围栏与不同放牧强度对东祁连山高寒草甸植被和土壤的影响

在东祁连山高寒草地,对围栏7年和不同放牧强度的草地进行了物种数、地上生物量、地下生物量、土壤理化性质等研究。结果表明,围栏7年的高寒草地鲜草产量为425.8 g·m-2,显著高于夏季中牧159.3 g·m-2和夏季重牧91.0 g·m-2,但与冬季轻牧、夏季轻牧差异不显著。围栏条件下的物种数为26.3种·16 m-2,显著低于其他放牧条件下的物种数,但显著高于夏季重牧条件下的物种数23.0种·16 m-2;轻度或重度放牧都会使物种数减少,夏季中牧下的物种数最高(33.5种·16 m-2)。在0~10 cm的表层土壤中,围栏7年的草地根系生物量显著高于其他放牧强度。随着放牧强度的增加,根系生物量在0~10 cm土壤中呈下降趋势,在30~40 cm土壤中则表现为升高趋势。围栏7年的土壤容重低于其他放牧强度下的土壤容重,但差异不显著;夏季重牧的土壤容重显著高于围栏7年和其他放牧强度的土壤容重。随着放牧强度的增加,0~10 cm土壤碱解氮增加,围栏7年草地最低。围栏封育可有效改善和恢复草地植被,但不能长时间禁牧不进行放牧利用。合理的放牧能够维护高寒草甸草地生态系统功能、促进物种丰富度和土壤营养的均衡。

Influence of enclosure and grazing intensity on alpine meadow vegetation and soil characteristics in the Eastern Qilian Mountains

In order to explore the influence of enclosure and different grazing intensities on alpine meadow vegetation and soil characteristics, plant species, aboveground biomass and underground biomass of forage, soil physical and chemical properties were measured in the Eastern Qilian Mountains. The results showed that the yield of alpine meadow grassland fenced for seven years was 425.8 g·m^-2, and significantly higher than that of summer moderate grazing (159.3 g·m^-2) and summer overgrazing (91.0 g·m^-2), but it was not significant compared with the light grazing both in summer and winter. The number of species after seven years fencing (26.3·16m^-2) was lower than that in other grazing patterns, but it was significantly higher than the grassland overgrazed in summer (23.0·16m^-2). Light grazing or/and overgrazing reduced the number of species, while the moderate grazing in summer increased the species diversity (33.5·16m^-2). Dry matter of underground biomass in 0 to 10 cm topsoil fenced for seven years was significantly higher than that of other grazing plot of alpine meadow grassland. Dry matter content of underground biomass in 0 to 10 cm soil depth increased with the increase in grazing intensity, but the reverse trend was observed in 30 to 40 cm soil depth. The soil bulk density fenced for seven years was lower than that of other grazing intensities, whereas that of overgrazing in summer was significantly higher than that fenced for seven years and other grazing intensities. Among the treatments, alkali-hydrolytic nitrogen of 0 to 10 cm soil depth was the lowest for seven years fencing. Reasonable grazing can maintains the function of ecological system of alpine meadow and increases species diversity and balances soil nutrients.