模拟干旱对青藏高原东北缘温性草原土壤水分及群落结构的影响OA

Soil moisture is a key factor regulating the structure and function of grassland ecosystems.This study investigated how the vulnerable ecosystem in the transitional zone between the Qinghai-Xizang Plateau and the Loess Plateau responds to drought,selecting a typical temperate steppe area on the northeastern edge of the Qing-hai-Xizang Plateau.A simulated precipitation reduction experiment with varying gradients was conducted contin-uously for 6 a(2019-2024)to examine the effects of six treatments—natural precipitation and 20%,30%,40%,60%,and 90%precipitation reduction—on soil moisture,community structure,species diversity,and ecological niches in the region.The results were as follows:(1)Shallow soil moisture was the most sensitive to drought,showing a clear decline and increasing drought severity as precipitation reduction intensified.(2)Plant communi-ty responses exhibited nonlinear transitions:species diversity increased under light to moderate drought but de-creased under extreme drought,leading to community simplification.(3)The drought resistance of Gramineae species,such as Agropyron cristatum,increased progressively with drought stress intensity.Under the 90%precip-itation reduction treatment,the importance value of Agropyron cristatum reached 37.8%,indicating clear domi-nance,whereas Cyperaceae species and legume species gradually declined.(4)Five key plant species—Kobresia humilis,Stipa krylovii,Agropyron cristatum,Medicago ruthenica,and Potentilla bifurca exhibited niche breadths greater than 0.9 and niche overlap values exceeding 0.8.Under drought stress,these species formed a competitive-ly dominant group and served as an important foundation for maintaining community stability.This study indi-cates that intensified drought driven by reduced precipitation is a key factor limiting the stability of temperate steppe ecosystems on the Qinghai-Xizang Plateau and that extreme drought events are likely to accelerate grass-land desertification.