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There is an increasing interest in mixed conifer-broadleaf stands as a way to increase the diversity and productivity of managed forests. This study examined the impacts of varying densities of planted broadleaf trees on conifer performance, total stand productivity, and understory plant cover 20 years after stand establishment. The study took place in the Malcolm Knapp Research Forest in Maple Ridge, British Columbia. It used a randomized complete block design to compare treatments containing low, moderate, or high broadleaf densities added to a constant conifer density. Each block contained a conifer-only plot as a control. Conifers were composed of equal amounts of western hemlock, western redcedar, and Douglas-fir. Broadleaves were composed of either red alder or paper birch. We found that conifer volume was significantly lower in most broadleaf treatments relative to the control, due to lower hemlock and redcedar volumes. Douglas-fir, on the other hand, had a higher volume--albeit not significant--in the broadleaf treatments. There were no significant differences in total stand volume between any of the treatments and the control. Shrub cover was significantly higher in the low and high alder treatments relative to the control, but there were no differences in shrub cover between birch treatments and the control. The results suggest that low alder density provides a good balance of conifer yield and understory development. Key words: deciduous trees, plant diversity, ecosystem-based management, mixed species stands, multi-value forestry, ecosystem services, 1. Introduction Industrial forest management in North America and Europe has historically focused on maximizing wood production, with the result that managed second-growth forests often have a homogeneous and simplified [...]

We examined the performance of sweetgum (Liquidambar styraciflua L.), cherrybark oak (Quercus pagoda Raf.), and loblolly pine (Pinus taeda L.) in two-species pine-hardwood mixtures (sweetgum : loblolly pine and cherrybark oak : loblolly pine) at various planting densities (1482-1976 trees per hectare (TPH)) over 23 years in northern Louisiana, USA. Species were planted in alternating rows with hardwood establishment occurring 1 year prior to loblolly pine. Mixtures were also compared to loblolly pine monocultures at a common density (1482 TPH) to assess whether mixing improved productivity. Sweetgum exerted more competitive pressure on loblolly pine than cherrybark oak. At final measurement, sweetgum survival statistically exceeded that of loblolly pine across mixture density. Moreover, sweetgum cumulative basal area and volume growth nearly tripled that of loblolly pine in balanced high-density mixtures (1976 TPH, 50 pine : 50 hardwood). In contrast, cherrybark oak basal area and volume growth did not significantly exceed loblolly pine at any density. At a common density (1482 TPH), loblolly pine monoculture cumulative basal area and volume significantly exceeded those of mixtures with sweetgum and cherrybark oak by 19% and 24%, respectively. Collectively, these results indicate that growing loblolly pine in mixture with these two species did not produce complementary interactions and negatively affected stand-level growth. Key words: overyielding, loblolly pine, cherrybark oak, sweetgum, interspecific competition, mixed stands Nous avons examine la performance du copalme d'Amerique (Liquidambar styraciflua L.), du chene a feuilles en pagode (Quercus pagoda Raf.) et du pin a encens (Pinus taeda L.) dans des melanges de pins et de feuillus a deux especes (copalme d'Amerique : pin a encens et chene a feuilles en pagode : pin a encens) a diverses densites de plantation (1482 a 1976 TPH) pendant 23 ans dans le nord de la Louisiane, aux Etats-Unis. Les especes ont ete plantees en rangs alternes, l'etablissement des feuillus ayant lieu un an avant celui des pins a encens. Les melanges ont egalement ete compares aux monocultures de pin a encens a une densite commune (1482 TPH) pour evaluer si le melange ameliorait la productivite. Le copalme d'Amerique a exerce une plus grande pression concurrentielle sur le pin a encens que le chene a feuilles en pagode. Lors de la mesure finale, la survie du copalme d'Amerique a statistiquement depasse celle du pin a encens, quelle que soit la densite du melange. De plus, la croissance cumulative de la zone basale et du volume du copalme d'Amerique a presque triple par rapport a celle du pin a encens dans les melanges equilibres a haute densite (1976 TPH, 50 pins : 50 feuillus). En revanche, la croissance de la surface terriere et du volume du chene a feuilles en pagode n'a pas depasse de maniere significative celle du pin a encens, quelle que soit la densite. A une densite commune (1482 TPH), la zone basale et le volume cumules de la monoculture du pin a encens ont depasse de maniere significative ceux des melanges avec le copalme d'Amerique et le chene a feuilles en pagode de 19% et 24%, respectivement. Collectivement, ces resultats indiquent que la culture du pin a encens en melange avec ces deux especes n'a pas produit d'interactions complementaires et a affecte negativement la croissance au niveau du peuplement. [Traduit par la Redaction] Mots-cles : rendement excessif, pin a encens, chene a feuilles en pagode, copalme d'Amerique, competition interspecifique, peuplements mixtes, Introduction Maintaining productive forests is a global priority. Historically, monocultures have been established to maximize forest productivity (Rubilar et al. 2018). However, concerns over declining biodiversity, enhanced risk of species-specific [...]

Understanding the magnitude and cause of variation in tree growth and forest productivity is central to sustainable forest management. Measurements of annual growth rings allow assessments of individual-tree, tree population, and forest ecosystem vulnerabilities to drought stress or other changing forest disturbance regimes (insects, diseases, fire), which can be used to identify areas at greatest risk of forest losses. Given a heightened demand for tree-ring data, we consolidated and synthesized tree-ring studies and datasets gathered over the past 30 years in Canada by scientists with the Canadian Forest Service and research partners. We incorporated these datasets into a data repository that currently contains tree-ring measurements from 40 206 tree samples from 4594 sites and 62 tree species from all Canadian provinces and territories. Through our synthesis, we demonstrate the value of such large ensembles of tree-ring data for identifying patterns in tree growth over large spatial scales by mapping pan-Canadian drought sensitivity. Overall, we found high coherence in the samples analyzed; low coherence was generally limited to data-poor regions and species. Drought sensitivity was widespread across species and regions: 34% of sampled trees displayed a significant positive relationship between annual growth increment and summer soil moisture index. Dependence upon water availability in species Picea mariana (Mill.) BSP, Pinus banksiana Lamb., Pinus contorta Douglas ex Loudon, and Pseudotsuga menziesii (Mirb.) Franco was more strongly expressed in the warmest regions of the species' range; for species Picea glauca (Moench) Voss and Populus tremuloides Michx., drought sensitivity was stronger in the driest regions. This unprecedented consolidation and synthesis of tree-ring data will enable new research initiatives (e.g., meta-analyses) aimed at improved understanding of the drivers, patterns, and implications of changes in tree growth, as well as facilitating new research collaborations in earth and environmental sciences. Among other things, there is a need for expanding the spatial distribution of sites across Canada's northern regions, increasing the number of samples collected from older stands and angiosperm species, and integrating datasets from studies that evaluate the effects of silvicultural experiments, including provenance and progeny trials, on tree growth. Key words: tree rings, multispecies database, annual growth responses, drought, Canada. II est essentiel de comprendre l'ampleur et la cause de la variation de la croissance des arbres et de la productivity des forets pour une gestion durable de celles-ci. Les mesures des cernes de croissance annuels permettent d'evaluer la vulnerabilite des arbres individuels, des populations d'arbres et des ecosystemes forestiers au stress de la secheresse ou a d'autres regimes changeants de perturbation des forets (insectes, maladies, incendies), ce qui peut etre utilise pour identifier les zones les plus exposees au risque de pertes forestieres. Compte tenu de la demande accrue de donnees sur les cernes de croissance des arbres, les auteurs ont consolide et synthetise les etudes et les ensembles de donnees sur les cernes de croissance d'arbres, recueillis au cours des 30 dernieres annees au Canada par les scientifiques du Service canadien des forets et des partenaires de recherche. lis ont integre ces ensembles de donnees dans un depot de donnees qui comprend actuellement les mesures des cernes de 40 206 echantillons d'arbres provenant de 4594 sites et de 62 especes d'arbres de toutes les provinces et territoires du Canada. Grace a cette synthese, les auteurs demontrent la valeur de ces grands ensembles de donnees sur les cernes de croissance des arbres pour identifier les patrons de croissance des arbres a de grandes echelles spatiales en cartographiant la sensibilite a la secheresse a l'echelle pancanadienne. Dans l'ensemble, ils ont constate une grande coherence dans les echantillons analyses; la faible coherence etait generalement limitee aux regions et aux especes pour lesquelles les donnees etaient insuffisantes. La sensibilite a la secheresse etait tres repandue parmi les especes et les regions : 34 % des arbres echantillonnes presentaient une relation positive significative entre l'augmentation annuelle de la croissance et l'indice d'humidite du sol en ete. La dependance a l'egard de la disponibilite de l'eau chez les especes Picea mariana (Mill.) BSP, Pinus banksiana Lamb., Pinus contorta Douglas ex Loudon et Pseudotsuga menziesii (Mirb.) Franco etait plus fortement exprimee dans les regions les plus chaudes de l'aire de repartition des especes; pour les especes Piceaglauca (Moench) Voss et Populus tremuloides Michx., la sensibilite a la secheresse etait plus forte dans les regions les plus seches. Cette consolidation et cette synthese sans precedent des donnees sur les anneaux des arbres permettront de nouvelles initiatives de recherche (par exemple, des meta-analyses) visant a ameliorer la comprehension des facteurs, des patrons et des implications des changements dans la croissance des arbres, ainsi qu'a faciliter de nouvelles collaborations de recherche en sciences de la terre et en environnement. II est notamment necessaire d'elargir la repartition spatiale des sites dans les regions nordiques du Canada, d'augmenter le nombre d'echantillons preleves dans les vieux peuplements et les especes d'angiospermes, et d'integrer les ensembles de donnees provenant d'etudes qui evaluent les effets des experiences sylvicoles, y compris des essais de provenance et de descendance, sur la croissance des arbres. [Traduit par la Redaction] Mots-cles: anneaux des arbres, base de donnees multiespeces, reponses de croissance annuelle, secheresse, Canada., 1. Introduction Tree rings--succeeding bands of light wood produced in the spring (earlywood) and dark wood formed at the end of the summer (latewood)--reflect the life history and environment of [...]

Predicting future stand yield as a function of current stand conditions is important to forest managers. Two machine-learning techniques, gradient boosting (GB) and random forests (RF), were used to predict stand mean height of dominant and codominant trees (HT), trees per hectare (Tree * [ha.sup.-1]), and basal area per hectare (BA * [ha.sup.-1]) based on data sets collected from extensively and intensively managed loblolly pine (Pinus taeda L.) plantations in the West Gulf Coastal Plain region. Models were evaluated using coefficient of determination ([R.sup.2]) and bias by applying models to independent tests and validation data sets and then comparing to conventional statistical models (Coble-2017) currently being used in the region. For extensively managed plantations, the GB models had less bias than the RF models. For model precision ([R.sup.2]), the GB models were consistently better than the RF models, and the HT model was the best, followed by those of Tree * [ha.sup.-1] and BA * [ha.sup.-1]. Even for BA * [ha.sup.-1], the GB and RF models had [R.sup.2] over 0.81. GB and RF models outperformed the Coble-2017 model; differences were not substantial for Tree * [ha.sup.-1] but were significant for HT and BA * [ha.sup.-1] ([R.sup.2] = 0.96, 0.95, and 0.88 for HT and 0.84, 0.81, and 0.76 for BA). Important predictors identified by GB and RF and their contributions to the models were similar. For intensively managed plantations, GB and RF were similarly accurate in predicting HT and Tree * [ha.sup.-1], but GB outperformed RF in predicting BA * [ha.sup.-1] ([R.sup.2] = 0.87 versus 0.75). We conclude that both GB and RF, although the former is preferred, can be effective in predicting future stand attributes. Forest managers can use the models presented here to predict quantitative information required for managing loblolly pine plantations in the region. Key words: stand growth and yield, forest management, stand basal area, stand tree number. Il est important pour les gestionnaires forestiers de prevoir la production future des peuplements en fonction des conditions actuelles. Deux techniques d'apprentissage automatique: l'amplification du gradient (AG) et la foret aleatoire (FA), ont ete utilisees pour predire la hauteur moyenne des tiges dominantes et codominantes (HT) dans le peuplement, le nombre de tiges a l'hectare (tiges * [ha.sup.-1]) et la surface terriere a l'hectare (G * [ha.sup.-1]) sur la base de jeux de donnees recoltees dans des plantations de pin a encens (Pinus taeda L.) sous amenagement extensif ou intensif dans la plaine cotiere de la region ouest du golfe du Mexique. Les modeles ont ete evalues a l'aide du coefficient de determination ([R.sup.2]) et du biais en appliquant ces modeles a des jeux de donnees d'essai et de validation independants et ils ont ensuite ete compares a des modeles statistiques conventionnels (Coble-2017) actuellement utilises dans la region. Dans le cas des plantations sous amenagement extensif, les modeles AG avaient moins de biais que les modeles FA. Quant a la precision des modeles ([R.sup.2]), les modeles AG etaient constamment meilleurs que le modeles FA et le modele HT etait le meilleur suivi de ceux des tiges * [ha.sup.-1] et de G * [ha.sup.-1]. Meme dans le cas de G * [ha.sup.-1], les modeles AG et FA avaient des valeurs de [R.sup.2] superieures a 0,81. Les modeles AG et FA avaient une meilleure performance que le modele de Coble-2017; les differences n'etaient pas enormes dans le cas de tiges * [ha.sup.-1] mais elles etaient significatives dans le cas de HT et G * [ha.sup.-1] ([R.sup.2] = 0,96, 0,95 et 0,88 pour HT et 0,84, 0,81 et 0,76 pour G). Les predicteurs importants identifies par AG et FA et leurs contributions aux modeles etaient semblables. Dans le cas des plantations sous amenagement intensif, AG et FA etaient aussi exacts pour predire HT et tiges * [ha.sup.-1], mais AG etait plus performant que FA pour predire G * [ha.sup.-1] ([R.sup.2] = 0,87 contre 0,75). Nous concluons que les techniques AG aussi bien que FA, bien qu'on prefere le premier, peuvent predire efficacement les attributs futurs des peuplements. Les gestionnaires forestiers peuvent utiliser les modeles presentes dans cet article pour predire les informations quantitatives requises pour gerer les plantations de pin a encens dans la region. Mots-cles: croissance et production des peuplements, gestion forestiere, surface terriere du peuplement, nombre de tiges dans le peuplement., Introduction Accurate information of future forest stand characteristics (i.e., per area unit basal area and number of trees) is crucial for forest management planning and harvest scheduling. Often this information [...]

Over half of the standing pine timber volume in the southeastern USA is composed of loblolly pine (Pinus taeda L.), making it the most important tree species in the region. Future climate variability may impact productivity of these forests due to reduced water availability. To determine the effects of nutrient availability and decreased water availability on stand-level water use efficiency and growth efficiency, we examined the interactive effects of fertilization and reduced throughfall on whole-tree water use, stand-level canopy transpiration, leaf area index (LAI), and stand-level stem volume growth. This study was conducted over the 6th and 7th growing seasons (2013-2014) of a loblolly pine plantation in southeastern Oklahoma. Across all plots, throughfall reduction reduced volumetric soil water content (VWC) from 13.6% to 10.9% for soil depths of 0-12 cm and from 22.3% to 19.9% for soil depths of 12-45 cm and reduced stand volume growth from 20.9 to 17.9 [m.sup.3] x [ha.sup.-1]. Across all plots, fertilization increased LAI by 12%, increased stand volume growth from 18.3 to 20.5 [m.sup.3] x [ha.sup.-1], and increased water use efficiency of stem volume production by 18%. These results indicate that fertilization can benefit stand growth of loblolly pine plantations even when soil moisture is limiting, in part, by increasing the efficiency of water use. Key words: water use efficiency, growth efficiency, throughfall reduction, fertilization, Pinus taeda. Plus de la moitie du volume en bois de pin sur pied dans le sud-est des Etats-Unis est constitue de pin a encens (Pinus teada L.), ce qui en fait la plus importante espece d'arbre dans la region. La variabilite du climat futur peut avoir un impact sur la productivite de ces forets a cause de la diminution de la disponibilite en eau. Afin de determiner les effets de la disponibilite des nutriments et de la diminution de la disponibilite en eau sur l'efficacite de l'utilisation de l'eau et l'efficacite de la croissance a l'echelle du peuplement, nous avons etudie les effets interactifs de la fertilisation et de la reduction de la pluie au sol sur l'utilisation de l'eau a l'echelle de l'arbre, la transpiration du couvert forestier a l'echelle du peuplement, l'indice de surface foliaire (LAI) et la croissance en volume de la tige a l'echelle du peuplement. L'etude a ete realisee au cours des 6e et 7e saisons de croissance (2013-2014) d'une plantation de pin a encens dans le sud-est de l'Oklahoma. Dans l'ensemble des places echantillons, la diminution de la pluie au sol a reduit la teneur volumetrique en eau du sol de 13,6 a 10,9 % et de 22,3 a 19,9 % a des profondeurs de respectivement 0-12 cm et 12-45 cm et reduit la croissance en volume du peuplement de 20,9 a 17,9 [m.sup.3] x [ha.sup.-1]. Dans l'ensemble des places echantillons, la fertilisation a augmente la valeur de LAI de 12 %, la croissance en volume du peuplement de 18,3 a 20,5 [m.sup.3] x [ha.sup.-1] et l'efficacite de l'utilisation de l'eau pour la production du volume de la tige de 18 %. Ces resultats indiquent que la fertilisation peut etre benefique pour la croissance des peuplements de pin a encens malgre un deficit d'humidite du sol en partie a cause de l'augmentation de l'efficacite de l'utilisation de l'eau. [Traduit par la Redaction] Mots-cles: efficacite de l'utilisation de l'eau, efficacite de la croissance, reduction de la pluie au sol, fertilisation, Pinus teada., Introduction The Southeast is the wood basket of the USA (Schultz 1997), producing more timber volume than any other region in the country (Oswalt et al. 2014). Over half of [...]

Numerous factors contribute to the variability in treeline change; however, the potential role of insect predation in limiting seed productivity is not well documented. Conditions for seed germination, establishment, and survival are not limiting at the Mealy Mountains treeline (Labrador, Canada), but seedlings are rarely encountered, suggesting a seed-related bottleneck to recruitment. Mature cones were collected in 2008 from four tree species (black spruce (Picea mariana (Mill.) Britton, Sterns & Poggenb.), balsam fir (Abies balsamea (L.) Mill.), eastern larch (Larix laricina (Du Roi) K. Koch), and white spruce (Picea glauca (Moench) Voss)) across three treeline zones (forest, transition, and krummholz) to assess potential seed limitation. During that year, an unexpectedly high diversity of insect larvae caused extensive reproductive loss and damaged the cones of ~85% of trees sampled, confirming that treeline change models should include seed predation. Seed germination was low and variable in all treeline zones, although significantly higher in black spruce and eastern larch. Most reproductive quality measures decreased significantly with elevation, although no differences among zones or tree species in the percentages of seeds damaged by insects were found (mean ± standard deviation: 31% [+ or -] 23%). Based on tree density and seed production, black spruce is predicted to lead the treeline expansion in the Mealy Mountains. Although climate warming may create conditions conducive for increased seed production, predispersal seed predation may limit future treeline expansion. Key words: climate change, forest-tundra ecotone, insect herbivory, multispecies, predispersal seed predation, reproductive bottleneck. Plusieurs facteurs contribuent a la variabilite de la modification de la limite des arbres mais le role potentiel des epidemies d'insecte dans la reduction de la productivite des graines a ete peu etudie. A la limite des arbres dans les montagnes Mealy (Labrador, Canada), les conditions sont adequates pour la germination, l'etablissement et la survie mais on trouve rarement des semis. Cela indique qu'il y a un probleme de recrutement relie aux graines. Des cones matures ont ete collectes en 2008 chez quatre especes (epicea noir (Picea mariana (Mill.) Britton, Sterns & Poggenb.), sapin baumier (Abies balsamea (L.) Mill.), meleze laricin (Larix laricina (Du Roi) K. Koch) et epicea blanc (Picea glauca (Moench) Voss)) dans trois zones de la limite des arbres (foret, transition et krummholz) pour evaluer les problemes potentiels relies aux graines. Durant cette annee, une diversite etonnamment elevee de larves d'insecte ont cause des pertes importantes en endommageant les cones d'environ 85 % des arbres echantillonnes. Cela a confirme que les modeles qui simulent les variations de la limite des arbres devraient inclure la predation par les insectes. La germination des graines etait faible et variable dans toutes les zones a la limite des arbres quoique significativement meilleure chez l'epicea noir et le meleze. La plupart des mesures de qualite de la reproduction diminuaient significativement avec l'altitude bien qu'aucune difference dans le pourcentage de graines endommagees par les insectes entre les zones ou les especes d'arbre n'ait ete observee (moyenne : 31% ± 23%ET). Sur la base de la densite des arbres et de la production de cones ou de graines, on prevoit que l'epicea noir dominera l'expansion de la limite des arbres dans les montagnes Mealy. Bien que le rechauffement du climat puisse creer des conditions favorables a l'augmentation de la production de graines, la predation des graines avant qu'elles n'aient ete dispersees pourrait limiter l'expansion future de la limite des arbres. [Traduit par la Redaction] Mots-cles : changements climatiques, ecotone entre la foret et la toundra, insectes herbivores, multiespeces, predation des graines avant leur dispersion, problemes de reproduction., Introduction At the global scale, upslope and northward advance of the thermally constrained forest-tundra ecotone (treeline; sensu Scott (1995)) is expected given projected warming scenarios associated with climate change (Grace [...]

: A survey was conducted among 126 experts to assess a comprehensive array of 44 research, development, and deployment (RD&D) needs previously identified by landowners (Marchand and Masse 2008) for four short-rotation plantation or agroforestry systems based on willow or hybrid poplar in Canada. Among the 44 initial needs, the study identified 16 needs that a significant majority of the experts who commented on them considered relevant to address in the short term (0-5 years), of which 11 needs applied to at least two of the four systems, half pertained to research and development, half to deployment, and most were related to economic or technical issues. The relevance of addressing these needs was expected to either remain stable or increase over the medium term (6-10 years). The needs identified in this study give a comprehensive overview of RD&D priorities for each of the four systems in Canada. As such, they should be useful for determining research directions and deployment policies and for designing broad program components. An updated list of needs is provided to facilitate the examination of potential need-system combinations other than those assessed as relevant. Key words: short-rotation woody crops, agroforestry, R&D and deployment priorities, poplar, willow. Resume : Une enquete a ete effectuee aupres de 126 experts afin d'evaluer 44 besoins en recherche, developpement et deploiement (RD&D) de differentes natures identifies precedemment par des proprietaires terriens (Marchand et Masse 2008) pour quatre systemes de plantation ou d'agroforesterie en courtes rotations a base de saule ou de peuplier hybride au Canada. Parmi ces 44 besoins initiaux, l'etude a identifie 16 besoins qu'une majorite significative d'experts les ayant commentes a juges pertinents de combler a court terme (0-5 ans) : onze besoins s'appliquaient a au moins deux des quatre systemes, la moitie relevait de la recherche et du developpement, la moitie, du deploiement, et la plupart etaient de nature economique ou technique. A moyen terme (6-10 ans), la pertinence de ces besoins ne devrait pas changer ou augmenterait. Les besoins identifies dans cette etude donnent une vue d'ensemble des priorites de RD&D pour chacun des quatre systemes au Canada. En tant que tels, ils devraient etre utiles pour determiner des directions de recherche et des politiques de deploiement, et pour concevoir de grandes composantes de programmes. Une liste des besoins mise a jour est fournie pour faciliter l'examen d'autres combinaisons potentielles de besoins et de systemes que celles jugees pertinentes. Mots-cles : systemes de boisement en courtes rotations, agroforesterie, priorites de R&D et de deploiement, peuplier, saule., Introduction Short-rotation plantation and agroforestry systems can produce a variety of private and public goods and services such as biomass for energy production, agricultural products, carbon sequestration, stream bank protection, [...]

Forest fragmentation threatens the reproduction of tree species, for which habitats overlap with urban and rural areas. An endangered maple, Acer miyabei f. miyabei, is such a species in northern Japan. We examined the effects of forest fragmentation on seed production and mate diversity and assessed gene flow within and between fragmented forests. We measured the density, viability, and kinship of seeds dispersed around 82 target trees in 21 fragmented forests in rural and urban areas. The dispersed seed density decreased as the size of the target trees and the number of adult trees in each forest decreased. The viable seed proportion also decreased as the number of adult trees in each forest decreased. We did not find any effects on the kinship co-efficient among seeds dispersed around each target tree. The regression line of the pairwise kinship co-efficient of the seeds against the distance had a higher intercept and a more gently declining slope between the forests than within the forests, indicating forest fragmentation altered gene flow patterns. The results suggest reduced seed production due to pollen limitation and changes in the genetic structure of regenerating populations of A. miyabei in fragmented forests., INTRODUCTION Land development occurring with urbanization and agriculture often destroys plant habitats and divides a plant population into multiple groups separated over altered landscapes (Saunders et al., 1991). Habitat fragmentation [...]

The identification of low-vigor trees with potential for sawlog production is a key objective of tree marking guidelines used for partial cuts in northern hardwoods. The aim of this study was to measure the impact of various vigor-related defects on the monetary value of hardwoods. To achieve this, we sampled 64 sugar maple (Acer saccharum Marshall) and 32 yellow birch (Betula alleghaniensis Britton) trees from two locations in southern Quebec, Canada. We identified over 420 defects, which were grouped into 8 categories. The trees were then harvested and processed into lumber, and the value per unit volume of each stem was calculated from the value of the product assortment (lumber, chips, and sawdust). We found that visible evidence of fungal infections (sporocarps and (or) stroma) and cracks had the largest negative influence on value in both species. A model that included these defects was almost as good at predicting value as one that included a specifically designed quality classification. A more accurate assessment of value could be achieved using wood decay assessment tools and (or) by considering site- specific variables. Results from this study showed that visual identification of fungal infections and cracks could be used to enhance tree marking guidelines for hardwoods. This would meet both the silvicultural objective of selection cuts, by removing low- vigor trees, and the wood supply objective, by improving stem quality assessment prior to harvest. Key words: hardwoods, tree marking, defects, tree vigor, tree quality. L'identification des arbres moribonds qui ont un potentiel pour la production de billes de sciage est un objectif cle des directives de martelage lors de coupes partielles dans les peuplements de feuillus nordiques. Cette etude avait pour but de mesurer l'impact de divers defauts relies a la vigueur sur la valeur monetaire des feuillus. A cette fin, nous avons echantillonne 64 erables a sucre (Acer saccharum Marshall) et 32 bouleaux jaunes (Betula alleghaniensis Britton) a deux endroits dans le sud du Quebec, au Canada. Nous avons identifie plus de 420 defauts que nous avons regroupes en huit categories. Ces arbres ont ensuite ete recoltes et transformes en sciage et la valeur par unite de volume de chaque tige a ete calculee a partir de la valeur de l'assortiment de produits (sciages, copeaux et sciures). Nous avons constate que les signes visibles d'infection fongique (sporocarpes ou stroma) et les fentes avaient la plus grande influence negative sur la valeur des deux especes. Un modele qui incluait ces defauts etait presque aussi bon pour predire la valeur qu'un modele base sur un systeme de classes de qualite specifiquement concu. On pouvait obtenir une evaluation plus precise de la qualite en utilisant des outils pour evaluer la carie du bois ou en tenant compte de variables propres au site. Les resultats de cette etude montrent que l'identiication visuelle des infections fongiques et des fentes peut etre utilisee pour ameliorer les directives de martelage chez les feuillus. Cela devrait satisfaire tant les objectifs sylvicoles des coupes de jardinage, en eliminant les arbres moribonds, que les objectifs d'approvisionnement en bois, en ameliorant l'evaluation de la qualite des tiges avant la recolte. [Traduit par la Redaction] Mots-cles : feuillus, martelage, defauts, vigueur des arbres, qualite des arbres., Introduction The natural disturbance regime of North American temperate deciduous forests is characterized by mortality of individual trees, or group of trees, with very rare occurrence of severe, large-scale disturbances [...]

: Estimating site productivity in irregular structures is complicated by variations in stand density, structure, composi-tion in mixed stands, and suppression experienced by subordinate trees. Our objective was to develop an alternate to site index (SI) and demonstrate its application in models of individual-tree and stand growth. We analyzed coast redwood (Sequoia sempervirens(Lamb. ex D. Don) Endl.) tree and stand growth in a grid of 234 permanent sample plots covering a 110 ha study area in north coastal California. Partial harvesting created a mosaic of densities and openings throughout the 60-year-old redwood-dominated forest. Redwood SI was a poor predictor of volume increment (VI) per hectare among redwood in each plot over two decades after harvest. A new index of redwood basal area increment (BAI) productivity, calculated using inventory data for all stems in even-aged stands and the oldest cohort of multiaged stands, was a stronger predictor of VI. Diameter increment of individual redwood trees correlated strongly with stand density and the new BAI index. Forest managers should expect widely divergent responses following partial harvesting in crowded even-aged stands, with the greatest response coming from dominant red-woods with long crowns retained in areas with low residual stand density and high BAI index. Key words: forest productivity, multiaged management, Sequoia sempervirens, site index, thinning response, tree growth, uneven-aged silviculture. Resume: L'estimation de la productivite des stations qui supportent des peuplements de structure irreguliere est complexifiee par la variation de leur densite, de leur structure, de leur composition dans le cas des peuplements melanges et de l'oppression subie par les arbres domines. Notre objectif etait de mettre au point une solution de rechange a l'indice de qualite de station (IQS) et de demontrer son application a des modeles de croissance aux echelles de l'arbre et du peuplement. Nous avons analyse la croissance du sequoia cotier (Sequoia sempervirens (Lamb. ex D. Don) Endl.) aux echelles de l'arbre et du peuplement a l'aide d'un reseau de 234 placettes echantillons permanentes couvrant une aire d'etude de 110 ha dans le nord de la Californie cotiere. Une coupe partielle a cree une mosaique de densites et d'ouvertures dans la foret de sequoia agee de 60 ans. L'IQS du sequoia etait un mauvais predicteur de l'accroissement en volume (AV) a l'hectare des sequoias dans chaque placette au cours des 20 premieres annees apres la coupe. Un nouvel indice de productivite fonde sur l'accroissement en surface terriere (AST) du sequoia et calcule en utilisant les donnees d'inventaire de tous les arbres dans les peuplements quiennes et de la plus vieille cohorte d'arbres dans les peuplements inequiennes, etait un meilleur predicteur de l'AV. L'accroissement en diametre de sequoias individuels etait fortement correle a la densite du peuplement et au nouvel indice d'AST. Les amenagistes forestiers devraient s'attendre a des reactions fortement divergentes a la suite d'une coupe partielle dans des peuplements equiennes de forte densite. Les sequoias dominants avec une cime allongee, laisses sur pied aux endroits ou la densite residuelle du peuplement est faible et ou l'indice d'AST est eleve, devraient reagir le plus fortement. [Traduit par la Redaction] Mots-cles: productivite de la foret, amenagement inequienne; Sequoia sempervirens, indice de qualite de station, reaction a l'eclaircie, croissance des arbres, sylviculture inequienne., Introduction Estimates of forest site productivity are a central element of forest management and planning. They provide critical information to forecast rates of change and estimate potential production of wood [...]

Spruce budworm (Choristoneura fumiferana (Clemens)) (SBW) outbreaks are a major disturbance that influence stand dynamics and succession in balsam fir (Abies balsamea (L.) Mill.) dominated forests of eastern Canada. We used stand and regeneration data collected from five plots in each of one immature and five mature stands before, during, and 30 years following the last major SBW outbreak in the Cape Breton Highlands to examine the role of stand and regeneration characteristics in shaping future stand development. Comparisons were also made between regeneration in four SBW out-break stands versus two SBW salvage stands, with and without a subsequent precommercial thinning, and with 25 plots that underwent SBW emulation harvest. In mature unharvested balsam fir stands, species composition 30 years following the SBW outbreak was closely related to predisturbance species composition, and in immature fir stands, hardwood composition increased from 0% to 4%-27%. Species composition in harvested stands varied depending on whether intolerant hardwoods had been precommercially thinned, where thinned stands had 30% less hardwood 30 years postdisturbance than unthinned stands. Seedling density decreased by 17%-85% from 1979 to 1989 in all SBW outbreak stands, but average seedling height increased by 17%-500% as live canopy cover decreased from an average of 50% to 4%. Results suggest that advanced re-generation should be protected during harvest of balsam fir dominated stands, post-outbreak precommercial thinning will in-crease tree growth, and live tree retention can help develop late-seral structural characteristics in second-growth stands. Resume: Les epidemies de tordeuse des bourgeons de l'epinette (Choristoneura fumiferana (Clemens)) (TBE) constituent une perturbation majeure qui influence la dynamique et la succession des peuplements dans les forets dominees par le sapin baumier (Abies balsamea (L.) Mill.) dans l'est du Canada. Nous avons utilise des donnees de peuplement et de regeneration collectees dans cinq places echantillons par peuplement, un peuplement immature et cinq peuplements matures, pendant et au cours des 30 annees qui ont suivi la derniere epidemie majeure de TBE dans les hautes-terres du cap Breton pour etudier le role des caracteristiques du peuplement et de la regeneration dans le developpement futur des peuplements. Des comparaisons ont aussi ete faites entre la regeneration dans quatre peuplements issus de l'epidemie de TBE versus deux peuplements issus d'une coupe de recuperation apres l'epidemie de TBE, avec et sans eclaircie precommerciale subsequente, et avec 25 parcelles soumises a une coupe qui imite la TBE. Dans les peuplements matures non recoltes de sapin baumier, la composition en especes 30 ans apres l'epidemie de TBE etait etroitement reliee a la composition en especes avant la perturbation; dans les peuplements immatures de sapin, la composition en especes feuillues a augmente de 0% a 4%-27%. Dans les peuplements recoltes, la composition en especes dependait de l'eclaircie precommerciale des feuillus intolerants, alors que les peuplements eclaircis avaient 30% moins de feuillus 30 ans apres la perturbation que les peuplements non eclaircis. La densite de semis a diminue de 17%-85% de 1979 a 1989 dans tous les peuplements issus de l'epidemie de TBE, mais la hauteur moyenne des semis a augmente de 17% a 500% alors que le couvert vivant a diminue de 50% a 4%. Les resultats indiquent que la regeneration pretablie devrait etre protegee lors de la recolte des peuplements domines par le sapin baumier, que l'eclaircie precommerciale apres une epidemie augmentera la croissance des arbres et que la conservation d'arbres vivants peut favoriser le developpement de caracteristiques structurales de fin de succession dans les peuplements de seconde venue. [Traduit par la Redaction], Introduction Stand succession determines how stands develop and change over time. Studying patterns and processes of succession can help one understand how forests of today developed and help predict what [...]

Assessing forest productivity is important for developing effective management regimes and predicting future growth. Despite some important limitations, the most common means for quantifying forest stand-level potential productivity is site index (SI). Another measure of productivity is gross primary production (GPP). In this paper, SI is compared with GPP estimates obtained from 3-PG and NASA's MODIS satellite. Models were constructed that predict SI and both measures of GPP from climate variables. Results indicated that a nonparametric model with two climate-related predictor variables explained over 68% and 76% of the variation in SI and GPP, respectively. The relationship between GPP and SI was limited ([R.sup.2] of 36%-56%), while the relationship between GPP and climate ([R.sup.2] of 76%-91%) was stronger than the one between SI and climate ([R.sup.2] of 68%-78%). The developed SI model was used to predict SI under varying expected climate change scenarios. The predominant trend was an increase of 0-5 m in SI, with some sites experiencing reductions of up to 10 m. The developed model can predict SI across a broad geographic scale and into the future, which statistical growth models can use to represent the expected effects of climate change more effectively. Il est important d'evaluer la productivite forestiere pour elaborer des regimes d'amenagement efficace et predire la croissance future. Malgre certaines limitations importantes, le moyen le plus frequemment utilise pour quantifier la productivite potentielle A l'echelle du peuplement forestier est l'indice de qualite de station (IQS). La production primaire brute (PPB) est une autre mesure de la productivite. Dans cet article, IQS est compare aux estimations de PPB obtenues A l'aide du modele 3-PG et de l'instrument satellitaire MODIS de la NASA. Nous avons bati des modeles qui predisent IQS et les deux mesures de PPB A partir des variables climatiques. Les resultats ont montre qu'un modele non parametrique avec deux variables explicatives reliees au climat expliquait respectivement 68 % et 76 % de la variation de IQS et de PPB. La relation entre PPB et IQS etait faible ([R.sup.2] de 36 % A 56 %) tandis que la relation entre PPB et le climat ([R.sup.2] de 76 % A 91 %) etait plus forte que la relation entre IQS et le climat ([R.sup.2] de 68 % A 78 %). Le modele qui a ete developpe pour IQS a ete utilise pour predire IQS A partir de differents scenarios previsibles de changement climatique. Une augmentation de IQS de 0 A 5 m etait la tendance predominante alors que certaines stations subissaient des reductions allant jusqu'A 10 m. Le modele qui a ete developpe peut predire IQS pour une large gamme d'echelles geographiques ainsi que dans le futur et la valeur de IQS ainsi obtenue peut etre utilisee par les modeles statistiques de croissance pour illustrer plus efficacement les effets anticipes du changement climatique. [Traduit par la Redaction], Introduction Measures of productivity are critical in efforts to understand and maintain forest ecosystems sustainably for a range of products and services, while managing risks related to wildfire, pests, and [...]

Comparisons of selection system and diameter-limit cutting based on trials in specific settings have often yielded conflicting results. We used a simulation approach to evaluate sawtimber production over three cutting cycles on 10 sugar maple (Acer saccharum Marsh.) dominated plots of varying initial forest structure. Treatments on each plot included light, moderate, and heavy intensities of selection system silviculture and diameter-limit cutting. Harvested sawtimber volumes were initially higher on all plots using diameter-limit cutting, but selection system outperformed diameter-limit cutting at later entries on 7 of the 10 plots. Volume differences between cutting types ranged among plots from 0.3 to 26 [m.sup.3]*[ha.sup.-1], equating to a less than 1% to as much as a twofold difference. Average volumes from selection system at later entries were 20%-40% greater than diameter-limit cutting, due in part to consistent production in large sawtimber (≥46 cm). Yields from real stands could vary from these simulations where mortality losses (not modeled here) differ between treatments as a result of competition or logging damage. Findings suggest that cumulative sawtimber volumes from repeated selection system silviculture could eventually surpass that of diameter-limit cutting, but at a rate depending on initial stand conditions and harvesting intensity. Les comparaisons entre les systemes de jardinage et de coupe a diametre limite ont souvent produit des resultats divergents lorsqu'elles etaient basees sur des essais realises dans des cadres specifiques. Nous avons utilise une approche par simulation pour evaluer la production de bois de sciage au cours de trois cycles de coupe appliques a 10 parcelles dominees par l'erable a sucre (Acer saccharum Marsh.) et qui se distinguaient par la structure initiale de la foret. Les traitements simules dans chaque parcelle comprenaient trois intensites (faible, moderee et forte) pour chaque systeme sylvicole. Le volume de bois de sciage recolte etait initialement plus eleve dans toutes les parcelles soumises a une coupe a diametre limite, mais le rendement de la coupe de jardinage a depasse celui de la coupe a diametre limite lors d'interventions ulterieures dans 7 des 10 parcelles. Les differences de volume entre les types de coupe variaient de 0,3 a 26 [m.sup.3]*h[a.sup.-1] selon la parcelle, ce qui correspond a de difference de moins de 1 % jusqu'a de difference double. Le volume moyen des interventions ulterieures de la coupe de jardinage etaient de 20 % a 40 % plus grand que celui de la coupe a diametre limite, notamment grace a la production soutenue de grosses billes de sciage (≥ 46 cm). Le rendement de peuplements reels peut etre different de ces simulations a cause des pertes dues a la mortalite (non simulees ici) qui peuvent varier selon le traitement en fonction de la competition ou des blessures d'exploitation. Les resultats indiquent que le volume cumule de bois de sciage provenant d'interventions repetees dans le cadre d'un systeme de jardinage pourrait eventuellement surpasser celui de la coupe a diametre limite, mais a un rythme dependant des conditions initiales du peuplement et de l'intensite de la recolte. [Traduit par la Redaction], Introduction Diameter-limit cutting provides high sawtimber volumes at the first entry (Fajvan et al. 1998; Nyland 2001), but its longterm viability for management of uneven-aged hardwood forests has been challenged. [...]

This data set reports woody plant species abundances in a network of 96 sampling sites spread across 22 000 [km.sup.2] in the central Western Ghats region, Karnataka, India (74[degrees]15'-75[degrees]40' E; 15[degrees]15'-13[degrees]30, N). Due to its varied climate and diverse topography, the study area, which is part of the Western Ghats--Sri Lanka biodiversity hotspot, supports a wide array of non-equatorial tropical habitats including wet evergreen, moist and dry deciduous, and intact as well as degraded forests and scrublands. These formations, floristically moderately rich and diversified, are characterized by a lower rate of endemism than in the southern part of the Western Ghats. This data paper provides abundance and girth data for 76 813 trees and lianas of 446 species collected in 96 sampling sites during 1996-1997. A total of 61 965 individuals [greater than or equal to] 10-cm girth at breast height (gbh) were recorded in 96 1-ha macroplots, while 14 848 individuals 1 m height, were sampled in three 0.1ha microplots located within each macroplot. Additional data regarding the stand structure (average canopy height, percent canopy cover, number of strata) and the level of degradation are available for the macroplots, along with environmental data derived from other sources and analyses, such as soil types, rainfall, length of the dry season, and altitude. These data have been used to produce ecological research papers, as well as to elaborate conservation value maps and recommendations toward sustainable management of the forests of the central Western Ghats region. Key words: biodiversity sampling plots; central Western Ghats; India; Karnataka; mesoscale plot network; plant species abundances; tropical forest types.

Mast seeding, the synchronous, highly variable seed production among years, is very common in tree species, but there is no consensus about its main causes and the main environmental factors affecting it. In this study, we first analyze a long-term data set on reproductive and vegetative growth of Quercus ilex in a mediterranean woodland in order to identify the main environmental drivers of interannual variation in flower and seed production and contrast the impact of climate vs. adaptive factors as main causes of masting. Second, we conducted an experiment of rainfall exclusion to evaluate the effects of an increasing drought (simulating predictions of global change models) on both reproductive processes. The annual seed crop was always affected by environmental factors related to the precipitation pattern, these abiotic factors disrupting the fruiting process at different periods of time. Seed production was strongly dependent upon water availability for the plant at initial (spring) and advanced (summer) stages of the acorn maturation cycle, whereas the final step of seed development was negatively affected by the frequency of torrential-rain events. We also found clear evidence that seed masting in the study species is not only regulated by selective endogenous rhythms, but is mainly a physiological response to the variable environment. Our results from the rainfall exclusion experiment corroborated the conclusions obtained from the 26-year fruiting record and demonstrated that the high interannual variation in seed crop was mainly determined by the success in seed development rather than by the flowering effort. Under a global change scenario, it could be expected that the drier conditions predicted by climate models reinforce the negative effects of summer drought on seed production, leading to negative consequences for tree recruitment and forest dynamics. Key words: abortions; acorn production; economy-of-scale hypothesis; global change; masting cycles; Puechabon State Forest. southern France; Quercus ilex: resource-matching hypothesis; water stress.

Extended rotations are increasingly used to meet ecological objectives on forestland; however, information about long-term growth and yield of these systems is lacking for most forests in North America. Additionally, long-term growth responses to repeated thinnings in older stands have received little attention. We addressed these needs by examining the growth and yield of red pine (Pinus resinosa Ait.) in a growing stock experiment in northern Minnesota. Stands were 85 years old at the onset of this experiment and were repeatedly thinned to five levels of basal area (13.8, 18.4, 23.0, 27.5, and 32.1 [m.sup.2]*[ha.sup.-1]) over 58 years. Cumulative volume production and volume growth were lowest within the lowest stocking treatment and similar across other stocking levels. Late-successional structural attributes, such as the density of trees with ≥40 cm diameter at breast height, was similar across stocking levels. The mean annual volume growth culminated between 130 and 140 years. Additionally, positive growth responses were observed within the highest stocking-level treatments after thinning at 138 years, demonstrating the ability of older red pine to respond to reductions in competition. These results illustrate that extended rotations with repeated thinnings in red pine help achieve ecological goals, including the restoration of old-forest structure, while also maintaining high levels of stand productivity. Resume: On utilise de plus en plus des rotations allongees pour atteindre des objectifs ecologiques en foret. Cependant, on manque d'information sur la croissance et la production a long terme de ces systemes pour la plupart des forets d'Amerique du Nord. De plus, la reaction en croissance a long terme a des eclaircies repetees dans les vieux peuplements est peu documentee. Pour combler ces besoins, nous avons etudie la croissance et la production associees a une experience de densite variable de pin rouge (Pinus resinosa Ait.) etablie au nord du Minnesota. Les peuplements etaient ages de 85 ans au debut de cette experience et ont ete eclaircis de facon repetee selon cinq niveaux de surface terriere (13,8, 18,4, 23,0, 27,5 et 32,1 [m.sup.2]*[ha.sup.-1]) pendant une periode de 58 ans. Les plus petites valeurs de production cumulative et de croissance en volume ont ete obtenues dans le cas du traitement qui maintenait la plus faible surface terriere, mais il n'y avait pas de difference entre les autres traitements. Les attributs de la structure en fin de succession, comme la densite des arbres ≥40 cm, etaient semblables peu importe la densite. L'accroissement annuel moyen en volume etait maximal entre 130 et 140 ans. De plus, une reaction positive en croissance a ete observee a la suite d'une eclaircie realisee a l'age de 138 ans dans le traitement qui maintenait la plus forte densite, ce qui demontre la capacite des vieux pins rouges a reagir a une diminution de la competition. Ces resultats indiquent que des rotations allongees accompagnees d'eclaircies repetees dans des peuplements de pin rouge permettent d'atteindre des objectifs ecologiques, notamment la restauration de la structure des vieilles forets, tout en maintenant de hauts niveaux de productivite a l'echelle du peuplement. [Traduit par la Redaction], Introduction Over the past several decades, many traditional silvicultural systems and approaches have been modified to address a greater range of objectives, including maintenance of native biodiversity, restoration of late-successional [...]

Pulp yield is an important breeding objective for Eucalyptus globulus Labill., but evaluation of its genetic control and genetic correlations with other traits has been limited by its high assessment cost. We used near infrared spectroscopy to study genetic variation in pulp yield and other traits in a 16-year-old E. globulus trial. Pulp yield was predicted for 2165 trees from 467 open-pollinated families from 17 geographic subraces. Significant differences between subraces and between families within subraces were detected for all traits. The high pulp yield of southern Tasmanian subraces suggested that their economic worth was previously underestimated. The narrow-sense heritability of pulp yield was medium (0.40). The significant positive genetic correlation between pulp yield and diameter (0.52) was at odds with the generally neutral values reported. The average of the reported genetic correlations between pulp yield and basic density (0.50) was also at odds with our nonsignificant estimate. Pulp yield of the subraces increased with increasing latitude, producing a negative correlation with density (-0.58). The absence of genetic correlations within subraces between pulp yield and density suggests that the correlation may be an independent response of the two traits to the same or different selection gradients that vary with latitude. Resume: Le rendement en fibres est un objectif d'amelioration important dans le cas d'Eucalyptus globulus Labill. mais l'evaluation de son controle genetique et des correlations genetiques avec d'autres caracteres a ete limitee par le cout eleve de son estimation. Nous avons utilise la spectroscopie dans le proche infrarouge pour etudier la variation genetique du rendement en fibres et d'autres caracteres dans un test de provenances d'E. globulus age de 16 ans. Le rendement en fibres a ete predit pour 2165 arbres provenant de 467 familles a pollinisation libre appartenant a 17 sous-races geographiques. Des differences significatives entre les sous-races et entre les familles des sous-races ont ete detectees pour tous les caracteres. Le rendement eleve en fibres des sous-races du sud de la Tasmanie indique que leur valeur economique a jusqu'ici ete sous-estimee. L'heritabilite au sens strict du rendement en fibres etait moyenne (0,40). La correlation genetique positive et significative entre le rendement en fibres et le diametre (0,52) ne correspondait pas aux valeurs neutres generalement rapportees. La moyenne des valeurs rapportees pour la correlation genetique entre le rendement en fibres et la densite basale (0,50) ne correspondait pas non plus avec notre estimation qui n'etait pas significative. Le rendement en fibres des sousraces augmentait avec la latitude produisant une correlation negative avec la densite (-0,58). L'absence de correlations genetiques entre ces caracteres au sein des sous-races indique que la correlation est peut-etre une reaction independante de deux caracteres aux memes ou a differents gradients de selection qui varie en fonction de la latitude. [Traduit par la Redaction], Introduction Eucalyptus globulus Labill. is a hardwood tree species widely used in industrial plantations in temperate regions of the world for the production of pulp for papermaking. Many physical, chemical, [...]

PhD student James Ball maps tree trunks to better understand a crucial ecosystem and its response to climate change. PhD student James Ball maps tree trunks to better understand a crucial ecosystem and its response to climate change., Author(s): Chris Woolston Author Affiliations: James Ball is a PhD student in ecology at the University of Cambridge, UK. Credit: Tom Hattermann James Ball, PhD student at University of Cambridge [...]

Recently, sugar maple (Acer saccharum Marsh.) decline in northeastern North America has been regarded as a major factor structuring hardwood forests by favouring American beech (Fagus grandifolia Ehrh.) in the understory of maple-dominated stands. To determine whether soil fertility differences associated with sugar maple decline may have promoted the expansion of American beech, we explored the relationships between the soil base status and the sapling and tree strata density and composition, using data from 426 permanent sample plots distributed throughout Quebec. Our results indicate that American beech is currently expanding in the sugar maple range of Quebec. The abundance and proportion of American beech in the sapling stratum are mainly associated with the proportion of American beech in the tree stratum, the relative basal area of dead sugar maple trees, and the base status of soils. In accordance with the many studies reporting on the high sensitivity of sugar maple to the acid--base status of soils and the decline of the sugar maple population, this study supports the hypothesis that soil base cation depletion, caused in part by atmospheric acid deposition, is among the main factors involved in the present-day expansion of American beech over a large area in Quebec. Resume: Le deperissement de l'erable a sucre (Acer saccharum Marsh.) dans le nord-est de l'Amerique du Nord a recemment ete considere comme un des principaux facteurs qui determinent la structure des forets feuillues en favorisant le hetre a grandes feuilles (Fagus grandifolia Ehrh.) en sous-etage des peuplements domines par l'erable. Dans le but de determiner si des differences de fertilite du sol associees au deperissement de l'erable a sucre pourraient avoir favorise l'expansion du hetre, nous avons etudie les relations entre la teneur en cations basiques du sol et la densite ainsi que la composition de la strate des gaules et celle des arbres a l'aide de donnees provenant de 426 placettes echantillons permanentes reparties a travers le Quebec. Les resultats indiquent que le hetre s'est considerablement repandu dans l'aire de repartition de l'erable a sucre au Quebec au cours des 30 dernieres annees. L'abondance et la proportion de hetre dans la strate des gaules sont principalement associees a la proportion de cette espece dans la strate arbustive, a la surface terriere relative des tiges mortes d'erable a sucre et a la teneur en cations basiques du sol. Conformement aux nombreuses etudes qui font etat de la grande sensibilite de l'erable a sucre a l'equilibre acide-base des sols et du declin de la population d'erable a sucre, cette etude supporte l'hypothese voulant que l'epuisement des cations basiques du sol cause par les depots atmospheriques acides soit un des principaux facteurs responsables de l'expansion actuelle du hetre a grandes feuilles sur une vaste superficie au Quebec. [Traduit par la Redaction], Introduction Since the late 1970s, Acer saccharum Marsh. (sugar maple (SM)) decline and dieback has been conspicuous in the deciduous forest of northeastern North America (Kolb and McCormick 1993; Horsley [...]

This paper describes the development and implementation of CAMBIUM, an agent-based forest sector model for strategic analysis. This model is designed as a decision-support tool for assessing the effects that changes in product demand and resource inventories can have on the structure and economic viability of the forest sector. CAMBIUM models aggregate product supply as an emergent property of individual companies' production decisions and stand-level ecological processes. Modeling the forest-products sector as a group of interacting autonomous economic agents makes it possible to include production capacity dynamics and the potential for mill insolvencies as factors in analyzing the effects of market and forest inventory based disturbances. The utility of this model is tested by assessing the impacts of a market downturn in the US forest products market on forest industry structure and mountain pine beetle (Dendroctonus ponderosae Hopkins) salvage harvesting in British Columbia, Canada. Simulation results indicate a significant medium-term timber supply shortage; reduced stumpage revenues; intensive cost competition among primary wood-products manufacturers; and a large number of insolvencies in the panel, lumber, and pulp sectors. Cet article decrit le developpement et l'implantation de CAMBIUM, un modele d'analyse strategique du secteur forestier base sur les agents. Ce modele est concu comme un outil d'aide a la decision pour evaluer les effets des changements dans la demande des produits forestiers et les stocks de la resource sur la structure et la viability economique du secteur forestier. Les modeles CAMBIUM regroupent l'offre de produits comme une propriete qui decoule des decisions de production de compagnies individuelles et des processes ecologiques a fechelle du peuplement. En modelisant le secteur des produits forestiers comme un groupe d'agents economiques autonomes qui interagissent, il est possible de considerer la dynamique de la capacity de production et la faillite potentielle des usines comme des facteurs dans l'analyse des effets des perturbations reliees aux marches et aux stocks de bois. L'utilite de ce modele a ete testee en evaluant les impacts d'un flechissement du marche des produits forestiers aux Etats-Unis sur la structure de findustrie forestiere et des coupes de recuperation reliees au dendroctone du pin ponderosa (Dendroctonus ponderosae Hopkins) en Colombie-Britannique, au Canada. Les resultats de la simulation prevoient une importante penurie de bois a moyen terme, une baisse des revenus provenant des droits de coupe, une forte competition des touts parmi les manufacturiers de produits primaires du bois et un grand nombre de faillites dans les secteurs des panneaux, du bois d'oeuvre et de la pulpe. [Traduit par la Redaction], Introduction The forest-products industry in British Columbia is facing an uncertain future. The mountain pine beetle (Dendroctonus ponderosae Hopkins) outbreak in the interior of the province has affected mature lodgepole [...]

Relationships between stand growth and structural diversity were examined in spruce-dominated forests in New Brunswick, Canada. Net growth, survivor growth, mortality, and recruitment represented stand growth, and tree species, size, and height diversity indices were used to describe structural diversity. Mixed-effects second-order polynomial regressions were employed for statistical analysis. Results showed stand structural diversity had a significant positive effect on net growth and survivor growth by volume but not on mortality and recruitment. Among the tested diversity indices, the integrated diversity of tree species and height contributed most to stand net growth and survivor growth. Structural diversity showed increasing trends throughout the developmental stages from young, immature, mature, and overmature forest stands. This relationship between stand growth and structural diversity may be due to stands featuring high structural diversity that enhances niche complementarities of resource use because trees exist within different horizontal and vertical layers, and strong competition resulted from size differences among trees. It is recommended to include effects of species and structural diversity in forest growth modeling initiatives. Moreover, uneven-aged stand management in conjunction with selective or partial cutting to maintain high structural diversity is also recommended to maintain biodiversity and rapid growth in spruce-dominated forests. La relation entre la croissance des peuplements et leur diversite structurale a ete etudiee dans des forets dominees par l'epinette au Nouveau-Brunswick, Canada. La croissance nette, la croissance des survivants, la mortalite et le recrutement ont ete utilises comme variables representant la croissance des peuplements alors que l'espece, la taille et des indices de diversite de hauteur des arbres ont ete utilises pour decrire la diversite structurale. Les analyses statistiques ont ete effectuees a l'aide de regressions polynomiales du deuxieme degre avec des effets mixtes. Les resultats montrent que la diversite structurale des peuplements a un effet positivement significatif sur la croissance nette et la croissance des survivants en volume, mais pas sur la mortalite ni le recrutement. Parmi les indices de diversite testes, celui qui integre l'espece d'arbre et la hauteur contribue le plus a expliquer la variation de la croissance nette du peuplement et la croissance des survivants. La diversite structurale a tendance a augmenter en fonction du stade de developpement du peuplement, de jeune, immature, mature a suranne. Cette relation entre la croissance des peuplements et la diversite structurale pourrait etre due a une meilleure complementarite des niches d'utilisation des ressources dans les peuplements montrant une grande diversite structurale puisque les arbres sont presents dans differentes strates horizontales et verticales, ainsi qu'a la forte competition entre les arbres de differentes tailles. Il est recommande d'inclure les effets de la diversite en espe ces et de la diversite structurale dans les efforts de modelisation de la croissance forestiere. De plus, l'amenagement des peuplements inequiennes conjointement avec des coupes partielles ou de jardinage dans le but de maintenir une forte diversite structurale est aussi recommande pour maintenir la biodiversite et la croissance rapide des forets dominees par l'epinette. [Traduit par la Redaction], Introduction Relationships between species diversity and ecosystem productivity have a long-standing relevance in ecology (Waide et al. 1999; Mittelbach et al. 2001). However, considerable controversy still exists concerning the general [...]

The rate of land-use conversion from forest to nonforest or natural forest to forest plantation is of interest for forest certification purposes and also as part of the process of assessing forest sustainability. Conversion rates can be estimated from remeasured inventory plots in general, but the emphasis here is on annual inventory data. A new estimator is proposed based on analysis of plot-level variables that indicate when a change in forest condition occurs between inventory remeasurements. A weighted maximum likelihood estimator is derived that incorporates the binomial nature of the indicator variables, mapped plot conditions, and varying remeasurement periods. Example applications demonstrate the utility of the proposed methodology. This approach is broadly useful for estimating the annual rate of change from an initial condition to another condition from annual forest inventory data. Il est important de connaitre le taux de conversion de l'utilisation du territoire, de la foret vers une utilisation non forestiere ou de la foret naturelle vers une plantation forestiere, a des fins de certification forestiere et dans le cadre du processus d'estimation de la durabilite de la foret. En general, des taux de conversion peuvent etre estimes a partir des mesures repetees de placettes d'inventaire, mais dans cet article l'accent est mis sur les donnees d'inventaire annuel. Nous proposons un nouvel estimateur base sur l'analyse de variables a l'echelle de la placette qui indiquent a quel moment un changement des conditions forestieres survient entre les mesures repetees d'un inventaire. Nous avons derive un estimateur base sur le maximum de vraisemblance pondere qui tient compte de la nature binomiale des variables indicatrices, des conditions de la placette estimees a l'aide d'outils cartographiques et des intervalles de temps variables entre deux mesures. Des exemples d'application montrent l'utilite de la methode proposee. Cette approche est generalement utile pour estimer le taux annuel de changement d'une condition initiale vers une autre condition a partir des donnees d'inventaire forestier annuel. [Traduit par la Redaction], 1. Introduction Sustainable forestry practices are meant to ensure that forests are managed for an even flow of products and other forest amenities (Brand 1997; Hall 2001; Rametsteiner and Simula [...]

We examined the effect of logging-debris retention and competing-vegetation control (CVC, initial or annual applications) on dissolved organic carbon (DOC), dissolved organic nitrogen, and nitrate-N leaching to determine the relative potential of these practices to contribute to soil C and N loss at two contrasting sites. Annual CVC resulted in higher soil water nitrate-N concentration and flux, with the magnitude and duration of the effect greatest at the high-N site. Most of the increase in nitrate-N at the low-N site occurred in treatments where logging debris was retained. Dissolved organic nitrogen increased at the high-N site in March of each year following annual CVC, but the contribution of this increase to total N concentration was small (2%-4% of total N flux). There was no effect of logging-debris retention or CVC treatment on soil water DOC concentrations, indicating that DOC inputs from logging debris and competing vegetation were either retained or consumed in the mineral soil. The estimated increase in leaching flux of dissolved C and N associated with the treatments was low relative to total soil pools, making it unlikely that loss of these elements via leaching will negatively affect future soil productivity at these sites. Nous avons etudie l'effet de la retention des dechets de coupe et de la maitrise de la vegetation competitrice (applications initiale ou annuelles) sur le carbone organique dissous (COD), l'azote organique dissous et le lessivage de N sous forme de nitrate pour determiner la contribution relative de ces pratiques a la perte de C et N dans le sol de deux stations contrastees. La maitrise annuelle de la vegetation a entraine une concentration et un flux accrus de nitrate dans le sol dont l'ampleur et la duree etaient les plus elevees dans la station riche en N. La majeure partie de l'augmentation du nitrate dans la station pauvre en N est survenue dans les traitements ou les dechets de coupe avaient ete conserves. L' azote organique dissous a augmente dans la station riche en N au mois de mars de chaque annee a la suite de la maitrise annuelle de la vegetation mais la contribution de cette augmentation a la concentration totale de N etait faible (2 % - 4 % du flux total de N). La retention des dechets de coupe et la maitrise de la vegetation n'ont pas eu d'effet sur la concentration de COD dans l'eau du sol, indiquant que les apports de COD provenant des dechets de coupe et de la vegetation competitrice ont ete fixes ou utilises dans le sol mineral. L'augmentation estimee du lessivage de C et N dissous associee aux traitements etait faible relativement aux pools totaux dans le sol, de telle sorte qu'il soit peu probable que la perte de ces elements par lessivage ait un impact negatif sur la productivite future du sol dans ces stations. [Traduit par la Redaction], Introduction Intensive forest management has posed unanswered questions for maintenance of soil quality and long-term productivity for decades (e.g., Boyle and Ek 1972; Weetman and Webber 1972; Wells and Jorgensen [...]

Regional estimation of potential forest productivity is important to diverse applications, including biofuels supply, carbon sequestration, and projections of forest growth. Using PRISM (Parameter-elevation Regressions on Independent Slopes Model) climate and productivity data measured on a grid of 3356 Forest Inventory and Analysis plots in Oregon and Washington, we evaluated four possible imputation methods to estimate potential forest productivity: nearest neighbour, multiple linear regression, thin plate spline functions, and a spatial autoregressive model. Productivity, measured by potential mean annual increment at culmination, is explained by the interaction of annual temperature, precipitation, and climate moisture index. The data were randomly divided into 2237 reference plots and 1119 target plots 30 times. Each imputation method was evaluated by calculating the coefficient of determination, bias, and root mean square error of both the target and reference data set and was also tested for evidence of spatial autocorrelation. Potential forest productivity maps of culmination potential mean annual increment were produced for all Oregon and Washington timberland. L'estimation regionale de la productivite forestiere potentielle est importante pour diverses applications, y compris les stocks de biocarburants, la sequestration du carbone et les projections de la croissance forestiere. A l'aide des donnees climatiques PRISM (Parameter-elevation Regressions on Independent Slopes Model) et des donnees de productivite mesurees sur une grille de 3356 placettes du programme d'analyse et d'inventaire forestiers dans les Etats de l'Oregon et de Washington, nous evaluons quatre methodes d'imputation pour estimer la productivite forestiere potentielle : le plus proche voisin, la regression lineaire multiple, les fonctions d'interpolation spline et un modele spatial autoregressif. Mesuree par f accroissement annuel moyen potentiel (AAMP) maximum, la productivite est expliquee par f interaction de la temperature annuelle, des precipitations et de l'indice d'humidite du climat. Les donnees ont ete reparties au hasard dans 2237 placettes de reference et 1119 placettes cibles une trentaine de fois. En plus d'etre testee pour la presence d'autocorrelation spatiale, chaque methode d'imputation a ete evaluee A l'aide du coefficient de determination, du biais et de (erreur quadratique moyenne calcules pour les ensembles de donnees cibles et de reference. Les cartes de productivite forestiere potentielle de l'AAMP maximum ont ete produites pour l'ensemble du territoire forestier exploitable des Etats de l'Oregon et de Washington. [Traduit par la Redaction], Introduction Forest productivity is of interest in a wide variety of applications and, correspondingly, is measured in a wide variety of ways. Net primary productivity of forests, i.e., the rate [...]

Planting with mixtures of tree species rather than single species is often considered during reforestation because of the potential increased productivity and other benefits. We examined tree growth at the stand and individual tree scales in two experiments contrasting monocultures with a 1:1 mixture of tree species: (1) Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) with a conifer of similar shade tolerance (western white pine (Pinus monticola Dougl. ex D. Don)) and (2) Douglas-fir with a more shade-tolerant conifer (western hemlock (Tsuga heterophylla (Raf) Sarg.)). There was no effect of mixture on growth or yield in the Douglas-fir--western white pine combination. In the Douglas-fir--western hemlock combination, yields in the mixture equaled those in Douglas-fir stands because of the enhanced performance of Douglas-fir in the mixture. For Douglas-fir, the height/diameter (h/d) ratio was significantly less in mixture, suggesting reduced competition for light when grown with western hemlock. In contrast, the h/d ratio for western hemlock was significantly greater in mixture, suggesting increased competition for light when grown with Douglas-fir. Neighborhood analyses showed that tree growth was directly related to initial size and inversely related to relative neighbor size and that the h/d ratio was positively related to relative neighbor size. In general, the size of a neighboring tree influenced growth more than species identity. Relationships between h/d ratios and growth rates suggest that growth differences between Douglas-fir and western hemlock in mixture will eventually increase. La plantation d'un melange de plusieurs especes d'arbre plutot que d'une seule est souvent envisagee a cause de l'augmentation potentielle de la productivite et d' autres benefices. Nous avons etudie la croissance des arbres aux echelles du peuplement et de l'arbre a partir de deux experiences comparant des monocultures a des melanges formes de deux especes en proportion egale : (1) le douglas de Menues (Pseudotsuga menziesii (Mirb.) Franco) avec un conifere de tolerance similaire a l'ombre (le pin blanc de fOuest (Pinus monticola Dougl.ex D. Don)) et (2) le douglas de Menues avec un conifere plus tolerant a (ombre (la pruche de l'Ouest (Tsuga heterophylla (Raf.) Sarg.)). La combinaison du Douglas de Menues et du pin blanc de l'Ouest n'a pas eu d'effet sur la croissance ou la production. Dans le cas du melange de douglas de Menues et de pruche de l'Ouest, la production de la plantation mixte etait egale a celle des peuplements purs de douglas de Menues a cause d'une meilleure performance du douglas de Menues en plantation mixte. Pour le douglas de Menues, le rapport entre la hauteur et le diametre (h/d) etait significativement plus petit dans la plantation mixte, ce qui indique une diminution de la competition pour la lumiere dans la plantation mixte. Toutefois, dans le cas de la pruche de (Ouest, le rapport h/d etait significativement plus grand dans la plantation mixte, ce qui indique une augmentation de la competition pour la lumiere lorsque la pruche se developpe avec le douglas de Menues. Des analyses de voisinage ont montre que la croissance des arbres etait directement reliee a leur taille initiale et inversement reliee a la taille relative des arbres voisins, et que le rapport h/d etait positivement relie a la taille relative des voisins. En general, la croissance etait davantage influencee par la taille que par l'espece d'un arbre voisin. La relation entre le rapport h/d et le taux de croissance indique que les differences de croissance entre le douglas de Menues et la pruche de l'Ouest plantes ensemble vont eventuellement augmenter. [Traduit par la Redaction], Introduction For forest managers worldwide, the decision to reforest with one or several tree species is an important one. In many areas of the world, planting single-species stands was the [...]

Population-averaged (PA) and subject-specific (SS) approaches for modeling the height of dominant or codominant lodgepole pine (Pinus contorta Dougl. ex Loud.) trees were evaluated using six candidate models derived from the Chapman-Richards and logistic functions. The true PA response obtained from separate fits of the models was compared with the typical mean (TM) response computed using only the fixed-effects parameters of the mixed-effects models. Results showed that the TM response had higher prediction errors than the PA response, suggesting that a true PA response and not the TM response is needed to reflect the overall mean response of the model. The SS approach produced improved height predictions relative to the PA approach when evaluated using independent validation data. In addition, the logistic performed better than the Chapman-Richards function, regardless of whether the SS or PA approach was applied. Among the candidate models, the logistic function with the inclusion of site index gave the most accurate predictions. Three scenarios of calibrating the mixed-effects models on the validation data set were compared. The SS predictions obtained using only one premeasured observation per subject were poorer than those using all observations, but they were still generally better than PA predictions. Des approches de modelisation par moyenne de population (MP) et par sujet specifique (SS) appliquees a la hauteur de pins tordus (Pinus contorta Dougl. ex Loud.) dominants et codominants ont ete evaluees a (aide de six modeles derives de fonctions logistiques et de Chapman-Richards. La vraie reponse de l'approche MP obtenue de l'ajustement separe des modeles a ete comparee a la reponse moyenne typique (MT) calculee a partir des parametres des seuls effets fixes des modeles a effets mixtes. Les resultats montrent que la reponse MT est associee a de plus grandes erreurs de prevision que celles de la reponse MP, ce qui indique que la vraie reponse MP, et non la reponse MT, est necessaire pour refleter la reponse moyenne totale du modele. L'approche SS a produit de meilleures previsions de hauteur que l'approche MP lorsqu'elle a ete evaluee a partir de donnees independantes de validation. De plus, la fonction logistique a produit de meilleurs resultats que la fonction de Chapman-Richards, que ce soit dans le cas de l'approche SS ou MP. Parmi les modeles testes, la fonction logistique incluant l'indice de qualite de station a produit les previsions les plus precises. Trois scenarios d'etalonnage des modeles a effets mixtes ont ete compares a partir d'un fichier de validation. Les previsions SS obtenues a partir de seulement une observation initiale par sujet etaient moins bonnes que celles obtenues a partir de trois observations initiales, mais elles etaient quand meme generalement meilleures que les previsions MP. [Traduit par la Redaction], Introduction Predicting height of dominant, codominant, or top height trees is important not only because it directly leads to the estimation of site index (SI) but also because it serves [...]

Large woody debris (LWD) is a key link between riparian forests and streams; however, the temporal dynamics of in-stream wood remains poorly quantified. Using dendrochronology, we evaluated the dynamics of five Pinusdominated and five Picea-dominated riparian forests in the foothills of Alberta and cross-dated the ring widths of 186 pieces of LWD. Time since death of LWD ranged from 2 to 143 years, with maximums of 86 and 143 years for Pinus and Picea, respectively. Recruitment of Pinus LWD was influenced by stand-replacing fires followed by self-thinning about 40 years after stand establishment. In uneven-aged Picea-dominated forests, tree mortality and LWD recruitment were due to fme-scale disturbances. Time since death increased significantly with decay and position classes, which resulted in changes in LWD function through time. LWD persisted in the bridge position for about 30 years. Bridged LWD was least decayed, was significantly longer, and had greater volume than LWD in other positions. LWD remained in partial bridge and loose positions about 15 years and >80 years when submerged in water and buried in sediment. Given the persistence of LWD, we conclude that management that alters wood abundance and recruitment has short- and long-term implications for the structure and function of small streams. Les debris ligneux grossiers (DLG) constituent un lien essentiel entre les forets riveraines et les cours d'eau. Cependant, la dynamique temporelle du bois dans les cours d'eau est encore peu quantifiee. A (l'aide de la dendrochronologie, nous avons evalue la dynamique de cinq forets riveraines dominees par le pin (Pinus spp.) et de cinq autres dominees par l'epinette (Picea spp.) dans les contreforts de l'Alberta et nous avons procede a la datation croisee des cernes annuels de 186 DLG. Le temps ecoule depuis la mort des DLG varie de 2 a 143 ans; les valeurs maximales sont respectivement de 86 et 143 ans pour le pin et l'epinette. Le recrutement des DLG de pin est influence par les feux qui entrainent le remplacement des peuplements suivis d'une eclaircie naturelle environ 40 ans apres l'etablissement du peuplement. Dans les forets inequiennes dominees par (epinette, la mortalite des arbres et le recrutement des DLG sont dus a des perturbations a echelle fine. Le temps ecoule depuis la mort augmente significativement avec les classes de decomposition et de position, ce qui entraine des changements dans la fonction des DLG avec le temps. Les DLG suspendus au-dessus du cours d'eau persistent pendant environ 30 ans. Les DLG suspendus sont les moins decomposes; ils sont significativement plus longs et ont un plus gros volume que les DLG dans les autres positions. Les DLG demeurent partiellement suspendus ou libres pendant environ 15 ans et pendant plus de 80 ans s'ils sont submerges ou enfouis dans les sediments. Etant donne la persistance des DLG, nous concluons que les pratiques d'amenagement qui modifient l'abondance et le recrutement des debris ligneux ont des consequences a court et long termes sur la structure et la fonction des petits cours d'eau. [Traduit par la Redaction], Introduction Sustainable management and effective restoration of streams requires understanding of the key structures and processes linking riparian forests and in-stream habitats (Palmer et al. 2005). Large woody debris (LWD) [...]

The amount and variability of living and dead wood in a forest stand are important indicators of forest biodiversity, as it relates to structural heterogeneity and habitat availability. In this study, we investigate whether light detection and ranging (lidar) can be used to estimate the distribution of standing dead tree classes within forests. Twenty-two field plots were established in which each stem (DBH >10 cm) was assigned to a wildlife tree (WT) class. For each plot, a suite of lidar-derived predictor variables were extracted. Ordinal regression using a negative log-log link function was then employed to predict the cumulative proportions of stems within the WT classes. Results indicated that the coefficient of variation of the lidar height data was the best predictor variable ([chi square] = 106.11, p < 0.00; Wald = 4.83, p = 0.028). The derived relationships allowed for the prediction of the cumulative proportion of stems within WT classes (r = 0.90, RMSE = 6.0%) and the proportion of dead stems within forest plots (r = 0.61, RMSE = 16.8%). Our research demonstrates the capacity of lidar remote sensing to estimate the relative abundances of standing living and dead trees in forest stands and its ability to characterize vegetation structure across large spatial extents. La quantite et la variabilite du bois vivant et du bois mort sont d'importants indicateurs de la biodiversite forestiere etant donne leurs relations avec (heterogeneite structurale et la disponibilite d'habitats. Dans cette etude, nous examinons si le lidar peut etre utilise pour estimer la distribution des classes d'arbres morts debout dans les forets. Vingt-deux placettes au sol ont ete etablies dans lesquelles chaque tige (DHP > 10 cm) a ete assignee a une classe d'arbres fauniques. Une suite de variables independantes derivees du lidar ont ete extraites pour chaque placette. Une regression ordinale utilisant une fonction lien log-log negative a ensuite ete utilisee pour predire la proportion cumulative de tiges dans les classes d'arbres fauniques. Les resultats indiquent que le coefficient de variation des donnees de hauteur obtenues avec le lidar est la meilleure variable independante ([chi square] = 106,11, p < 0,00; Wald = 4,83, p = 0,028). Les relations qui ont ete derivees ont permis de predire la proportion cumulative des tiges dans les classes d'arbres fauniques (r = 0,90, EQM = 6,0 %) et la proportion de tiges mortes dans les placettes en foret (r = 0,61, EQM = 16,8 %). Nos travaux de recherche demontrent la capacite de la teledetection avec le lidar a estimer l'abondance relative des arbres vivants et des arbres morts dans les peuplements forestiers et sa capacite a caracteriser la structure de la vegetation sur de vastes etendues spatiales. [Traduit par la Redaction], Introduction Forests are renewable resources that must be managed in a sustainable fashion while balancing economic, cultural, and social needs. The Canadian province of British Columbia, which contains approximately half [...]

Belowground C and N storage is important in maintaining forest productivity and to C[O.sub.2] sequestration. How these pools respond to management is poorly understood. We investigated effects of repeated applications of complete fertilizer and competing vegetation control with herbicides on C and N storage in forest-floor, fine-root, and mineral-soil C and N pools to 1-m depth at three Pinus ponderosa P. Lawson & C. Lawson var. ponderosa plantations across a site quality gradient in northern California. Belowground C pools without treatment were 66, 153, and 199 Mg C [ha.sup.-1] for the low-, intermediate-, and high-quality sites, respectively, and N pools were 5.1, 6.7, and 6.5 Mg N [ha.sup.-1], respectively. Treatments increased tree-bole volume at 20 yr as much as 400%, while changes in C and N pools belowground were less dramatic. Herbicide treatment increased forest-floor C pools 35% at the poorer quality site. Fertilization increased forest-floor C and N storage 46 to 106% at all sites. Fertilization decreased fine-root C pools at 0 to 0.3 m at the most productive site 43% and increased this N pool 43% at the least productive site, but did not influence fine-root pools to 1 m. Fertilization increased mineral-soil C pools on lower quality sites, resulting in 12 to 57% more belowground C storage. At the intermediate site, fertilization increased total belowground N storage 12%. Results of this study suggest that the major sequestration mechanism up to this point in stand development is through gains in tree biomass rather than storage in fine roots and soil belowground. Abbreviations: SOM, soil organic matter.

During outbreaks the mountain pine beetle (Dendroctonus ponderosae Hopkins) kills large lodgepole pine trees (Pinus contorta Dougl. ex Loud.) more frequently than smaller ones. There is, however, considerable variation in the relation of diameter to incidence of attack. In a meta-analysis of published data we found that the relationship was primarily determined by geographic location (elevation, latitude, and longitude). We propose a new tree mortality measure, the probability of death index, defined as the average percentage of mortality for trees >23 cm. The index may improve the precision in predictive modeling of tree mortality, as it provides a biologically relevant measure of mortality, since it only includes trees that contribute to the growth of an epidemic and is not influenced by the number of trees within a diameter class. To be useful to forest managers, it must be possible to predict the index from stand parameters that are easily measured. The usefulness of the index was supported by a meta-analysis, which showed that 53% of the variation in the mortality index was explained by geographic location. Tree density did not explain any additional variation. Future research is needed to evaluate the performance of the probability of death index compared with that of other mortality measures. Durant les epidemies, le dendroctone du pin ponderosa (Dendroctonus ponderosae Hopkins) tue plus souvent les grosses tiges de pin tordu (Pinus contorta Dougl. ex Loud.) que les plus petites. Cependant, la relation entre le diametre et l'incidence des attaques varie enormement. Dans une meta-analyse des donnees publiees, nous avons decouvert que la relation est principalement determinee par la position geographique (altitude, latitude et longitude). Nous proposons une nouvelle mesure de mortalite des arbres : l'indice de probabilite de mortalite, definie comme etant le pourcentage moyen de mortalite des tiges de plus de 23 cm. L'indice peut ameliorer la precision des modeles de prediction de la mortalite des arbres parce qu'il fournit une mesure de la mortalite pertinente du point de vue biologique etant donne qu'il inclut uniquement les arbres qui contribuent a la croissance d'une epidemie et qu'il n'est pas influence par le nombre d'arbres dans une classe de diametre. Pour etre utile aux amenagistes forestiers, l'indice doit pouvoir etre predit a partir de parametres du peuplement qui sont facilement mesurables. L'utilite de l'indice est supportee par une meta-analyse qui montre que 53 % de la variation de l'indice de mortalite est expliquee par la position geographique. La densite des arbres n'explique aucune variation additionnelle. D'autres travaux seront necessaires pour evaluer la performance de l'indice de probabilite de mortalite comparativement a d'autres mesures de la mortalite. [Traduit par la Redaction], Introduction Most bark beetles that attack living trees seem to prefer certain tree sizes (Rudinsky 1962; van Hees and Holsten 1994). During epidemics of the mountain pine beetle (Dendroctonus ponderosae [...]

A three-year (2001-2003) study was carried out on the home range characteristics of seven wild white-handed gibbon (Hylobates lar) groups focusing on the spatio-temporal distribution of food resources at Khao Yai National Park in northeastern Thailand. These results were combined with 23 years (1980-2003) of reproductive performance data on seven females from the same focal groups. Reproductive performance was equal among females with regard to birth, weaning and maturation ratios, and independent of variation in food availability. Offspring mortality, however, was significantly positively correlated with home-range size. In addition, there was an increase in offspring mortality just after weaning, suggesting that the increase in the daily distance traveled by juveniles contributed to this mortality. Conceptions clustered during the first half of the year when food production was at its peak, which presumably allowed females to accumulate sufficient body reserves to resume ovarian cycling. Our results place Khao Yai gibbons closer to Cercopithecidae than great apes in terms of the temporal pattern of reproductive events, though gestation, lactation, inter-birth interval, and offspring maturation are considerably longer in gibbons, placing them closer to the other apes. Our findings underline the unique phylogenetic position of these small-bodied apes in terms of reproductive patterns in primates. KEY WORDS offspring mortality; forest productivity; seasonal reproduction

Future climate change is expected to have many impacts on forest ecosystems. It is important to have some understanding of these impacts in order to make informed forest management decisions. A major consideration in making forest management decisions is the productivity of a site, as measured by site index. In this study, I relate Douglas-fir site index to accumulated growing degree-days greater than 5[degrees]C (DD5), as well as to soil moisture and nutrient regime. This allows the impact of climate change on forest productivity to be estimated. A two step approach was followed. The first step derived models to estimate various climate variables to latitude, longitude, and elevation using data from climate stations. Then, these climate variables were used along with soil moisture and nutrient data to predict site index for the site index plots. A two step approach was taken because climatic data were not available for the site index plots. The trend was for site index to increase with both increasing soil moisture and nutrients, although the site index decreased on the wetter sites. Site index also increased with DD5 at the rate of 1.2 m for every increase of 100 units in DD5. These models can be used together to evaluate the impact of various climate change scenarios on site index.

A study was conducted on regional disparities in capturing transmitted productivity gains by stimulating a 0.63 percent TFP improvement in the U.S. in the logging sector. It was found that depending on the absorptive capacity and structural similarity, the technological progress could have different impacts on productivity improvements of trading.

Human population growth places increasing demands on the world's forests. Sustaining these forests will depend to a considerable extent on sustaining soil structure and function. Traditional scientific concerns about sustaining timber production focused largely on soil fertility, but recent interest has focused attention on the plant and animal community and on 'biodiversity'. Neither of these approaches is satisfactory on its own. They should be replaced with an ecosystem analysis approach that includes the biotic and abiotic components. The most fundamental issue in sustainable forest management is the long-term productive capacity of individual sites, which is determined to a considerable extent by the availability of soil resources. Understanding the sustainability of site productivity requires knowledge of the determinants of leaf area and its photosynthetic efficiency, and of the allocation of net production. Keys that determine production ecology in boreal and cool temperate forests include low soil temperature, slow rate of litter decomposition and the resultant character of the forest floor, and, in some areas, impeded soil drainage; these lead to limitations on nutrient availability. Natural disturbance influences these factors and thereby plays a vital role in maintaining productivity and several measures of biological diversity. Without stand-replacing disturbances, closed forest may not be the climax vegetation in many western and northern Canadian landscapes. While forests and soils should be protected from 'damage', sufficient disturbance should be sustained to respect the disturbance-related ecology of these forests. Ecological site classification and use of ecosystem-level management simulation models are important for the design of appropriate disturbance regimes.

Many forest management treatments are directly aimed at maintaining or enhancing forest productivity. There may also be secondary effects that detract from this goal. We discuss three case studies in Washington state in which several mechanisms may have led to adverse secondary impacts. In the first study, pulp and paper (PII) sludges were mixed into soil and growth of Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco], noble fir (Abies procera Rehder) and western white pine (Pinus monticola Douglas ex D. Don) was monitored. There was a significant negative correlation of height and diameter growth and C/N ratio for Douglas-fir and western white pine (0.05 level). In a second study, effects of 50 yr of red alder (Alnus rubra Bong.) and Douglas-fir growth on soil chemistry and stand productivity were compared. When the 50-yr-old stands were cut and red alder was established by planting into the soil of the former Douglas-fir and red alder forests, lowered available P in the soil of the previous red alder stand was observed. In a third study, high rates of low C/N ratio organic matter (300 Mg [ha.sup.-1]) were added in municipal biosolids (N amount about 8000 kg [ha.sup.-1]) to Douglas-fir and grand fir [Abies grandis (Dougl.) Forbes] plantations. Excess organic N in the biosolids apparently mineralized, nitrified, and contributed to soil acidification and accelerated cation leaching. Severe Mg deficiency (0.25 g [kg.sup.-1] in biosolids-treated vs. 0.93 g [kg.sup.-1] in untreated area) might be the cause of observed foliar chlorosis and poor growth rates.

We assess the appropriateness of using regression- and process-based approaches for predicting biogeochemical responses of ecosystems to global change. We applied a regression-based model, the Osnabruck Model (OBM), and a process-based model, the Terrestrial Ecosystem Model (TEM), to the historical range of temperate forests in North America in a factorial experiment with three levels of temperature (+0 [degrees]C, +2 [degrees]C, and +5 [degrees]C) and two levels of [CO.sub.2] (350 ppmv and 700 ppmv) at a spatial resolution of 0.5[degrees] latitude by 0.5[degrees] longitude. For contemporary climate (+0 [degrees]C, 350 ppmv), OBM and TEM estimate the total net primary productivity (NPP) for temperate forests in North America to be 2,250 and 2.602 x [10.sup.15] g C [muliplied] [yr.sup.-1], respectively. Although the continental predictions for contemporary climate are similar, the responses of NPP to altered climates qualitatively differ; at +0 [degrees]C and 700 ppmv [CO.sub.2], OBM and TEM predict median increases in NPP of 12.5% and 2.5%, respectively. The response of NPP to elevated temperature agrees most between the models in northern areas of moist temperate forest, but disagrees in southern areas and in regions of dry temperate forest In all regions, the response to [CO.sub.2] is qualitatively different between the models. These differences occur, in part, because TEM includes known feedbacks between temperature and ecosystem processes that affect N availability, photosynthesis, respiration, and soil moisture. Also, it may not be appropriate to extrapolate regression-based models for climatic conditions that are not now experienced by ecosystems. The results of this study suggest that the process-based approach is able to progress beyond the limitations of the regression-based approach for predicting biogeochemical responses to global change.

Estimates of annual net primary productivity since 1880 for four high-elevation forest stands in western Washington indicated that productivity has increased 60% during the 20th century. Because these stands were separated by up to 200 km and differed in species composition, elevation, and time since establishment, the observed trends in productivity imply a response to regionwide changes in environmental factors rather than to site-specific stand dynamics. Annual production is significantly correlated with long-term variation in summer temperature and short-term variation in annual precipitation since 1893, the beginning of continuous local meteorological records. Production is uncorrelated with atmospheric [CO.sub.2] concentrations, suggesting that direct [CO.sub.2] fertilization is currently unimportant in these forests.

Numerous explanatory theories have been developed about patterns found in nature. One such pattern is the tendency of the relationship between plant species richness and above-ground biomass to be unimodal when exploring an environment gradient. Since it was first described by Al-Mufti et al. in 1977, the trend has been examined extensively by other researchers using more rigorous calculation tools. These include Rosenzweig and Abramsky (1993) who formulated nine hypotheses regarding the relationship of productivity. Oksanen (1996) developed a 10th hypothesis known as the non-interaction model.

An analysis is presented of the compatibility between wildlife and timber from economic and biological perspectives, using production possibilities frontier methodology.