高寒草甸土壤团聚体碳氮磷对退化的响应及其影响因素

Response and Its Influencing Factors of Soil Aggregates Carbon,Nitrogen and Phosphorus to the Degradation in Alpine Meadows

植物和土壤微生物是土壤团聚体黏合物和养分的重要来源,因此土壤团聚体组成及其养分库的变化可指示生态系统退化过程。本文在长江源区根据植被群落特征选取未退化、中度和严重退化高寒草甸,研究其土壤中大团聚体(>250μm)、微团聚体(55~250μm)和游离态粉粒黏粒(<55μm)含量、不同粒级团聚体碳氮磷含量及储量随草地退化的变化特征,并分析了植物和微生物活动与这些变化特征的关系。结果表明:未退化和中度退化高寒草甸土壤以微团聚体为主。退化使高寒草甸大团聚体和微团聚体碳氮含量及储量显著下降,但磷含量及储量未发生显著变化。游离态粉粒黏粒氮磷储量在严重退化高寒草甸显著增加。各团聚体碳氮含量与地上生物量和微生物量碳正相关,磷含量与微生物量碳负相关。本研究表明植物及受其影响的土壤微生物变化是造成高寒草甸退化后不同团聚体碳氮磷库变化的主要原因。

Plants and soil microorganisms are important sources of adhesion substance for soil aggregates formation.Therefore,changes of the composition and nutrient pools of soil aggregates can indirectly indicate the process of ecosystem degradation.In this paper,undegraded,moderately degraded and severely degraded alpine meadows were selected according to the characteristics of meadow vegetation communities in the source region of the Yangtze River in Qinghai Tibet Plateau.The contents of macroaggregates(>250μm),microaggregates(55~250μm)and free silt+clay particles(<55μm),the contents and storage of total organic carbon,total nitrogen and total phosphorus in the aggregates with different sizes were examined.The relationship between the changes in soil aggregates and plant biomass and other soil properties were analyzed.Results showed:the microaggregates were the main aggregates of soil in the non-degraded and moderately degraded alpine meadow.The degradation significantly reduced the carbon and nitrogen content and storage in the macroaggregates and microaggregates in the alpine meadow soil;while the content and storage of phosphorous in soil showed no significant change.The nitrogen and phosphorus storage of the free silt+clay particles in soil increased significantly in the seriously degraded alpine meadow.The content of organic carbon and nitrogen in each aggregates of soils were significantly positively correlated with the aboveground biomass and microbial biomass carbon.Furthermore,the content of phosphorus of soil aggregates was significantly negatively correlated with microbial biomass carbon.This study indicated that the changes of plant and soil microbial activities may be the main explanation to the changes of carbon,nitrogen and phosphorus pools in the soil aggregates after the degradation of alpine meadow.