高寒草地灌丛化对土壤团聚体稳定性及有机碳分布特征的影响

Stability of Soil Aggregates and Soil Organic Carbon under Shrub Encroachment Sites in Alpine Meadow

灌丛化是草地生态系统面临的重大生态环境问题之一,是影响高寒草地土壤碳库储量的重要因素。采集青藏高原灌丛化和未灌丛化草地土壤样本,用Cambardella和Elliott湿筛法和沉降虹吸法测定土壤团聚体含量及其稳定性、有机碳(SOC)和全氮(TN)含量,分析了草地灌丛化对土壤团聚体数量及其稳定性的影响。结果表明,灌丛化和未灌丛化草地土壤团聚体以2~0.25 mm粒径为主,但灌丛化草地土壤微团聚体(≤0.053 mm)含量显著低于未灌丛化草地,表明草地灌丛化主要影响土壤微团聚体而对大团聚体含量影响不显著。灌丛化草地土壤团聚体稳定性低于未灌丛化草地土壤,表明草地灌丛化后土壤结构稳定性降低。灌丛化草地土壤SOC和TN含量显著低于未灌丛化草地土壤,说明在气候变化影响下高寒草地灌丛化可能会降低土壤碳库储量。

Shrub encroachment is one of the major ecological environment problems in a grassland and is one of the factors that influences soil carbon(C) stock in the alpine meadows. We used wet sieving of Cambardell and Elliott, the stability of soil aggregates, SOC content, and relationships between SOC and soil particles were investigated. The results showed that the soil aggregate contents in both shrub and non-shrub grassland primarily presented 2-0.25 mm. Microaggregate content(≤0. 053 mm) in the shrub encroachment grassland was significantly reduced compared with the non-shrub grassland. This indicated that shrub encroachment mainly affects the content of soil microaggregates, but not the content of macroaggregates. Stability of soil aggregates in shrub encroachment were lower than those in the non-shrub grassland, indicating stability of the shrub encroachment soil structure decreases. SOC and total nitrogen were significantly lower in the shrub encroachment grassland than those in the non-shrub grassland,which indicated that shrub encroachment grassland, especially under global warming, may reduce soil C reserves.