疏勒河源区高寒草甸中型土壤动物群落特征及对土壤水分变化的响应

Characteristics of soil mesofauna community and its response to soil moisture in alpine meadow ecosystems of the Shule River headwaters

高寒草甸退化会引起土壤水分含量下降,这会强烈影响土壤动物多样性及其功能。然而,我们对高寒草甸土壤动物群落组成的认识十分有限,还不清楚高寒草甸退化过程中土壤水分变化对土壤动物分布及多样性的影响。本文以祁连山西段的疏勒河源区为研究区,于2021年6月和10月系统调查了沼泽化草甸、草甸、草原化草甸和沙化草甸4种草甸生境中型土壤动物群落组成及土壤水分含量变化,解析高寒草甸中型土壤动物多样性对高寒草甸退化的响应规律,确定高寒草甸退化过程中土壤水分变化对中型土壤动物群落特征的影响。结果表明:沼泽化草甸、草甸、草原化草甸和沙化草甸的中型土壤动物群落组成明显不同,6月和10月草原化草甸生境中型土壤动物密度、类群丰富度和多样性指数均显著高于其他高寒草甸生境,10月沼泽化草甸中型土壤动物密度和类群丰富度显著高于草甸和沙化草甸。中型土壤动物QBS-ar指数变化与中型土壤动物多样性指数变化一致,螨类和跳虫密度比值(A/C)变化与中型土壤动物QBS-ar指数相反。螨类对高寒草甸退化的响应模式不同并存在明显的季节变异,6月和10月革螨亚目的密度在草原草甸均显著高于其他生境;6月和10月甲螨亚目的密度在草原草甸均显著高于草甸和沙化草甸;6月辐螨亚目的密度在草原化草甸的密度显著高于沼泽化草甸,10月它在草原化草甸的密度显著高于草甸和沙化草甸。跳虫对高寒草甸退化的响应模式相近,6月和10月跳虫中的长角跳科和等节跳科在草原化草甸的密度均显著高于其他高寒草甸生境。土壤水分与中型土壤动物密度、类群丰富度、多样性指数和QBS-ar指数均呈显著的二次曲线关系,它们均随着土壤水分含量的增加先增后降。总之,高寒草甸退化过程中草原化草甸中型土壤动物密度、多样性和QBS-ar指数均较高,表明高寒草甸退化过程中土壤水分含量的适度降低可以提升中型土壤动物多样性及其功能。

Soil water availability is affected by alpine meadow degradation,which profoundly affects soil fauna diversity and ecological function.However,little knowns about the composition of soil fauna in alpine meadow ecosystems.How changes in soil water content affect their distribution and diversity during alpine meadow deg⁃radation is still unclear.Our study area was the Shule River headwaters in the western Qilian Mountains,alpine marsh meadow(AMM),alpine meadow(AM),alpine steppe meadow(ASM)and desertification alpine mead⁃ow(DAM)formed a gradient of degradation of the Shule River headwaters.In June and October 2021,soil me⁃sofauna was collected using the improved Tullgren funnel method in the AMM,AM,ASM,and DAM habitats of the Shule River headwaters,at the same time soil water content was also measured in four alpine meadow hab⁃itats.Further,soil mesofauna diversity,Acarina/Collembola(A/C)ratios,and the soil biological quality index(QBS-ar)in four alpine meadow habitats were calculated,and a regression analysis was performed to determine the impact of soil water content on soil mesofauna community indices during the degradation process of alpine meadows in the Shule River headwaters.Results showed that soil mesofauna communities differed considerably between the four alpine meadow habitats,degradation of alpine meadows in the Shule River headwaters strongly affected the density changes of soil mesofauna such as mites(Acarina)and springtails(Collembola),and their response patterns to alpine meadow degradation determined the assemblage of soil mesofauna community.Fur⁃thermore,the density,group richness,and Shannon-Wiener index in soil mesofauna communities in ASM habi⁃tats was significantly higher than those in AMM,AM,and DAM habitats in June and October in the Shule River headwaters,respectively.In October,the density and group richness of soil mesofauna communities in AMM habitats was significantly higher than those in AM and DAM habitats of the Shule River headwaters.Changes in soil mesofauna QBS-ar indices of four alpine meadow habitats during two sampling periods are consistent with the Shannon-Wiener index of soil mesofauna community,and A/C ratios over two sampling periods followed the opposite pattern.Alpine meadow degradation caused soil mites to respond differently,and there were seasonal and taxon-specific differences.The density of Oribatida in ASM habitats was significantly greater than those in the other alpine meadow habitats in June and October.As compared to AM or DAM habitats,ASM habitats had a significantly higher density of Mesotigmata in June and October.In June,the density of Prostigmata was sig⁃nificantly higher in ASM habitats than in AM and DAM habitats,and in October,it was significantly higher in ASM habitats than in AM and DAM habitats.Soil springtails responded in the same way to alpine meadow deg⁃radation in June and October,and the density of Entomobryidae and Isotomidae significantly outnumbered other alpine meadow species in ASM habitats.Alpine grassland degradation was associated with changes in soil mois⁃ture content and soil mesofauna community indices in the Shule River headwaters.During the degradation of al⁃pine meadows,soil water content and the density,group richness,and Shannon-Wiener index of soil mesofauna community showed a significant quadratic curve relationship,and soil mesofauna community indices and soil water content first increased and then decreased.We also found a similar relationship QBS-ar index of the soil mesofauna community and soil water contents with other soil mesofauna community indices.In conclusion,the density,Shannon-wiener index,and QBS-ar index of soil mesofauna community in ASM habitats were higher during the degradation of the alpine meadow,indicating that a certain degree of declined soil water availability due to degradation of an alpine meadow could improve the diversity and ecological functions of soil mesofauna in the Shule River headwaters.