Water-use strategies of two dominant desert plants along a precipitation gradient in north-western China

Abstract

Aims In arid and semiarid regions, precipitation is the most important water source for plants. Our objective was to investigate the water-use strategies of two dominant desert plants along a precipitation gradient in northwestern China. Methods We determined stable hydrogen and oxygen isotope compositions of the stem water from Artemisia ordosica and Nitraria tangutorum and potential water sources (rain water, groundwater and soil water) at three study sites with different annual precipitation (Hanggin Banner and Dengkou County of Inner Mongolia Autonomous Region and Minqin County of Gansu Province). The IsoSource model was then used to calculate probable contributions of potential water sources to total plant water uptake. We also determined foliar carbon isotope ratios and free proline contents of both species to indicate water use efficiency and osmotic-adjustment ability. Important findings At the Hanggin Banner site (highest annual precipitation), both species obtained the highest proportion of water from shallow soil water and A. ordosica took up water mostly from the 0–50 cm soil layer. However, they depended mainly on deep soil water or groundwater at the Dengkou and Minqin sites with lower annual precipitation. The water use efficiency of both species decreased with increasing annual precipitation. There was a positive correlation between carbon isotope ratio and free proline content in A. ordosica. These results suggest that desert plants can adjust their capabilities for up-take from different water sources and other physiological properties with variation in natural precipitation, but the strategies are species-specific.