Decomposition Characteristics Of Common Plant Litters In The Stipa Breviflora Desert Grassland Of Inner Mongolia

Under the background of global climate change,atmospheric nitrogen deposition and precipitation variation are increasingly significant,which lie a great deal of uncertainty on litter decomposition of desert grassland.The experiment was set up with a split-plot design.Three rainfall treatments included natural rainfall(CK),an increase of 30%(W)and a decrease of 30%(R).Nitrogen application at four levels,including 0(NO),30(N30),50(N50)and 100 kg·hm-2·a-1(N100).A two-year decomposition experiment aimed to explore how water and nitrogen interactively influence on litter decomposition.To examine the combined action of water and nitrogen on litter decomposition,three dominant species,Salsola collina,Stipa breviflora and Kochia prostrata were studied in a desert grassland.Our results showed that:1.Litter mass remaining rate decreased over time,which was consistent with Olson negative exponential decay model.Litter decomposition rate was found to be highest for Sal,followed by Stipa and Koc.The decomposition coefficient(k=0.028)under the treatment of WN100 level was the highest.Under single treatments the decomposition of litter was the fastest under W and N50 level.Under the combined water and nitrogen treatments,litter decomposition under WN100 level was the fastest.Under CK and R treatment,N100 level inhibits litter decomposition.The initial nitrogen concentration was maximum for Sal,followed by:Stipa and Koc.The decomposition coefficients were positively correlated with initial nitrogen concentrations for Sal and Stipa.The total carbon content,Cellulose content,Lignin content,Total carbon/total nitrogen ratio,Lignin/total nitrogen ratio and Cellulose/total nitrogen ratio were higher in Koc than in Stipa and Sal.These litter characteristics were negatively correlated with decomposition coefficient for Sal.For Stipa and Koc,the decomposed coefficients decreased with increasing Total carbon/total nitrogen ratio,Lignin/total nitrogen ratio and Cellulose/total nitrogen ratio.2.After litter-decomposition tests for 21 months,In the decomposition process of the three litters,the total carbon showed a pattern of release-enrichment-release,lignin showed a pattern of accumulation-release,and cellulose showed a pattern of release.Total nitrogen has been enriched twice during the whole process.The N50 level under CK and R treatment and N100 level under W treatment,are beneficial to the decomposition of Total Carbon,Cellulose and Lignin and the accumulation of Total Nitrogen as well as the reduction of Total carbon/total nitrogen ratio,Lignin/total nitrogen ratio and Cellulose/total nitrogen ratio.Under different water and nitrogen treatments,CKN50,RN50 and WN100 significantly reduced the values of Total carbon/total nitrogen ratio,Lignin/total nitrogen ratio and Cellulose/total nitrogen ratio.These results indicate that the decomposition rate was the highest in Sal,and lowest in Koc.These findings suggest that appropriate amounts of added water and nitrogen will contribute to accelerating litter decomposition,promoting nutrients cycling in this desert grassland,and will play an important role in grassland sustainability management.