Legacy Effects Of Fertilization And Sowing Methods On Soil Microbial Communities In Abandoned Alpine Meadow On The Qinghai-tibet Plateau

Qinghai-Tibet Plateau,as the ’ third pole ’ of the earth,is an important ecological safety barrier of our country.As one of the main grassland ecosystems on the QinghaiTibet Plateau,alpine meadow breeds rich biodiversity and plays a pivotal role in ecosystem function and geochemical cycle maintenance,and in such aspects as livestock production and regional economic development plays a decisive role.Due to its unique geographical location and climatic conditions,the alpine meadow on the Qinghai-Tibet Plateau is facing serious degradation problems due to the impact of global climate change and human activities.In order to maintain the sustainable development of grassland ecosystem,a series of measures of returning farmland to forest or grassland have been introduced.After the cessation of these land use activities,large areas of abandoned land appeared in the alpine meadow of Qinghai-Tibet Plateau.Soil microorganisms are the most important components of subsurface ecosystems and the important nodes linking aboveground and subsurface ecosystems,driving and affecting many key ecosystem functions and services.In recent years,a large number of studies have focused on soil microorganisms in alpine meadows on the QinghaiTibet Plateau,but it is still unclear how the legacy effects of land abandonment in this region affect soil microbial communities.In this study,a 100m×100m abandoned land(Abandoned from 2009 to 2019)with different fertilization(There were 4 treatments including No fertilization,Nitrogen fertilization,Phosphorus fertilization,Nitrogen and phosphorus fertilization)and sowing(There were 5 treatments including No sowing,Elysium dahuricus sowing,Avena sativa sowing,Vicia sativa sowing,Mixed sowing of Avena sativa and Vicia sativa)methods backgrounds in Haibei National Field Research Station of Alpine Grassland Ecosystem from 2008 to 2009 was selected as the research object.By setting the sample area of natural recovery by contrast,explores the legacy effects of abandoned in alpine meadow after 10 years of abandonment under different human farming activities on soil physical and chemical properties,the key function(microbial biomass,enzyme activity,microbial(archaea,bacteria,fungi and protist)diversity of community and community building process,and evaluate for 10 years abandoned the natural recovery process,the following main results are obtained:(1)The content of available phosphorus in soil of Phosphorus fertilization and Nitrogen and phosphorus fertilization was significantly higher than that of other fertilization treatments and Natural plots,indicating that the influence of phosphorus addition on soil phosphorus storage was long-term and its legacy effect enhanced soil phosphorus sequestration capacity of alpine meadow.After 10 years of abandonment,microbial biomass carbon,microbial biomass nitrogen,and saccharase activity in No sowing were significantly higher than those in Avena sativa sowing and Mixed sowing of Avena sativa and Vicia sativa,indicating that several key soil functions were impaired by the legacy effects of Avena sativa cultivation.(2)The legacy effects of Phosphorus fertilization and Nitrogen and phosphorus fertilization significantly increased the relative abundance of dominant eukaryotic microorganisms such as Sordariomycetes,Bacillariophyta and Chlorophycophyta,and available phosphorus was a major predictor of its variation among different fertilization methods.The legacy effects of Avena sativa sowing and Mixed sowing of Avena sativa and Vicia sativa significantly increased the relative abundance of dominant prokaryotic microbial groups such as Euryarchaeota,Nanoarchaeaeota,Acidobacteria,Planctomycetes,Verrucomicrobia,and the relative abundance of α-proteobacteria and Actinobacteria was decreased.Saccharase activity was the main predictor of soil sucrase activity in different sowing treatments.(3)There were no significant differences in the species diversity and phylogenetic diversity of soil archaea,bacteria,fungi and protist between different fertilization methods and Natural plots,indicating that the legacy effects of fertilization methods had a weak impact on soil microbial α diversity in alpine meadow.The legacy effects of Avena sativa sowing and Mixed sowing of Avena sativa and Vicia sativa were significant,which decreased the α-diversity of soil bacterial community,among which saccharase activity was the main predictor of the variation of bacterial community species diversity among different sowing treatments.(4)The species composition and phylogenetic structure of soil fungal communities were significantly different between different fertilization treatments and Natural plots,and different sowing methods significantly affected the species composition and phylogenetic structure of soil bacteria,fungi and protist communities,indicating that the legacy effects of different fertilization and sowing methods drove the formation of soil microbial community β diversity in alpine meadow.Among them,available phosphorus,microbial biomass carbon,microbial biomass nitrogen and saccharase activity mainly explained the variation of microbial community β diversity.(5)The composition of archaea communities under different fertilization and sowing different kinds of pasture was mainly affected by deterministic processes,while the composition of bacteria,fungi and protist communities was mainly controlled by stochastic processes,and the relative influence of stochastic processes was higher than that of Natural plots.The legacy effect of fertilization led to the transition of stochastic/deterministic balance in bacterial communities.Stochastic processes regulated soil microbial community construction in alpine meadow.The above studies systematically evaluated the legacy effects of human activities on soil physical and chemical properties,soil microbial diversity and community structure of the alpine meadow after 10 years of abandonment and natural restoration under the disturbance of human reclamation and farming activities.This study provided data support and theoretical basis for exploring the effects of human farming activities on alpine grassland ecosystems and the ecological restoration and restoration process of degraded ecosystems.