Water Relations of Obligate Riparian Plants as a Function of Streamflow Diversion on the Bishop Creek Watershed

2 Assistant Professor Department of Biological Sciences, University of NevadaLas Vegas, Las Vegas, Nev.; Staff Ecologist and Executive Director, respectively and Biological Sciences Center, Desert Research Institute, Reno, Nev.; and Research Fellow Ecosystem Dynamics Research Group, Research School of Biological Sciences, Australian National University, Canberra, Australia. Abstract: We investigated the water relations of obligate riparian plants on paired diverted and undiverted reaches on Bishop Creek, Eastern Sierra Nevada. Riparian plants on diverted reaches had reduced stomatal conductance and water potential compared to plants on undiverted reaches in a dry year, but not in a high runoff year. Juvenile plants on diverted reaches had reduced stomatal conductance and lower midday water potentials relative to surrounding mature trees, a trend that was not observed on undiverted reaches. Plants on diverted reaches possessed significantly smaller, thicker leaves and a reduced total leaf area relative to trees on streamside reaches. Reduced community leaf area and effective stomatal control of water loss may allow riparian corridors on diverted reaches to retain their canopies in low runoff years. However, a long term consequence of partial streamflow diversion may be selective mortalty of juvenile plants because of the elimination of floods and high flows.