Effects Of Simulated Nitrogen Deposition And Rainfall Changes On The Decomposition Of Litter In Desert Grassland

In recent decades,with the burning of fossil fuels,deforestation,the production and use of chemical fertilizers and other human activities led to the active N concentrations in the atmosphere increase rapidly,atmospheric nitrogen deposition and precipitation pattern has changed greatly.As the most widely distributed vegetation type in terrestrial ecosystem,grassland ecosystem plays an irreplaceable role in environmental protection and improvement.As the product of plant metabolism,litters play an important role in maintaining stability and biological circulation of grassland.In this study,the study was conducted on the subjects of Cleistogenes songorica and Artemisia frigida,design of crack zone test is adopted,the main area is there water treatment of natural rainfall?CK?,precipitation 30%?W?and rainfall reduction 30%?R?,the subregion is four nitrogen levels 0?N0?,30?N30?,50?N50?and 100 kg(hm^2.a)^-1?N100??not including atmospheric nitrogen deposition?,two years from 2016 to 2017 water nitrogen treatment,the research of water and nitrogen control effects on litter decomposition and nutrient release,rate of litter decomposition and its main influencing factors,the relationship between the background of global climate change in the region desert grassland ecosystem structure and function,management and utilization to provide basic data.The main findings of this study are as follows:1.The residue rate of Artemisia frigida and Cleistogenes songorica decreased with time,which was better than that of Olson negative exponential decay model,and the decomposition coefficient?k?was the highest under W-N100.2.After 21 months of decomposing,the quality loss rate of Cleistogenes songorica was 35.07-44.97%,and the quality loss rate of Artemisia frigida was32.57%-41.17%,and the decomposition rate Cleistogenes songorica was faster than of Artemisia frigida.3.Under the treatment of single nitrogen factor,nitrogen deposition promoted the decomposition of litters,which was the fastest at the N50 level;Under the treatment of single water factor,increasing rain promotes decomposition of litters,reducing rain inhibits decomposition of litters;Under the interaction of water and nitrogen,litter decomposition is the fastest under W-N100 treatment.4.As the decomposition time goes on,the total carbon residue rate of Cleistogenes songorica and Artemisia frigida shows a release mode.Overall,the total nitrogen content showed a trend of first rising and then falling.The total nitrogen residue rate had a nitrogen enrichment process of 1-2 times under each treatment,which quickly changed to the net nitrogen release mode.The content of cellulose decreased gradually,and the cellulose residue rate showed a release mode.Lignin content in first after rising downward trend,the residue rate of Cleistogenes songorica lignin was characterized by release-enrichment-release mode under CK-N and W-N treatment,R-N treatment characterized by enrichment-release pattern,Artemisia frigida residual rate of lignin are characterized by enrichment-release pattern.5.Under the processing single nitrogen factors,N application significantly increased soil organic matter,total nitrogen,ammonium nitrogen,nitrate nitrogen,soil animal individual number,the number of groups,the microbial carbon and nitrogen content?P<0.05?,reduce the soil pH value;Under the treatment of single water factor,increasing rainfall can increase soil moisture content,the number of soil animals,the number of species,and the content of microbial carbon and nitrogen,which is more significant under the interaction of water and nitrogen.6.Litter decomposition is influenced by environmental factors and their properties,each factor's contribution to the litter decomposition of different size,the litterquality?fullcarbon,totalnitrogen,C/N,cellulose,lignin?explainthe decomposition rate of 39.8%of the variation,K value of soil animals and microbes carbon and nitrogen explain 20.4%of the decomposition rate of K value variation,soil physical and chemical properties?moisture content,organic matter,total nitrogen,nitrate nitrogen,ammonium nitrogen?explain 12.8%of the decomposition rate of K value variation.Litter quality,soil animal and microbial carbon nitrogen and soil physical and chemical properties all accounted for 72.6%of the variation in K value of decomposition rate.