The influence of landscape‐level heterogeneity in fire frequency on canopy composition in the boreal forest of eastern Canada

Abstract

AbstractQuestionWill a three‐fold variation in fire frequency among large patches (≈105–106 ha) of boreal forest generate differences in canopy composition and, more specifically, will it influence the relative abundance of species with regard to their typical position along the succession gradient.LocationA landscape of 1.6 Mha in the boreal forest of eastern Canada (Quebec).MethodsWe sampled 160 circular plots in closed‐canopy forest in which we measured canopy vegetation composition, local fire history (time since last fire) and edaphic conditions. We conducted multivariate analyses (NMDS, multi‐response permutation procedure) and pair‐wise comparisons to probe differences in canopy composition between areas of contrasting fire frequency before and after controlling for the influence of local environmental factors.ResultsThere are significant differences between areas of contrasting fire frequency in terms of relative species abundance, even after analytically removing the effect of important local environmental factors. In old stands,Picea marianais significantly more abundant in high fire frequency areas whileAbies balsameais significantly more abundant in low fire frequency areas, both before and after controlling for local environmental factors, including time since last fire. Young stands do not differ in terms of individual species relative abundance but show more variability among stands in low fire frequency areas.Main conclusionThe low fire frequency areas allow late‐successional specialistA. balsameato dominate over ubiquitous successional generalistP. marianabecause of the typically longer time elapsed since the last fire. This suggests that succession fromP. marianatoA. balsameacan occur long after what is typically covered by dendroecologically reconstructed fire history in this type of boreal landscape (> 200–300 yr).