放牧对高寒嵩草草甸土壤微生物量碳的影响及其与土壤环境的关系

通过对高寒嵩草草甸不同放牧压力下土壤微生物量碳、土壤物理性状和速效养分的变化特征及其相互关系的研究,表明随着放牧压力的增大,土壤微生物量碳、有机质及速效磷显著降低;土壤pH值、容重及根土比显著升高;速效氮和速效钾变化不一致。相关性分析表明,土壤有机质、根土比、有效磷、土壤容重与微生物量碳具有较大的关联度;土壤有机质、有效磷、土壤容重和根土比对微生物量碳的形成有较强的直接作用,有效氮表现出较强的间接效应;根土比-有效磷、有机质-土壤容重、有效氮-土壤容重之间互相调节,互相制约,间接调控着微生物量碳形成。过度放牧使土壤系统的微环境恶化,速效养分的供给能力及有机物质的转化能力降低,从而导致了植被和土壤系统的双重退化和微生物量碳的低下。

Grazing impact on soil microbial biomass carbon and relationships with soil environment in alpine Kobresia meadow

The grazing impact on soil microbial biomass carbon,soil physical properties,available nutrients and the relationship with soil environmental factors under different grazing intensities in alpine Kobresia meadows was studied.The soil microbial biomass carbon,organic matter and available phosphorus decreased with increasing grazing intensity,while the soil pH,bulk density and root soil ratio showed the opposite effect.The direct effects of soil organic matter,available P,bulk density and root soil ratio on metabolization of microbial biomass carbon were significant,while the indirect effect of available N were relatively distinct.The interaction between root-soil ratio to available P,organic matter to bulk density,and available N to bulk density indirectly regulate the formation of microbial biomass carbon.Intensive grazing led to destruction of the soil system microenvironment,blocking the supply capacity and transformation ability of nutrients and thus resulting in lower microbial biomass carbon and a double degradation of vegetation and soil.