Trees growing through impervious surfaces use shallower water sources: A stable isotope study

Abstract

Impervious surfaces account for a large proportion of urban land surface. However, little is known about tree water use in impervious surfaces. Here, we compared the water sources of trees growing through impervious and pervious surfaces using oxygen and hydrogen isotopic compositions from stem water and other potential water sources before and during the wet season. The proportion of topsoil water in the water source, calculated using a simple linear mixing model, showed that trees growing through impervious surfaces took up more water from shallow layers than control trees before the wet season. An IsoSource model applied in the wet season confirmed that trees growing through impervious surfaces took most of their water from depths of around 20 cm, while control trees took the greatest portion of their water from a depth of 70 and 100 cm. These findings could improve urban hydrological cycle models and suggest that urban trees growing through impervious surfaces might be more vulnerable to drought.