Impacts of drought on soil retention and water conservation services over the Tibetan Plateau

Abstract

Drought is a major challenge for the Tibetan Plateau (TP), severely affecting ecosystem services (ESs). Quantifying the impacts of drought on vital ESs, such as soil retention and water conservation, is essential for understanding and addressing extreme weather events. This study evaluated the ESs by the Revised Universal Soil Loss Equation and water balance method, and assessed the drought using the probability distribution method. The impacts of drought on ESs at multi-time scales within the TP ecosystem are investigated by examining the relationship between the Standardized Precipitation Evapotranspiration Index (SPEI) and the Z-scored soil retention (SR_z) and water conservation (WC_z) services. The results indicated that the transition from wet to dry conditions reduced the ESs, with SR_z and WC_z decreasing by an average of 1.45 and 1.37 standard deviations, respectively. Hydrological drought (represented by SPEI6) had stronger impacts on soil retention services, while meteorological drought (represented by SPEI1) more significantly affected water conservation services. Trend analysis revealed strong correlations between ESs and drought conditions across the TP. ESs in the eastern and western humid regions remained relatively stable, whereas those in the central and southern regions underwent continuous degradation. Overall, drought not only diminished ESs but also destabilized the TP ecosystem. Therefore, it is vital to strengthen the restoration and protection of the ecosystem in this region to mitigate the adverse effects of drought.

Keywords: Drought; Ecosystem services; Soil retention; Tibetan Plateau; Water conservation.