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Habitat fragmentation and structure and composition of tree populations in a agroforestry landscape (southern Québec, Canada)

Saint-Laurent, Diane, Berthelot, Jean-Sébastien, Gervais-Beaulac, Vernhar
Agroforestry systems 2018 v.92 no.6 pp. 1517-1534
agroforestry, animals, anthropogenic activities, correspondence analysis, cutting, drainage, floods, forest regeneration, growth curves, habitat fragmentation, landscapes, multivariate analysis, pH, riparian forests, risk, saplings, soil, soil quality, space and time, urban development, woodlands, woody plants, Quebec
A number of forests in agroforestry environments are at risk due to urban development or agricultural expansion. These forests often consist of patches of wooded areas scattered in the agricultural and urban grid, and often constitute green corridors that enable a flow between animal and plant species (migration corridors). This study evaluates the composition and structure of riparian forests in agroforestry areas that are subject to various natural and anthropogenic disturbances. This study aims to understand the dynamics of these riparian forest populations and evaluate the effects of the disturbances on the tree stands (e.g. floods, partial cutting), while taking into account their development over space and time based on a diachronic assessment from 1945 to 2010. Although these woodlands are subject to various disturbances, a fairly large diversity of tree species can be noted, and the regeneration of the saplings and small trees follows a normal growth curve (asymmetric) with a high contingency of young tree population comparable to a typical reverse-J distribution. However, lower densities are observed for riparian stands subject to frequent flooding, which could over time compromise recruitment and forest regeneration for some tree species (e.g. woody plants with weak adaptive strategies). The multivariate analyses (Redundancy Analysis and Canonical Correspondence Analysis) conducted over all the soil, environmental and forest data reveal that some variables are more strongly related to the composition of the forest populations, including pH, ground litter and soil drainage. However, these variables must still be considered as being part of a set of interacting soil conditions. Lastly, the future of these woodlands may appear uncertain because there are no government policies or measures to ensure their protection and preservation.