution across Canada and to estimate the within-pixel fractional change (FC). When this approach was applied to the period from 2000 to 2011, the accuracy of detection of burnt, harvested, or flooded areas against our validation dataset was 82%, 80%, and 85%, respectively. With FC, 77% of the area burnt and 82% of the area harvested within the validation dataset were correctly identified. The methodology was optimized to reduce the commission error but tended to omit smaller disturbances as a result. For example, the omitted area for harvest blocks greater than 80 ha was less than 14% but increased to between 38% and 50% for harvest blocks of 20 to 30 ha. Detection of burnt and harvested areas in some regions was hindered by persistent haze or cloud cover or by insect outbreaks. All resulting data layers are available as supplementary material. Key words: boreal forest, National Burned Area Composite, remote sensing, regression tree, decision tree, change detection. Les perturbations telles que le feu et la coupe faconnent la dynamique forestiere et doivent etre prises en compte lorsqu'on modelise les proprietes de la foret. Cependant, l'acquisition rapide de l'information au sujet des perturbations pour l'ensemble des vastes superficies de foret du Canada a toujours presente un defi. Nous avons par consequent developpe une approche pour detecter les changements annuels de la foret dus au feu, a la coupe ou aux inondations en utilisant l'imagerie MODIS avec une resolution spatiale de 250 m partout au Canada et pour estimer le changement fractionnel (FC) a l'echelle du pixel. Lorsque appliquee a la periode allant de 2000 a 2011, la precision de la detection des superficies brulees, coupees ou inondees sur la base de notre jeu de donnees de validation atteignait respectivement 82,80 et 85%. Avec le FC, 77% des superficies brulees et 82% des superficies coupees ont ete correctement identifiees dans le jeu de donnees de validation. La methodologie a ete optimisee pour reduire les erreurs dues a la detection de faux changements avec le resultat cependant qu'elle a tendance a ne pas detecter les plus petites perturbations. Par exemple, les superficies non detectees pour les aires de coupe plus grandes que 80 ha etaient inferieures a 14%, mais atteignaient entre 38 et 50% pour les aires de coupe de 20 a 30 ha. La detection des superficies brulees et coupees etait difficile dans certaines regions du a la brume ou au couvert nuageux persistant, ou par les epidemies d'insecte. Toutes les couches de donnees resultantes sont disponibles dans la section Materiel supplementaire. [Traduit par la Redaction] Mots-cles: foret boreale, Composite nationale des superficies brulees, teledetection, arbre de regression, arbre de decision, detection de changement., Introduction The managed forests of Canada cover approximately 229 Mha (Environment Canada 2012). Much of this area is in the boreal forest, which is characterized by slow growth and significant [...]

Successful canopy recruitment is one of the most important components of sustainable forestry practices. For many desirable species in oak-dominated forests, insufficient sapling growth is a common limitation to successful recruitment. The objectives of this study were to (i) examine the impact of overstory density on sapling growth in the Missouri Ozarks, (ii) investigate the potential for overstory retention to promote compositional shifts via interspecific differences in sapling height growth, and (iii) compare the use of mean and near-maximum growth rates to quantify the impact of overstory density on sapling growth and height differentiation among species. We found that the periodic annual height increment of saplings decreased with increasing overstory density for all species groups in this study (red oaks (Quercus spp.), white oaks (Quercus spp.), hickories (Carya spp.), sassafras (Sassafras spp.), blackgum (Nyssa spp.), dogwood (Cornus spp.), red maple (Acer spp.), ashes (Fraxinus spp.), and elms (Ulmus spp.)). There was evidence of interspecific differentiation in growth rates during the sapling stage, and the observed differences were more pronounced at low overstory densities. Increasing overstory densities either reduced or eliminated the differences in growth among species. Although red oaks displayed the greatest maximum growth rates of all species under low overstory densities ( Key words: silviculture, regeneration, recruitment, differentiation, quantile. Resume: Le succes du recrutement dans le couvert dominant est une des plus importantes composantes des pratiques de foresterie durable. Dans le cas de plusieurs especes desirees des forets dominees par le chene, la croissance insuffisante des gaules est le facteur qui limite couramment la reussite du recrutement. Les objectifs de cette etude consistaient a (i) examiner l'impact de la densite du couvert dominant sur la croissance des gaules dans les monts Ozarks du Missouri, (ii) evaluer le potentiel de mesures de retention du couvert dominant pour favoriser des changements de composition induits par des differences interspecifiques de croissance en hauteur des gaules et (iii) comparer l'utilisation des taux de croissance moyen et pres du maximum pour quantifier l'impact de la densite du couvert dominant sur la croissance des gaules et sur les differences de croissance entre les especes. Nous avons trouve que l'accroissement annuel periodique en hauteur des gaules diminuait avec l'augmentation de la densite du couvert dominant pour tous les groupes d'especes dans cette etude (chenes rouge et blanc, caryers, sassafras, nyssa, cornouiller, erable rouge, frenes et ormes). Il y avait des signes de differences interspecifiques du taux de croissance des gaules et les differences observees etaient plus prononcees lorsque la densite du couvert dominant etait faible. L'augmentation de la densite du couvert dominant reduisait ou eliminait les differences de croissance entre les especes. Bien que le chene rouge ait montre le taux maximal de croissance le plus eleve parmi toutes les especes lorsque la densite du couvert dominant etait faible ( Mots-cles: sylviculture, regeneration, recrutement, differentiation, quantile., Introduction Regeneration and canopy recruitment are two vital ecosystem processes necessary for sustainable forestry (Dey 2014). Unfortunately, difficulties and failures to regenerate either economically or ecologically important species are common [...]

Tree mortality because of beetle outbreaks has become substantial and widespread in conifer forests in western North America. A number of environmental and physiological factors influence patterns of mortality. Tree diversity may reduce the severity and extent of insect damage to host trees by providing associational resistance, but the existence and importance of associational resistance varies by forest type and by tree and insect species. We assessed whether plot-level tree diversity contributed to survival of Engelmann spruce (Picea engelmannii Parry ex Engelm.) following a spruce beetle (Dendroctonus rufipennis Kirby) epidemic. Our study plots comprised 2 to 5 tree species including Engelmann spruce, subalpine fir (Abies lasiocarpa (Hook) Nutt.), Douglas- fir (Pseudostuga menziesii (Mirb.) Franco), quaking aspen (Populus tremuloides Michx.), and white fir (Abies concolor (Gordon & Glend.) Hildebr.). We used a model-selection analysis to compare the importance of tree diversity with other known factors that influence spruce survival. We found lower rates of spruce survival in stands where spruce was the dominant tree species (by percent of stand density index) and higher survival in stands where nonspruce conifers (Douglas-fir, subalpine, and white fir) were dominant. We also found that tree diversity (Shannon index) did not show a positive correlation to spruce survival and that there was no additional benefit derived from the presence of aspen, which has higher phylogenetic distance from Engelmann spruce than the other trees in this study. The relationship between diversity and survival is complicated by factors that naturally co-vary with diversity, such as elevation, aspect, and stand density of spruce. Our results best support an explanation that if associational resistance does increase spruce survival during a beetle epidemic, it is due to host or resource dilution, which may be an indirect effect of higher stand diversity. Key words: associational resistance, biodiversity, Engelmann spruce (Picea engelmannii), host dilution, insect epidemic, Shannon index of diversity, spruce beetle (Dendrotonus rufipennis). La mortalite des arbres due a des epidemies de scolytes est devenue importante et tres repandue dans les forets de l'ouest de l'Amerique du Nord. Plusieurs facteurs physiologiques et environnementaux influencent les patrons de mortalite. La diversite des especes d'arbre peut reduire la severite et l'etendue des dommages causes par les insectes sur les arbres hotes en procurant une resistance d'association mais l'existence et l'importance de la resistance d'association varient selon le type de foret et l'espece d'arbre et d'insecte. Nous avons determine si la diversite des arbres a l'echelle de la parcelle contribuait a la survie de l'epicea d'Engelmann (Picea engelmannii Parry ex Engelm.) a la suite d'une epidemie de dendroctone de l'epinette (Dendroctonus rufipennis Kirby). Nos parcelles experimentales comprenaient 2 a 5 especes d'arbre incluant l'epicea d'Engelmann, le sapin subalpin (Abies lasiocarpa (Hook.) Nutt.), le douglas de Menzies (Pseudotsuga menziesii (Mirb.) Franco), le peuplier faux-tremble (Populus tremuloides Michx.) et le sapin concolore (A. concolor (Gordon & Glend.) Hildebr.). Nous avons utilise une procedure de selection de modeles pour comparer l'importance de la diversite des arbres a d'autres facteurs connus qui influencent la survie de l'epicea. Nous avons observe des taux de survie plus faibles dans les peuplements ou l'epicea etait l'espece dominante (en pourcentage et indice de densite du peuplement) et des taux de survie plus eleves dans les peuplements ou d'autres coniferes que l'epicea (douglas de Menzies, sapins subalpin et concolore) etaient dominants. Nous avons trouve que la diversite des arbres (indice de Shannon) n'etait pas positivement correlee avec la survie de l'epicea et qu'il n'y avait aucun benefice additionnel du a la presence du peuplier faux-tremble qui a une plus grande distance phylogenique de l'epicea que les autres arbres dans cette etude. La relation entre la diversite et la survie est compliquee par des facteurs qui varient naturellement en meme temps que la diversite tels que l'altitude, l'exposition et la densite des peuplements d'epicea. Nos resultats supportent davantage une explication selon laquelle la resistance d'association, si elle augmente la survie de l'epicea durant une epidemie de scolyte, serait due a la dilution de l'hote ou des ressources qui pourrait etre un effet indirect d'une plus grande diversite du peuplement. [Traduit par la Redaction] Mots-cles : resistance d'association, biodiversite, epicea d'Engelmann (Picea engelmannii), dilution de l'hote, epidemie d'insecte, indice de diversite de Shannon, dendroctone de l'epinette (Dendroctonus rufipennis)., Introduction Biodiversity is a central guiding value in resource management and conservation. This has led to a widespread search for connections between biological diversity and ecosystem functions (Hooper et al. [...]

The uniform angle index (UAI) is used to characterize the spatial distribution of a forest community or of individual tree species within that community. This study presents an empirical assessment of the performance of a new statistical test used in conjunction with the UAI. In this study, the UAI is applied to observed and simulated communities. The effect of plot size and density are examined and the results are compared with the criteria of the aggregation index R of Clark and Evan (CE-R) and Ripley's L function (RL). The results suggest that the UAI performs well in determining a particular class of spatial pattern and that, in contrast to the CE-R index, it is unaffected by population density because the standard deviation can be estimated when the density is known using a new empirical relationship presented in this paper. The results of this study represent an improvement in the development of the UAI, verifying its performance and confirming its overall utility. Our comparative analysis positions the UAI among its historical competitors, the CE-R and RL criteria. The UAI index, which does not require expensive mapping of tree positions, can produce results that are equivalent to those obtained by RL and more robust and reliable than those obtained by CE-R. Key words: forest, spatial patterns of trees, uniform angle index, significance test, method. L'indice d'angle uniforme (UAI) est utilise pour caracteriser la distribution spatiale d'une communaute ou d'une espece particuliere dans cette communaute. Cette etude presente une evaluation empirique de la performance d'un nouveau test statistique utilise avec l'UAI. Dans cette etude l'UAI est applique a des communautes reelles et simulees. L'effet de la dimension et de la densite des places echantillons ainsi que les resultats sont compares aux fonctions R de Clark et Evans (CE-R) et L de Ripley (RL). Les resultats indiquent que l'UAI a une bonne performance pour determiner une classe particuliere de configuration spatiale et que, contrairement a la fonction CE-R, il n'est pas influence par la densite de la population parce que l'ecart-type peut etre estime lorsque la densite est connue, en utilisant une nouvelle relation empirique presentee dans cet article. Les resultats de cette etude constituent une amelioration dans le developpement de l'UAI car ils corroborent sa performance et confirment sont utilite generale. Notre analyse comparative place l'UAI au meme rang que ses competiteurs historiques: les fonctions CE-R et RL. L'UAI, qui ne requiert pas une cartographie couteuse de la position des arbres, peut produire des resultats qui sont equivalents a ceux obtenus avec la fonction RL et plus robustes et plus fiables que ceux obtenus avec la fonction CE-R. [Traduit par la Redaction] Mots-cles: foret, configurations spatiales des arbres, indice d'angle uniforme, test d'hypothese, methode., 1. Introduction The tree distribution in horizontal space reflects very specific relationships among the individuals in a particular forest community and among individuals within a given species in that community. [...]

Sustainable forest practices are often designed to mimic natural disturbance and successional processes, yet succession is poorly understood in many ecosystems. On northeastern Vancouver Island, the 'disturbance hypothesis' is a widely assumed succession model asserting that shade-tolerant western redcedar (Thuja plicata Donn ex D. Don) and the ericaceous shrub salal (Gaultheria shallon Pursh) invade and colonize highly productive western hemlock (Tsuga heterophylla (Raf.) Sarg.)--Pacific silver fir (Abies amabilis Douglas ex J. Forbes) stands (HA) on zonal sites in the absence of stand-replacing wind disturbance. This leads to the development of low-productivity, low-density, uneven-aged, open-crowned redcedar-hemlock-salal stands (CH). In conflict with this model, old, apparently stable HA stands lacking redcedar can be found on such sites as well. We sought evidence for the predicted transition to CH stands by examining stand composition, crown closure, tree size class frequency distributions, salal cover, and redcedar establishment on young HA (~90 years old), old HA (>160 years), and CH (>160 years) stands. When adjacent to a redcedar stand, young HA stands had fewer redcedar seedlings but more redcedar adult trees than old HA stands. However, redcedar abundance did not differ between young and old HA stands at distances further than 10 m from adjacent redcedar stands. This could indicate that redcedar recruits into HA stands at stand establishment and that redcedar seedling establishment is low under the thick canopy of young HA stands. The chronosequence data also suggest that both old HA and CH stands are self-replacing stand types in these forests, contrary to the disturbance hypothesis. We develop a new, multipathway model for this ecosystem that is based on the chronosequence data and life-history traits of the focal tree species and suggest that disturbance plays a role opposite to the equilibrium model. Key words: forest succession, multiple-pathway model, forest regeneration, stand-replacing disturbance, forest ecotones. Les pratiques forestieres durables sont souvent con^ues pour imiter les perturbations naturelles et les processus de succession bien que la succession de plusieurs ecosystemes soit mal comprise. Dans le nord-est de l'ile de Vancouver, <> est un modele de succession largement hypothetique qui soutient qu'en l'absence de chablis majeur, le thuya geant (Thuja plicata Donn ex D. Don) tolerant a l'ombre et la gaultherie shallon (Gaultheria shallon Pursh), une ericacee arbustive, envahissent et colonisent les peuplements hautement productifs de pruche de l'Ouest (Tsuga heterophylla (Raf.) Sarg.) et de sapin gracieux (Abies amabilis Douglas ex J. Forbes) (HA) etablis sur des stations zonales. Ceci conduit au developpement de peuplements ouverts, inequiennes, peu productifs et a faible densite composes de thuya, de pruche et de gaultherie (CH). Contrairement a ce modele, de vieux peuplements HA sans thuya et apparemment stables peuvent aussi se developper sur de telles stations. Nous avons cherche des preuves de la transition prevue vers des peuplements CH en etudiant la composition des peuplements, la fermeture du couvert, la distribution du diametre des arbres, le couvert de gaultherie shallon et l'etablissement du thuya geant dans des peuplements HA jeunes (environ 90 ans), HA vieux (plus de 160 ans) et CH (plus de 160 ans). Lorsqu'ils sont adjacents a un peuplement de thuya, les jeunes peuplements HA comportent moins de semis de thuya, mais plus de thuyas adultes que les vieux peuplements HA. Cependant, l'abondance du thuya etait similaire dans les jeunes et les vieux peuplements HA a des distances plus grandes que 10 m du peuplement adjacent de thuya. Ceci pourrait indiquer que le thuya se regenere dans les peuplements HA lors de l'etablissement du peuplement et que l'etablissement de cette regeneration est faible sous le couvert dense des jeunes peuplements HA. Les donnees de la chronosequence indiquent aussi que les vieux peuplements HA et CH sont des types de peuplement qui s'autoregenerent dans ces forets, contrairement a l'hypothese de la perturbation. Nous avons mis au point un nouveau modele a voies multiples pour cet ecosysteme qui est fonde sur les donnees de chronosequence et les caracteristiques du cycle biologique des especes d'arbre visees. Nous croyons que la perturbation joue un role inverse a celui du modele d'equilibre. [Traduit par la Redaction] Mots-cles: succession forestiere, modele a voies multiples, regeneration forestiere, perturbation majeure, ecotones forestiers., Introduction Modern community ecology relies on dynamic events (disturbances, fluctuations in seedling establishment, and mortality rates) that result in multiple pathways of forest succession (Holt 2006; Clark 2009). These successional [...]

As climate changes, boreal forest ecosystems may become subject to disturbances that were previously uncommon in some regions. In recent decades, large tracts of northeastern boreal forest of Canada have been affected by different types of climatic events causing a lot of partial and some total stand mortality. Since these disturbances may become more important drivers of forest dynamics, there is a need to document their impact on forest structure. The objectives of this study were to describe temporal dynamics of partial windthrows and determine the effect of partial windthrow on stand composition and understory vegetation. The study was conducted in the North-Shore region of Quebec (Canada). Eighteen plots in closed forests were paired with 18 adjacent windthrow areas, in which trees experienced similar edaphic and climatic conditions. Dendroecological analyses, combined with vegetation sampling, were conducted on each site to determine stand structure and vegetation development through time. Significant increases in balsam fir and shade-tolerant species were observed in windthrow gaps. Tree mortality in windthrown stands was a slow process until the mid-1990s, a period during which spruce budworm defoliation may have played a role in weakening trees and making them more vulnerable to partial windthrow. Greater mortality observed following the mid-1990s was most certainly related to a regional storm. The initial composition of stands plays an important role in driving postwindthrow succession, as balsam fir is more susceptible to treefall. As opposed to stand-replacing windthrow and spruce budworm outbreaks that generate various postdisturbance responses, partial windthrow appears to only create opportunities for pre-established balsam fir to undergo release in gaps. Key words: windthrow, plant communities, growth release, Picea mariana, Abies balsamea, vegetation shift, spruce budworm outbreak. Compte tenu du changement climatique, les ecosystemes forestiers boreaux pourraient devenir assujettis a des perturbations naturelles qui etaient peu communes auparavant. Au cours des dernieres decennies, de grandes superficies de la foret boreale ont ete affectees par des perturbations causant la mortalite partielle ou totale des peuplements forestiers. Ces perturbations peuvent devenir plus importantes dans la dynamique naturelle de la foret boreale pressant la documentation de leur effet sur la structure de la foret. Les objectifs de cette etude etaient de decrire la dynamique temporelle des chablis partiels et determiner leur effets sur la composition forestiere et du sous-bois. Cette etude a ete realisee dans la region de la Cote-Nord, Quebec (Canada). Dix-huit placettes experimentales en foret fermee ont ete appariees avec dix-huit parcelles en foret affectee par les chablis ou les arbres poussaient dans des conditions climatiques et edaphiques similaires. Des analyses dendrochronologiques combinees avec des releves de vegetation ont ete realisees dans chacune des parcelles pour determiner l'evolution du couvert forestier et de la vegetation dans le temps. La mortalite des arbres dans les chablis a ete progressive jusqu'au milieu des annees 1990, periode au cours de laquelle la defoliation causee par la tordeuse des bourgeons de l'epinette a pu jouer un role en affaiblissant les arbres, les rendant plus vulnerables au chablis. Une tempete regionale a egalement accelere la mortalite des arbres a la fin des annees 1990. La composition initiale des peuplements joue un role important dans la succession apres chablis ou le sapin baumier est plus susceptible au chablis. Contrairement au chablis total et aux epidemies de tordeuse des bourgeons de l'epinette qui peuvent generer une variete de reponses post perturbation, le chablis partiel semble seulement creer des opportunites permettant a la regeneration preetablie de sapin baumier d'occuper les trouees. Mots-cles: chablis, communautes vegetales, detente de croissance, Picea mariana, Abies balsamea, epidemies de tordeuse des bourgeons de l'epinette., Introduction Wind damage has a strong ecological impact on a range of forest ecosystems, from tropical (Boose et al. 1994) to temperate (Peterson and Pickett 1991) and boreal forests (Kuuluvainen [...]

Resprouting is advantageous for plants in pyrogenic ecosystems because it allows for quick re-acquisition of space after fire. Resprouting species build multiple stems during their lifetime and have an established root system, which may affect growth and biomass allocation and whether resprouts conform to predicted scaling relationships. We measured height, basal diameter, and biomass of stems of five resprouting shrub species in scrubby flatwoods sites in Florida, varying in time after fire (6 w, 1 y, 8-9 y, 20-21 y). Differences among species in size and allocation ratios tended to be greater in recently burned sites. Six weeks after fire, the dominant species, Quercus inopina, had the highest height:diameter and leafistem biomass ratios, which may contribute to the ability of this species to persist over fire cycles. The slope of the relationship between stem height and diameter was higher in recently burned sites than 8 to 21 y after fire, whereas the slope of the relationship between stem height and biomass was higher 8 to 21 y after fire than in recently burned sites. Height and biomass of resprouts generally scaled differently with respect to diameter and height than predicted by allometric theory, but biomass of resprouts, on average, scaled with diameter as predicted. Therefore, resprouted stems were taller for a given diameter and accumulated less biomass with height growth. In pyrogenic ecosystems, it may be more advantageous to grow tall, to maximize light capture, than to invest in strength to avoid damage because fire will eventually remove stems. Our results indicated that current allometric theory does not adequately represent scaling of growth and biomass of resprouting shrubs., INTRODUCTION Disturbances such as fire often result in the nearly complete removal of aboveground biomass. Woody species in many ecosystems persist after fire by resprouting from surviving belowground organs (Menges [...]

Climate adaptation is being embraced by many municipalities worldwide. An element of this is the planting and protection of urban trees. However, the fact that climate change will also have an impact on urban trees has been largely overlooked. We argue that climate vulnerability assessments are necessary for addressing climate adaptation in urban forests and contribute to successful climate adaptation in cities. We review and integrate the literature on climate vulnerability and urban forests to explore how the general notion of urban forest vulnerability to climate change can be developed into an operational framework for undertaking a vulnerability assessment. The framework characterizes climate exposure, impact, sensitivity, and adaptive capacity, as well as nonclimatic drivers and factors, in urban forests. The most important themes in this discussion include urban tree species selection and diversity, naturalization, resource access, social awareness and engagement, budget and economic valuation, liability issues, and governance structures. Climate change vulnerability assessments help us understand how and why urban forests are vulnerable to climate change, identify future areas for research, and determine what adaptation measures could be included in urban forest management. These assessments help bring climate change to the forefront of the decision-making process and contribute to successful urban adaptation to climate change. Key words: climate change, urban forest, climate adaptation, climate vulnerability assessment. L'adaptation au climat preoccupe plusieurs municipality partout au monde. Parmi ces preoccupations, on retrouve la plantation et la protection des arbres urbains. Cependant, le fait que le changement climatique exercera egalement un impact sur les arbres urbains n'est generalement pas considere. Les auteurs avancent que des evaluations de la vulnerabilite au climat sont necessaries pour prendre en compte l'adaptation climatique des arbres urbains et contribuer a une adaptation efficace au climat dans les villes. Les auteurs passent en revue et integrent la litterature sur la vulnerabilite au climat et les forets urbaines fin d'explorer comment la notion generale de la vulnerabilite des forets urbaines au changement climatique peut etre developpe en un cadre operationnel pour entreprendre une evaluation de la vulnerabilite. Ce cadre caracterise l'exposition au climat, l'impact, la sensibilite et la capacite adaptative ainsi que les forces et les facteurs non climatiques dans les forets urbaines. Les themes les plus importants dans cette discussion incluent la selection et la diversite des essences urbaines, la naturalisation, l'acces a la ressource, la sensibilite et l'engagement social, le budget et la valorisation economique, les questions de responsabilite et les structures de gouvernance. Les evaluations de vulnerabilite au changement climatique nous aident a comprendre comment et pourquoi les forets urbaines sont vulnerables au changement climatique, a identifier de futurs sites de recherche et a determiner quelles mesures d'adaptation pourraient etre incluses dans l'amenagement forestier urbain. Ces evaluations aident a mettre le changement climatique a l'avant du processus de decision et contribuent a une adaptation urbaine efficace, face au changement du climat. [Traduit par la Redaction] Mots-cles: changement climatique, foret urbaine, adaptation au climat, evaluation de la vulnerabilite au climat., Introduction Accelerated climate change is a problem affecting all ecosystems on Earth. It is unequivocal that temperature has increased since preindustrial times more rapidly than earlier and extremely likely that [...]

ABSTRACT. The forest-tundra ecotone is expected to experience some of the initial effects of climate change. At the forefront of this transition zone, we find clonal growth forms of stunted [...]

Intact soil cores from two adjacent forest ecosystems (natural coniferous forest and dragon spruce plantation) were incubated in the laboratory to examine effects of temperature, reforestation and their interactions on rates of nitrogen (N) mineralisation, nitrification and ammonification in the subalpine forest of the eastern Tibetan Plateau. Two contrasting soils were incubated at five temperatures (-5, 0, 5, 15 and 25°C) for 4 weeks. Rates of N mineralisation and nitrification were insensitive to temperature at lower temperatures (0°C and 5°C) but increased over higher temperatures (15°C and 25°C). Large amounts of ammonium were released for each incubation time in both soils when the incubation temperature was -5°C. Therefore, the rates of mineralisation and ammonification at -5°C were significantly higher than at the other temperatures. Both the accumulations of inorganic N and rates of N transformation were significantly higher in the natural forest than in the plantation. Moreover, temperature sensitivity of net nitrification and N mineralisation were greater in the natural forest than the spruce plantation. Effects of temperature on accumulations of inorganic N and rates of N transformation were dependent on incubation time and forest ecosystem. Our results suggested that -5°C might be a key low temperature for N mineralisation in subalpine forest on the eastern Tibetan Plateau; the effect of projected warming on soil N transformation rate may be less significant in plantation forests than natural forests in this specific region. Additional keywords: coniferous forest, Eastern Tibetan Plateau, net N mineralisation, reforestation, temperature., Introduction As the Earth's 'third pole', the Tibetan Plateau has experienced a pronounced warming in recent decades (IPCC 2007). The forest in cold regions may have greater carbon sink strength [...]

The synchronization of nutrient release and demand in early stand establishment is important to maximizing resource use in forest plantations. We explored the impacts of forest floor manipulations on the dynamics of forest floor and mineral soil nutrient pools in a Pinus taeda L. plantation in North Carolina prior to and during 2 years following harvest and replanting. We present a novel method to estimate forest floor decomposition that avoids the exclusion of large detritivores. Decomposition and nutrient release rates from the forest floor were higher than rates typically observed in older stands (averaging 81% mass loss and 75% N loss across treatments over the 2-year period), highlighting the potential importance of the forest floor nutrient pool in early stand nutrition. Doubling the forest floor increased available C, N, and P pools in the mineral soil 46%, 47%, and 49%, respectively. Incorporating the forest floor into mineral soil through mixing had only transient positive effects on nutrient pools. Across treatments, an expected postharvest flush of soil available N was observed; however, removing the forest floor caused an earlier flush of available N in comparison with the control treatment, and doubling the forest floor caused a year delay in maximum N availability, better synchronizing the site's available N with stand demand. Key words: Assart effect, forest floor manipulations, Pinus taeda, forestry, nutrient dynamic. La synchronisation de la disponibilite et de la demande des nutriments tot lors de l'etablissement du peuplement est importante pour maximiser l'utilisation des ressources dans les plantations forestieres. Nous avons etudie les impacts des manipulations de la couverture morte sur la dynamique des bassins de nutriment de la couverture morte et du sol mineral dans une plantation de Pinus taeda L., en Caroline du Nord, avant et durant les deux annees qui ont suivi la recolte et la replantation. Nous presentons une nouvelle methode pour estimer la decomposition de la couverture morte sans exclure de larges detritivores. Les taux de decomposition et de liberation des nutriments dans la couverture morte etaient plus eleves que les taux typiquement observes dans les peuplements plus vieux (atteignant en moyenne 81% de perte de masse et 75% de perte de N dans l'ensemble des traitements sur une periode deux ans), faisant ressortir l'importance potentielle des bassins de nutriment de la couverture morte pour la nutrition du jeune peuplement. Le doublement de la couverture morte a augmente la disponibilite des bassins de C, N et P dans le sol mineral de respectivement 46, 47 et 49%. L'incorporation de la couverture morte dans le sol mineral en les melangeant n'a eu que des effets temporaires sur les bassins de nutriment. La liberation prevue d'une grande quantite de N disponible dans le sol a ete observee apres la recolte dans l'ensemble des traitements. Cependant, l'elimination de la couverture morte a entraine la mise en disponibilite plus precoce d'une grande quantite de N comparativement au traitement temoin et le doublement de la couverture morte a retarde d'un an la disponibilite maximum de N, entrainant une meilleure synchronisation de la disponibilite de N dans la station avec la demande du peuplement. [Traduit par la Redaction] Mots-cles: effet du a l'essartage, manipulations de la couverture morte, Pinus taeda, foresterie, dynamique des nutriments., Introduction Litterfall inputs in forests accumulate over time to form a forest floor layer (Switzer and Nelson 1972; Berg 1986) that is an important organic matter and nutrient pool potentially [...]

The rate at which trees regenerate following stand-replacing wildfire is an important but poorly understood process in the multi-century development of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) and western hemlock (Tsuga heterophylla (Raf.) Sarg.) forests. Temporal patterns of Douglas-fir establishment reconstructed from old-growth forests (>450 year) have generated contradictory models of either rapid (100 year) periods of establishment, while patterns of tree establishment in mid-aged (100 to 350 year) forests remains largely unknown. To determine temporal patterns of Douglas-fir establishment following stand-replacing fire, increment cores were obtained from 1455 trees in 18 mature and early old-growth forests in western Washington and northwestern Oregon, USA. Each of the stands showed continuous regeneration of Douglasfir for many decades following initiating fire. The establishment period averaged 60 years (range: 32-99 years). These results contrast both with the view of rapid (one- to two-decade) regeneration of Douglas-fir promoted in the early forestry literature and with reports of establishment periods exceeding 100 years in older (>400 year) Douglas-fir-western hemlock stands. These results have important implications for management designed to create and promote early-seral forest characteristics. Key words: Douglas-fir, tree establishment, canopy closure, age structure, stand development, early-seral, single-cohort. Le taux auquel les arbres se regenerent a la suite d'un feu severe est un processus important, mais mal compris, du developpement multiseculaire des forets composees de douglas de Menzies (Pseudotsuga menziesii (Mirb.) Franco) et de pruche de l'Ouest (Tsuga heterophylla (Raf.) Sarg.). Le patron temporel d'etablissement du douglas de Menzies reconstitue a partir de vieilles forets (>450 ans) a produit des modeles contradictoires de periode d'etablissement rapide ( 100 ans) alors que le patron d'etablissement des arbres dans les peuplements ages de 100 a 350 ans est peu connu. Pour determiner le patron temporel d'etablissement du douglas de Menzies a la suite d'un feu severe, des carottes ont ete prelevees sur 1455 arbres provenant de 18 forets matures et surmatures etablies dans l'ouest de l'Etat de Washington et dans le nord-ouest de l'Oregon, aux Etats-Unis. Un etablissement continu de la regeneration de douglas de Menzies pendant plusieurs dizaines d'annees a ete observe a la suite du feu a l'origine de chaque peuplement. La periode moyenne d'etablissement etait de 60 ans (de 32 a 99 ans). Ces resultats sont differents de ceux vehicules dans la vieille litterature forestiere soit une regeneration rapide (10 a 20 ans) du douglas de Menzies et de ceux mentionnes dans des rapports qui evaluent la periode d'etablissement a plus de 100 ans dans les vieux peuplements (>450 ans) de douglas de Menzies et de pruche de l'Ouest. Ces resultats ont des implications importantes pour l'amenagement visant a creer et a promouvoir des caracteristiques forestieres de debut de succession. [Traduit par la Redaction] Mots-cles: douglas de Menzies, etablissement d'arbres, developpement des peuplements, debut de succession, structure d'age., Introduction Temporal patterns of tree regeneration following stand-replacement disturbances strongly influence subsequent forest development (Ashton 1976; Foster et al. 1997; Cooper-Ellis et al. 1999; Franklin et al. 2002). The initial [...]

This study introduces five facets that can improve inference in small area estimation (SAE) problems: (1) model groups, (2) test of area effects, (3) conditional EBLUPs, (4) model selection, and (5) model averaging. Two contrasting case studies with data from the Swiss and Norwegian national forest inventories demonstrate the five facets. The target variable of interest was mean stem volume per hectare on forested land in 108 Swiss forest districts (FD) and in 14 Norwegian municipalities (KOM) in the County of Vestfold. Auxiliary variables from airborne laser scanning (Switzerland) and photogrammetric point clouds (Vestfold) with full coverage and a resolution of 25 m x 25 m (Switzerland) and 16 m x 16 m (Vestfold) were available. Only the data metric mean canopy height was statistically significant. Ten linear fixed-effects models and three mixed linear models were assessed. Area effects were statistically significant in the Swiss case but not in Vestfold case. A model selection based on AIC favored separate linear regression models for each FD and a single common regression model in Vestfold. Model averaging increased, on average, an estimated variance by 15%. Reported estimates of uncertainty were consistently larger than corresponding unconditional EBLUPs. Key words: model groups, tests of area effect, model selection, model averaging, conditional EBLUP. Cette etude presente cinq aspects qui peuvent ameliorer l'inference dans les cas d'estimations pour de petites regions geographiques: (1) les groupes de modeles; (2) les tests de l'effet de region; (3) les meilleures predictions empiriques lineaires sans biais (EBLUP) conditionnelles; (4) la selection de modeles; et (5) la combinaison de modeles. Deux etudes de cas contrastantes, utilisant des donnees des inventaires forestiers nationaux de la Suisse et de la Norvege sont utilisees pour demontrer ces cinq aspects. La variable d'interet ciblee etait le volume moyen a l'hectare par tige des terrains forestiers de 108 Districts forestiers (DF) de la Suisse et de 14 municipalites du Comte de Vestfold en Norvege. Des variables auxiliaires provenant de couvertures completes de balayage laser aeroporte (Suisse) et de nuages de points photogrammetriques (Vestfold), avec une resolution de 25 m x 25 m (Suisse) et de 16 m x 16 m (Vestfold) etaient disponibles. La hauteur moyenne du couvert forestier etait la seule donnee metrique statistiquement significative. Dix modeles lineaires a effets fixes et trois modeles lineaires mixtes ont ete evalues. Les effets de region etaient statistiquement significatifs dans le cas de la Suisse mais pas dans le cas du Vestfold. Une selection de modele sur la base du critere d'information d'Akaike a prefere des modeles de regression lineaires separes pour chaque DF, mais un seul modele de regression commun pour le Vestfold. La combinaison de modeles a augmente la variance estimee de 15 % en moyenne. Les estimations d'incertitude rapportees etaient toujours plus grandes que les meilleures predictions empiriques lineaires sans biais non conditionnelles correspondantes. [Traduit par la Redaction] Mots-cles: groupes de modeles, tests de l'effet de region, selection de modeles, combinaison de modeles, meilleure prediction empirique lineaire sans biais (EBLUP) conditionnelle., Introduction National forest inventories (NFIs) with sample plots established on a national grid provide accurate national and regional (statewide) estimates of important forest resource variables (McRoberts et al. 2010). In [...]

Calcium amendment is a restorative option for nutrient-depleted, acidic soils in the forests of the northeastern United States. We studied the effects of watershed-scale wollastonite (CaSi[O.sub.3]) application on the structural composition of soil organic matter (SOM) and hot-water-extractable organic matter (HWEOM) at the Hubbard Brook Experiment Forest in New Hampshire 7-9 years after treatment, along an elevation gradient. Soils in the high-elevation spruce-fir-birch (SFB) zone contained significantly greater amounts of HWEOM compared with lower elevation hardwood soils, likely due to differences in litter quality and slower decomposition rates in colder soils at higher elevation. The only significant difference in hot-water-extractable organic carbon concentration between reference and calcium- treated watersheds was in Oie horizons of the SFB zone, which also exhibited the greatest degree of soil chemical change after treatment. The [sup.13]C nuclear magnetic resonance (NMR) spectra showed no significant patterns in O- alkyl C abundance for either soil or HWEOM along the elevation gradient, suggesting that there were no elevation- related patterns in carbohydrate concentration. The general absence of long-term effects in this study suggests that effects of Ca amendment at this dosage on the composition of SOM were small or short-lived. Key words: soil organic matter, soil carbon, calcium, liming, NMR spectroscopy. L'amendement calcique est une option de rehabilitation des sols acides appauvris en nutriments dans les forets du nord-est des Etats-Unis. Nous avons etudie les effets de l'application de wollastonite (CaSiO3) a l'echelle du bassin versant sur la composition structurale de la matiere organique du sol et sur la matiere organique extractible a l'eau chaude (MOEEC) a la foret experimentale de Hubbard Brook au New Hampshire, 7-9 ans apres le traitement, le long d'un gradient altitudinal. Dans la foret d'epicea, de sapin et de bouleau (ESB) situee en altitude, les sols contenaient des quantites significativement plus elevees de MOEEC que les sols de la foret feuillue situee a plus faible altitude, vraisemblablement a cause des differences dans la qualite de la litiere et des taux de decomposition plus faibles dans les sols plus froids a plus haute altitude. La seule difference significative dans la concentration du carbone organique extractible a l'eau chaude entre les bassins chaules et les bassins temoins apparaissait dans l'horizon Oie de la foret ESB oU les changements dans les caracteristiques chimiques du sol apres le traitement ont ete les plus importants. Les spectres par resonnance magnetique nucleaire (RMN) du [sup.13]C n'ont montre aucun patron significatif de l'abondance du C O-alkyle, ni dans le sol, ni dans la MOEEC le long du gradient altitudinal; ce qui indique que la concentration des hydrates de carbone n'est pas fonction de l'altitude. L'absence generalisee d'effets a long terme dans cette etude indique que les effets de l'amendement calcique a la dose utilisee sur la composition de la matiere organique du sol etaient faibles et passagers. [Traduit par la Redaction] Mots-cles : matiere organique du sol, carbone du sol, calcium, chaulage, spectroscopie de RMN., Introduction In glaciated environments of New England, many higher elevation forests are characterized by shallow soils with small pools of weatherable minerals, resulting in higher soil acidity, lower stream calcium, [...]

Forest bryophytes are sensitive to the disturbances and environmental changes associated with forest management. We asked whether the substrates on which bryophytes grow mediate responses to exposure following canopy removal. We measured bryophyte cover and richness in 0.1 [m.sup.2] quadrats on the forest floor, decayed logs, and tree bases along a gradient of dispersed overstory retention (100%, 40%, and 15% of initial basal area) 7 to 8 years after harvest of mature Pseudotsuga forests. Cover, local richness, and, to a lesser degree, species evenness declined steeply across the retention gradient on decayed logs and tree bases but not on the forest floor. Liverworts were more sensitive than mosses, particularly on decayed logs and on the southwestern aspects of trees (>97% declines in cover under 15% retention). Richness and evenness at the treatment scale also declined sharply on decayed logs and on the southwestern aspects of trees but changed little or increased under 40% retention on the forest floor. Our results indicate that even moderate levels of dispersed retention cannot sustain the abundance and overall diversity of wood-associated bryophytes in these forests. During regeneration harvests, conservation of these species may require retention of intact forest aggregates in which substrate quality and microclimatic stability can be maintained. Key words: aspect, biological diversity, mosses, liverworts, substrates, Pacific Northwest, variable retention. Les bryophytes forestieres sont sensibles aux perturbations et aux changements environnementaux relies a l'amenagement forestier. Nous nous demandons si les substrats sur lesquels se developpent les bryophytes modifient leurs reactions a l'exposition provoquee par l'enlevement du couvert forestier. Nous avons mesure le couvert et la richesse des bryophytes dans des quadrats de 0,1 [m.sup.2] etablis sur la couverture morte, sur des billes de bois decomposees et sur la base des arbres le long d'un gradient de retention dispersee du couvert forestier (100, 40 et 15 % de la surface terriere initiale), de 7 a 8 ans apres la coupe de forets matures de Pseudotsuga. Le couvert, la richesse locale et, dans une moindre mesure, la regularite des especes ont fortement diminue sur les billes decomposees et la base des arbres le long du gradient de retention, maispas sur la couverture morte. Les hepatiques etaient plus sensibles que les mousses, particulierement sur les billes decomposees et du cote sud-ouest des arbres (diminution du couvert superieure a 97 % sous une retention de 15 %). La richesse et la regularite a l'echelle du traitement ont aussi fortement diminue sur les billes decomposees et le cote sud-ouest des arbres, mais ont peu change ou ont augmente sous 40 % de retention sur la couverture morte. Nos resultats indiquent que meme un niveau modere de retention dispersee ne peut soutenir l'abondance et la diversite totale des bryophytes associees au bois dans ces forets. Lors des coupes de regeneration, la conservation de ces especes peut necessiter la retention de bouquets intacts de foret dans lesquels la qualite du substrat et la stabilite microclimatique peuvent etre maintenues. [Traduit par la Redaction] Mots-cles : orientation, diversite biologique, mousses, hepatiques, substrats, nord-ouest du Pacifique, retention variable., Introduction Changes in land management are among the leading threats to biological diversity worldwide (Sala et al. 2000). Primary forests provide critical habitats for many species but have been dramatically [...]

Trees play pivotal roles in urban ecosystems through reducing temperature, increasing humidity, reducing wind speed, absorbing air pollutants, and reducing carbon dioxide, among other benefits. The urban forest will become increasingly influential through the 21st century. Urban development, however, alters the relationships and interactions between humans and trees, making their management complex. The values held by urbanites about trees in their towns and cities are critical to socially responsive urban forest management. The purpose of our research, therefore, was to determine how residents of the city of Winnipeg value their urban forests. Our data were collected through site tours, participant journals, photo-elicitation, and interviews. The results indicate that the people of Winnipeg feel strongly about trees, and their urban forest values are most often associated with the naturalness of the urban forest as experienced through recreational activities. Key words: urban forests, values, photo-elicitation, urban forest management, Canada. Les arbres jouent un role cle dans les ecosystemes urbains oU ils ont plusieurs effets benefiques en reduisant en autres la temperature, en augmentant l'humidite, en reduisant la vitesse du vent, en absorbant les polluants atmospheriques et en reduisant le dioxyde de carbone. La foret urbaine va avoir de plus en plus d'influence au cours du 21e siecle. Cependant, le developpement urbain modifie les relations et les interactions entre les humains et les arbres, ce qui complique la gestion des arbres. Les valeurs que les urbanistes accordent aux arbres dans leurs cites et villes sont essentielles pour une gestion de la foret urbaine qui tient compte des facteurs sociaux. Par consequent, le but de nos travaux de recherche consistait a determiner l'importance que les residents de la ville de Winnipeg accordent a leurs forets urbaines. Nos donnees ont ete collectees via des visites sur le terrain, des journaux participants, des photos interviews et des entrevues. Les resultats indiquent que les habitants de Winnipeg attachent beaucoup d'importance aux arbres et que les valeurs qu'ils attribuent a la foret urbaine sont le plus souvent associees au caractere naturel de la foret urbaine par le biais d'activites recreatives. [Traduit par la Redaction] Mots-cles : forets urbaines, valeurs, photo-interviews, gestion de la foret urbaine, Canada., Introduction An urban forest is defined broadly as all the trees within an urban area (Canadian Urban Forest Network 2010; Ordonez and Duinker 2010). Whether in stands or rows, or [...]

Methods for constructing a sampling design for large area forest inventories are presented. The methods, data sets used, and the procedures are demonstrated in a real setting: constructing a sampling design for the first national forest inventory for Tanzania. The approach of the paper constructs a spatial model of forests, landscape, and land use. Sampling errors of the key parameters as well as the field measurement costs of the inventory were estimated using sampling simulation on data. Forests and land use often vary within a country or an area of interest, implying that stratified sampling is an efficient inventory design. Double sampling for stratification was taken for the statistical framework. The work was motivated by the approach used by The Food and Agriculture Organization of the United Nations (FAO) in supporting nations to establish forest inventories. The approach taken deviates significantly from the traditional FAO approaches, making it possible to calculate forest resource estimates at the subnational level without increasing the costs. Key words: forest inventory, double sampling for stratification, sampling simulation, cost assessment, remote sensing. Des methodes visant a elaborer un plan d'echantillonnage pour effectuer l'inventaire forestier d'un vaste territoire sont presentees. Les methodes, les bases de donnees utilisees et les procedures sont demontrees pour un cas reel, soit l'elaboration d'un plan d'echantillonnage pour le premier inventaire forestier national de la Tanzanie. L'approche de cet article consiste a construire un modele spatial des forets, du paysage et de l'utilisation des terres. L'erreur d'echantillonnage des parametres cles ainsi que les couts de mesure de l'inventaire sur le terrain ont ete estimes a l'aide d'une simulation d'echantillonnage sur les donnees. Les forets et l'utilisation des terres varient souvent a l'interieur d'un pays ou d'un territoire d'interet, ce qui implique qu'un inventaire stratifie est une strategie d'echantillonnage efficace. Un plan d'echantillonnage a deux degres stratifie a ete utilise comme cadre statistique. Ce travail a ete inspire par l'approche utilisee par l'Organisation des Nations Unies pour l'alimentation et l'agriculture (FAO) pour aider les pays a etablir des inventaires forestiers. L'approche retenue differe significativement de l'approche traditionnelle de la FAO et permet de calculer des estimations des ressources forestieres a un niveau sous-national sans augmenter les couts. [Traduit par la Redaction] Mots-cles : inventaire forestier, echantillonnage a deux degres stratifie, simulation d'echantillonnage, evaluation des couts, teledetection., 1.0. Introduction Since the early 2000s, the Forestry Department of the Food and Agriculture Organization of the United Nations (FAO) has invested substantial resources in developing a programme of support [...]

This paper addresses the constraints that are often laid upon the tree value or timber volume function of analyses employing the Faustmann model. Frequently employed assumptions unnecessarily restrict the relevant domain in which maximal land expectation values can possibly occur such that boundary solutions may arise. The overly restrictive constraints might be set when growth functions are inadvertently treated as production functions. Key words: land expectation value, growth function, production function, model assumptions, optimal investment. Cet article traite des contraintes souvent imposees lors d'analyses qui utilisent le modele de Faustmann et portent sur la valeur de l'arbre ou la fonction de volume de bois. Frequemment utilisees, ces hypotheses limitent inutilement le domaine des valeurs d'attente du sol maximales, ce qui favorise des solutions frontieres. Ces contraintes trop restrictives peuvent etre etablies lorsque des fonctions de croissance sont traitees par inadvertance comme fonctions de production. [Traduit par la Redaction] Mots-cles : valeur d'attente du sol, fonction de croissance, fonction de production, hypotheses de modelisation, investissement optimal., Problem The Faustmann model is the heart of a theory seeking to explain the management and evolution of forests as a social process in the market environment of an open [...]

Wind-farm development may be an important contributor to forest fragmentation, but how such developments impact bats is poorly understood. We hypothesized that bat activity at a wind farm would be explained, at least in part, by attraction and avoidance behaviours caused by deforestation. We tested predictions of this hypothesis via a landscape- level acoustic, capture, and radiotelemetry survey of little brown bats (Myotis lucifugus (Le Conte, 1831)) and northern long-eared myotis (Myotis septentrionalis (Trouessart, 1897)). Acoustic and capture data indicated no significant difference in magnitude of activity between the fragmented wind farm and the less-fragmented surrounding areas. However, only 2 of 19 radio-tracked bats were ever located inside the wind farm despite being captured adjacent to it. Bat locations were compared against randomly generated locations within the same area in a logistic regression framework to rank landscape variables in order of association with bats. A multicriteria evaluation of forest metrics showed that, over a 3-year period, there was an increase of suitable habitat inside the wind farm for M. lucifugus and a decrease for M. septentrionalis. These results support the contention that, at this level of disturbance, M. lucifugus may use the cleared areas, while M. septentrionalis is negatively impacted by increased deforestation caused by wind-farm development. Key words: little brown bat, Myotis lucifugus, northern long-eared myotis, Myotis septentrionalis, forest fragmentation, distribution, movement, multicriteria evaluation, radiotelemetry, logistic regression. Si l'amenagement de parcs eoliens pourrait etre une importante cause de morcellement forestier, ses effets sur les chauves-souris ne sont pas bien compris. Nous avons postule que l'activite des chauves-souris dans un parc eolien s'expliquerait, en partie du moins, par des comportements d'attraction ou d'evitement causes par la deforestation. Nous avons verifie des predictions decoulant de cette hypothese en menant une etude acoustique, de capture et de radiotelemetrie a l'echelle du paysage des vespertilions brun (Myotis lucifugus (Le Conte, 1831)) et nordique (Myotis septentrionalis (Trouessart, 1897)). Les donnees acoustiques et de capture n'indiquaient aucune difference significative de la magnitude de l'activite entre le parc eolien morcele et des zones voisines moins morcelees. Seulement 2 des 19 chauves-souris suivies par radiotelemetrie ont toutefois ete decelees dans le parc eolien, malgre qu'elles aient ete capturees juste a cote. Les emplacements des chauves-souris ont ete compares a des emplacements generes aleatoirement dans la meme zone dans un cadre de regression logistique afin de classer les variables du paysage en ordre d'association avec les chauves-souris. Une evaluation multicriteres de parametres forestiers a demontre que, sur une periode de 3 ans, il y avait une augmentation des habitats convenables a l'interieur du parc eolien pour M. lucifugus et une diminution de ces habitats pour M. septentrionalis. Ces resultats appuient la these voulant que, a ce degre de perturbation, M. lucifugus pourrait utiliser les zones defrichees, alors qu'une deforestation accrue causee par l'amenagement de parcs eoliens a une incidence negative sur M. septentrionalis. [Traduit par la Redaction] Mots-cles : vespertilion brun, Myotis lucifugus, vespertilion nordique, Myotis septentrionalis, morcellement forestier, repartition, deplacement, evaluation multicriteres, radiotelemetrie, regression logistique., Introduction Anthropogenic alteration of natural environments can have major impacts on populations of local species (Tilman et al. 1994). The specific impacts may vary by species life-history traits, where some [...]

Investigating the composition and structure of old-growth forests provides information about the spatial and temporal variability of processes responsible for stand development, succession, and biogeographic patterns of forests. This study [...]

Forest openings, or canopy gaps, are an important resource for many forest songbirds, such as Cerulean Warblers (Setophaga cerulea). We examined canopy gap selection by this declining species to determine if male Cerulean Warblers selected particular sizes, vegetative heights, or types of gaps. We tested whether these parameters differed among territories, territory core areas, and randomly-placed sample plots. We used enhanced territory mapping techniques (burst sampling) to define habitat use within the territory. Canopy gap densities were higher within core areas of territories than within territories or random plots, indicating that Cerulean Warblers selected habitat within their territories with the highest gap densities. Selection of regenerating gaps with woody vegetation >12 m within the gap, and canopy heights >24 m surrounding the gap, occurred within territory core areas. These findings differed between two sites indicating that gap selection may vary based on forest structure. Differences were also found regarding the placement of territories with respect to gaps. Larger gaps, such as wildlife food plots, were located on the periphery of territories more often than other types and sizes of gaps, while smaller gaps, such as treefalls, were located within territory boundaries more often than expected. The creations of smaller canopy gaps, Key words: canopy gaps, Cerulean Warbler, kernel home range, Setophaga cerulea, territory size, vegetation structure., Cerulean Warblers (Setophaga cerulea) have declined ~75% since 1966 (Sauer et al. 2011), and habitat loss and degradation are thought to be contributing factors (Hamel et al. 2004). Although the [...]

Tropical forests are global epiCenters of biodiversity and important modulators of climate change (1), and are mainly constrained by rainfall patterns (1-3). The severe short-term droughts that occurred recently in Amazonia have drawn attention to the vulnerability of tropical forests to climatic disturbances (4-9). The central African rainforests, the second-largest on Earth, have experienced a long-term drying trend (10,11) whose impacts on vegetation dynamics remain mostly unknown because in situ observations are very limited. The Congolese forest, with its drier conditions and higher percentage of semi-evergreen trees (12,13), may be more tolerant to short-term rainfall reduction than are wetter tropical forests (11), but for a long-term drought there may be critical thresholds of water availability below which higher-biomass, closed-canopy forests transition to more open, lower-biomass forests (1,2,14). Here we present observational evidence for a widespread decline in forest greenness over the past decade based on analyzes of satellite data (optical, thermal, microwave and gravity) from several independent sensors over the Congo basin. This decline in vegetation greenness, particularly in the northern Congolese forest, is generally consistent with decreases in rainfall, terrestrial water storage, water content in aboveground woody and leaf biomass, and the canopy backscatter anomaly caused by changes in structure and moisture in upper forest layers. It is also consistent with increases in photo-synthetically active radiation and land surface temperature. These multiple lines of evidence indicate that this large-scale vegetation browning, or loss of photosynthetic capacity, may be partially attributable to the long-term drying trend. Our results suggest that a continued gradual decline of photosynthetic capacity and moisture content driven by the persistent drying trend could alter the composition and structure of the Congolese forest to favor the spread of drought-tolerant species (1,2,14)., The impact of changes in precipitation patterns, such as short-term and long-term droughts, on tropical rainforests is poorly understood and currently under debate (4-11). Systematic monitoring of the forests is [...]

Abstract: Hawaiian lowland wet forests are heavily invaded and their restoration is most likely to be successful if native species selected for restoration have efficient resource-use traits. We evaluated growth, [...]

The spruce budworm (Choristoneura fumiferana Clemens) is perhaps the single most important disturbance agent in Canada's eastern forests. Climate and forest composition are dominant factors in spruce budworm outbreak dynamics through their direct influences on the pest, its natural enemies, and its hosts, and through their influence on the multitrophic interactions that are important in outbreak dynamics. A combination of four climate variables, three forest composition variables, and one location variable explained 60% of the multivariate variability in outbreak characteristics (duration and severity) in eastern Canada. Outbreak duration was most strongly influenced by April--May accumulation of degree-days; outbreak severity was most strongly influenced by the extreme maximum temperatures of April--May. The basal area of balsam fir had a stronger influence than that of black spruce on duration and on severity. Both outbreak characteristics declined in more northerly locations. Under a projected future (2011-2040) climate scenario the largest increases in outbreak duration and severity are predicted to occur on the Gaspe Peninsula and the north shore of the St. Lawrence River (Quebec). The largest decreases in duration and severity are predicted to occur in southern Ontario and along the Bay of Fundy in New Brunswick and Nova Scotia. The predicted average change in outbreak duration is around -1.3 years. The predicted average change in outbreak severity is only slightly different from zero (around -1.5% defoliation). Resume: La tordeuse des bourgeons de l'epinette (Choristoneura fumiferana Clemens) est peut-etre le plus important agent de perturbation dans les forets de l'est du Canada. Le climat et la composition de la foret sont les principaux facteurs dans la dynamique des epidemies de tordeuse etant donne l'influence directe qu'ils ont sur le ravageur, ses ennemis naturels et ses hotes ainsi que sur les interactions multitrophiques qui sont importantes dans la dynamique des epidemies. Une combinaison de quatre variables climatiques, trois variables de composition forestiere et une variable de localisation expliquaient 60% de la variabilite multivariee des caracteristiques des epidemies (duree et severite) dans l'est du Canada. La duree des epidemies etait fortement influencee par l'accumulation de degres-jours durant les mois d'avril et mai alors que la severite etait surtout influencee par les temperatures maximales extremes durant les mois d'avril et mai. La surface terriere du sapin baumier avait plus d'influence que celle de l'epinette noire sur la duree et la severite des epidemies. Les deux caracteristiques des epidemies diminuaient dans les endroits les plus septentrionaux. Selon un scenario de prevision du climat futur (2011-2040), la Gaspesie et la rive nord du fleuve Saint-Laurent (Quebec) connaitront les plus fortes augmentations de la duree et de la severite des epidemies alors que les plus fortes diminutions surviendront dans le sud de l'Ontario et le long de la baie de Fundy au Nouveau-Brunswick et en Nouvelle-Ecosse. Le changement moyen predit est d'environ -1,3 an dans le cas de la duree des epidemies et seulement legerement different de zero, soit environ -1,5% de defoliation, dans le cas de la severite. [Traduit par la Redaction], Introduction The spruce budworm (Choristoneura fumiferana Clemens) is arguably the most damaging insect of North America's forest (Hardy et al. 1983), and, in Canada, it occurs throughout most of the [...]

A better understanding of the growth-climate relationship for subalpine trees is key to improving predictions about their future distributions under climate change. In subalpine regions of Mediterranean mountains, drought is an annual event, yet many sites can have long-lasting snowpack. We analyzed the growth-climate relationship from 1896 to 2006 for the six most abundant subalpine tree species (red fir (Abies magnifica A. Murray bis), whitebark pine (Pinus albicaulis Engelm.), Sierra/Cascade lodgepole pine (Pinus contorta var. murrayana (Balf.) Engelm.), Jeffrey pine (Pinus jeffreyi Balf.), western white pine (Pinus monticola Douglas ex D. Don), and mountain hemlock (Tsuga mertensiana (Bong.) Carriere)) of the central Sierra Nevada, California, USA, a region with deep spring snowpack followed by strong summer drought. Chronologies for the six species exhibited a high degree of synchrony in their response to annual fluctuations in temperature and precipitation. For all six species, cool, wet conditions in the year prior to growth are conducive to good radial growth, as well as warm springs with sufficient moisture during the year of growth. For species more common on protected slopes, such as mountain hemlock, deep spring snowpack can limit growth. Although predictions of future precipitation trends in the region are uncertain, drought stress appears to already be increasing. If this trend continues, radial growth is likely to be inhibited for most or all species in our study. Trees growing where snowpack is deep may be least likely to suffer reduced growth. Resume: Il est essentiel d'avoir une meilleure comprehension de la relation entre la croissance des arbres subalpins et le climat pour mieux prevoir l'impact des changements climatiques sur leur repartition future. La secheresse est un evenement annuel dans les regions subalpines des montagnes mediterraneennes mais dans plusieurs sites, le manteau neigeux peut persister longtemps. Nous avons analyse la relation entre la croissance et le climat de 1896 a 2006 chez les six especes subalpines d'arbre (le sapin rouge (Abies magnifica A. Murray bis), le pin a ecorce blanche (Pinus albicaulis Engelm.), le pin tordu de Murray (Pinus contorta var. murrayana (Balf.) Engelm.), le pin de Jeffrey (Pinus jeffreyi Balf.), le pin argente (Pinus monticola Douglas ex D. Don) et la pruche subalpine (Tsuga mertensiana (Bong.) Carriere) les plus abondantes dans la Sierra Nevada centrale, en Californie, aux E.-U., une region ou l'epais manteau neigeux au printemps est suivi d'une forte secheresse estivale. Il y avait un haut degre de synchronisation dans les series dendrochronologiques des six especes quant a leur reaction aux fluctuations annuelles de temperature et de precipitation. Chez les six especes, des conditions fraiches et humides durant l'annee qui precede sont propices a une bonne croissance radiale, ainsi qu'un printemps chaud et suffisamment d'humidite durant l'annee en cours. Dans le cas des especes plus communes dans les sites ou le manteau neigeux est epais au printemps, telles que la pruche subalpine, l'epais manteau neigeux peut limiter la croissance. Bien que les predictions concernant la tendance future des precipitations dans la region soient incertaines, le stress cause par la secheresse semble deja etre en train d'augmenter. Si cette tendance se maintient, la croissance radiale de la plupart sinon toutes les especes visees par notre etude sera probablement inhibee. Les arbres qui poussent dans les endroits ou le manteau neigeux est epais sont les moins susceptibles de subir une reduction de croissance. [Traduit par la Redaction], Introduction Despite broad consensus among scientists that the earth's climate will continue to warm over the next 100 years (IPCC 2007), our understanding of how individual species will respond to [...]

The resilience of the boreal forest field layer (herbs plus dwarf shrubs) to anthropogenic disturbances is insufficiently understood because of the multitude of direct or indirect driver pathways and environmental conditions involved. We hypothesized that the impact of the forest-management-induced disturbances on field layer varies along the gradient of site productivity. To explore that we proposed a method for estimating the proportional effect of each driver on the field-layer composition, in a survey data of 273 mature or overgrown boreal forests, by combining variogram analysis with multifactorial general linear modelling. In forest types of very low and high productivity, field-layer composition was sensitive to the management disturbances in general and, particularly, to the management-controlled variations in the structure of the stand and its understory, i.e., in environmentally stressful conditions the main limiting factors were light availability and its spatiotemporal variability. At intermediate productivity, instead, the natural heterogeneity of ground layer conditions was the dominant driver, pointing to the limitation of regeneration microsites. Accordingly, on soils with low and high productivity, biodiversity-oriented sustainable forestry should diversify silvicultural approaches among stands and (or) enhance the within-stand mosaic, whereas small-scale natural disturbances of the ground-level 'organic blanket' should be promoted in forests of intermediate productivity. Resume: La resilience aux perturbations anthropiques de la strate de sous-bois (herbacees et petits arbustes) de la foret boreale n'est pas suffisamment comprise a cause de l'implication directe ou indirecte d'une multitude de facteurs de changement et de conditions environnementales. Nous avons pose l'hypothese que l'impact des perturbations induites par l'amenagement forestier sur la strate de sous-bois varie selon un gradient de productivite des stations. Pour tester cette hypothese, nous avons propose une methode pour estimer l'effet proportionnel de chaque facteur sur la composition de la strate de sous-bois a l'aide de releves effectues dans 273 peuplements boreaux matures ou surannes en combinant l'analyse de variogramme et la modelisation lineaire generalisee multifactorielle. Dans les types forestiers ayant une productivite tres faible ou forte, la composition de la strate de sous-bois etait generalement sensible aux perturbations causees par l'amenagement, plus particulierement dans le cas des amenagements provoquant des changements de structure du peuplement et de sa strate de sous-bois. Ainsi, les facteurs limitatifs sous des conditions de stress environnementaux etaient la disponibilite de la lumiere et sa variabilite spatio-temporelle. Par ailleurs, dans les peuplements dont la productivite est intermediaire, l'heterogeneite naturelle des conditions de la strate de sous-bois etait le facteur dominant, ce qui indique une limitation des microsites de regeneration. Selon ces resultats, sur les sols dont la productivite est faible ou forte, la foresterie durable orientee vers la biodiversite devrait diversifier les approches sylvicoles parmi les peuplements ou ameliorer la mosaique intra-peuplement. Dans le cas des forets dont la productivite est intermediaire, on devrait favoriser les perturbations naturelles de dimensions reduites sur la couverture organique du sol. [Traduit par la Redaction], Introduction Resilience in a broad sense is the capacity of communities to resist disturbances or to recover after exogenous disturbance events, and it has two more specific subtypes--engineering resilience (also [...]

Retreat of the Laurentide Ice Sheet 20 000 years ago tremendously altered environmental conditions and opened territory to the boreal spruce forest expansion. However, the details of forest colonization during the rapid climate warming and the adaptation of the newly developed stands to short cooling episodes during the warming and degradation of the ice sheet are not known. Preservation of wood from the glacial to postglacial transition offers the opportunity for examination of high-frequency growth variability in response to hemispheric and local forcings on temperature and hydrology. Here we consider growth of spruce at three sites from the interior of Northern America developed at ca. 13 700, 12 100, and 11 300 calibrated years before present (cal years BP), with well-replicated tree-ring chronologies spanning from 116 to 310 years. The data show at least two generations of trees established at each of the sites promoted by short, warm intervals. The tree mortality was variously affected by both cold conditions and the influence of rising water table and sediment burial. The history of these stands indicates breaks in forest colonization following a century (or two) of successful migrations. Interestingly, the thinning of the spruce forest did not seem to open pioneering opportunities for other tree species at those times. Le retrait de l'inlandsis laurentidien il y a 20 000 ans a considerablement modifie les conditions environnementales et cree de l'espace pour l'expansion de la foret boreale d'epicea. Cependant, on ne connait pas les details de la colonisation par la foret durant le rechauffement rapide du climat ni comment les peuplements nouvellement etablis se sont adaptes a de cours episodes de refroidissement durant ce rechauffement et la degradation de la nappe glaciaire. La preservation de pieces de bois datant de la periode de transition entre les periodes glaciaire et postglaciaire fournit l'occasion d'etudier les variations de croissance tres frequentes en reaction aux forcages hemispheriques et locaux de la temperature et de l'hydrologie. Dans cet article, nous examinons la croissance de l'epicea qui se developpait a trois endroits sur le continent nord americain il y a approximativement 13 700, 12 100 et 11 300 ans a l'aide de series dendrochronologiques repetees plusieurs fois et s'etendant sur 116 a 310 ans. Les donnees montrent qu'au moins deux generations d'arbres, profitant de brefs intervalles de chaleur, se sont etablies a chacun des endroits. La mortalite des arbres etait influencee de facon variable tant par le froid que par l'influence de la remontee de la nappe phreatique et l'ensevelissement par les sediments. L'histoire de ces peuplements indique que la colonisation par la foret a connu des pauses apres un (ou deux) siecle de migrations reussies. Il est interessant de constater que l'eclaircie de la foret d'epicea ne semble pas avoir cree de nouvelles opportunites pour d'autres especes d'arbre a ces moments-la. [Traduit par la Redaction], Introduction During deglaciation, ca. 15 000 to 11 000 years ago, oxygen isotopes in Greenland ice cores chronicled large temperature variations prior to entering the more climatically stable Holocene period [...]

We consider two-phase sampling schemes where one component of the auxiliary information is known in every point ('wall-to-wall') and a second component is available only in the large sample of the first phase, whereas the second phase yields a subsample with the terrestrial inventory. This setup is of growing interest in forest inventory thanks to the recent advances in remote sensing, in particular, the availability of LiDAR data. We propose a new two-phase regression estimator for global and local estimation and derive its asymptotic design-based variance. The new estimator performs better than the classical regression estimator. Furthermore, it can be generalized to cluster sampling and two-stage tree sampling within plots. Simulations and a case study with LiDAR data illustrate the theory. Resume: Cet article propose un nouvel estimateur pour les inventaires forestiers utilisant des plans de sondage a deux phases pour lesquels l'information auxiliaire consiste en une premiere composante exhaustive connue en chaque point et une seconde composante connue seulement aux points du grand echantillon de la premiere phase. La deuxieme phase consiste en un sous-echantillon des points de la premiere phase dans lesquels l'inventaire terrestre est effectue. Ce contexte est appele a jour un role croissant grace aux developpements recents dans l'aquisition de donnees par teledetection. Nous proposons un nouvel estimateur par regression, aussi bien pour l'estimation globale que locale, et nous donnons sa variance asymptotique sous le plan de sondage. Le nouvel estimateur peut etre adapte aux inventaire par satellites et avec tirage double des arbres au niveau de la placette terrestre. Un exemple utilisant des donnees LiDAR et des simulations illustrent la theorie. Le nouvel estimateur a de meilleures performance que l'estimateur de regression classique., 1. Introduction The motivation for this work is due to the increasing need for using national or regional inventories for local estimation to meet tighter budgetary constraints, which is only [...]

Quantifying how understory vegetation responds to individual neighboring trees is critical to understanding forest dynamics. To do so, we used a spatial neighborhood approach to quantify the competitive effect of individual trees on the density and height of dwarf bamboo (Sasa senanensis (Franch. et Savat.) Rehder) in a mixed conifer-broadleaf forest on the island of Hokkaido, northern Japan. Using hierarchical Bayesian models, we analyzed how the effect of neighboring trees varies with stem size, distance to the dwarf bamboo, and tree species. The effect of neighbors peaked when the tree reached a medium size (33.0-45.0 cm in diameter at breast height) and decreased for larger trees. The effect of neighbors decreased with increasing distance to the dwarf bamboo. The slope of the decrease was gentler for larger trees. Conifers exerted an average of 7.2 times the effect of broadleaved trees. Species with higher shade tolerance exerted larger effects. Species with late leaf flush and early defoliation tended to exert smaller effects. Our results provide evidence that neighborhood analysis is an effective approach for quantifying the effects of individual trees on understory vegetation and represents a critical step toward understanding how fine-scale interactions between understory vegetation and trees influence overall forest dynamics. Resume: Il est essentiel de quantifier la reaction de la vegetation du sous-etage a chacun des arbres avoisinants pour comprendre la dynamique forestiere. A cette fin, nous avons utilise une approche spatiale de voisinage pour quantifier l'effet de competition d'arbres individuels sur la densite et la hauteur du bambou nain (Sasa senanensis (Franch. & Savat.) Rehder) dans une foret mixte sur l'ile d'Hokkaido, dans le nord du Japon. A l'aide de modeles bayesiens hierarchiques, nous avons analyse la facon dont l'effet des arbres voisins varie selon le diametre de la tige, la distance du bambou nain et l'espece d'arbre. L'effet des voisins culmine lorsqu'un arbre atteint une taille moyenne (33 a 45 cm de diametre a hauteur de poitrine) et diminue lorsque les arbres sont plus gros. L'effet des voisins diminue avec l'augmentation de la distance du bambou nain. La pente de la diminution etait plus faible pour les arbres plus gros. L'effet produit par les coniferes etait en moyenne 7,2 fois plus grand que celui des feuillus. Les especes les plus tolerantes a l'ombre avaient plus d'effet. Les especes qui debourraient tardivement et perdaient leur feuilles tot avaient tendance a avoir moins d'effet. Nos resultats montrent que l'analyse de voisinage constitue une approche efficace pour quantifier les effets d'arbres individuels sur la vegetation du sous-etage et represente une etape essentielle pour comprendre comment les interactions a petite echelle entre la vegetation du sous-etage et les arbres influencent la dynamique forestiere globale. [Traduit par la Redaction], Introduction In many of the world's forest ecosystems, understory vegetation plays a crucial role in forest dynamics (Nakashizuka 1988; Abe et al. 2002; Royo and Carson 2006, 2008). The attributes [...]

The self-thinning rule has been used extensively to predict population dynamics under intraspecific and interspecific competition. In forestry, it is an important silvicultural concept for maintaining stand health in the face of climate change and biotic stress, but uncertainty exists because traditional self-thinning limits were set subjectively without regard to site quality. We addressed this by analyzing ponderosa pine (Pinus ponderosa Lawson & C. Lawson) data from 109 research plots measured repeatedly and 59 inventory plots measured once across California. Self-thinning boundaries were fitted to the data with quantile regression and stochastic frontier function (SFF) techniques with and without site index (SI) as a covariate. The models from both methods fitted the data well with either research plots or all plots. Slopes for size-density trajectories were -0.45 with the 0.99 quantile and -0.47 for SFF. Maximum stand density indices (SDI) were 1250 trees per hectare (TPH) with the 0.99 quantile and 1050-1060 TPH with SFF. Mortality occurred when site occupancy from SFF reached 0.75, suggesting a zone of imminent mortality. Curvilinear trends in maximum SDI across SI for both methods indicate that self-thinning varies with site quality. Any management regimes that increase site quality and productivity will increase the self-thinning boundary. Resume: La loi de l'auto-eclaircie a ete beaucoup utilisee pour prevoir la dynamique des populations soumises a une competition intra et interspecifique. En foresterie, c'est un concept sylvicole important pour maintenir la sante des peuplements face aux changements climatiques et aux stress biotiques, mais des incertitudes subsistent parce que les limites traditionnelles de l'auto-eclaircie ont ete fixees subjectivement sans egard a la qualite de station. Nous avons traite cette problematique en analysant des donnees sur le pin ponderosa (Pinus ponderosa Lawson & C. Lawson) recoltees dans 109 placettes de recherche mesurees de facon repetee et 59 placettes d'inventaire mesurees une seule fois a travers la Californie. Les limites de l'auto-eclaircie ont ete ajustees aux donnees a l'aide de techniques de regression quantile et de fonction limite aleatoire (FLA) avec et sans l'ajout de l'indice de qualite de station (IQS) comme covariable. Les modeles obtenus avec chacune des deux methodes se sont bien ajustes aux donnees provenant uniquement des placettes de recherche ou de l'ensemble des placettes. La pente des trajectoires entre la taille des arbres et la densite des peuplements etait de -0,45 avec le quantile 0,99 et de -0,47 avec la FLA. La valeur maximale de l'indice de densite des peuplements (IDP) etait de 1250 arbres a l'hectare avec le quantile 0,99 et de 1050 a 1060 arbres a l'hectare avec la FLA. La mortalite des arbres debutait lorsque l'occupation de la station atteignait 0,75 selon la FLA, ce qui indique une zone de mortalite imminente. Une tendance curvilineaire entre l'IDP maximal et l'IQS dans le cas des deux methodes indique que l'auto-eclaircie varie selon la qualite de station. Tout regime d'amenagement qui augmente la qualite et la productivite de la station va produire une augmentation de la limite de l'auto-eclaircie. [Traduit par la Redaction], Introduction Competition among trees is an important factor determining stand dynamics in both natural forest and plantations. Stand density strongly relates to intensity of competition. Foresters often manipulate stand density [...]

Abstract. The overall objective was to assess the quantity of carbon stored by New Jersey forests (i.e., carbon stock) and estimate the amount of carbon being sequestered annually. This assessment [...]