Mechanism Of The Degradation Of Alpine Meadow On Ecosystem Multifunctionality

Ecosystem has the ability to simultaneously provide a variety of ecosystem functioning(ecosystem multifunctionality).Nowadays,exploring the relationship between biodiversity or environmental factors and ecosystem multifunctionality,and clarifying the mechanism of biotic and abiotic factors on ecosystem multifunctionality has become one of the hotspots of ecological research.Most studies focus on the response mechanism of ecosystem multifunctionality to biotic and abiotic factors in the tropical,subtropical and temperate forest and grassland ecosystems,however,little is known about the impact and mechanism of alpine meadow degradation on ecosystem multifunctionality,and there are few studies that explore the mechanism of biotic and abiotic factors regulating the effects of alpine meadow degradation on ecosystem multifunctionality.In this study,we chose Maqu County in the east of the Qinghai-Tibet Plateau as the experimental site and chose alpine meadow with varying degrees of degradation as the experimental object.Then we explored the relative importance and mechanism of above-and belowground biodiversity,soil water content and soil p H regulating the effects of alpine meadow degradation on ecosystem multifunctionality through the collection of plant and soil samples and the measure of soil physicochemical properties,soil nematode communities and soil microbial communities.We used one-way analysis of variance to assess the effects of alpine meadow degradation on ecosystem multifunctionality.Generalized linear model was used to evaluate the impact of biotic and abiotic factors on ecosystem multifunctionality.Finally,we applied structural equation modelling to explore the direct and indirect ways that alpine meadow degradation affects ecosystem multifunctionality.Our study found that:(1)The degradation of alpine meadow significantly decreased ecosystem multifunctionality.However,the components of ecosystem multifunctionality responded differently to alpine meadow degradation: alpine meadow degradation significantly increased total nitrogen and nitrate nitrogen,while total phosphorus,plant abundance,DNA concentration and nematode biomass decreased with alpine meadow degradation.(2)Ecosystem multifunctionality was significantly and positively related to aboveand belowground biodiversity and soil moisture,while there was no significant linear relationship between soil p H and ecosystem multifunctionality.And the interaction between above-and belowground biodiversity enhanced the negative impact of alpine meadow degradation on ecosystem multifunctionality.(3)Alpine meadow degradation reduced ecosystem multifunctionality through both direct and indirect ways.Specifically,there was a directly negative effect of alpine meadow degradation on EMF.And we found that the degradation of alpine meadow increased ecosystem multifunctionality through abiotic factors,while it reduced ecosystem multifunctionality by biotic factors.Moreover,above-and belowground biodiversity was more important factor that drive the degradation of alpine meadow to ecosystem multifunctionality than soil moisture and soil p H,therefore,alpine meadow degradation decreased ecosystem multifunctionality through indirect effects as well.Our results showed that alpine meadow degradation had a significantly negative effect on ecosystem multifunctionality,and the interaction between above-and belowground biodiversity enhanced this negative effect.And our study reveals the direct and indirect pathways and mechanisms of alpine meadow degradation impacting ecosystem multifunctionality.It provides us a better understanding of mechanism of biotic and abiotic factors regulating the effects of alpine meadow degradation on ecosystem multifunctionality,which provides theoretical support for the ecological restoration of alpine meadow and the maintenance of ecosystem functions.