Effect Of Simulated Rainfall On Plant Community And Litter Decomposition In Alpine Meadow

Global climate change has changed the temporal and spatial pattern of temperature and rainfall in the Qinghai-Tibet Plateau,and it further affected the decomposition of litter and the circulation of nutrients in the ecosystem of the cold region,especially the litters decomposition in the alpine meadow ecosystem.A simulating rainfall was established in an alpine meadow of the Northwest Sichuan Province,including decreasing rainfall supply by 50%,30%,90%,an increase by 50% and natural rainfall.Litter bag technique was used to study the decomposition and nutrient dynamics of meadow litter in the four functional groups(grass,sedge,forbs,and the whole plant litters.The results indicated that:1.The topsoil moisture(0-10 cm)would increase with increasing rainfall.At the end of growing season,soil moisture decreased significantly and soil compactness increased significantly under the 90% rainfall supply decreased.2.The effects of different rainfall gradients on the functional traits of the dominant plants changed with plant species and organs.The height of vegetative shoot,the length of leaves and the average number of flowering per plant of Anemone rivularis and the height of vegetative shoot of Elymus natans under the 50% rainfall supply decreased were significantly higher than those of CK.The length of leaves of Gueldenstaedtis siversifolia under the 90% rainfall supply decreased was significantly lower than CK.The height of vegetative shoot of Kobresia humilis under the 90% rainfall supply decreased than CK.3.The Richness,Abundance,Coverage,Biomass,Simpson index,Shannon-Wiener index of the plant community were not significantly changed when the decreased rainfalls were no more than 50%.However,the forbs and legumes coverage were significantly decreased and the coverage and biomass of grass significantly increased compared with CK although the plant community biomass were not significantly changed.4.Changes in rainfall had significant effects on hemicellulose,cellulose,total phosphorus(TP)and total nitrogen(TN)of different plant functional groups initial litter.The total nitrogen content of grass,sedge,and mixed litters in 30% rainfall supply decreased was significantly higher than CK.The total phosphorus content TP of grass,sedge and mixed litter in 50% rainfall supply increased was significantly higher than CK.5.The grass litter had the slowest decomposition rate while the forb litters was sensitive to the changed rainfalls.Sedge litter in 90% rainfall supply decreased and mixed litter in 50% rainfall supply increased have lowest remaining mass.The effects of rainfall on litters were happened in middle and late period of decomposition.There was no significant promoting or inhibiting effect among grass,sedge and forbs in mixed litters.6.The litter decomposition was mainly affected by the decompos ition time of litters,rainfall,cellulose content and C/N ratio.90% rainfall supply decreased inhibited the decomposition of hemicellulose,cellulose and the release of TC,TN,and TP.In total,changes in rainfall not only change the quantitative characteristics of plant communities and soil physical environment,but also affect the decomposition of litter and the release of nutrients.Among them,90% rainfall supply decreased had the greatest impact on the structure and function of the alpine meadow ecosystem.Under this treatment,the soil surface moisture was significantly reduced,the number of above-ground vegetation groups was significantly changed,and the decomposition of litter was significantly inhibited.