贡嘎山东坡土壤有机质及氮素分布特征

Distribution Characteristics of Soil Organic Matter and Nitrogen on the Eastern Slope of Mt. Gongga

对贡嘎山东坡自然垂直带土壤有机质和氮素的分布特征的研究表明,贡嘎山东坡表层土壤有机质和全氮含量随海拔升高有上升趋势,但在针阔混交林以上出现波动,在群落过渡带处出现显著峰值,气候和植被类型的综合作用决定了有机质和氮素的空间分布.土壤有机质和氮素在土壤剖面中的垂直分布趋势一致,凋落物层和土壤A层高于B、C层,这与动植物残体在土壤中的垂直分布格局类似.群落过渡带在腐殖质A层出现氮素累积峰.土壤碳氮比介于7～25之间,相对较低,利于土壤腐殖质化和有机氮矿化.碳氮比随海拔升高而升高,在土壤剖面中的分布随植被类型不同而有所差异.土壤中的氮素主要以有机氮的形式存在于土壤有机质中,土壤碳氮比与有机质含量显著相关.

The distribution of soil organic matter (SOM) and nitrogen of Gongga Mountain were studied in this paper. The results showed that the contents of SOM and N of A horizon had an ascending trend with the increase of the elevation. The vegetation types distributed higher than the mixed broad-leaved conifer forest had the irregular trends. In the transitional communities such as mixed forest and treeline, the contents of SOM and N were higher than other vegetation types. The distribution of SOM and N of A horizon was determined by the mutual effect of climate and vegetation types. The vertical distribution of SOM and N in soil profile had the similar trends in all kinds of vegetation types, i.e., the content of A horizon was higher than that of the B and C horizons, which was the same to the distribution of dead animals and plants in soil. There were N accumulation peaks in A horizon of the transitional communities. The soil C:N is between 7 and 25, which is lower relative to the appropriate C:N of 25-30. The soil C:N increased with the increase of the elevation, but its vertical distribution in the soil profile varied with different vegetation types. The N in the SOM existed mainly in the form of organic nitrogen, and the soil C:N was significantly correlated with SOM.