Impacts of various soil moisture replenishment patterns on plant water use strategies in the Third Pole region

Abstract

This study investigates the impacts of soil moisture replenishment patterns on plant water use strategies in the source region of the Yangtze River on the Qinghai-Tibet Plateau. Understanding these patterns is crucial for ecological security and vegetation restoration in the face of global environmental change. In August 2021, plant, soil, and water samples were collected across the study area. Stable isotope analysis was conducted using the MixSIAR and End-Member Mixing Analysis (EMMA) models to identify the sources of plant and soil water. In the study area, plants primarily utilize soil water but also rely on additional sources, such as glacier snow meltwater, supra-permafrost water, ground ice and precipitation. Plant water use strategies vary with altitude, reflecting the influence of distinct soil moisture replenishment patterns across the region. Specifically, between 4 100 m-4 400 m, plants predominantly use soil water, with relatively lower use of other sources. Between 4 400 m-4 600 m, plants increasingly rely on soil water, while their reliance on other sources diminishes. Between 4 600 m-4 800 m, the contribution of soil water decreases, while the use of glacier snow meltwater and supra-permafrost water intensifies. These variations reflect the impact of altitude on plant water use strategies. The results emphasize the crucial role of altitude in shaping plant water use strategies and underscore the importance of understanding soil moisture replenishment in high-altitude ecosystems.