三江源农牧交错区植被群落及土壤固碳持水能力对退耕还草措施的响应

Response of vegetation community structure,soil carbon sequestration,and water-holding capacity in returning farmland to grassland plots,in the agro-pastoral transitional zone in the Three Rivers Source Region

为探讨三江源农牧交错区植被群落演替、土壤固碳及水源涵养能力对退耕还草措施的响应,以青海省过马营镇退耕还草封育示范区为研究区域,通过野外实地监测及室内试验相结合的方法,分析了油菜(Brassica campestris)地经退耕还草措施后,植被群落演替、土壤固碳及持水能力的变化状况。结果显示,1)退耕还草11年后,其植被群落盖度、平均高度、植物分层及地上生物量均达到原生植被水平;而Shannon-Wiener群落多样性指数和Pielou均匀度指数分别达到原生植被的80.9%和97.5%。2)退耕还草11年后,0-40cm土层的土壤容重降低5%,土壤饱和持水量、毛管持水量及田间持水量分别较原生植被样地增加了12.6、9.4和11.2mm。3)退耕还草11年后,0-20cm土层土壤有机碳密度和C/N显著高于原生植被样地31.85%和37.63%(P<0.05),土壤全氮密度与原生植被样地的无显著差异(P>0.05)。综上所述,退耕还草措施有利于农牧交错区荒漠化草地生态环境的恢复,是遏制和改善三江源区草地荒漠化的有效措施之一。

The present study aimed to explore the response of vegetation community succession, soil carbon sequestration, and water conservation capacity in returning farmland to grassland plots in the agro-pastoral transitional zone in the source region of the Three Rivers. The study region was a returning farmland to grassland demonstration zone in Guomaying town, Qinghai province and the study analyzed the changes in plant commu- nity succession, soil carbon sequestration, and water-holding capacity by field monitoring and laboratory experiments. The results demonstrated that： 1） After 11 years, total coverage, average height, number of layers of plants, and aboveground biomass in returning farmland to grassland plots all reached the same levels as the original vegetation, and the Shannon-Wiener diversity index and Pielou evenness index reached 80.9% and 97.5%, respectively, of the original vegetation. 2） After 11 years, the soil bulk density of the 0--40 cm layer of returning farmland to grassland plots decreased by 5% compared to the original vegetation plots, and the saturation moisture capacity, capillary moisture capacity, and field capacity of returning farmland to grassland plots were 12.6, 9.4, and 11.2 mm greater than that of the original vegetation plots, respectively. 3） After 11 years in the returning farmland to grassland plots, the soil organic carbon density and C/N had significantly increased by 31.85% and 37.63%, respectively, compared to the original vegetation plots （P〈0.05）, and there was no significant difference between the soil total nitrogen density of the returning farmland to grassland plots and the original vegetation plots （P〉0.05）. The results indicate that the returning farmland to grassland plots have benefited from restoration of the ecological environment in desert pastures in the agro-pastoral transitional zone. This is an effective measure to contain and improve the desertification in the source region of the Three Rivers.