不同放牧强度和围封对高寒灌丛草地土壤微生物量的影响

Effect of grazing intensity and fencing on soil microbial biomass in alpine shrubland

以祁连山高寒灌丛草地为对象,研究了不同放牧强度和围封对土壤理化性质、土壤微生物特征的影响。结果表明:随着放牧强度的增大,同一土层微生物量碳、微生物量氮含量、有机碳、全氮含量降低,而pH值升高,土壤含水量在中度放牧区最高,且差异显著(P<0.05)。各个放牧强度灌丛草地围封后不同土层微生物量碳、微生物量氮含量、有机碳、全氮含量、含水量均高于放牧处理,pH显著低于放牧处理;同一放牧强度和围封处理,土壤含水量、有机碳、全氮、微生物量碳、微生物量氮含量均随土壤深度的增加而减少,而pH值随土壤深度的增加而增加。相关性分析表明,土壤微生物量碳与有机碳、含水量呈显著正相关,与pH呈显著负相关。土壤微生物氮与微生物量碳,有机碳、全氮、含水量呈显著正相关,与pH呈显著负相关。过度放牧降低了高寒灌丛草地土壤养分和微生物生物量,围封有利于过度放牧草地土壤养分库及土壤微生物系统的功能恢复。

Grazing is an important factor affecting the grassland soil system and causing grassland degradation.Fencing is beneficial to the restoration of grassland ecological function.The effects of grazing intensity and fencing on the physical and chemical properties of soil and the characteristics of soil microorganisms in alpine shrubland were studied in Qilian Mountains.The results showed that with the increase of grazing intensity,the microbial biomass carbon,microbial biomass N,organic carbon and total N content were reduced in the same soil depth,while the pH value increased,the soil water content was the highest under the middle grazing intensity(P<0.05).The soil microbial biomass C,microbial biomass N,organic carbon,total N content and soil moisture content were higher after the fencing treatment,and the pH value was significantly lower.Under the same grazing intensity and fencing treatment,the soil water content,organic carbon,total N,microbial biomass carbon,and microbial biomass N content all decreased with soil depth.The pH increased with soil depth.The correlation analysis showed that soil microbial biomass carbon was positively correlated with organic carbon and water contents,and negatively correlated with pH value(P<0.05).Soil microbial N was positively correlated with microbial biomass carbon,organic carbon,total N and water content,and negatively correlated with pH value(P<0.05).Overgrazing reduced the soil nutrients and microbial biomass in the alpine shrubland,and the fencing was beneficial to the functional recovery of soil N pools and soil microbial systems in overgrazed grassland.