Search

Wood ash may be useful as a forest soil amendment in Canada, but trace metals can have detrimental effects if they accumulate in, or are transported from, forest ecosystems. Metal concentrations in soil water and sugar maple (Acer saccharum Marsh.) seedling tissue chemistry were measured in a north temperate hardwood forest over 4 years following a biomass boiler ash addition field trial. Twenty plots (3 m x 3 m) were established in Haliburton Forest with both fly and bottom ash treatments of 0, 4, and 8 Mg * [ha.sup.-1] with four replicates, and tension lysimeters were positioned in each plot at 30, 50, and 100 cm depths. Over the 4 years, soil water metal concentrations in treated plots were not significantly different from those of the control plots. No differences in metal concentrations in foliage of sugar maple seedlings could be detected, but there were significantly higher concentrations of some metals (Al, Fe, Zn, Pb, Ni, and Sr) in roots of treated plots. Simulated drought mobilized several metals in upper mineral soil, but this mobilization occurred similarly in controls and ash-treated soils. These results suggest that doses below 8 Mg * [ha.sup.-1] industrial wood ash with trace metal concentrations below Canadian regulatory limits do not cause an increase in trace metal mobility or availability in northern hardwood forests with acidic soils during the first 5 years after application. Key words: fly ash, bottom ash, sugar maple, metal toxicity, forest soil amendments. On peut utiliser la cendre de bois pour amender les sols au Canada mais les metaux-traces peuvent avoir des effets nefastes s'ils sont exportes des ecosystemes forestiers ou s'y accumulent. La concentration des metaux dans l'eau du sol et les proprietes chimiques des tissus des semis d'erable a sucre (Acer saccharum Marsh.) ont ete mesurees dans une foret feuillue nordique temperee pendant quatre annees suivant l'apport de cendres de chaudieres alimentees en biomasse dans le cadre d'un essai sur le terrain. Vingt placettes (3 m x 3 m) ont ete etablies dans la foret Haliburton et traitees avec des cendres volantes et residuelles a raison de 0, 4 et 8 Mg * [ha.sup.-1] avec quatre repetitions. Des lysimetres a tension ont ete places dans chaque placette a 30, 50 et 100 cm de profondeur. Au cours des quatre annees, la concentration des metaux dans l'eau du sol des placettes traitees n'etait pas significativement differente de celle des placettes temoins. Aucune difference dans la concentration des metaux n'a pu etre detectee dans le feuillage des semis d'erable a sucre mais la concentration de certains metaux (Al, Fe, Zn, Pb, Ni et Sr) etait significativement plus elevee dans les racines des placettes traitees. Une secheresse simulee a entraine la mobilisation de plusieurs metaux dans la partie superieure du sol mineral, mais cette mobilisation est survenue de facon similaire dans les sols temoins et les sols traites avec la cendre. Ces resultats indiquent que des doses inferieures a 8 Mg * [ha.sup.-1] de cendre de bois industrielle avec des concentrations de metaux-traces inferieures aux limites permises au Canada n'entrainent pas d'augmentation de la mobilisation ou de la disponibilite de metaux-traces dans les forets feuillues nordiques sur des sols acides durant les premieres cinq annees apres une application. Mots-cles: cendre volante, cendre residuelle, erable a sucre, toxicite des metaux, amendement du sol en foret., Introduction Concerns over soil acidification and associated ecological impacts has promoted the potential use of wood ash as an amendment to increase soil pH and nutrient levels. Increased production of [...]

This study explored practices that Canadian soil scientists use to educate postsecondary students, K-12 students, and the general public. The most commonly used type of educational activities described by survey respondents, regardless of the settings and the type of target audience, were field-based hands-on activities. The other two commonly used educational activities were lectures and laboratory activities; and they were predominantly implemented at the postsecondary institutions. Educational activities in K-12, outreach, and professional development settings were generally delivered through one-time events (e.g., workshops, school visits, field days), offering less opportunities for a greater variety of practices relative to the postsecondary settings. At postsecondary institutions, where soil science education is delivered in a more structured manner, there are more opportunities for educators to implement a range of educational practices (e.g., lectures, laboratory activities, games, case studies, quizzes). The learning objectives of the field-based hands-on activities and lectures were to describe specific soil properties or to describe and classify soils, whereas for laboratory activities, the learning objectives focused more on the application of those concepts. The insights offered by this study on educational practices used by Canadian soil scientists to encourage more students to study soil science and raise awareness about the importance of soil are valuable teaching resources for both new and seasoned educators within Canada and abroad.

Accurate soil information is critically important for forest management planning and operations but is challenging to map. Digital soil mapping (DSM) improves upon the limitations of conventional soil mapping by explicitly linking a variety of environmental data layers to spatial soil point data sets to continuously predict soil variability across a landscape. Thus far, much DSM research has focussed on the development of ultrafine-resolution soil maps within agricultural systems; however, increasing availability of light detection and ranging (LiDAR) data presents new opportunities to apply DSM to support forest resource applications at multiple scales. This project describes a DSM workflow using LiDAR-derived elevation data and machine learning models (MLMs) to predict key forest soil attributes. A case study in the Hearst Forest in northeastern Ontario, Canada, is used to illustrate the workflow. We applied multiple MLMs to the Hearst Forest to predict soil moisture regime and textural class. Both qualitative and quantitative assessment pointed to the random forest MLM producing the best maps (63% accuracy for moisture regime and 66% accuracy for textural class). Where error occurred, soils were typically misclassified to neighbouring classes. This standardized, flexible workflow is a valuable tool for practitioners that want to undertake DSM as part of forest resource management and planning. Key words: digital soil mapping, machine learning, forest management. Des informations precises sur les sols sont absolument essentielles pour la planification et les operations d'amenagement forestier mais elles sont difficiles a cartographies La cartographie numerique des sols (CNS) constitue un progres par rapport aux limites de la cartographie conventionnelle des sols en reliant une variete de couches de donnees environnementales a des ensembles de donnees spatiales ponctuelles des sols pour predire la variabilite a travers un paysage de facon continue. Jusqu'a maintenant, beaucoup de travaux de recherche sur la CNS ont mis l'accent sur le developpement de cartes des sols a tres haute resolution pour des systemes agricoles. Cependant, la disponibilite croissante de donnees lidar offre de nouvelles opportunites d'appliquer la CNS en support a des applications qui concernent les ressources forestieres a de multiples echelles. Ce projet decrit un flux de travail de CNS qui utilise des donnees altimetriques derivees du lidar et des modeles d'apprentissage automatique (MAA) pour predire des attributs importants des sols. Une etude de cas dans la foret de Hearst, dans le nord-est de l'Ontario, au Canada, est utilisee pour illustrer le flux de travail. Nous avons applique plusieurs MAA a la foret de Hearst pour predire le regime d'humidite et la classe de texture. Une evaluation tant qualitative que quantitative indiquait que le MAA de foret aleatoire produisait les meilleures cartes (precision de 63 % pour le regime d'humidite et de 66 % pour la classe de texture). Lorsqu'il y avait des erreurs, les sols mal classes etaient typiquement places dans les classes voisines. Ce flux de travail standardise et flexible est un outil precieux pour les praticiens qui veulent entreprendre la CNS en tant que composante de la planification et de la gestion des ressources forestieres. [Traduit par la Redaction] Mots-cles: cartographie numerique des sols, apprentissage automatique, amenagement forestier., 1. Introduction Soils are a critical element of forest ecosystems in that soil mineralogy, nutrient supply, moisture retention, texture, structure, and porosity collectively influence forest composition and productivity (Leniham 1993; [...]

Intensified biomass harvesting in northern forests could potentially negatively impact soils. This study measured microbial community structure and function to assess the impacts of intensified biomass removal on soil from a managed northern jack pine (Pinus banksiana Lamb.) forest in Ontario, Canada. Four clear-cut harvesting removal intensities were compared with uncut controls and mature, fire-regenerated forest reference plots: stem-only removal, full-tree biomass removal, full-tree biomass with stump removal, and full-tree biomass with stump removal and soil blading that eliminated all aboveground and much belowground organic matter. A nearby recently burned forest site, representing common natural disturbance in the region, was also studied. Within the first two years after harvesting, there were significant differences in community structure and degradation of various C compounds among all harvested and unharvested sites, but little difference in communities across the different harvest intensities. Communities within the fire site were not comparable with those of harvested treatments, indicating that clear-cut logging may not initially produce an ecologically comparable disturbance with that of fire, although this conclusion is based on only one fire disturbance site. In the two years after harvesting, an important time for seedling establishment in managed forest systems, it appears that intensification of harvesting does not further disrupt microbial community structure and functioning beyond impacts from current harvest practices. Key words: bioenergy, whole-tree harvesting, bacteria, fungi, substrate-induced respiration, extracellular enzymes, high-throughput sequencing. La recolte intensive de biomasse dans les forets nordiques pourrait avoir un impact negatif sur les sols. Cette etude a mesure la structure et le fonctionnement des communautes microbiennes pour evaluer les impacts de la recolte intensive de biomasse sur le sol d'une foret amenagee de pin gris (Pinus banksiana Lamb.) dans le nord de l'Ontario, au Canada. Nous avons compare des peuplements temoins non recoltes et des parcelles de reference dominees par des forets matures regenerees par le feu a quatre intensites de recolte par coupe a blanc : recolte des troncs seulement, recolte par arbres entiers, recolte par arbres entiers avec enlevement des souches, et recolte par arbres entiers avec enlevement des souches et coupe a la cisaille pour eliminer toute la matiere organique sur le sol et une grande partie de la matiere organique sous la surface du sol. Nous avons aussi etudie une station forestiere adjacente ayant recemment brUle, representative d'une perturbation naturelle frequente dans la region. Au cours des deux premieres annees qui ont suivi la recolte, nous avons detecte des differences significatives dans la structure des communautes et la degradation de plusieurs composes carbones entre les stations non recoltees et l'ensemble des stations recoltees, mais peu de differences dans les communautes entre les differentes intensites de recolte. Les communautes presentes dans la station brUlee n'etaient pas comparables a celles des stations recoltees. Ce resultat indique qu'initialement, la coupe a blanc ne serait pas une perturbation ecologiquement comparable au feu, bien que cette conclusion soit basee sur une seule station brUlee. Au cours des deux annees suivant la recolte, qui correspondent a une periode importante pour l'etablissement des semis dans les systemes forestiers amenages, il semble que l'intensification de la recolte n'accentue pas davantage la perturbation de la structure et du fonctionnement des communautes microbiennes au-dela des impacts lies aux pratiques forestieres courantes. [Traduit par la Redaction] Mots-cles : bioenergie, recolte par arbre entier, bacteries, champignons, respiration induite par le substrat, enzymes extracellulaires, sequencage a haut debit., Introduction The market for biomass-derived energy is anticipated to grow as global climate change drives the energy sector to seek alternative energy solutions (Berch et al. 2011). Forestry companies in [...]

As global issues continue to place increasing demands on soil resources, the need to provide soil science education to the next generation of soil scientists and the general public is becoming more imminent. In many countries around the world, including Canada, soil is either not included in the high school curriculum or it is not covered in depth. To address this need for better integration of soil science into high school programs in Canada, a national collaborative program entitled Soil 4 Youth (soilweb.landfood.ubc.ca/youth/), was established in 2009. The goals of the Soil 4 Youth program are to: (1) promote the discipline of soil science to high school students and teachers, (2) create open access soil education resources that can be directly implemented in high school curricula in Canada, and (3) raise awareness about the importance of soil. During the initial 4 years of the Soil 4 Youth program, we developed a variety of soil education resources, struck collaboration with several provincial high school teachers' associations and not-for-profit organizations focused on promotion of science, and focused our efforts toward reaching a broader group of high school teachers and students. Our initial efforts of building the Soil 4 Youth program indicate that it is a viable platform through which collaboration among Canadian soil scientists and high school teachers can take place to ensure that high school students are better informed about the importance of soil. Impact Statement: The Canadian collaborative program, Soil 4 Youth, was established to promote the discipline of soil science to high school students and teachers. The program provides a platform for collaboration among soil scientists and high school teachers to ensure that high school students are better informed about the importance of soil. This article describes the development of the Soil 4 Youth program, offering insights into the challenges and potential solutions to advance soil science education for youth.

Wood ash may be an effective soil amendment in North America to restore acidified and low-nutrient forest soils, but little research exists beyond its effects on soil and plants. Eastern Red-backed Salamander (Plethodon cinereus (Green, 1818)) abundance was assessed in a northern hardwood forest 1 year following an ash-addition field trial. Plots were established with fly ash and bottom ash treatments of 0, 1, 4, and 8 Mg x [ha.sup.-1] (n = 4), and cover boards were positioned both with and without ash beneath. One year following ash additions, salamander abundance had increased under boards with fly ash beneath, and bottom ash had no effect. Soil pH and electrical conductivity increased under cover boards with ash beneath them and for uncovered soil, and the effects were strongest under cover boards with ash beneath. The effects of ash were generally stronger at higher dosages, and fly ash was stronger than bottom ash. The moisture holding capacity of fly ash was 60% higher than the soil and was 63% lower than the soil for bottom ash, but they had little effect on moisture of the forest floor. These results suggest that ash altered salamander abundance via soil pH and moisture and would not inhibit salamander movement over the forest floor. Key words: fly ash, bottom ash, liming, cover boards, Haliburton Forest and Wildlife Reserve. En Amerique du Nord la cendre de bois permet d'amender efficacement et de restaurer les sols acidifies et pauvres en nutriments mais ses effets ont ete peu d'etudies, outre ceux sur le sol et les plantes. L'abondance de salamandres rayees (Plethodon cinereus (Green, 1818)) a ete evaluee dans une foret de feuillus nordiques une annee apres l'ajout de cendre dans le cadre d'une experimentation au champ. Les places-echantillons comprenaient des traitements de cendre volante et de cendre residuelle a raison de 0, 1, 4 et 8 Mg x [ha.sup.-1] (n = 4) et des panneaux de contreplaque ont ete places au sol avec ou sans cendre en dessous. L'annee suivant l'ajout de cendres, l'abondance de salamandres a augmente sous les panneaux recouvrant de la cendre volante tandis que la cendre residuelle n'a pas eu d'effet. Le pH du sol et la CE ont augmente sous les panneaux places sur de la cendre ainsi que dans les sols exposes, et les effets etaient plus prononces sous les panneaux places sur de la cendre. Les effets de la cendre etaient en general plus prononces avec les doses les plus elevees et avec la cendre volante comparativement a la cendre residuelle. La capacite de retention de l'humidite de la cendre volante etait 60% plus grande que celle du sol alors que celle de la cendre residuelle etait 63% plus faible, mais cela avait peu d'effets sur l'humidite du parterre forestier. Ces resultats indiquent que la cendre aeuun impact sur l'abondance de salamandres via le pH et l'humidite du sol et qu'elle n'empecherait pas leurs deplacements sur le parterre forestier. [Traduit par la Redaction] Mots-cles: cendre volante, cendre residuelle, chaulage, panneaux de contreplaque, Reserve forestiere et faunique Haliburton., 1. Introduction Forest soils in eastern North America have experienced acidification and nutrient depletions as a result of acid rain (Likens and Bormann 1974; Watmough and Dillon 2003; McLaughlin 2014). [...]

Concerns about climate change and the desire to develop a domestic, renewable energy source are increasing the interest in forest biomass extraction, especially in the form of logging residues, i.e., tree tops and branches. We reviewed the literature to determine the site and soil conditions under which removal of logging residues along with the stem (i.e., whole-tree harvesting), especially at clearcut, results in negative impacts on soil productivity compared with conventional stem-only harvesting in boreal and temperate forests. Negative impacts of biomass harvesting on soil nutrient pools (e.g., nitrogen, phosphorus and base cations) and soil acid-base status are more frequent in the forest floor than in the mineral soil. In the first years post-harvest, however, biomass harvesting has the greatest potential to influence tree survival and growth, either positively or negatively, through its effects on microclimate and competing vegetation. Later in the rotation, impaired nitrogen and (or) phosphorus nutrition on whole-tree harvested sites has been shown to reduce tree growth for at least 20 years in some stands. Biomass removal can also reduce the concentrations of base cations in soils and foliage, but this has not, to date, been shown to affect tree productivity. There are no consistent, unequivocal and universal effects of forest biomass harvesting on soil productivity. However, climate and microclimate, mineral soil texture and organic C content, the capacity of the soil to provide base cations and phosphorus, and tree species autecology appear to be critical determinants of site sensitivity to biomass harvesting. Rigorous, long-term experiments that follow stand development through a rotation will facilitate the identification of categories of site or stand conditions under which negative impacts of biomass harvesting are likely. Key words: forest biomass, whole-tree harvesting, soil productivity, tree nutrition, stand productivity. Les preoccupations au sujet des changements climatiques et la volonte de developper des sources d'energie domestique renouvelable augmentent l'interet pour l'extraction de la biomasse forestiere, surtout sous la forme de residus de coupe, c.-a-d., les cimes et les branches des arbres. Les auteurs ont conduit une revue de litterature pour determiner les conditions de site et de sol pour lesquelles l'enlevement des residus de coupe en plus de la tige (c.-a-d., la coupe par arbre entier ), surtout lors de coupes a blanc, conduit a des impacts negatifs sur la productivite des sols comparativement a la recolte conventionnelle du tronc seulement, en forets boreales et temperees. Les impacts negatifs de la recolte de la biomasse sur les reserves du sol en nutriments (p. ex. azote, phosphore et cations basiques) et sur le statut acidite-alcalinite apparaissent plus frequents dans l'humus que dans le sol mineral. Cependant, au cours des premieres annees suivant la recolte, le prelevement de la biomasse montre le plus fort potentiel pour influencer la survie des arbres et leur croissance, soit positivement soit negativement, par ses effets sur le microclimat et la vegetation competitrice. Plus tard dans la revolution, on observe que pour certains peuplements, une nutrition amoindrie en azote et (ou) phosphore sur les sites avec coupe par arbre entier reduit la croissance des arbres pendant au moins 20 ans. Le prelevement de la biomasse peut egalement reduire les teneurs en cations basiques dans les sols et le feuillage, mais ceci ne semble pas se traduire en effet sur la productivite. Il n'y a pas d'effets non equivoques et universels de la recolte de la biomasse sur la productivite des sols. Cependant, le climat et le microclimat, la granulometrie du sol, sa teneur en C organique, sa capacite a fournir les cations basiques et le phosphore, ainsi que l'autecologie des especes semblent constituer des determinants importants de la sensibilite des sites a la recolte de la biomasse. Des experiences rigoureuses, conduites a long terme pour suivre le developpement des peuplements tout au long de la revolution, faciliteront l'identification des categories de sites ou les conditions des peuplements pour lesquels des impacts negatifs sont susceptibles de se developper. [Traduit par la Redaction], Introduction Biomass from forests and byproducts from the manufacturing of traditional forest products are increasingly used to generate a range of bioproducts, of which bioenergy is currently the most common. [...]

Logging disturbances in boreal forest watersheds can alter biogeochemical processes in soils by changing forest composition, plant uptake rates, soil conditions, moisture and temperature regimes, soil microbial activity, and water fluxes. In general, these changes have often led to short-term increases in soil nutrient availability followed by increased mobility and losses by leaching to receiving waters. Among the studies we reviewed, dissolved organic carbon (DOC) exports usually increased after logging, and nitrogen (N) mineralization and nitrification often increased with resulting increased N availability and exports to receiving waters. Similar processes and responses occurred for phosphorus (P), but to a lesser extent than for N. In most cases, base cations were released and exported to receiving waters after logging. Several studies demonstrated that stem-only or partial-harvest logging reduced the impacts on nutrient release and exports in comparison to whole-tree clear-cutting. Despite these logging-induced increases in soil nutrient availability and movement to receiving waters, most studies reported little or no change in soil chemical properties. However, responses to logging were highly variable and often site specific. The likelihood, extent and magnitude of logging impacts on soil nutrient cycling and exports in boreal forest watersheds will be dependent on soil types, stand and site conditions, hydrological connectivity, post-logging weather patterns, and type and timing of harvest activities. Additionally, logging impacts can interact with, and be confounded by, atmospheric pollutant deposition and climate change. Further watershed-level empirical studies and modeling efforts are required to elucidate these interactions, to improve predictive capabilities, and to advance forest management guidelines for sustaining forest soil productivity and limiting nutrient exports. Key words: boreal forest, logging, soils, biogeochemistry, nutrient export. Les perturbations causees par la recolte du bois dans les bassins versants de la fork boreale peuvent affecter les processus biochimiques des sols en modifiant la composition de la fork, les taux d'absorption par les plantes, les conditions du sol, les regimes de temperature et d'humidite, l'activite des microorganismes du sol, et les mouvements de 'eau. En general, ces modifications engendrent souvent des augmentations de courte duree de la disponibilite des nutriments du sol, suivi par une augmentation de la mobility et des pertes par lessivage vers les eaux receptrices. Les etudes analysees font etat d'une augmentation des exportations de carbone organique dissout (DOC) apres la coupe, et d'une mineralization de l'azote (N) avec une augmentation frequente de la nitrification conduisant a une augmentation de la disponibilite de N et son exportation vers les eaux receptrices. On observe des processus et reactions similaires pour le phosphore (P), mais a un moindre degre que pour le N. Dans la plupart des cas, il y a relachement des cations basiques et exportation vers les eaux receptrices apres la coupe. Plusieurs etudes ont demontre que la recolte des tiges seulement on la coupe partielle, reduisent les impacts sur le relachement et 'exportation des nutriments, comparativement a la coupe a blanc. En depit de ces augmentations de la disponibilite des nutriments et de leur deplacement vers les eaux receptrices, occasionnees par la recolte, la plupart des etudes ne rapportent que pen on pas de changement dans les proprietes chimiques du sol. Cependant, les reactions a la recolte sont tres variables et souvent specifiques an site. La probabilite, l'etendue et 'amplitude des impacts des coupes sur le cyclage et 'exportation des nutriments du sol dans les bassins versants de la fork boreale dependent du peuplement et des conditions du site, de la connectivite hydraulique, des patrons meteorologiques apres coupe, ainsi que du type et du moment des activites de recoltes. De plus, les impacts de la coupe peuvent interagir et etre confondus avec ceux de la deposition des polluants atmospheriques et du changement climatique. On doit poursuivre les efforts mis dans les etudes empiriques et la modelisation afin d'elucider ces interactions, ameliorer les capacites de prediction et proposer des lignes directrices d'amenagement pour assurer une productivity soutenue des sols forestiers et limiter les exportations de nutriments. Mots-cles : fork boreale, coupe forestiere, sols, biogeochimie, exportation des nutriments. [Traduit par la Redaction], Introduction Headwater systems in forest landscapes have strong ecological linkages to their surrounding terrestrial catchments (Kaushik and Hynes 1971; Hynes 1975). Forest streams, ponds and headwater lakes obtain most of [...]

Abstract: We measured organic matter removal and soil compaction effects on soil surface C[O.sub.2] efflux (F) from a jack pine (Pinus banksiana Lamb.) forest and developed an analytical framework involving [...]

Long‐term ecosystem studies are valuable for understanding integrated ecosystem response to global changes in atmospheric deposition and climate. We examined trends for a 35‐year period (1982/83–2017/18) in concentrations of a range of solutes in precipitation and stream water from nine headwater catchments spanning elevation and surficial geology gradients at the Turkey Lakes watershed (TLW) in northeastern Ontario, Canada. Average annual water year (WY, October to September) concentrations in precipitation significantly declined over the period for sulphate (SO42−), nitrate (NO3−) and chloride (Cl−), while calcium (Ca2+) and potassium (K+) concentrations increased, resulting in a significant pH increase from 4.2 to 5.7. Trends in stream chemistry through time are generally consistent with expectations associated with acidification recovery. Concentration of many stream water solutes (SO42−, Cl−, calcium [Ca2+], magnesium [Mg2+] and NH4+ generally decreased, while others (silica [SiO2] and dissolved organic carbon [DOC]) generally increased. Increases were also observed for alkalinity (six of nine catchments), acid neutralizing capacity ([ANC]; six of nine catchments) and pH (eight of nine catchments), while conductivity declined (six of nine catchments). Variability in trends among catchments are associated with differences in surficial geology and wetland cover. While absolute solute concentrations were generally lower at bedrock dominated high‐elevation catchments compared to till dominated lower elevation catchments, the rate of change of concentration was often greater for high elevation catchments. This study confirms continued, but non‐linear stream chemistry recovery from acidification, particularly at the less buffered high and moderate elevation sites. The heterogeneity of responses among catchments highlights our incomplete understanding of the relative importance of different mechanisms influencing stream chemistry and the consequences for downstream ecosystems. [ABSTRACT FROM AUTHOR]

Wood ash amendment to forest soils contributes to the sustainability of the growing bioenergy industry, not only through decreased wood ash waste disposal in landfills but also by increasing soil/site productivity and tree growth. However, tree growth studies to date have reported variable responses to wood ash, highlighting the need to identify proper application rates under various soil/site conditions to maximize their benefits. We explored the influence of tree species, wood ash nutrient application rates, time since application, stand development stage, and initial (i.e., before wood ash application) soil pH and N on short‐term tree growth response to wood ash amendment across eight unique study sites spanning five Canadian Provinces. Jack pine (Pinus banksiana Lamb) had the most positive response to wood ash amendment compared to white (Picea glauca Moench), hybrid (Picea engelmannii x glauca Parry), and black spruce (Picea mariana Miller), where increasing nutrient application rates increased height growth response. In comparison, black spruce had the most negative response to wood ash amendment, where increasing nutrient application rates slightly decreased height growth response. Site as a random effect explained additional variation, highlighting the importance of other unidentified site characteristics. By examining trends in short‐term growth response across multiple studies with variable site characteristics, we found growth response differed by tree species and nutrient application rates, and that jack pine is a promising candidate for wood ash amendment. These results contribute to our knowledge of optimal wood ash amendment practices and environmentally sustainable bioenergy production. [ABSTRACT FROM AUTHOR]

Forest harvesting often increases catchment quickflow (QF, water delivered rapidly to the stream channel), a metric of high‐flow events controlling a catchment's solute and sediment export. Nevertheless, our understanding of QF responses to various silvicultural strategies (e.g., clearcutting, selection harvest, and shelterwood harvest) is incomplete. We present a 31‐year examination of QF delivery from treatment (clearcut, selection harvest, and shelterwood harvest) and control catchments in a deciduous forest landscape in central Ontario, Canada. Growing season root‐zone storage capacity was estimated using a water balance approach to evaluate temporal changes in QF response to precipitation (P) for pretreatment and posttreatment periods. Threshold relationships between QF and P were assessed for control and treatment catchments for pretreatment and posttreatment periods using piecewise regression. Root‐zone storage capacity demarcated shifts in the hydrologic regime arising from forest harvesting and subsequent regeneration. This was particularly pronounced for clearcutting where postharvest decline in root‐zone storage capacity was followed by a rise to preharvest values. Similar pretreatment threshold relationships between QF and P, and near‐identical P thresholds for producing significant QF, reflected similar soil and overburden depths in the catchments. Harvesting effects were indicated by increases in QF/P ratios for relative small P and the number of P events that generated QF, thus changing treatment QF vs. P threshold relationships. Prior to harvesting there was no significant increase in QF with P below a threshold P of 35–45 mm; however, there was a significant QF vs. P relationship below this threshold for all treatments postharvest. Clearcutting increased the number of QF events for the entire postharvest period and the first 9‐year postharvest compared to the other treatments; nevertheless, evidence for intertreatment differences in total QF depth delivered from the catchments during the growing season was inconclusive. Our work suggests that changes in threshold relationships between QF and P, coupled with knowledge of the physical processes underlying them, are useful when evaluating hydrologic responses to forest harvesting. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Forest Research is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Emerald ash borer (EAB) is an alien invasive species that is spreading across Canada and the United States killing ash trees. In riparian forests where ash may be abundant; loss of ash can induce significant structural changes; including the creation of canopy gaps; changes in light penetration; expansion of ground vegetation; and alteration of soil nitrogen and carbon cycling. In 2014 and 2015, we examined the effects of EAB-caused gaps in riparian forests on soil nutrient dynamics. Two sites with different infestation timelines, a "new" site (mortality in past 2–3 years) and an "old" site (infested 10 years previous) were selected to determine temporal differences in effects of canopy gaps created by ash loss on litterfall, herbaceous ground vegetation, and soil nutrient cycling. Within both sites, plots with clustered dead ash (canopy gap plots—CG) were paired with nearby plots of full canopy and no ash (canopy closed plots—CC), and differences between paired plots determined. Total litterfall was observed at all sites but was only significant at the new infestation site. Reductions in leaf litter deposition in CG plots resulted in reduced N and C flux to the forest floor but soil C and N concentrations, and nitrogen mineralization rates, were not significantly different between CG and CC plots. Nitrate concentration in soil solution was significantly greater in CG plots compared to CC plots at the new infestation sites but showed the opposite trend at the old infestation sites. Herbaceous ground vegetation biomass was significantly greater (up to 10×) in CG plots than in CC plots. Overall, despite changes to riparian forest canopy structure and litterfall, there was no significant difference in soil nutrient cycling between EAB-induced canopy gaps and closed canopy plots after 10 years, suggesting a high resilience of riparian forest soils to EAB infestation [ABSTRACT FROM AUTHOR]