Plant water use strategies in the Shapotou artificial sand-fixed vegetation of the southeastern margin of the Tengger Desert, northwestern China

摘要

Stable oxygen and hydrogen isotopic compositions (δ18O and δD) of plant xylem water and its potential water sources can provide new information for studying water sources,competitive interactions and water use patterns of plants.The contributions of different water sources to three plants,Hedysarum scoparium (HS),Caragana Korshinskii (CK) and Artemisia ordosica (AO),were investigated in the artificial sand-fixed vegetation of Shapotou,the southeastern margin of the Tengger Desert of northwestern China,based on meteorological data and δ18O and δD values of precipitation,groundwater,soil water and xylem water of HS,CK and AO.Our results indicated that soil water infiltration through precipitation was the main water source of the artificial sand-fixed vegetation.Obvious differences in soil water content and in δ18O of soil water and xylem water were found among different seasons.No relationship was found between the δ18O in plant xylem water and in soil water in January.The same water use patterns were found in CK,HS and AO in May,suggesting they have the same water sources.The different water sources of CK,HS and AO in August indicate that water competition occurred.In addition,the main water sources of CK,HS and AO in August mainly come from shallow soil water,while they use relatively deep soil water in May.This phenomenon is related to the differences of soil water content throughout soil profile,precipitation,transpiration and water competition under different growth periods.The water use patterns of CK,HS and AO respond to soil water content throughout the soil profile and their competition balance for water uptake during different growth season.The results indicate that these sandfixed plants have developed into a relatively stable stage and they are able to regulate their water use behavior as a response to the environmental conditions,which reinforces the effectiveness of plantation of native shrubs without irrigation in degraded areas.