Plant-Water-Hydrology Relationships in Native Trees and Invasive Giant Reed (Arundo Donax) in a Southern California Floodplain
Alex Pivovaroff1
1 Department of Biology and Environmental Science at Whittier College
The Santa Clara River is one of the most dynamic river systems in southern California. This mixed-use watershed provides habitat for native plants and animals and water for human use such as farmland irrigation. However, invasive Arundo donax threatens this valuable ecosystem. Arundo grows in huge, monoculture stands that allegedly use more water than native flora, but does not provide acceptable habitat for native fauna. Our objective is to quantify the water use of Arundo as compared to native riparian trees across scales, and linking this with groundwater hydrology to understand if removing Arundo and restoring native vegetation on the Santa Clara River will result in water savings for the region. To do this, we are using leaf-level gas exchange, stand-level sap flow, continuous measurements of water potentials with stem psychrometers, functional traits, groundwater wells monitoring, and modelling. Preliminary results show that among native trees, water potentials show a distinct seasonal pattern, while stomatal conductance does not. For Arundo, leaf-level gas exchange reveals incredibly high water use efficiency. However, stand-level transpiration tells a different story. However, these findings support efforts to restore vegetation at the Santa Clara River.