Water use strategies of the desert riparian forest plant community in the lower reaches of Heihe River Basin,China

The object of this paper is the different plant communities in the Ejina desert riparian forest. Groundwater depth, soil moisture, plant water potential, relative leaf moisture content and water use efficiency was monitored, and the response of soil moisture and plant ecology to the groundwater depth and the water use efficiency of the different plant communities was analyzed. The results showed that: (1) Along with the groundwater depth increasing, predawn and midday water potential of the plants, with the exception of Reaumuria soongorica, did not decrease significantly, indicating that when the groundwater depth is less than 3 m, the plant communities in the range of 4 km from the river way did not suffer or slightly suffer from water stress; (2) The distribution of higher soil moisture content within 0–3 m soil layer is suitable with the plants’ root system, as indicated in the communities of coexisting overripe Populus euphratica or Taramrix chinensis, both of which can release excessive water into soil for shallow rooted shrubs or herbaceous plants when there is water shortage; (3) R. soongorica can absorb deep soil moisture through deep roots for their own survival; (4) The community consisting of Sophora alopecuroides, Karelinia caspica, T. chinensis, and overripe P. euphratica has the best species combination for restoring the damaged eco-environment in the lower reaches of Heihe River; (5) The order of plants’ relative leaf water contents is K. caspica > S. alopecuroides > young P. euphratica > overripe P. euphratica > mature P. euphratica = T. chinensis coexisting with other species > single R. soongorica > single T. chinensis and the order of WUE is single T. chinensis > single R. soongorica > T. chinensis living in symbiosis with other species > S. alopecuroides = young P. euphratica > mature P. euphratica > overripe P. euphratica > K. caspica. Therefore, with ample soil moisture, the plant community helps rapid growth of T. chinensis, young P. euphratica and R. soongorica plants of less moisture content. Despite this they do not have much water storage capability, but have strong drought resistance, and higher moisture contents of S. alopecuroides and K. caspica, thus leaving them with poor drought resistance. Overall, the desert riparian forest plant community in the lower reaches of Heihe River helps the species of higher WUE live on it.