锡林河流域草原生态系统地上生物量时空分布特征及其影响因子

Distribution Characteristics and Influencing Factors of Aboveground Biomass in Typical Grassland Ecosystem in Xilin River Basin

为系统地量化环境因子之间的协同关系及其对生物量时空格局的调控,以锡林河流域为研究区域,测量了2020年5月—9月典型草原生态系统地上生物量以及气象因子(包括降水量和气温)、地形因子(包括高程)、土壤因子(包括土壤含水量、干密度、有机碳质量分数、全氮质量分数和pH)等三大类共8个环境因子,并通过地理探测器方法定量分析了地上生物量与各环境因子之间的关系。结果表明:1)时间维度上,研究区地上生物量在生长季初期稳定增长,在水热条件最好的7月,植被地上生物量增长最为迅速,在9月3日地上生物量达到峰值,此时流域上、下游地上生物量分别为209.12、147.19 g/m^(2);空间维度上,上游地上生物量显著高于下游(显著性水平p<0.05),地上生物量空间分布格局呈现从东南向西北整体减小的趋势。2)整个生长季中,气象因子(降水量和气温)是地上生物量空间格局的关键驱动因子,其对地上生物量分布格局的解释率在60.0%以上;生长季末期,除气象因子外,土壤pH也成为影响研究区地上生物量分布格局的主要驱动因子。3)生长季各阶段,各环境因子对地上生物量的交互作用均呈现出非线性增强和双因子增强关系。生长季初期,降水量和土壤干密度之间交互作用的影响力最大;生长旺期及末期,随着土壤含水量达到较高水平,土壤干密度与其他环境因子(降水量、气温、pH)的交互作用对流域植被地上生物量影响显著。

In order to systematically quantify the synergistic relationship between environmental factors and their regulation of spatial and temporal patterns of biomass,taking the Xilin River basin as the study area,this study measured the aboveground biomass(AGB),soil water content,soil density,organic carbon mass fraction,total nitrogen mass fraction,soil pH and other environmental factors of the typical grassland ecosystem from May to September 2020.The relationship between AGB and driving factors were analyzed by using the geographic detector method.The results show that:1)Watershed-level AGB increases stably at the beginning stage of the growing season,displays the highest increase rate in July,and reaches the maximum on September 3rd.AGB in the upstream and downstream is 209.12 and 147.19 g/m^(2),respectively.AGB in the upstream of the watershed is significantly higher than that in the downstream(significance level p<0.05),and the overall spatial pattern of AGB shows a decreasing trend from the southeast to the northwest in the watershed.2)During the entire vegetation growing season,meteorological factors(precipitation and air temperature)are key factors driving the changes in AGB,with an explanation rate of more than 60.0%in the regression model.At the end of the growing season,in addition to meteorological factors,soil pH also significantly influences the dynamics of AGB in time and space.3)At each stage of the growing season,the interaction between environmental factors shows nonlinear enhancement and double-factor enhancement.At the beginning of the growing season,the interaction between precipitation and dry density of soil shows the most influential.When soil water content reaches a relatively high level,the interaction of soil dry density with other environmental factors(precipitation,air temperature,pH)exerts a significant impact on the AGB in the peak and late stages of the growing season vegetation growth in the basin.