Effects of Hydrologic Connectivity and Species Differences on Riparian Poplar Growth (Rhône River, France)

Understanding how ecosystems will respond to the projected increase in drought conditions is a key factor in the larger debate on how to combat climate change. This is especially important for ecosystems intrinsically linked to the hydro system, such as riparian zones. We performed a dendrochronological analysis using the basal area increment of Populus alba and Populus nigra along the Rhône River in Brégnier-Cordon (France) to investigate how the two species respond to water stress. Samples were taken from sites of varying connectedness to the water table in order to simulate different drought conditions. Our goal was to understand if one of the species was more drought resistant, and therefore better adapted to survive declining groundwater levels. Results show that there is a significant correlation between annual growth and the species and site connectiveness to the water table. Not only was growth correlated to both variables separately, but there was significant correlation between growth and the interaction between the two. Our results indicate that the ecosystem structure regarding P. alba and P. nigra along this portion of the Rhône will change as drought conditions worsen as the species are affected significantly differently by water stress.