围封与放牧对土壤微生物和酶活性的影响

以阿拉善高原微温干旱温带半荒漠类草地为对象，研究了围封与放牧对土壤微生物量碳、氮及土壤酶活性的影响，旨在为荒漠区退化草地的恢复与重建提供科学依据。结果表明，1）围封与放牧地土壤微生物量碳含量无显著差异（P＞0.05），而围封样地内土壤微生物量氮含量显著高于放牧样地（P＜0.05），从而使得其土壤微生物量碳氮比显著低于放牧样地，且围封与放牧条件下不同土层的土壤微生物量碳、氮含量变化规律均为表层（0~10 cm）土壤高于下层（10~20 cm）土壤。2）围封样地表层土壤脲酶和碱性磷酸酶的活性均高于放牧样地，下层土壤的碱性磷酸酶的活性也高于放牧样地，而脲酶活性则显著低于放牧样地。对于土壤蔗糖酶活性，围封样地仅下层土壤显著高于放牧样地，而表层土壤无差异。另外，围封和放牧条件下3种酶的活性在不同土层间的高低规律也不一致。3）围封与放牧条件下土壤微生物量碳和氮含量与土壤酶活性的关系表现不同，围封条件下，仅土壤微生物量碳含量与土壤脲酶活性呈显著正相关，而与土壤蔗糖酶活性呈显著负相关。放牧条件下，土壤微生物量碳和氮均与土壤脲酶活性呈显著负相关，而与蔗糖酶和碱性磷酸酶活性呈显著正相关。另外，土壤微生物量碳氮比与脲酶活性在放牧条件下也呈显著正相关性。

Effects of grazing and fencing on soil microorganisms and enzymes activities

This research was conducted in the temperate semi desert ecosystems of Alxa Plateau, and studied the effects of grazing and fencing on soil microbial biomass carbon, nitrogen and soil enzymes activities, aiming to provide scientific basis for restoration and reconstruction of degraded temperate semi deser ecosystems. The results showed that: (1)There was no significant difference on microbial biomass carbon between fencing and grazing lands, but soil microbial biomass nitrogen in fencing land was significantly higher than that of grazing lands, which caused soil microbial carbon and nitrogen ratio in fencing lands was significantly lower than that of grazing lands. Soil microbial carbon and nitrogen contents in surface layer (0-10 cm) was higher than those of subsoil (10-20 cm) in fencing lands and grazing lands, respectively; (2) Urease and alkaline phosphatase activities of the surface layer in fencing lands were higher than the grazing. For the subsoil, alkaline phosphatase activities in fencing lands was also higher than that of grazing，while urease activities in fencing lands was significantly lower than that of grazing. For the soil saccharase activities, the subsoil in the fencing lands was significantly higher than the grazing lands，and there was no difference among the surface layers. In addition, the variation of the three enzymes activities in different soil layers under fencing and grazing conditions was inconsistent; (3) The relationships between soil microbial biomass (C and N) and enzyme activities in fencing lands and grazing lands are different. Under fencing conditions, there is a significantly positve correlation between soil microbial biomass carbon and urease activities, while a significant negative correlation was found between soil microbial biomass carbon and saccharase activities. However, under grazing conditions, soil microbial biomass carbon and nitrogen were significantly negative correlated with soil urease activities, and significantly positive correlated with soil saccharase and alkaline phosphatase activities. Furthermore, soil microbial carbon and nitrogen ratio showed a significantly positive correlation with soil urease activities under grazing conditions.