A Study Of Soil Microbial Biomass Content Along Altitudinal Gradient Of The Typical Forest Communities On The Eastern Slope Of The Gongga Mountain And The Glacial Retreat Field Of The Hailuogou Glacier

Soil microbial biomass, the most sensitive and variable part of soil organic matter, playsan important role in soil nutrient cycling and ecological system stability. Soil microbialbiomass is the live indicator of soil fertility level and sensitive index of the soil microbevariation, indicating the variation trend of soil organic matter and the microflora in the soil,thus also an important index for the sustainability of soil quality. In this paper, we firstlystudied the soil microbial biomass content along altitudinal gradient of the eastern slope of theGongga Mountain and the glacial retreat sites of the Hailuogou Glacier with Fumigationextraction method, and then analyzed the relationship between soil microbial biomass and soilchemical properties.In the study at the eastern slope of Gongga Mountain we got the following results:1)The soil available nitrogen, dissolved organic carbon and soil microbial biomass varied alongthe altitudinal gradient, and decreased from the soil surface to subsurface, probably due to thedifferent return plant residue, decomposition rate, as well as temperature and moisture indifferent elevations.2) The range of NH4+-N content was from1.7mg kg^-1to134.2mg kg^-1,NO₃^-+NO₂—N from2.6mg kg^-1to202.0mg kg^-1, dissolved organic carbon from30.6mg kg^-1to610.2mg kg^-1, soil microbial biomass carbon from41.4mg kg^-1to2538.5mg kg^-1, and soilmicrobial biomass nitrogen from0.6mg kg^-1to410.7mg kg^-1. Soil available nitrogen,dissolved organic carbon and soil microbial biomass were all significantly related to eachother, indicating that all these three indexes are dependent on soil organic matter.3) The ratioof soil microbial biomass carbon to soil microbial biomass nitrogen ranged from2.4to65.3,mostly less than6.0, which meant that bacteria dominate the soil microbial community in theeastern slope of the Gongga Mountain.For the study of soil microbial biomass along the glacial retreat sites of the HailuogouGlacier, we had the following results:1) The soil available nitrogen, dissolved organic carbon,total nitrogen and soil microbial biomass varied along the glacier succession time, anddecreased from the soil surface to subsurface, probably due to the different return plant residue, decomposition rate, as well as temperature and moisture in different succession sitesof different time.2) The range of NH4+-N content was from4.78mg kg^-1to145.53mg kg^-1,NO₃-+NO₂--N from1.23mg kg^-1to46.08mg kg^-1, total nitrogen from284.38mg kg^-1to1980.56mg kg^-1, dissolved organic carbon from45.89mg kg^-1to338.77mg kg^-1, soilmicrobial biomass carbon from2.76mg kg^-1to1230.57mg kg^-1, and soil microbial biomassnitrogen from0.16mg kg^-1to245.30mg kg^-1.3) The ratio of soil microbial biomass carbonto soil microbial biomass nitrogen ranged from0.36to22.99, mostly less than6.0, whichmeant that bacteria dominate the soil microbial community in our study sites at the glacierretreat sites of the Hailuogou Glacier.