青藏高原草地植物多样性沿降水梯度的分布格局及影响因素

Distribution patterns and driving factors of grassland plant diversity along a precipitation gradient on the Qinghai⁃Tibet Plateau

青藏高原不同尺度的植物多样性具有不同的空间分布格局,而形成这种格局的影响因素尚不清楚。本研究对青藏高原不同地区的33个样点进行植被群落和土壤调查,从α多样性、β多样性和γ多样性3个尺度阐明了植物物种多样性沿降水梯度的分布格局,采用线性回归和结构方程模型(SEM)探讨影响植物多样性分布格局的直接或间接因素。结果表明:青藏高原植物α和γ多样性随着降水量增加而增加,植物β多样性随着降水量增加而减少;降水量增加通过改变土壤湿度直接增加了植物α多样性,通过增加土壤无机氮含量间接增加植物α多样性;并且,降水量增加会通过增加土壤氮磷比和降低土壤pH值间接增加植物γ多样性。综上所述,随着降水量的变化,土壤理化性质会发生相应的变化,进而影响不同空间尺度的植物多样性。

The distribution patterns of plant diversity in the Qinghai-Tibet Plateau vary across spatial scales.However,the factors that drive these patterns are still unclear.We investigated plant community and soils in 33 grassland sites along a precipitation gradient from Qinghai-Tibet Plateau,and elucidated the patterns of plant species diversity from three aspects:α,β,andγdiversity.Linear regression and structural equation modeling(SEM)were used to explore the direct or indirect factors affecting the distribution patterns of plant diversity.We found thatαdiversity andγdiversity increased,whileβdiversity decreased with increasing precipitation.Increased precipitation enhancedαdiversity directly by changing soil moisture and indirectly by increasing soil inorganic nitrogen content.Moreover,increased precipitation indirectly increasedγdiversity by increasing soil N/P ratio and decreasing soil pH.In summary,changes of precipitation can alter soil physicochemical properties,and thus affect plant diversity at different spatial scales.