Contrasting Effects of Flood Disturbance on Alluvial Soils and Riparian Tree Structure and Species Composition in Mixed Temperate Forests

Abstract

This study deals with the effects of flooding on alluvial soils and riparian forests in the basins and sub-basins of southern Québec (Canada). These riparian environments are sensitive to hydroclimatic variations, which may increase with current climate change, which is why it is important to analyse them. The study areas were divided by flood frequency based on government maps that show flood recurrence intervals of 0 to 20 years and 20 to 100 years. Woodlands located outside of the floodplains were also analysed for comparison to measure and better determine the effect of floods on soils and forest stands. Soil depletion is found in the frequent-flood zones (FFZ), which results in lower total organic carbon (mean values of 1.9%-3.7% in FFZ vs 3.2%-5.9% in no-flood zones [NFZ]) and total nitrogen (mean values of 0.1%-0.2% in FFZ vs 0.2%-0.3% NFZ). Field observations and measurements show that the aboveground biomass (plant litter) is reduced or absent from the active flood zones. The structure and composition of tree stands are relatively comparable from one zone to another, but a slightly lower rate of small (5-10 cm dbh [diameter at breast height]) and intermediate (10-15 cm dbh) trees can be noted in FFZ, and tree diversity (Shannon index) and species richness are also slightly lower. The mechanical action of water in trees during floods and the burial of seedlings through the accumulation of fine alluvial deposits could negatively impact forest regeneration in active floodplains.

Comparing the Hydrological Response of Forested Headwaters (Unregulated and Regulated with Check Dams) under Mediterranean Semi-Arid Conditions

“…In headwaters, where water and sediment flows can be activated, the direct effects of check dams can be better identified among the factors influencing the catchment evolution (e.g., agriculture activities, urbanization, mining), since these environments are little affected by anthropogenic activities [16]. Moreover, the influence of check dams goes beyond the local scale of the headwaters, allowing mitigation of the hydrological effects in valley areas, resulting in floods and debris flows [17][18][19]. These beneficial actions have made check dams one of the most common strategy to protect catchments in semi-arid environments in combination with reforestation works [12,[20][21][22].…”

“…It is well known how check dams impact catchment hydrology and morphology (for instance, by reducing channel profile slope, e.g., Zema et al [90], and favoring the growth of riparian vegetation, e.g., Bombino et al [11] and Zaimes et al [91]). These effects influence the flow regime by reducing the water velocity, which in turn modifies the travel time of water particles, and thus, affects the peak flow [19,92]. However, a deeper analysis highlights that the check dam action depends on structure functioning after construction [81].…”

Flooding drives tropical dry forest tree community assembly in Southeast Brazil

“…Floodplain ecosystems tend to be sensitive to climate change, due to their high degree of human occupation and climate dependence (Capon et al 2013, Stella et al 2019). Effects of hydroclimatic variations on soils and forest floodplains may increase with current climate change, which predictions for some areas include increased precipitation intensities that could increase flood hazards (González et al 2015, Saint‐Laurent et al 2019).…”

Assessing the hydrological effects of land-use changes on a catchment using the Markov chain and WetSpa models

“…The importance of vegetation processes in catchment hydrological systems is well documented too (e.g. (Wang et al 2013, Kavian et al 2017, Minea et al 2019, Saint-Laurent et al 2019. In this regard, the Markov chain model has been widely used to predict future land cover changes (Keshtkar and Voigt 2016, Hamad et al 2018, Gebremedhin 2019).…”