Biophysical control of whole tree transpiration under an urban environment in Northern China

In China, there is concern about the impacts of urban trees on water resources. This study quantified whole tree transpiration, the most important source of water flux, under urban conditions. Four species (three of which may have some relevance for California: Cedrus deodara, a species of the Zelkova genus, and Metasequoia glyptostroboides) were studied using thermal dissipation probe techniques. Transpiration was found to be relatively stable even as the weather conditions varied dramatically over the 15-month study period. Vapor pressure deficit was the main driver of transpiration. Access to water deep in the soil and nocturnal water uptake allowed the urban trees to survive in times of water stress.