半干旱草 地 植 物 枯 落 物 碳、氮 和 磷 元 素 释 放 对 放 牧 和封育管理的响应

In semi-arid grassland, plant litter decomposition and its interaction with litter arthropods under grazing and enclosure management play implications on material cycling and ecological restoration process. The litter from Leymus secalinus, Lespedeza potaninii, and their mixture were selected as samples, and they were set in situ in Ningxia semi-arid grasslands under enclosure and grazing management. This study probed into the distribution of litter arthropod and its relation to the release of C, N and P contents by using two sizes (30-mesh and 250-mesh) litterbag to quantify the role of small and medium litter arthropod collected in September of 2017, May and September of 2018, as well as May and September of 2019. The results showed that: (1) In the enclosed grassland, there was no significant difference in the final remaining rate of litter C in between L. potaninii, L. secalinus, and mixture; however, there was significantly greater final remaining rate of litter N and P in the 250-mesh, and that of litter N in the 30-mesh in L. potaninii than in L. secalinus and mixture; there was significantly greater final remaining rate of litter P in L. potanini and mixture than in L. secalinus. In the grazed grassland, there was significantly greater final remaining rate of litter C and P in the 250-mesh, and that of litter N and P in the 30-mesh in L. potaninii than in mixture, with intermediate values in L. secalinus. Regarding the final remaining rate of N, there were significantly higher values in L. potaninii than in L. secalinus and mixture, whereas there was no significant difference between L. secalinus and mixture. (2) There was little effect of litter arthropods on the final remaining rate of C, N and P in the three plant treatments. However, there was significantly lower final remaining rate of N in mixture from both 30- and 250 mesh in grazed grassland than in enclosed grassland. There was significantly higher remaining rate of P in L. secalinus in grazed grassland than in enclosed grassland. (3) The Mantel test and principal components analysis indicated a considerable effect of litter arthropods and soil physicochemical properties on the decomposition of litter C, N and P content. It was suggested that litter C, N and P contents were affected by soil properties and plant chemical properties in semi-arid grassland. The effect of grazing management on litter arthropod distribution induced the differences in C, N and P nutrient release between various species of plant litter. The grazing disturbance could weaken the linkage between litter decomposition, arthropod and soil, while in feedback grazing could promote the litter decomposition of N and P content in mixture.