Abstract: The distribution area of the alpine steppe was gradually increased by climate warming across the Tibetan Plateau. However,productivity changes and species richness of alpine steppe,and driven factors were uncertain. In this study,we studied the community variation of Stipa purpurea alpine steppe in the Qinghai Lake region,for 13 consecutive years from 2010 to 2022. Furthermore,controlling factors were analyzed by using a structural equation model involving meteorological factors and normalized difference vegetation index. Meanwhile,these results indicated that the aboveground biomass and species richness showed a fluctuation increase. Average fresh weight and species number were 215.41 g·m^-2 and 15,respectively. Moreover,there was a weak positive interaction between productivity and species richness,and high biodiversity promoted the productivity of alpine steppe. Both coverage and average height increased significantly. In addition,the aboveground biomass and total coverage were significantly driven by annual mean air temperature and productivity,respectively. In conclusion,the future warming climate scenario would significantly increase the biomass of alpine steppes,but increased rainfall could reduce the species richness in the Qinghai Lake region.

Key words: Alpine steppe, Aboveground biomass, Species richness, Average annual temperature

摘要： 气候变暖促进青藏高原高寒草原分布面积逐渐增加，但有关紫花针茅(Stipa purpurea)型高寒草原生产力与物种丰富度长期变化特征及其驱动因素尚不明确。本研究连续13年观测青海湖地区高寒草地地上生物量、物种丰富度和盖度等指标，阐明了植被群落特征的长期变化规律，采用结构方程模型，解析了紫花针茅型高寒草原生产力和物种丰富度的主要影响因素。结果表明，高寒草原地上生物量和物种丰富度均呈现较强的波动上升趋势，平均鲜重和物种数分别为215.41 g·m^-2和15，高物种丰富度促进生产力增加；高寒草原群落总盖度和平均高度呈现显著增加趋势。紫花针茅型高寒草原地上生物量和总盖度分别受到年均气温和生产力的显著影响。未来增温气候情景将会显著增加青海湖地区紫花针茅型高寒草原生物量，但降雨量增加会降低物种丰富度。

关键词: 高寒草原, 地上生物量, 物种丰富度, 年均气温