Isotope variations and interrelationship characteristics of different water reservoirs during non-rainfall events in revegetation desert area, northwest China

Abstract

The formation and utilization of non-rainfall water can modulate isotope variation characteristics of the atmosphere, plants and soil water reservoirs. This is especially significant for water resource management in arid desert areas where non-rainfall is an important supplemental water source. In this study, we analyzed the isotope variation and interaction characteristics of rainfall, non-rainfall, atmospheric water vapor, xylem water, leaf water and shallow soil water during non-rainfall events over two years in a revegetation desert area in northwest China. The results indicated that air temperature was the most important meteorological factor influencing isotope characteristics of rainfall, non-rainfall and atmospheric water vapor. The isotope composition was also affected by rainfall and non-rainfall amounts, which decreased with event quantity. Back trajectory analysis showed that the variation of rainfall d values were induced by different moisture sources from arid Gobi and local evapotranspiration. The non-rainfall water line is close to local meteoric water line, with both having similar origins. Non-rainfall was mainly formed by radiative cooling of evaporated water produced shortly after rain and participated in the local water recycling. The atmospheric, plant and soil water all had high d values which indicated that evaporated water was a significant water source of different water reservoirs in this area. The leaf water of Artemisia ordosica was largely replenished by non-rainfall water compared to xylem water during non-rainfall events, so foliar water uptake was an important survival mechanism for Artemisia ordosica to adapt to drought environment during non-rainfall formation. Non-rainfall water contributed to 8–16% of the xylem water and the less rainfall, the higher the contribution rate. Our results are especially meaningful for arid desert regions where global climate change increases the importance of non-rainfall water.