放牧对祁连山高寒典型草原土壤质量的影响

Effect of grazing on soil quality of typical alpine steppe in Qilian Mountains

土壤质量是维持陆地生态系统稳定性与功能多样性的基础。放牧作为草地资源最广泛的利用方式之一,其对草地土壤质量的影响却缺乏量化标准,且两者之间的作用机理尚不明确。以祁连山高寒草原两个季节性牧场为研究对象,结合生态系统耦合与生态系统多功能性,探究了放牧对高寒草原土壤质量的影响与潜在机制。试验结果表明:基于最小数据集,不同放牧率下土壤质量指数差异显著(P<0.05),冬季牧场和春秋季牧场放牧率分别在2.45头月^(-1)hm^(-2)和0.80头月^(-1)hm^(-2)时土壤质量指数最高。土壤速效磷、有机碳、氮磷比和土壤pH是决定冬季牧场土壤质量的关键因子,而春秋季牧场中则是土壤有机碳、碳氮比和土壤pH;两个季节性牧场土壤质量指数与物种丰富度指数(P<0.05)和香浓维纳多样性指数(P<0.0001)呈显著正相关。高寒草原季节性牧场放牧地植物群落物种多样性与土壤因子耦合度在0.67—0.81之间,平均耦合度为0.74,属于中度协调;随着放牧率的增加,生态系统多功能性指数逐渐减低且与土壤质量指数变化趋势相似,间接证明了本研究最小数据集构建的合理性。本试验通过探究放牧对高寒草原不同季节性牧场土壤质量与生态系统功能的影响,结合草地植物群落物种多样性与土壤因子之间的耦合关系,深入挖掘了土壤质量变化规律与其潜在机制,为更好地保护与利用高寒草原草地资源提供了理论依据。

Soil quality is the basis for maintaining stability and functional diversity of the terrestrial ecosystems.While grazing is one of the most widely used methods of grassland resources,its effects on grassland soil quality lack quantitative criteria,and the mechanism of action between the two is unclear.In this study,two seasonal grazing lands in the alpine steppe of the Qilian Mountains were used to investigate the effects and potential mechanisms of grazing on soil quality,combining ecosystem coupling and ecosystem multifunctionality.Results indicated that soil quality index was controlled by grazing rate based on minimum data set(MDS).The soil quality index was the highest at 2.45 red deer month^(-1)hm^(-2)for winter grazing land,and 0.80 red deer month^(-1)hm^(-2)for spring and autumn grazing land.Soil available phosphorus,organic carbon,N to P ratio,and soil pH were the major factors driving soil quality in winter grazing land,while soil organic carbon,C to N ratio,and soil pH were the major factors in spring and autumn grazing land,and the soil quality indexes were positively correlated with species richness index(P<0.05)and Shannon-Wiener index(P<0.0001)in the two grazing lands.The coupling degree between plant community species diversity and soil factors were in the range of 0.67 to 0.81(average degree=0.74),which belonged to middle coordination.The ecosystem multifunctionality index(EMFI)and soil quality index were negatively correlated with grazing rate.The results further highlighted the effects of grazing on soil quality and ecosystem function in two seasonal grazing lands of alpine steppes.Combined with coupling relationships between plant community species diversity and soil factors,this study explored the potential momentum of soil quality fluctuation,which provided a theoretical basis for better protection and utilization of alpine steppes′resources.