Abstract:

In order to explore the vertical distribution characteristics and influencing factors of soil labile organic carbon (SLOC) in desert steppe, the Leymus secalinus community, Agropyron mongolicum community, Stipa capillata community and Penniseturn centrasiaticum community were investigated, and the SLOC contents of different plant communities were analyzed at vertical distribution. The results showed that the vertical distribution of SLOC significantly differed among different typical vegetation communities in desert steppe. The SLOC contents of Leymus secalinus, Agropyron mongolicum and Penniseturn centrasiaticum communities increased first then decreased at the soil layers of 0~100 cm, whereas that of Stipa capillata community showed continuous reduction and "surface accumulation" obviously. The highest SLOC contents of Penniseturn centrasiaticum and Leymus secalinus communities were measured at the soil layer of 10~20 cm, while Agropyron mongolicum and Stipa capillata communities were at the soil layer of 0~10 cm. Correlation analysis showed that there was a significant correlation between SLOC content and soil total organic carbon (R²=0.9595). Pearson's correlation coefficients showed that the content of SLOC in desert steppe was positively correlated with aboveground biomass, surface litter and vegetation coverage. These results confirmed that surface litter was an important source of SLOC in desert steppe and the vertical distribution of SLOC could be more influenced by vegetation characteristics and root distribution than soil physical and chemical parameters.

Key words: Desert steppe, Plant community, Soil labile organic carbon, Vertical distribution

摘要：

以荒漠草原赖草（Leymus secalinus）、蒙古冰草（Agropyron mongolicum）、针茅（Stipa capillata）和白草（Penniseturn centrasiaticum）群落4种典型群落为研究对象，分析不同群落土壤活性有机碳（SLOC）的垂直分布特征及其影响因素。结果表明：不同典型群落SLOC垂直分布特征具有明显差异，赖草群落、蒙古冰草群落和白草群落SLOC含量在0~100 cm垂直分布表现为先增加后降低的趋势，浅根型的针茅群落SLOC含量垂直分布则持续降低，白草和赖草群落SLOC含量在10~20 cm最大，针茅和蒙古冰草群落SLOC含量在0~10 cm最大。相关性分析结果显示，SLOC与土壤总有机碳含量呈现极显著相关性（R²=0.9595）；与土壤理化性质等因子相关性比较，SLOC更依赖于植被覆盖度、地上生物量和地表枯落物，尤其是地表枯落物与SLOC的相关性更高。表明除了植被和根系分布特征，荒漠草原的枯落物对SLOC垂直分布特征有更大的影响。

关键词: 荒漠草原, 植物群落, 土壤活性有机碳, 垂直分布