碳、氮、钾添加对荒漠草原凋落物分解特征的影响OA北大核心

Decomposition of litter is an important component process of energy flow and material cycling in grassland ecosystems.However it is not clear how litter decomposition in desert grasslands responds to the addition of carbon(C),nitrogen(N),and potassium(K).Clarification of this relationship is needed to improve our understanding of the nutrient cycling process in desert grasslands.In this study,the mesh bag decomposition method was used in a randomized block design,to study the effects of exogenous C,N,and K addition on the litter decomposition characteristics of the dominant species Stipa breviflora and Leymus secalinus in Ningxia desert grassland.Litter decomposition was tested in soils fertilized with one of three rates of C(vermicompost,30%C),N(urea,46%N)or K(KCl,60%K)as follows:C1(0 g·m-2·yr-1),C2(52.54 g·m-2·yr-1)and C3(705.09 g·m-2·yr-1)set at the experimental site;along with nutrient addition treatments.N1(0 g·m-2·yr-1),N2(5 g·m-2·yr-1)and N3(20 g·m-2·yr-1),three C,N,and K concentration gradients,K1(0 g·m-2·yr-1),K2(9.0 g·m-2·yr-1)and K3(18.0 g·m-2·yr-1).It was found that significant differences in the effects of C,N,and K addition on litter decomposition and different decomposition rates of litter from S.breviflora and L.secalinus(P<0.05).Half-lives for L.secalinus decay ranged from 4.93 to 17.54 months and for S.breviflora from 10.76 to 20.51 months.The decomposition rates of litter from S.breviflora and L.secalinus began to slow down at 120 and 240 days,respectively.Leaves of the two grass species displayed different responses to the addition of C,N,and K nutrients.Under the K3 and K3+N3+C2 treatments,the decomposition rate of L.secalinus litter was faster,while under the CK and K2+N2 treatments,the decomposition rate of S.breviflora litter was faster.According to the exponential decay model,the predicted decomposition rate for L.secalinus litter is greater than for S.breviflora litter.The litter of both L.secalinus and S.breviflora decomposed quickly in autumn.In summary,there were differences in litter decomposition rates of the two grass species in the same habitat,and high additions of K and N and low additions of C promoted litter decomposition rates more strongly than other nutrient addition combinations.