青藏高原不同类型高寒草地物种多样性与生物量的关系及影响要素

Correlations of species diversity and biomass with environmental factors in alpine grasslands across the Qingzang Plateau

本研究以青藏高原为研究区,基于实测的115个样点调查数据,包括群落结构、土壤因素以及气候指标,利用单因素方差和线性回归分析,结合结构方程模型探究了不同类型高寒草地(高寒草甸和高寒草原)地上生物量和物种多样性的差异及其关系,并试图厘清不同草地类型生物多样性与地上生物量的主要驱动要素。结果表明:1)地上生物量与物种多样性在高寒草甸与高寒草原之间均存在显著差异(P<0.05),且二者关系在两种草地类型均呈显著正相关关系(P<0.05)。2)驱动因子分析表明,年均降水量(AMP)与地上生物量(AGB)和物种多样性存在显著正相关关系(P<0.05);高寒草甸中土壤有机碳(SOC)、土壤速效氮(SAN)和土壤速效磷(SAP)含量与地上生物量呈显著正相关关系(P<0.01),而物种多样性(Shannon-Wiener指数)仅与土壤含水量(SWC)呈显著正相关关系(P<0.05);高寒草原的SOC、SAN含量与地上生物量和物种多样性呈显著正相关关系(P<0.01),且SWC、SAP含量与地上生物量和物种多样性之间的相互关系均不显著(P>0.05)。3)结构方程模型分析指示年均降水量分别解释了高寒草甸和高寒草原55.8%和60.3%的物种多样性变异,且物种多样性与地上生物量关系密切,对高寒草甸和高寒草原的地上生物量影响分别为51.3%和30.2%,同时土壤养分也进一步制约着高寒草地的生物量。综上可知,水分主导了高寒草地物种多样性和地上生物量的空间格局和关键生态过程,该研究结果可为未来高寒草地应对青藏高原暖湿化气候趋势提供基础数据和理论参考。

To clarify the correlations of productivity and species diversity with critical environment factors in alpine grasslands,we conducted a field survey of the vegetation community structure,soil factors,and climate indicators at 115 sites across alpine grasslands.The differences and relationships between aboveground productivity and species diversity in alpine meadows and steppes were evaluated using one-way analysis of variance,linear regression analysis,and structural equation modeling.The results were as follows:1)there was a remarkable positive response of aboveground productivity to species diversity(P<0.05),with a significant difference between alpine meadows and steppes(P<0.05).2)Annual mean precipitation significantly affected the aboveground productivity and species diversity(P<0.05).Aboveground productivity was significantly positively correlated with soil organic carbon,soil available nitrogen,and soil available phosphorus(P<0.01),whereas species diversity(Shannon-Wiener index)was positively correlated with only soil water content(P<0.05).However,soil organic carbon and soil available nitrogen significantly affected aboveground productivity and species diversity(P<0.01),and there were no significant correlations among soil water content,soil available phosphorus,aboveground productivity,and species diversity(P>0.05).3)Structural equation modeling analysis indicated that the annual mean precipitation explained 55.8%and 60.3%of the variations in species diversity in alpine meadows and steppes,respectively.In addition,species diversity explained 51.3%and 30.2%of the variations in aboveground productivity in alpine meadows and alpine steppes,respectively.Soil nutrients may constrain the increase in productivity in alpine grasslands.Moisture may dominate spatial patterns and critical ecological processes of species diversity and aboveground productivity in alpine grasslands.Our results provided documents and theoretical references for alpine grasslands to cope with future climate warming and humid trends across the Qingzang Plateau.