短期放牧对高寒草甸土壤水稳性团聚体构成及稳定性的影响

Effects of Short-term Grazing on Constitution and Stability of Soil Water-stable Aggregates in Alpine Meadow

土壤水稳性团聚体是土壤肥力的基础。以青藏高原东北边缘地区高寒草甸为对象,采用放牧控制试验研究不同放牧强度下各粒级水稳性团聚体含量、根系和微生物数量的变化特征,以期阐明短期放牧对水稳性团聚体及其稳定性的影响。结果表明,中牧能够增加土壤内水稳性大团聚体的含量。土壤水稳性团聚体有机碳含量随土层深度增加而减少,中牧时在0—10cm土层,粒径>1mm的土壤水稳性团聚体有机碳含量显著低于对照,但在10—20cm土层,粒径<1mm土壤水稳性团聚体有机碳含量大于对照和其他放牧处理;随着放牧梯度的增大,地下生物量也递增,在0—10cm土层表现最为明显;中牧处理下土壤中真菌数量最大,而放线菌的数量随着放牧强度的增大而增大。

Soil water-stable aggregates are the base of soil fertility. The content of water-stable aggregates was measured under controlled conditions to determine how short-term grazing influences soil aggregate stability and biomass in an alpine meadow on the northeastern edge of the Qinghai--Tibetan Plateau. Results showed that the content of water-stable macro-aggregates increased under moderate grazing. Organic carbon in water-stable aggregates was reduced with increasing soil depth. Compared with the control, organic carbon in 〉1 mm water-stable aggregates within 10 cm of soil surface was significantly reduced under moderate grazing, but 〈1 mm water-stable aggregates in the 10--20 cm soil layer increased. The biomass was signifi- cantly increased within 10 cm of soil surface with the increasing grazing intensity. Rhizosphere soil under moderate grazing had the largest amount of fungi and the number of actinomycetes increased with the increasing grazing intensity.