A Comparison of the Composition and Diversity of Tree Populations along a Hydrological Gradient in Floodplains (Southern Québec, Canada)

Abstract

With the current climate changes, it is essential to understand the mechanisms that govern floods and flow regimes and their effects on the dynamics of riparian forests. The aim is to assess the effects of new hydrological conditions (increase in flood frequency) on forest stands subject to frequent floods. The sampling sites (total of 94 quadrats) are located in riverine woodlands, and the choice of location corresponds to the boundaries of the flood-risk zones established by official government maps. Our study shows that there are significant differences in the composition and diversity of forest communities following differences in the flood recurrence zones. In the active floodplains (i.e., recurrence interval of 0–20 years), the tree population stands are clearly distinguished from other intermediate flood zones (interval of 20–100 years). Differences are also noted in the structure of the communities, in particular in the frequent flood zones, which are characterized by a low renewal rate, low density and less-diversified forest stands. The frequent floods risk forest stand rejuvenation and creating decline as a result of increased tree mortality and the low renewal rate. With the expected increases in the number of flood events in the coming decades, there may be greater tree mortality and a gradual disappearance of the forest communities.