The Response Of Vegetation-soil Ecological Stoichiometry To Precipitation Changes Of Desert Grassland

Desert steppe ecosystem is the predominant ecological type in arid and semi-arid regions,and precipitation is the main limiting factor for the stability and anti-interference ability of desert grassland ecosystem.The change of precipitation will inevitably affect the plant community structure and nutrient cycle process.Therefore,this paper takes the desert grassland in Yanchi County,Ningxia as the research object,simulates five precipitation gradients(33%,66%,100%,133%and 166%of normal precipitation,denoted as P33,P66,PCK,P133 and P166,respectively)based on the rain shelter and water supplement technology,to systematically study the coupling relationship between vegetation-soil ecological stoichiometry and its correlation with plant community characteristics in desert grassland under precipitation changes.In order to provide a scientific foundation for greater comprehension of how variations in precipitation patterns affect the plant-soil nutrition cycles in desert grasslands.The main findings from the study of vegetation-soil ecological stoichiometry under different precipitation gradients for three years(2020-2022)are as follows:(1)Plant ecological stoichiometry is significantly impacted by precipitation gradient and interannual precipitation fluctuation.The C,N,P,C:N and C:P of the aboveground plant community are significantly different between years.In the second year of precipitation teatment,the C,C:N and C:P of aboveground plant are higher than those in the other two years,and N and P are significantly lower than those in the other years.The contents of N and P in the belowground part of the community are less than those in the aboveground part,and the contents of C,N and P in P33 precipitation reduction treatment are significantly higher in the third year than in other years.(2)Soil ecological stoichiometry is significantly influenced by soil depth,interannual fluctuation,and precipitation gradient.After 1-2 years’ treatment,the contents of C and N in the deep soil layer(2030 cm)were higher than those in the surface layer(0-10 cm)and the contents of P were lower than those in the surface layer.In the third year of treatment,the P content in each soil layer decreased with the increase of precipitation.The contents of C,N and P in the surface layer were higher than those in the bottom layer under P133 treatment in each year.The C:N,C:P and N:P of topsoil decreased with the decrease of precipitation.(3)Under the treatment of precipitation change,the dominant species are Lespeseza potaninii and Artemisia scoparia,and the community coverage decreases with the decrease of precipitation gradient,and the change of community coverage is greatly influenced by the coverage of associated species(forbs).the highest diversity index and lowest evenness index were found under the P133 treatment,and the increase of annual precipitation improved species diversity.The temporal stability of the community reached the highest in treatments P66,P33 and PCK,and the aboveground and belowground biomass decreased with the decreasing precipitation gradient.(4)Under the change of precipitation,the correlation between the above-ground and belowground ecological stoichiometric characteristics of plants and community diversity is low,but it is highly correlated with coverage and biomass,and the temporal stability of communities is significantly positively correlated with C and P of aboveground parts.Soil C,N and P in different soil layers have little explanation for the change of community characteristics,among which soil N and P have significant influence on plant community characteristics.(5)Under the change of precipitation,there is no significant correlation between aboveground parts of plants C,N,P and their stoichiometric ratio and belowground parts,but there is a strong negative correlation between aboveground parts of plants N,P and soil N,P,and the influence of subsoil on aboveground parts of plants is higher than that of topsoil,while the coupling relationship between belowground parts of plants and subsoil soil is stronger.(6)There is an allometric relationship between the above-ground and belowground parts of plants,which changes from isokinetic growth to allometric growth in three years,and the increase of annual precipitation makes the accumulation of C in plants gradually unbalanced;In three years,the growth of aboveground N and P changed from allometric growth to isometric growth,and then to no allometric growth,and the relationship between aboveground N and P was decoupled.The contents of C and N in the belowground part are allometric growth in three years,and the coupling relationship is stable,which is less affected by precipitation.The internal stability characteristics of P content in aboveground parts of plants are sensitive in the first year of treatment,weak stable in C:P in the second year of treatment,weak sensitive in C:P and N:P in the third year,and absolute stable in belowground parts.To sum up,under the change of precipitation,the nutrient coupling between aboveground and belowground parts of desert grassland plant community is weak,but the ecological stoichiometry of aboveground part of plant community is highly correlated with soil ecological stoichiometry;Precipitation changes affect the coupling relationship between community ecological stoichiometry in different parts and soil by changing the coverage and biomass of different species functional groups;The interannual precipitation changes the stoichiometric homeostasis of P in the aboveground parts of plants.