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

在半干旱草地，关于放牧和封育管理对草地植物枯落物分解及其与土壤动物互作关系的研究一直是该区域生态系统物质循环与生态恢复过程研究的重要科学问题。以放牧和封育样地中赖草(Leymus secalinus)、牛枝子(Lespedeza potaninii)及其混合枯落物为研究对象。于2017年9月、2018年5月和9月、2019年5月和9月，采用2种不同孔径(30目和250目)网袋量化中小型土壤动物的作用，调查了宁夏半干旱草地枯落物碳、氮和磷元素分解与土壤动物群落分布及其对放牧和封育样地的响应规律。结果显示：(1)封育样地中，枯落物碳元素最终残留率均表现为3种枯落物处理间无显著差异；但250目网孔中枯落物氮、磷元素最终残留率和30目网孔中氮元素最终残留率均表现为牛枝子显著高于赖草和混合物，而后两者间无显著差异；仅30目网孔中磷元素最终残留率表现为牛枝子和混合物显著高于赖草，而前两者间无显著差异。放牧样地中，250目网孔的碳、磷元素最终残留率和30目网孔中的氮、磷元素最终残留率均表现为牛枝子显著高于混合物，而赖草居中；氮元素最终残留率表现为牛枝子显著高于赖草和混合物，后两者间无显著差异。(2)...

Response of C, N and P release dynamics of plant litter to grazing and enclosure management in semiarid grassland ecosystem

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.