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Summary: High‐latitude ecosystems are warming faster than other biomes and are often dominated by a ground layer of Ericaceous shrubs, which can respond positively to warming. The carbon‐for‐nitrogen (C‐for‐N) exchange between Ericaceous shrubs and root‐associated fungi may underlie shrub responses to warming, but has been understudied.In a glasshouse setting, we examined the effects of warming on the C‐for‐N exchange between the Ericaceous shrub Empetrum nigrum ssp. hermaphroditum and its root‐associated fungi. We applied different 13C and 15N isotope labels, including a simple organic N form (glycine) and a complex organic N form (moss litter) and quantified their assimilation into soil, plant biomass, and root fungal biomass pools.We found that warming lowered the amount of 13C partitioned to root‐associated fungi per unit of glycine 15N assimilated by E. nigrum, but only in the short term. By contrast, warming increased the amount of 13C partitioned to root‐associated fungi per unit of moss 15N assimilated by E. nigrum.Our study suggests that climate warming affects the short‐term exchange of C and N between a widespread Ericaceous shrub and root‐associated fungi. Furthermore, while most isotope tracing studies use labile N sources, we demonstrate that a ubiquitous recalcitrant N source may produce contrasting results. [ABSTRACT FROM AUTHOR]

Fire is a major disturbance worldwide, and it produces significant amounts of wood-derived charcoal. There is increasing evidence that the key properties ('traits') of charcoal vary greatly, with consequences for ecosystem processes, but how the key factors drive variability of charcoal traits, i.e., species identity and charring conditions, remain poorly understood. Here, we experimentally produced charcoal from three common boreal tree species under six charring conditions representing those encountered during boreal fires and then analyzed their structural and chemical traits. Overall, we found that species identity affected charcoal traits more than did charring conditions. Among the structural traits, density and microporosity varied among tree species, and density decreased with increasing temperature. Among the chemical traits, electrical conductivity, total nitrogen (N) and phosphorus (P) contents, and phosphate concentration differed among species, whereas pH, total N content, and ammonium concentration responded to charring conditions. No traits except nitrate concentration responded to the interactive effect of species identity and charring condition. Our results reveal that traits of charcoal, and potentially its ecological functions, are driven by a combination of fire behavior and tree species identity; such information is relevant for understanding ecological consequences of altered fire regimes due to the changing climate and to forest management. Key words: boreal forest, black carbon, charcoal trait, fire, pyrogenic carbon, pyrolysis. Le feu est une perturbation majeure partout dans le monde et il produit d'importantes quantites de charbon de bois. Il est de plus en plus evident que les proprietes cles (trait) du charbon de bois varient enormement, ce qui a des consequences pour les processus ecosystemiques. Mais on comprend mal comment agissent les principaux facteurs qui determinent la variabilite des trait du charbon de bois, c.-a-d. l'espece d'arbre et les conditions de carbonisation. Dans le cadre de cette etude, nous avons produit du charbon de bois de facon experimentale en utilisant trois especes d'arbre communes en zone boreale et des conditions de carbonisation representatives de six situations rencontrees durant les feux en zone boreale. Nous avons ensuite analyse les trait structurelles et chimiques de ce charbon de bois. Globalement, nous avons trouve que l'espece avait plus d'effet sur les trait du charbon de bois que les conditions de carbonisation. Parmi les trait structurelles, la densite et la microporosite variaient selon l'espece d'arbre et la densite diminuait avec l'augmentation de la temperature. Parmi les trait chimiques, la conductivite electrique, la teneur en N total et P total ainsi que la concentration de phosphate variaient selon l'espece d'arbre tandis que le pH, la teneur en N total et la concentration d'ammonium dependaient des conditions de carbonisation. Aucune trait, a l'exception de la concentration de nitrate, ne reagissait a l'effet de l'interaction entre l'espece et les conditions de carbonisation. Nos resultats revelent que les trait du charbon de bois, et potentiellement ses fonctions ecologiques, sont determinees par une combinaison du comportement du feu et de l'espece d'arbre. Cette information est pertinente pour comprendre les consequences ecologiques de l'alteration des regimes de feu due au changement climatique et a l'amenagement forestier. [Traduit par la Redaction] Mots-cles: foret boreale, carbone noir, trait du charbon de bois, feu, carbone pyrogene, pyrolyse., Introduction Fire is a major natural disturbance that operates as an ecological driver in many ecosystems worldwide, including boreal forests (Bond-Lamberty et al. 2007). In much of the Fennoscandian boreal [...]

Elevational gradients are useful for predicting how plant communities respond to global warming, because communities at lower elevations experience warmer temperatures. Fine root traits and root trait variation could play an important role in determining plant community responses to warming in cold‐climate ecosystems where a large proportion of plant biomass is allocated belowground. Here, we investigated the effects of elevation‐associated temperature change on twelve chemical and morphological fine root traits of plant species and plant communities in a Swedish subarctic tundra. We also assessed the relative contributions of plant species turnover and intraspecific variation to the total amount of community‐level root trait variation explained by elevation. Several root traits, both at the species and whole community levels, had significant linear or quadratic relationships with elevation, but the direction and strength of these relationships varied among traits and plant species. Further, we found no support for a unidirectional change from more acquisitive root trait values at the lower elevations towards trait values associated with greater nutrient conservation at the higher elevations, either at the species or community level. On the other hand, root trait coefficients of variation at the community level increased with elevation for several root traits. Further, for a large proportion of the community‐level traits we found that intraspecific variation was relatively more important than species turnover, meaning that trait plasticity is important for driving community‐level trait responses to environmental factors in this tundra system. Our findings indicate that with progressing global warming, intraspecific trait variation may drive plant community composition but this may not necessarily lead to shifts in root resource–acquisition strategy for all species. [ABSTRACT FROM AUTHOR]