Effects Of Shrubging On Soil Fauna Structure And Diversity In Alpine Grasslands Of Tibet

In recent years,under the background of global warming,grasslands around the world have generally shown the phenomenon of "shrubland".Affected by natural and man-made disturbances such as climate change and overgrazing,the alpine grassland vegetation of the Qinghai-Tibet Plateau shows a trend of intensified degradation,and also creates certain conditions for shrubland invasion.Soil fauna is an indispensable part of grassland ecosystem,which can be used as an indicator of energy flow and nutrient cycling in grassland ecosystem,and the intensification of grassland "shrubland" changes the composition structure of herbaceous plant communities and the physicochemical properties of soils,which may affect the composition and structure of soil fauna communities.Therefore,studying the impact of "shrubland" on soil fauna in alpine grassland is an important ecological issue in the study of alpine grassland ecosystem.In this study,two vegetation types of alpine meadow and alpine grassland were selected on the southern slope of Nianqing Tanggula Mountain in Dangxiong County,Tibet,and shrubland invasion and non-shrubland invasion were selected among the two grassland types.In June and August 2022,the vegetation community structure and soil physicochemical properties of each plot were investigated,and the dry funnel method(Tullgren)was used to separate soil animals,and then soil animals were identified into families,the number of individuals,taxa,and dominant taxa were counted,the diversity index of soil fauna was calculated,and the relationship between soil fauna,herbaceous plants and soil characteristics was explored by combining various indicators such as vegetation community structure and soil physicochemical properties,and the effect of soil fauna community structure and diversity on the "shrubification" of Tibet alpine grassland was elucidated response.The following research results were mainly obtained:1.Alpine meadows are dominated by alpine pine grass(Kobresia pygmaea),and alpine grasslands are dominated by alpine pine and Stipa capillacea.After shrub invasion,alpine meadow sedges and grasses decreased,weeds and legumes increased,alpine steppe grasses decreased,sedges,weeds and legumes increased.Shrubland invasion increases vegetation height,subsurface biomass,organic carbon content and total nitrogen content in alpine meadows and alpine grasslands,and reduces vegetation cover,soil temperature,moisture,bulk density and p H.Shrub invasion reduced the subsurface biomass and uniformity index of alpine meadows and increased the subsurface biomass and uniformity index of alpine grasslands,while the diversity index and richness index showed a significant growth trend in alpine meadows(p<0.05)and basically unchanged in alpine steppe(p>0.05).2.A total of 351 soil animals were captured,belonging to 39 taxa of 13 orders in 2 phyla,5 orders.Among them,the dominant taxa were Cyclobiidae and Cryptognathidae,whose individual numbers accounted for 17.09% and16.24% of the total number of individuals,respectively,15 common taxa,and 24 rare taxa,whose individual numbers accounted for 10.83% of the total number of individuals.Shrubland invasion increased the number of individuals,taxa and soil animal density in alpine meadows,but reduced the number of individuals,taxa and soil animal densities in alpine meadows,shrubland invasion significantly increased the diversity index,uniformity index and richness index of soil animals in alpine meadows(p<0.05),but there was no significant difference in alpine grasslands(p>0.05).The diversity index,richness index,uniformity index and dominance index were significantly higher than those in the non-growing season(p<0.05).3.The influence of vegetation and soil properties on soil fauna was different,and the number of soil fauna was positively correlated with vegetation diversity,richness,soil temperature and bulk density,and negatively correlated with soil compactness and underground biomass.Soil animal diversity was positively correlated with vegetation diversity,richness,soil temperature,bulk density,and negatively correlated with vegetation uniformity,aboveground biomass and soil p H,and vegetation diversity,vegetation biomass,soil temperature and humidity,and total nitrogen content were the main factors affecting soil animal composition.In summary,this paper clarifies the influence of shrubland on soil fauna in alpine grassland,and then on soil fauna,and the results can be used as biological indicators of shrubland on soil fauna in alpine grassland in Tibet,which provides an important reference for evaluating its ecological environment.