围封对青海湖流域高寒草甸植被特征和土壤理化性质的影响

以青海湖流域退化的高寒草甸2个草地类型为对象，比较分析了围封2年样地植物群落生物量、群落结构和土壤理化性质的变化。结果表明，1）围封后高山嵩草和矮生嵩草的地上生物量较放牧地分别增加了33．8％和31．5％；且禾本科植物生物量的比例显著增加，杂类草的比例降低。2）功能群多样性指数和均匀度指数显著增加。3）围封2年后，2个草地型0～10 cm 土层土壤有机碳含量分别增加了10．15％和12．74％，10～30 cm 土层均无显著变化；矮生嵩草草地0～10 cm 土层土壤全磷含量增加了16．13％，其余无显著变化；表层土壤容重分别降低了6．61％和6．25％，pH 值降低了4．04％和3．69％，10～30 cm 土层均无显著变化；土壤全磷含量在各土层均无显著变化。

Effects of fencing and grazing on vegetation and soil physical and chemical properties in an alpine meadow in the Qinghai Lake Basin

The aim of this study was to determine the effects of fencing on the productivity and structure of plant communities and on the physical and chemical properties of soil in alpine meadows.A field study was conducted in two types of degraded alpine meadows,one dominated by Kobresia pygmaea and the other domi-nated by Kobresia humilis ,in the Qinghai Lake Basin.The results showed that the aboveground biomass of K .pygmaea and K .humilis increased by 33.8%,and 31.5%,respectively,after 2 years of exclosure.Exclo-sure significantly increased the proportion of aboveground biomass of sedges and members of the gramineae, and decreased the proportion of aboveground biomass of forbs.Exclosure also resulted in significant increases in plant community diversity and evenness indexes.In the K .pygmaea and K .humilis alpine meadows, grassland soil organic carbon content in the 0-10 cm soil layer increased by 10.15% and 12.74%,respective-ly,after 2 years of exclosure.The soil organic carbon content in the 10-30 cm soil layer did not change signifi-cantly after 2 years of exclosure.In K .humilis meadow soil,the total phosphorus content increased by 16.13% in the 0-10 cm soil layer,but was unchanged in 10-30 cm soil layer after 2 years of exclosure.In the K .pygmaea and K .humilis alpine meadows,soil bulk density increased by 6.61% and 6.25%,respectively, and pH decreased by 4.04% and 3.69%,respectively,in the 0-10 cm layer after 2 years of exclosure.In the 10-30 cm soil layers of both types of meadows,neither soil bulk density nor pH was affected after 2 years of exclosure.