Differences in the Hydration State of Riparian Pecan Trees Between Rural and Urban Settings

Urbanization causes changes in near-surface meteorology and rainfall-runoff relationships that threaten to place hydraulic stress on vegetation. The goal of this study was to investigate the differences in riparian zone tree hydration state, as indicated by leaf water potential, between an urban and a rural stream site, and to understand how the trees respond differently to precipitation events. At the rural stream site, the streambed was dry due to persistent drought conditions, whereas the urban stream site had established flow due to urban water inputs. The trees at the urban site were found to suffer less hydraulic stress than the trees at the rural site, as indicated by predawn leaf water potential measurements. Additionally, trees at the rural site were found to regulate stomatal openness to reduce transpiration on the day before rain, but not after, due to the presence of near-surface moisture introduced by the rain event. Trees at the urban site did not have to regulate stomatal openness before or after the rain, as the established flow in the stream provided consistent water access. These findings support the viability of protecting and preserving riparian ecosystems in urban settings.