Seasonal variation in water uptake patterns of two greening species and their responses to rainfall events in a subtropical megacity of China

With rapid urbanization and climate change, water consumption and land-use pattern has dramatically changed, resulting in altered eco-hydrological processes and high ecological water requirements in megacities. However, the water uptake strategies may differ in urban and natural environment, and which remains largely unknown. Therefore, this study investigated the water use patterns of two greening plants species (Ficus concinna and Ligustrum vicaryi) and their responses to rainfall events in a megacity of subtropical China using the stable isotope methods. The results indicated that the two greening plants species showed different water use strategies. F. concinna mainly absorbed water from the shallower soil layer (0-20 cm, 56.29 %) in the wet season and deeper soil water (30-50 cm, 41.13 %) in the dry season, whereas L. vicaryi mainly relied on the shallower soil water (0-20 cm, 48.28 %) throughout the whole year. L. vicaryi absorbed water from the shallower soil layer (0-20 cm) before rainfall events and changed into deeper soil water (30-50 cm) after rainfall events in both dry and wet season; on the contrary, F. concinna did not show these dynamics throughout the year. These results suggested that the water use pattern of F. concinna showed more ecological plasticity, facilitating the adaptation of the plant to seasonal drought and other environment fluctuations in subtropical China urban areas.