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Observations of the rapid growth and slow decomposition of American chestnut (Castanea dentata (Marsh.) Borkh.) suggest that its reintroduction could enhance terrestrial carbon (C) sequestration. A suite of decomposition models was fit with decomposition data from coarse woody debris (CWD) sampled in Wisconsin and Virginia, U.S. The optimal (two-component exponential) model was integrated with generic growth curves and documented longevity and typical stem density to evaluate how CWD and biomass pools relate to decomposition. CWD decomposed faster in Wisconsin (4.3% ± 0.3% per year) than in Virginia (0.7% ± 0.01% per year), and downed dead wood decomposed faster (8.1% ± 1.9% per year) than standing dead wood (0.7% ± 0.0% per year). We predicted considerably smaller CWD pools in Wisconsin (maximum 41 ± 23 Mg C x [ha.sup.-1]) than in Virginia (maximum 98 ± 23 Mg C x [ha.sup.-1]); the predicted biomass pool was larger in the faster growing Wisconsin trees (maximum 542 ± 58 Mg C x [ha.sup.-1]) compared with slower growing trees in Virginia (maximum 385 ± 51 Mg C x [ha.sup.-1]). Sensitivity analysis indicated that accurate estimates of decomposition rates are more urgent in fertile locations where growth and decomposition are rapid. We conclude that the American chestnut wood is intermediate in resistance to decomposition. Due to the interrelatedness of growth and decomposition rates, CWD pool sizes likely do not depend on species alone but on how the growth and decomposition of individual species vary in response to site productivity. Key words: American chestnut, coarse woody debris, decomposition, carbon cycling, carbon sequestration, forest carbon simulations, forest growth, modeling, plantation development. Les observations ayant trait a la croissance rapide et a la decomposition lente du chataignier d'Amerique (Castanea dentata (Marsh.) Borkh.) indiquent que sa reintroduction pourrait accroitre la sequestration terrestre du carbone. Une serie de modeles de decomposition ont ete ajustes aux donnees de decomposition de debris ligneux grossiers (DLG) echantillonnes au Wisconsin et en Virginie, aux Etats-Unis. Le modele optimal (exponentiel a deux composantes), des courbes generiques de croissance, la longevite documentee et la densite typique de la tige ont ete integres pour evaluer comment les DLG et les reservoirs de biomasse sont relies a la decomposition. Les DLG se decomposaient plus rapidement au Wisconsin (4,3 ± 0,3 % x [an.sup.-1]) qu'en Virginie (0,7 ± 0,01 % x [an.sup.-1]) et les debris au sol se decomposaient plus rapidement (8,1 ± 1,9 % x [an.sup.-1]) que les debris sur pied (0,7 ± 0,0 % x [an.sup.-1]). Nous avons predit que les reservoirs de DLG seraient considerablement plus petits au Wisconsin (maximum de 41 ± 23 Mg C x [ha.sup.-1]) qu'en Virginie (maximum de 98 ±23 Mg C x [ha.sup.-1]); nous avons aussi predit que le reservoir de biomasse serait plus gros chez les arbres du Wisconsin qui croissent plus vite (maximum de 542 ± 58 Mg C x [ha.sup.-1]) comparativement a ceux de la Virginie (maximum de 385 ± 51 Mg C x [ha.sup.-1]). Une analyse de sensibilite a indique qu'il etait plus urgent d'obtenir des estimations precises du taux de decomposition dans les endroits fertiles oU la croissance et la decomposition sont rapides. Nous arrivons a la conclusion que le bois du chataignier d'Amerique a une resistance intermediaire a la decomposition. Etant donne l'interdependance des taux de croissance et de decomposition, la taille des reservoirs de DLG ne depend probablement pas seulement de l'espece mais de la facon dont la croissance et la decomposition de chaque espece varie en reponse a la productivite de la station. [Traduit par la Redaction] Mots-cles: chataignier d'Amerique, debris ligneux grossiers, decomposition, recyclage du carbone, sequestration du carbone, simulations du carbone forestier, croissance forestiere, modelisation, developpement des plantations., Introduction Forested ecosystems sequester atmospheric CO2 in living biomass, dead wood, leaf litter and other detritus, and soil carbon (C). Once disturbances are controlled for, the magnitude of C fluxes, [...]

: Extensive outbreaks of the mountain pine beetle (Dendroctonus ponderosae Hopkins) will alter the structure of many stands that will likely be attacked again before experiencing a stand-replacing fire. We examined a stand of lodgepole pine (Pinus contorta var. latifolia Engelm. ex S. Watson) in Grand Teton National Park currently experiencing a moderate-level outbreak and previously attacked by mountain pine beetle in the 1960s. Consistent with published studies, tree diame-ter was the main predictor of beetle attack on a given tree, large trees were preferentially attacked, and tree vigor, age, and cone production were unimportant variables for beetle attack at epidemic levels. Small trees killed in the stand were killed based mainly on their proximity to large trees and were likely spatially aggregated with large trees as a result of the previous outbreak. We concluded that the driving factors of beetle attack and their spatial patterns are consistent across outbreak severities but that stand structure altered by the previous outbreak had implications for the current outbreaks in the same location. This study should catalyze additional research that examines how beetle-altered stand structure affects future outbreaks-an important priority for predicting their impacts under climate change scenarios that project increases in out-break frequency and extent. Resume: De vastes epidemies du dendroctone du pin ponderosa (Dendroctonus ponderosae Hopkins) vont modifier la structure de plusieurs peuplements qui vont probablement etre attaques de nouveau avant d'etre detruits par un feu qui en-traine le remplacement du peuplement. Nous avons etudie un peuplement de pin pin tordu latifolie (Pinus contorta var. lati-folia Engelm. ex S. Watson) dans le parc national de Grand Teton qui subit presentement une epidemie moyennement severe et qui a dejaete attaque par le dendroctone du pin ponderosa dans les annees 1960. Conformement aux etudes pu-bliees, le diametre des arbres etait le principal predicteur de l'attaque de l'insecte sur un arbre en particulier; l'insecte pre fere les gros arbres et la vigueur de l'arbre, son age et la production de cones ne sont pas des variables importantes en lien avec l'attaque de l'insecte lors d'une epidemie. Les petits arbres qui ont ete tues dans le peuplement l'ont ete surtout parce qu'ils etaient situes a proximite de gros arbres et ils etaient probablement regroupes avec de gros arbres a cause de l'epide-mie precedente. Nous arrivons a la conclusion queles facteurs qui sont a l'origine de l'attaque de l'insecte et leur repartition spatiale sont les memes pour differents niveaux de severite, mais que la structure du peuplement qui a ete modifiee par une epidemie precedente avait des consequences sur l'epidemie actuelle qui sevit au mee endroit. Cette etude devrait susciter d'autres travaux de recherche pour determiner comment la structure du peuplement qui est modifiee par l'insecte influence les epidemies futuresune importante priorite pour predire leurs impacts dans l'optique de scenarios de changement cli-matique qui prevoient une augmentation de a frequence et de l'etendue des epidemies. [Traduit par la Redaction], Introduction Insect outbreaks are pervasive and significant disturbance agents that are important in shaping the structure of coniferous forests in western North America (Nigh et al. 2008; Axelson et al. [...]

Many conifer forests experience stand-replacing wildfires, and these fires and subsequent recovery can change the amount of carbon released to the atmosphere because conifer forests contain large carbon stores. Stand-replacing [...]

The 1988 Yellowstone fires resulted in a complex mosaic within which post-fire lodgepole pine seedling densities varied by over five orders of magnitude. Investigators have speculated that such postfire mosaics of vegetation structure may persist until the next large disturbance, but the fate of the initial structural variability of postfire communities is currently poorly understood. We studied lodgepole pine (Pinus contorta var. latifolia Englem. ex Wats.) stands in Yellowstone National Park (Wyoming, USA) unburned by the 1988 fires to determine how variation in stand structure changes with increasing stand age. The coefficient of variation in stand density decreased from 231% in 12-yr-old stands to 91% in stands aged 50-100 yr, and to 37% for stands ages 200-250 yr. Substantial variability in age distributions both within and among age classes suggested that both gradual infilling of initially sparse stands and self-thinning of initially dense stands are important processes affecting variation in stand density. Variation in stand density was explained primarily by stand age (P < 0.0001) and by geographic location (P < 0.01). Field estimates and reconstructions of stand density trajectories suggest the importance of biotic processes and the contingent effects that produce initial patterns of stand density. Variation in stand density is substantially reduced 125 yr following fire and remains relatively unchanged beyond approximately 200 yr. These results suggest that large, infrequent fires impose a pattern of stand structural variability that may persist for centuries, but stand density likely converges within the fire-free interval in this landscape. Key words: convergence; fire; forest; landscape; lodgepole pine; self-thinning; stand density, stand dynamics, stand structure; subalpine forests; succession; Yellowstone National Park, Wyoming (USA).