OVERLAND WATER FLOW CONTRIBUTES LITTLE TO SURVIVAL, GROWTH, REPRODUCTION, AND ECOPHYSIOLOGY OF OLNEYA TESOTA (DESERT IRONWOOD) TREES

摘要

We studied the responses of Desert Ironwood trees (Olneya tesota), located in desert washes of the Sonoran Desert in California, to a reduction in overland water flow. We hypothesized that trees with access to overland water runoff would have different morphological and ecophysiological responses than trees that did not. We studied responses including branch growth, water potentials, leaf carbon isotope ratios, leaf mass per area, flower production, seed production, and tree population densities. Only branch growth and predawn water potentials were found to be significantly different between treatments. Predawn water potentials indicated seasonally increased water stress in trees without access to overland water runoff. Trees with access to overland water runoff also responded with increased branch growth. The lack of differences between treatments observed for all other morphological and ecophysiological responses may indicate that environmental conditions, especially water availability, were similar in both treatments during the production of these structures.