Water utilization characteristics of typical vegetation in the rocky mountain area of Beijing, China

Seasonal drought are expected to occur more frequent and intense in the some regions due to global climate change, which may significantly influence in the competitive interactions of water uptake depth for vegetation communities. We investigated the impacts of seasonal drought on water utilization for vegetation communities using hydrogen-2 and oxygen-18 stable isotope techniques in Beijing rocky mountainous area. Our results indicate that the water sources of the four plant species varied by season. Platycladus orientalis largely absorbed water from middle (31.5% in May and 35.9% in November) and deep (32.8% in May and 38.4% in November) soil layers during the dry season and switched its main water source to surface layers (50.3% in July and 37.2% in September) during the wet season. Contrary to P. orientalis, Quercus variabilis mainly absorbed water from surface and middle soil layers during the dry season and changed its dominant water sources to the deep soil layer throughout the wet season; at same time, this species utilized water from natural springs in July and the middle soil layer in September. V. negundo var. heterophylla mostly utilized water from deep soil layers (38.7%) in May and transferred its main water source to surface (43.5%) and middle (33.1%) layers in July. This species primarily utilized water from surface (29.2%) and middle (30.8%) soil layers in September, and from middle (35.4%) and deep (27.8%) layers in November, similar to the findings of P. orientalis in this season. In contrast the above three plant species, C. heterophylla Fisch mainly absorbed water from surface and middle soil layers throughout the year, having very little reliance on water from deep soil layers. P. orientalis and Q. variabilis showed the opposite characteristics of water utilization, which suggests that these two species are suitable for a mixed forest vegetation when selecting plant species for afforestation. However, since the water sources of P. orientalis and V. negundo var. heterophylla were from similar soil depths, there may be potential competition for moisture between these two species. Our findings provide an indication as to which vegetation species are suitable to grow together when undertaking restoration in drought prone environments.