Search Results (2)

A better understanding of the mechanisms influencing compositional changes in understory plant communities is crucial to protect temperate forests against global change stressors, including anthropogenic disturbances and invasion by exotic species. We assessed changes in species composition after a 14-year period in 20 rural temperate forest stands located in the northern hardwood biome of eastern Canada. We identified species that underwent the largest changes in relative occurrence during that period and assessed the influence of biotic and anthropogenic filters on the trajectory of those understory communities. We found small but significant compositional changes after 14 years, mostly related to a decrease in species diversity in the younger forest stands originating from abandoned pasture. The largest occurrence gains for understory species were observed in these stands, but also in stands with lower understory community diversity. Understory species occurrence losses could not be linked to any of the biotic and anthropogenic filters considered in this study presumably because they were difficult to isolate from secondary successional dynamics. Shade tolerant exotic species showed a small but significant increase in relative occurrence over 14 years, with notable gains in only a few stands. We observed generalized occurrence gains for sensitive spring geophytes during the same period throughout most sites. Overall, the understory vegetation community of rural temperate forests in this region was found to be relatively stable and seems to retain its potential for natural recovery after disturbance. Full article

Sugar maple (Acer saccharum) forests are among the main forest types of eastern North America. Sugar maple stands growing on Appalachian soils of the Lower St-Lawrence region are located at the northeastern limit of the northern hardwood forest zone. Given the biogeographical position of these forests at the edge of the boreal biome, we aimed to reconstruct the fire history and document the occurrence of temperate and boreal trees in sugar maple sites during the Holocene based on soil macrocharcoal analysis. Despite having experienced a different number of fire events, the fire history of the maple sites was broadly similar, with two main periods of fire activity, i.e., early- to mid-Holocene and late-Holocene. A long fire-free interval of at least 3500 years separated the two periods from the mid-Holocene to 2000 years ago. The maple sites differ with respect to fire frequency and synchronicity of the last millennia. According to the botanical composition of charcoal, forest vegetation remained relatively homogenous during the Holocene, except recently. Conifer and broadleaf species coexisted in mixed forests during the Holocene, in phase with fire events promoting the regeneration of boreal and temperate tree assemblages including balsam fir (Abies balsamea) and sugar maple. Full article