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An immunosuppressive microenvironment causes poor tumor T cell infiltration and is associated with reduced patient overall survival in colorectal cancer. How to improve treatment responses in these tumors is still a challenge. Using an integrated screening approach to identify cancer-specific vulnerabilities, we identified complement receptor C5aR1 as a druggable target, which when inhibited improved radiotherapy, even in tumors displaying immunosuppressive features and poor [CD8.sup.+] T cell infiltration. While C5aR1 is well-known for its role in the immune compartment, we found that C5aR1 is also robustly expressed on malignant epithelial cells, highlighting potential tumor cell-specific functions. C5aR1 targeting resulted in increased NF-[kappa]B-dependent apoptosis specifically in tumors and not normal tissues, indicating that, in malignant cells, C5aR1 primarily regulated cell fate. Collectively, these data revealed that increased complement gene expression is part of the stress response mounted by irradiated tumors and that targeting C5aR1 could improve radiotherapy, even in tumors displaying immunosuppressive features., Introduction The composition of the tumor microenvironment (TME) affects treatment responses in cancer (1-3). Immunosuppressive TME features, which act as a barrier to extensive [CD8.sup.+] T cell infiltration typically characterize [...]

Ecological forestry is based on the idea that forest patterns and processes are more likely to persist if harvest strategies produce stand structures, return intervals, and severities similar to those from natural disturbances. Taylor et al. (2020) reviewed forest natural disturbance regimes in Nova Scotia, Canada, to support implementation of ecological forestry. In this follow-up paper, we (i) review the use of natural disturbance regimes to determine target harvest rotations, age structures, and residual stand structures; and (ii) describe a novel approach for use of natural disturbance regimes in ecological forestry developed for Nova Scotia. Most examples of ecological forestry consider only the local, dominant disturbance agent, such as fire in boreal regions. Our approach included: (i) using current ecological land classification to map potential natural vegetation (PNV) community types; (ii) determining cumulative natural disturbance effects of all major disturbances, in our case fire, hurricanes, windstorm, and insect outbreaks for each PNV; and (iii) using natural disturbance regime parameters to derive guidelines for ecological forestry for each PNV. We analyzed disturbance occurrence and return intervals based on low, moderate, and high severity classes (60% of biomass of living trees killed, respectively), which were used to determine mean annual disturbance rates by severity class. Return intervals were used to infer target stand age-class distributions for high, moderate, and low severity disturbances for each PNV. The range of variation in rates of high severity disturbances among PNVs was from 0.28%*[year.sup.-1] in Tolerant Hardwood to 2.1%*[year.sup.-1] in the Highland Fir PNV, equating to return intervals of 357 years in Tolerant Hardwood to 48 years in Highland Fir PNVs. As an example, this return interval for the Tolerant Hardwood PNV resulted in target rotation lengths of 200 years for 35% of the PNV area, 500 years for 40%, and 1000 years for 25%. The proposed approach of determining natural disturbance regimes for PNV communities and calculating target disturbance rates and corresponding harvest rotation lengths or entry times appears to be a feasible method to guide ecological forestry in any region with a strong ecological land classification system and multiple disturbance agents. Key words: natural disturbance, ecological forestry, sustainability, potential natural vegetation, ecological land classification, landscape planning. La foresterie ecologique est fondee sur l'idee que les patrons et les processus forestiers ont davantage de chances de persister si les strategies de recolte produisent des structures de peuplements, des intervalles de retour et des niveaux de severite similaires a ceux des perturbations naturelles. Taylor et al. (2020) ont examine les regimes de perturbations naturelles des forets en Nouvelle-Ecosse, au Canada, afin d'appuyer la mise en ceuvre de la foresterie ecologique. Dans cet article de suivi, les auteurs (i) passent en revue l'utilisation des regimes de perturbations naturelles pour determiner les rotations cibles de recoltes, les structures d'age et les structures des peuplements residuels ; et (ii) decrivent une nouvelle approche d'utilisation des regimes de perturbations naturelles dans la foresterie ecologique developpee pour la Nouvelle-Ecosse. La plupart des exemples de foresterie ecologique ne tiennent compte que de l'agent de perturbation local et dominant, comme le feu dans les regions boreales. Leur approche comprenait (i) l'utilisation de la classification ecologique actuelle des terres pour cartographier les types de communautes de vegetation naturelle potentielle (VNP) ; (ii) la determination des effets cumulatifs des perturbations naturelles de toutes les perturbations majeures, dans leur cas le feu, les ouragans, les tempetes de vent et les epidemies d'insectes pour chaque VNP ; et (iii) l'utilisation des parametres du regime de perturbation naturelle pour deriver des lignes directrices pour la foresterie ecologique pour chaque VNP. Ils ont analyse la presence des perturbations et les intervalles de retour en fonction des classes de severite faible, moderee et elevee (60 % de la biomasse des arbres vivants tues), qui ont ete utilises pour determiner les taux de perturbation annuels moyens par classe de severite. Les intervalles de retour ont ete utilises pour deduire les distributions cibles des classes d' age des peuplements pour les perturbations de severite elevee, moderee et faible pour chaque VNP. La gamme de variation des taux de perturbations de severite elevee parmi les VNP etait de 0,28 %*annee (--1) dans la VNP des feuillus tolerants a 2,1 %*annee (--1) dans la VNP des sapins de moyenne montagne, ce qui correspond a des intervalles de retour de 357 ans dans la VNP des feuillus tolerants a 48 ans dans la VNP des sapins de moyenne montagne. a titre d'exemple, cet intervalle de retour pour la VNP de feuillus tolerants a donne lieu a des durees de rotation cibles de 200 ans pour 35 % de la superficie de la VNP, de 500 ans pour 40 % et de 1000 ans pour 25 %. L'approche proposee, qui consiste a determiner les regimes de perturbation naturelle pour les communautes de VNP et a calculer les taux de perturbation cibles et les durees de rotation de recolte ou les periodes d'entree correspondantes, semble etre une methode realisable pour guider la foresterie ecologique dans toute region dotee d'un solide systeme de classification ecologique des terres et de multiples agents de perturbation. Mots-cles : perturbation naturelle, foresterie ecologique, durabilite, vegetation naturelle potentielle, classification ecologique des terres, planification du paysage., 1. Introduction Ecological forestry (also known as 'ecosystem-based forestry') emphasizes the conservation of native biodiversity and ecological integrity (Christensen et al. 1996; Seymour and Hunter 1999). At the core of [...]

Dormant seeds that require long periods of cold stratification to become germinable may be most sensitive to increases in winter temperatures caused by anthropogenic climate change. In this study, we used outdoor plots with infrared heaters to simulate the effects of projected winter warming (+6 [degrees]C) for Canada's Acadian Forest Region and compared seed germination success of tree species with varying stratification requirements. We evaluated four seedlots each of balsam fir (Abies balsamea (L.) Mill.), red spruce (Picea rubens Sarg.), white pine (Pinus strobus L.), red maple (Acer rubrum L.), sugar maple (Acer saccharum Marshall), and yellow birch (Betula alleghaniensis Britton). Three central findings emerged from this study: (i) none of the tested species were significantly affected by warming; (ii) the random effect of seedlot explained more variation in germination success of deciduous species than it did for conifers; and (iii) balsam fir seedlots exhibited considerable differences in their response to warming, implying intraspecific variation in depth of dormancy. These results suggest seed germination success of the tested tree species may not be impeded by their individual seed characteristics under the magnitude of winter warming projected over the coming century in our study area. Key words: seed dormancy, climate change, winter warming, germination, stratification, Acadian Forest, balsam fir, sugar maple. Les graines dormantes qui ont besoin de longues periodes de stratification a froid pour germer pourraient etre tres sensibles a l'augmentation des temperatures hivernales causee par le changement climatique d'origine anthropique. Dans cette etude, nous avons eu recours a des parcelles echantillons situees a l'exterieur avec des radiateurs a infrarouge pour simuler les effets du rechauffement (+6 [degrees]C) hivernal anticipe dans la region de la foret acadienne au Canada et nous avons compare le taux de germination des graines d'especes d'arbres dont les exigences de stratification different. Nous avons evalue quatre lots de graines dans chaque cas pour le sapin baumier (Abies balsamea (L.) Mill.), l'epicea rouge (Picea rubens Sarg.), le pin blanc (Pinus strobus L.), l'erable rouge (Acer rubrum L.), l'erable a sucre (Acer saccharum Marshall) et le bouleau jaune (Betula alleghaniensis Britton). Trois principaux resultats decoulent de cette etude : (i) le rechauffement n'a eu aucun impact significatif peu importe l'espece testee; (ii) l'effet aleatoire des lots de graines explique plus de variation dans le taux de germination des especes decidues que dans celui des coniferes; et (iii) des differences considerables ont ete observees entre les lots de graines du sapin baumier en ce qui a trait a leur reaction face au rechauffement, ce qui implique qu'il existe une variation intraspecifique de la profondeur de la dormance. Ces resultats indiquent que l'ampleur du rechauffement hivernal anticipe au cours du siecle a venir dans la zone d'etude n'est peut-etre pas suffisante pour que les caracteristiques des graines des especes d'arbres testees aient un impact sur leur taux de germination. [Traduit par la Redaction] Mots-cles : dormance des graines, changement climatique, rechauffement hivernal, germination, stratification, foret acadienne, sapin baumier, erable a sucre., Introduction Evaluating the effects of climate change on forest stand regeneration is of increasing importance to forest managers and stakeholders. In particular, the role of winter warming on successful tree [...]

We compared three methods for estimating current-year spruce budworm (Choristoneura fumiferana (Clem.)) defoliation from 2014 to 2021 using a network of 99 permanent sample plots in central Gaspé Peninsula, Québec. Percent current-year defoliation was measured by assessing shoots from mid-crown branches, ocular ratings of all individual trees using binoculars, and provincial government aerial surveys. Ocular survey defoliation differed from branch sample defoliation in 5–6 out of 7 years, consistently underestimating defoliation, across the full range of defoliation severity observed. Nested mixed-effect models for fir–spruce combined, balsam fir, white spruce, and black spruce ocular survey defoliation bias resulted in marginal R2 of 0.40, 0.47, 0.82, and 0.86, respectively. Current defoliation severity and its interaction with previous year defoliation and weather conditions significantly affected ocular survey bias. Correspondence of aerial survey estimates and mean plot defoliation occurred in only 43% of all plot-years and ranged from 14%–58% in individual years. Differences between aerial survey defoliation and plot values mainly resulted from assigning an adjacent class (e.g., light <30% assigned as moderate 31%–70% defoliation) or misplaced defoliation polygon boundaries, suggesting that assignment of aerial survey defoliation to plots or specific ground areas needs ground truth sampling. [ABSTRACT FROM AUTHOR]

In this study, we conducted a controlled experiment to assess the growth and survival of balsam fir (Abies balsamea (L.) Mill.), red spruce (Picea rubens Sarg.), and red maple (Acer rubrum L.) seedlings in response to warming, drought, and elevated C[O.sub.2], as projected under RCP 8.5 for North America's Acadian Forest Region. In response to warming, only red spruce increased in height; however, this effect varied by C[O.sub.2] and soil moisture treatments. Under the drought treatment, red spruce biomass was not affected, but mortality increased by 2%. With warming, increases in balsam fir height growth were only detected under certain soil moisture and C[O.sub.2] conditions. Balsam fir biomass decreased by 24% under drought, while mortality increased by 5%. Warming did not improve red maple height growth, but it remained 7-50 times greater than that of the conifers and no mortality was observed. Overall, C[O.sub.2] enrichment increased height growth of draughted seedlings relative to the ambient treatment, demonstrating an amelioration of the negative drought effect. Balsam fir was the least adapted to warming and drought, while red spruce displayed some positive responses. Although growth of red maple seedlings did not increase with warming, they exhibited greater absolute growth and survival, which suggests red maple may outperform both conifers under a warming climate. Key words: plant-climate interactions, autecology, seedling, forest, climate change, drought, growth, photosynthesis. Cette etude traite d'une experience en conditions controlees que nous avons realisee pour evaluer la croissance et la survie de semis de sapin baumier (Abies balsamea (L.) Mill.), d'epicea rouge (Picea rubens Sarg.) et d'erable rouge (Acer rubrum L.) en reaction au rechauffement du climat, a la secheresse et a une concentration elevee de dioxyde de carbone (C[O.sub.2]), tel que le prevoit le scenario RCP 8.5 pour la region de la foret acadienne en Amerique du Nord. Seul l'epicea rouge avusa croissance augmenter en reaction au rechauffement du climat. Cependant, cet effet a varie selon les traitements de C[O.sub.2] et d'humidite du sol. Le traitement de secheresse n'a pas eu d'impact sur la biomasse de l'epicea rouge mais la mortalite a augmente de 2 %. Des augmentations de croissance en hauteur ont ete observees chez le sapin baumier en reaction au rechauffement du climat mais seulement lorsque certaines conditions d'humidite du sol et de concentration de C[O.sub.2] etaient presentes. La biomasse du sapin baumier a diminue de 24 % a cause de la secheresse tandis que la mortalite a augmente de 5 %. Le rechauffement du climat n'a pas ameliore la croissance en hauteur de l'erable rouge mais elle est demeuree 7 a 50 fois plus elevee que celle des coniferes et aucune mortalite n'a ete observee. Globalement, l'enrichissement en C[O.sub.2] a augmente la croissance en hauteur des semis soumis a la secheresse relativement aux conditions ambiantes, ce qui demontre une amelioration de l'effet negatif de la secheresse. Le sapin baumier etait le moins bien adapte au rechauffement du climat et a la secheresse, tandis que l'epicea rouge a montre certaines reactions positives. Bien que la croissance des semis d'erable rouge n'ait pas augmente avec le rechauffement du climat, leur croissance absolue et leur survie etaient plus elevees, ce qui indique que l'erable rouge pourrait performer mieux que les deux coniferes face au rechauffement du climat. [Traduit par la Redaction] Mots-cles: interaction entre la vegetation et le rechauffement du climat, autoecologie, semis, foret, changement climatique, secheresse, croissance, photosynthese., 1. Introduction The early life stages of plant species are the most sensitive to environmental stress and may greatly influence plant community assembly and succession under climate change (Johnstone et [...]

Mixedwood stands are composed of hardwoods and softwoods, with neither comprising greater than 75%-80% of basal area or aboveground biomass. By conferring associational resistance and greater resilience to forests when stressed or disturbed, the more diverse composition of mixedwood stands contributes to forest health. We analyzed three examples where mixedwood stands are more resistant to insect infestations in eastern North America. In balsam fir (Abies balsamea L. Mill.) and spruce (Picea spp.) forests, susceptibility and vulnerability to spruce budworm infestations is reduced with increasing hardwood density. In mid-Atlantic oak-dominated forests, oak mortality following gypsy moth infestations was much greater in oak-dominated forests than in oak-pine mixedwoods, while pine mortality during southern pine beetle infestations was greater in pine-dominated forests than in oak-pine mixedwoods. Overall, mixedwood stands have greater resistance to infestations of defoliators and bark beetles and recover more rapidly from disturbances, reducing economic losses associated with tree mortality and mitigating short-term impacts to ecosystem functioning resulting from insect damage, especially carbon sequestration. Finally, we discuss challenges and opportunities for mixedwood management to minimize insect damage. Management strategies that incorporate mixedwood stands may provide better continuity in supply of forest products and ecosystem services in the face of projected increases in insect infestations associated with changing climate. Key words: insect outbreaks, insect epidemics, associational resistance, silviculture, defoliation, tree mortality. Les peuplements mixtes sont composes de feuillus et de resineux, ni l'un ni l'autre ne pouvant constituer plus de 75-80% de la surface terriere ou de la biomasse aerienne. En conferant une resistance d'association et une plus grande resilience aux forets lorsqu'elles subissent un stress ou une perturbation, la composition plus diversifiee des peuplements mixtes contribuent a la sante de la foret. Nous avons analyse trois exemples ou des peuplements mixtes sont plus resistants aux infestations d'insectes dans l'est de l'Amerique du Nord. Dans les forets de sapin baumier (Abies balsamea L. Mill.) et d'epicea (Picea spp.), la sensibilite et la vulnerabilite aux infestations de la tordeuse des bourgeons de l'epinette diminuent avec l'augmentation de la densite des feuillus. Dans les forets du centre du littoral atlantique dominees par le chene, la mortalite du chene due aux infestations de la spongieuse etait beaucoup plus elevee dans les forets dominees par le chene que dans les forets mixtes de chene et de pin, tandis que la mortalite du pin lors des infestations du dendroctone meridional du pin etait plus elevee dans les forets dominees par le pin que dans les forets mixtes de chene et de pin. Dans l'ensemble, les peuplements mixtes ont une plus grande resistance aux infestations d'insectes defoliateurs et de scolytes et recuperent plus rapidement apres une perturbation, ce qui reduit les pertes economiques associees a la mortalite des arbres et attenue les impacts a court terme des dommages causes par les insectes sur le fonctionnement de l'ecosysteme et plus particulierement sur la sequestration du carbone. Finalement, nous abordons dans la discussion les defis et opportunites concernant l'amenagement de la foret mixte dans le but de minimiser les dommages causes par les insectes. Les strategies d'amenagement qui incluent les peuplements mixtes peuvent assurer une meilleure continuite de l'approvisionnement en produits forestiers et services de l'ecosysteme face a l'augmentation prevue des infestations d'insectes associees au changement climatique. Mots-cles: infestations d'insectes, epidemies d'insectes, resistance d'association, sylviculture, defoliation, mortalite des arbres., Introduction Forests composed of a diversity of tree species have a greater range of shade tolerances, growth rates, longevities, phenology, and crown and root structures than pure species stands (Kabrick [...]

As interest in managing and maintaining mixedwood forests in the northern United States (US) grows, so does the importance of understanding their abundance and distribution. We analyzed Forest Inventory and Analysis data for insights into mixedwood forests spanning 24 northern US states from Maine south to Maryland and westward to Kansas and North Dakota. Mixedwoods, i.e., forests with both hardwoods and softwoods present but neither exceeding 75%-80% of composition, comprise more than 19 million hectares and more than onequarter of the northern US forest. They are most common in the Adirondack--New England, Laurentian, and Northeast ecological provinces but also occur elsewhere in hardwood-dominated ecological provinces. These mixtures are common even within forest types nominally categorized as either hardwood or softwood. The most common hardwoods within those mixtures were species of Quercus and Acer, and the most common softwoods were species of Pinus, Tsuga, and Juniperas. Although mixedwoods exhibited stability in total area during our analysis period, hardwood saplings were prominent, suggesting widespread potential for eventual shifts to hardwood dominance in the absence of disturbances that favor regeneration of the softwood component. Our analyses suggest that while most mixedwood plots remained mixedwoods, harvesting commonly shifts mixedwoods to either hardwood- or softwood-dominated cover types, but more specific information is needed to understand the causes of these shifts. Key words: hardwood, softwood, deciduous, coniferous, Forest Inventory and Analysis (FIA). Au fur et a mesure qu'augmente l'interet pour l'amenagement et le maintien des forets mixtes dans le nord des Etats-Unis, la comprehension de leur abondance et de leur repartition devient de plus en plus importante. Dans le but d'obtenir de l'information, nous avons analyse les donnees du programme d'inventaire forestier et d'analyse portant sur les forets mixtes de 24 Etats du nord des Utats-Unis, a partir du Maine vers le sud jusqu'au Maryland et vers l'ouest jusqu'au Kansas et au Dakota du Nord. Les forets mixtes, c'est-a-dire les forets composees a la fois de feuillus et de resineux, dont la proportion n'excede pas 75 a 80% dans un cas comme dans l'autre, representent plus de 19 millions d'hectares, ce qui correspond a plus du quart des forets du nord des Etats-Unis. Elles sont plus frequentes dans les provinces ecologiques des Adirondacks en Nouvelle-Angleterre, Laurentienne et du Nord-Est, mais elles sont aussi presentes ailleurs dans les provinces ecologiques dominees par les feuillus. Les forets mixtes sont courantes meme dans les types forestiers categorises nominalement comme etant feuillus ou resineux. Les feuillus les plus courants dans ces forets sont des especes des genres Quercus et Acer alors que les resineux les plus courants sont des especes des genres Pinus, Tsuga et Juniperus. Bien que la superficie totale des forets mixtes soit demeuree stable au cours de notre periode d'analyse, les gaules de feuillus etaient predominantes, ce qui indique que la composition d'une forte proportion de ces forets pourrait tendre vers une dominance des feuillus s'il n'y a pas de perturbations favorisant la regeneration de la composante resineuse. Nos analyses indiquent que meme si la plupart des parcelles de forets mixtes sont demeurees des forets mixtes, la recolte de bois modifie generalement la composition des forets mixtes vers des types de couvert domines par des feuillus ou des resineux, mais la comprehension des causes de ces changements necessite de l'information plus specifique. Mots-cles: feuillus, resineux, especes decidues, coniferes, programme d'inventaire forestier et d'analyse (FIA)., Introduction Forests with both hardwoods and softwoods (i.e., generally broadleaf, deciduous, and needle-leaf, evergreen trees, respectively) present but neither exceeding 75%-80% of basal area, crown cover, or other metric are [...]

Defoliation level and site type are thought to influence tree response during spruce budworm (Choristoneura fumiferana (Clemens)) outbreaks. We determined the effects of four manual defoliation treatments (0%, 50%, 100%, and 100% + bud removal of current foliage) for 3 years on foliage production of balsam fir (Abies balsamea (L.) Mill.), black spruce (Picea mariana (Mill.) Britton, Sterns & Poggenb.), and white spruce (Picea glauca (Moench) Voss) trees on four site-quality classes. After 3 years of defoliation and 2 years of recovery, foliage biomass was reduced by 34%-98%. During defoliation, the number of shoots generally increased and shoot length of spruce generally decreased, especially on rich sites. During recovery, the number of shoots increased substantially, shoot length decreased, and bud destruction reduced the number of shoots by about 50% compared with that of trees that received the 100% defoliation treatment. Defoliation did not substantially affect needle length. Trees on rich sites had two- to fourfold greater foliage production than trees on poor sites. Effects of site and defoliation differed among species, but site quality, especially nutrition, played an important role in production of shoots and needles and the tree's ability to withstand defoliation. Black spruce had more limited ability to recover foliage biomass, only producing more shoots, whereas balsam fir and white spruce had stronger ability to recover needle and shoot length, respectively. Key words: Choristoneura fumiferana, manual defoliation, foliage biomass. On croit que l'intensite de la defoliation et le type de station influencent la reaction des arbres lors des epidemies de tordeuse des bourgeons de l'epinette (Choristoneurafumiferana (Clemens)). Nous avons determine les effets de quatre traitements de defoliation manuelle (0, 50,100% et 100% + destruction des bourgeons du feuillage de l'annee en cours) pendant trois ans sur la production de feuillage chez des tiges de sapin baumier (Abies balsamea (L.) Mill.), d'epinette noire (Picea mariana (Mill.) Britton, Sterns & Poggenb.) et d'epinette blanche (Picea glauca (Moench) Voss) sur des stations de quatre classes de qualite. Apres trois annees de defoliation et deux annees de recuperation, la biomasse du feuillage a ete reduite de 34 a 98%. Durant la periode de defoliation, le nombre de pousses a generalement augmente et la longueur des pousses de l'epinette a generalement diminue, particulierement sur les stations riches. Durant la periode de recuperation, le nombre de pousses a augmente de facon importante, la longueur des pousses a diminue et la destruction des bourgeons a reduit d'environ 50% le nombre de pousses comparativement au traitement de defoliation a 100%. La defoliation n'a pas eu d'impact important sur la longueur des aiguilles. Les arbres situes sur les stations riches ont produit deux a quatre fois plus de feuillage que sur les stations pauvres. Les effets de la station et de la defoliation differaient selon l'espece mais la qualite de la station, particulierement la nutrition, jouait un role important dans la production de pousses et d'aiguilles et la capacite des arbres a supporter la defoliation. L'epinette noire avait une capacite plus limitee de recuperer la biomasse foliaire; elle produisait seulement plus de pousses tandis que le sapin baumier et l'epinette blanche avaient respectivement une plus grande capacite de recuperer les aiguilles et la longueur des pousses. [Traduit par la Redaction] Mots-cles: Choristoneura fumiferana, defoliation manuelle, biomasse foliaire., 1. Introduction During spruce budworm (Choristoneura fumiferana (Clemens)) outbreaks, larvae repeatedly consume current-year foliage of balsam fir (Abies balsamea (L.) Mill.) and species of spruce (Picea A. Dietr.), leading to [...]

Balsam fir (Abies balsamea (L.) Mill.) is projected to decline in the Acadian Forest Region under climate change. We hypothesized that along a 700 km latitudinal gradient with increasing mean annual temperature from New Brunswick to Nova Scotia, Canada, balsam fir regeneration density and growth rates would (1) decline with warming and (2) decline more in immature than in mature stands due to greater exposure to adverse climate conditions. Regeneration density, height growth, and lateral branch growth were measured in 30 mature and 28 immature plots and related to climate and stand variables using generalized additive models. Balsam fir regeneration density was negatively affected by increased mean annual temperature and increased with summer precipitation, supporting our first hypothesis, but varied by height class. Canopy cover significantly affected seedling density, but its effect varied by substrate type (coniferous litter and dry moss litter), with seedling density being greatest under low canopy cover for large seedlings and greatest at intermediate canopy cover for small seedlings. Seedling growth rates were determined by height class, canopy cover, precipitation, and coniferous litter cover. Stand maturity did not significantly affect fir regeneration density or growth rates. Our results indicate that over time, increasing mean annual temperature may reduce balsam fir regeneration density within the Acadian Forest Region, while the marginal summer precipitation increases may lead to small gains in growth. [ABSTRACT FROM AUTHOR]

The purpose of the present study was to utilize the microdialysis technique in rat skeletal muscle to perfuse varying concentrations of AMP, ADP, and ATP into the interstitium to examine the effects that these adenine nucleotides have on the production of adenosine in the interstitial space. Interstitial adenosine production appears to be related to the type (ATP, ADP, or AMP) and concentration (2-60 [micro]mol/L) of the adenine nucleotide perfused. Interstitial adenosine levels increased (P < 0.05) from baseline (0.18 [+ or -] 0.02 and 0.22 [+ or -] 0.02 [micro]mol/L) to 0.23 [+ or -] 0.02 and 0.41 [+ or -] 0.05 [micro]mol/L following 5 and 30 [micro]mol/L AMP perfusion, respectively. Similarly, perfusion with 30 [micro]mol/L ADP and 30, 40, and 60 [micro]mol/L ATP resulted in an increase (P < 0.05) in interstitial adenosine concentration from baseline (0.25 [+ or -]0.02,0.26 [+ or -] 0.02,0.19 [+ or -]0.03, and 0.14 [+ or -] 0.02 [micro]mol/L) to 0.30 [+ or -]0.02, 0.32 [+ or -] 0.02, 0.36 [+ or -] 0.04, and 0.33 [+ or -] 0.04 [micro]mol/L, respectively. Interestingly, the most prominent increase in interstitial adenosine production occurred during the perfusion of 60 [micro]mol/L ATP (126% increase from baseline). These data strongly suggest that interstitial ATP may play a more potent role in stimulating interstitial adenosine production as compared with ADP or AMP. In addition, interstitial adenosine production can occur independent of muscle contraction (voluntary or involuntary) or hypoxia when adequate concentrations of adenine nucleotides are available. Key words: ATP, ADP, AMP, microdialysis, dialysate. La presente etude avait pour but d'utiliser la technique de microdialyse dans le muscle squelettique de rat pour perfuser diverses concentrations d'AMP, d'ADP et d'ATP a l'interieur de l'espace interstitiel en vue d'examiner les effets de ces nucleotides d'adenine sur la production d'adenosine interstitielle. La production d'adenosine interstitielle semble etre liee au type (ATP, ADP et AMP) et a la concentration de nucleotides d'adenine perfuses (de 2 a 60 [micro]mol/L). Les taux d'adenosine interstitielle de depart augmentaient (P < 0,05) de 0,18 [+ or -] 0,02 a 0,23 [+ or -]0,02 et de 0,22 [+ or -] 0,02 a 0,41 [+ or -] 0,05 [micro]mol/Lavec les perfusions d'AMP a 5 et a 30 [micro]mol/L, respectivement. De la meme maniere, la perfusion d'ADP a 30 [micro]mol/L et d'ATP a 30, 40 et 60 [micro]mol/L entrainait une augmentation (P < 0,05) des concentrations d'adenosine interstitielle de depart (0,25 [+ or -] 0,02, de 0,26 [+ or -] 0,02, de 0,19 [+ or -] 0,03 et de 0,14 [+ or -] 0,02 [micro]mol/L) a 0,30 [+ or -] 0,02,0,32 [+ or -] 0,02,0,36 [+ or -] 0,04 et 0,33 [+ or -] 0,04 [micro]mol/L, respectivement. Il est interessant de noter que l'augmentation de la production d'adenosine interstitielle la plus importante est survenue pendant la perfusion d'ATP a 60 [micro]mol/L (augmentation de 126% depuis le depart). Ces donnees laissent clairement entendre que l'ATP pourrait jouer un role de stimulation de la production d'adenosine interstitielle plus important que ceux de l'ADP ou de l'AMP. De plus, la production d'adenosine interstitielle peut survenir independamment de la contraction musculaire (volontaire ou involontaire) ou de l'hypoxie quand des concentrations adequates de nucleotides d'adenine sont accessibles. [Traduit par la Redaction] Mots-cles: ATP, ADP, AMP, microdialyse, dialysate., Introduction Adenosine and the adenine nucleotides ATP, ADP, and AMP are important mediators of several physiological responses including neurotransmission and metabolic homeostasis, and play a key vasodilatory role in the [...]

Defoliation reduces the growth and survival of trees, but this influence can be difficult to evaluate largely because of its interplay with various stand and site factors, especially for the highly dynamic defoliation of spruce-fir (Picea-Abies) forests caused by spruce budworm (SBW; Choristoneurafumiferana (Clem.)), the primary tree defoliator in North America. In this study, we developed statistical models to evaluate the influence of SBW defoliation, while considering its interaction with various stand and site factors, on spruce-fir stand dynamics of annual volume net growth, mortality, and ingrowth. The data were collected at intervals of 1 to 3 years from 560 permanent sample plots during the last SBW outbreak (1970s-1980s) in Maine, USA, and New Brunswick, Canada. These data comprise a wide range of observations of cumulative defoliation, especially at relatively low levels, that have been largely overlooked in previous studies. Our results strongly demonstrated that even relatively low levels of cumulative defoliation were significantly related to stand-level mortality and ingrowth, while net growth was more competition driven. Additionally, these stand dynamics were found to be not significantly affected by any of the site factors evaluated. These findings were consistent for Maine and New Brunswick despite their differences in forest management and SBW outbreak histories. Key words: growth, mortality, ingrowth, spruce budworm, defoliation. La defoliation reduit la croissance et la survie des arbres, mais son impact peut etre difficile a evaluer largement a cause de son interaction avec differents facteurs associes au peuplement et a la station, particulierement dans le cas de la defoliation hautement dynamique des forets d'epinettes et de sapins (Picea et Abies) causee par la tordeuse des bourgeons de l'epinette (TBE; Choristoneurafumiferana(Clem.)), le principal defoliateur des arbres enAmerique duNord. Dans cette etude, nous avons developpe des modeles statistiques pour evaluer l'influence de la defoliation causee par la TBE, tout en tenant compte de son interaction avec differents facteurs associes au peuplement et a la station sur la dynamique de la croissance annuelle nette en volume, de la mortalite et du recrutement dans les peuplements d'epinettes et de sapins. Les donnees ont ete recoltees a des intervalles de 1 a 3 ans dans 560 places echantillons permanentes durant la derniere epidemie de la TBE (annees 1970 a 1980) dans le Maine, aux Etats-Unis, et au Nouveau-Brunswick, au Canada. Ces donnees comprenaient une vaste gamme d'observations de la defoliation cumulative, particulierement a de relativement faibles intensites, en grande partie ignorees dans les etudes precedentes. Nos resultats demontrent de facon convaincante que la defoliation cumulative, meme a des intensites relativement faibles, etait significativement reliee a la mortalite et au recrutement a l'echelle du peuplement tandis que la croissance nette etait davantage determinee par la competition. De plus, cette dynamique du peuplement n'etait significativement influencee par aucun des facteurs associes a la station parmi ceux que nous avons evalues. Ces resultats etaient constants pour le Maine et le NouveauBrunswick malgre leurs differences quant a l'amenagement forestier et a l'historique des epidemies de la TBE. [Traduit par la Redaction] Mots-cles: croissance, mortalite, recrutement, tordeuse des bourgeons de l'epinette, defoliation., 1. Introduction Loss of photosynthetic material through insect defoliation results in reduced growth and survival of trees and is one of the most important natural disturbances influencing forests (e.g., Kulman [...]

Measures of forest productivity generally rely on site index, which can be problematic for multicohort and mixed-species stands. Using stand growth and dominant tree height-age (i.e., site tree) measurements from ~10 900 plot locations from Maine, Nova Scotia, New Brunswick, and Prince Edward Island, a forest productivity model for the Acadian Forest Region was developed as a function of climate, lithology, soils, and topographic metrics. Approximately 65% of variation in observed aboveground dry-biomass growth rate (BG) was explained by a Chapman-Richards function of temperature, bedrock, soil root space, slope, and depth to water in combination with stand structure and species predictors. Productivity was then defined in terms of the predicted asymptote of BG, holding structure and species constant, which was termed biomass growth index (BGI), i.e., the site-influenced component of the BG relationship. BGI was mapped on a 20 m grid throughout the region. BGI explained 0%-30% of the variability in spruce (Picea sp.) and balsam fir (Abies balsamea (L.) Mill.) site index and had similar site index predictive performance (± 5%) when compared with existing land productivity classifications in each province. BGI provides a direct relationship between site variables and growth and can help guide forest management decisions and future research. Key words: productivity, mixed species, site index, Acadian Forest Region, biomass growth. Les mesures de productivite forestiere reposent generalement sur l'indice de qualite de station, ce qui peut etre complique dans le cas des peuplements comportant plusieurs cohortes ou especes d'arbres. A l'aide de mesures de croissance des peuplements et de la relation entre la hauteur et l'age de l'arbre dominant (c.-a-d. l'arbre de la station) prises dans 10 900 placettes du Maine, de la Nouvelle-Ecosse, du Nouveau-Brunswick et de l'ile-du-Prince -Edouard, un modele de productivite forestiere a ete mis au point pour la region forestiere acadienne en fonction de mesures portant sur le climat, la lithologie, les sols et la topographie. Environ 65 % de la variation observee du taux de croissance en biomasse seche aerienne (CB) etait explique par une fonction de Chapman-Richards prenant en compte la temperature, la roche mere, l'espace racinaire du sol, la pente et la profondeur de la nappe phreatique en combinaison avec des variables associees a la structure des peuplements et aux especes. La productivite a ensuite ete definie en termes d'asymptote predite de la CB, de la structure permanente et de la constante par espece pour former l'indice de croissance en biomasse (ICB). Cet indice correspond a la composante de la relation de la CB qui est influencee par la station. L'ICB a ete cartographie a une resolution de 20 m pour l'ensemble de la region. L'ICB expliquait de 0 a 30 % de la variation de l'indice de qualite de station pour les epinettes (Picea sp.) et le sapin baumier (Abies balsamea (L.) Mill.), et sa capacite predictive de l'indice de qualite de station etait similaire (± 5 %) a celle des classifications de productivite territoriale disponibles dans chaque province. L'ICB fournit une relation directe entre les variables de la station et la croissance, et peut aider a orienter les decisions d'amenagement forestier et les futures pistes de recherche. [Traduit par la Redaction] Mots-cles: productivite, especes mixtes, indice de qualite de station, region forestiere acadienne, croissance en biomasse., Introduction Determining site productivity is an important yet difficult issue for forest management and planning (e.g., Carmean 1975; Skovsgaard and Vanclay 2008, 2013). A variety of direct and indirect, as [...]

Effects of commercial thinning on downed coarse woody debris (CWD) and standing dead trees (snags) were examined in six intensively managed 22--to 30-year-old white spruce (Picea glauca (Moench) Voss) plantations in northern New Brunswick, Canada. Four alternative treatments were applied: (i) an unthinned control and three commercial thinning 40% basal area removals, with (ii) slash and tops remaining on the site (status quo), (iii) most of the branches and tops extracted from the site (biomass removal), and (iv) clumps of unthinned trees left, with one-half of the trees in each clump girdled to create snags (enhanced structure). Three years after thinning, CWD volume increased by 14%-27% in the status quo and enhanced structure treatments, by 6% in the biomass removal treatment, and by 0.1% in the unthinned treatment. Mean snag volume changed little, i.e., less than 1 [m.sup.3] x [ha.sup.-1] among treatments, and stumps of thinned trees were 4.6-4.9 [m.sup.3] x [ha.sup.-1]. The girdled trees added 0.7 [m.sup.3] x [ha.sup.-1] of snags, and 1.3 [m.sup.3] x [ha.sup.-1] is expected to be added from girdling the remaining live trees in the unthinned clumps in 2016. The girdled trees and future to-be-girdled trees added up to 50% of the new deadwood in the enhanced structure treatments, but thinning treatments did not significantly affect total deadwood. The results indicate that commercial thinning produced fine debris but had little effect on overall deadwood amount. Girdling trees during commercial thinning, at the intensity used in this study, is unlikely to produce sufficient snags. Leaving islands and clumps during harvest before plantation establishment would be a more effective way of adding structure. Key words: Picea glauca, plantations, commercial thinning, deadwood, coarse woody debris, snags, girdling trees. Les effets de l'eclaircie commerciale sur les debris ligneux grossiers au sol et les arbres morts sur pied (chicots) ont ete examines dans six plantations d'epicea blanc (Picea glauca (Moench) Voss) agees de 22 a 30 ans et sous amenagement intensif dans le nord du Nouveau-Brunswick, au Canada. Quatre traitements differents ont ete appliques: (i) temoin non eclairci et trois traitements comportant une eclaircie commerciale oU 40% de la surface terriere etait preleve et (ii) les residus et les cimes etaient laisses surplace (statu quo), (iii) la plupart des branches et des cimes etaient retirees du site (retrait de la biomasse) et (iv) la moitie des tiges etaient annelees dans des bouquets d'arbres non eclaircis (structure amelioree). Trois ans apres l'eclaircie, le volume de DLG avait augmente de 14% a 27% avec le statu quo et le traitement qui ameliorait la structure, de 6% avec le retrait de la biomasse, versus 0,1% dans le temoin. Le volume moyen des chicots a peu change parmi les traitements, moins de 1 [m.sup.3] x [ha.sup.-1], et les souches des arbres eclaircis representaient 4,6 a 4,9 [m.sup.3] x [ha.sup.-1]. Les arbres anneles ont ajoute 0,7 [m.sup.3] x [ha.sup.-1]de chicots et un volume de 1,3 [m.sup.3] x [ha.sup.-1] devrait s'ajouter lorsque les arbres vivants restants dans les bouquets d'arbres non eclaircis seront anneles en 2016. Les arbres anneles et ceux qui doivent l'etre plus tard representaient jusqu'a 50% du nouveau bois mort dans le traitement qui ameliorait la structure, mais les traitements avec eclaircie n'ont pas influence de facon significative le bois mort total. Les resultats indiquent que l'eclaircie commerciale a produit des debris fins mais a eu peu d'effet sur la quantite globale de bois mort. Il est peu probable que l'annelation des arbres lors d'une eclaircie commerciale, avec l'intensite adoptee dans cette etude, produise suffisamment de chicots. Une facon plus efficace d'ameliorer la structure consisterait a laisser des ilots et des bouquets d'arbres lors de la recolte avant l'etablissement des plantations. [Traduit par la Redaction] Mots-cles: Picea glauca, plantations, eclaircie commerciale, bois mort, debris ligneux grossiers, chicots, annelation des arbres., Introduction Downed deadwood, referred to here as coarse woody debris (CWD), and snags (standing dead trees) play important roles in the functioning of forest ecosystems. Deadwood contributes to physical and [...]