Study On The Biodiversity Of Soil Microorganism In Eucalyptus Grandis Plantation

Soil microbial ecology is one of the hot fields in soil science world wide in recent years. Recently, soil microbial ecology focuses on the following fields: soil microbial community and biomass, nitrogen fixation, mycorrhizas, rhizospheric microbes, and microorganism activity in microcosm, etc. Researches on soil microbial ecology will be helpful to understand the process of forest ecosystem. To find out the ecological distribution regulations of soil microbes group in Eucalyptus grandis plantation, The amount and group distribution of soil microbes including bacteria, fungi and actinomycetes were investigated in 2004 in Eucalyptus grandis plantation of Hongya county.The results showed that the microorganisms population in soils under the soil in Eucalyptus grandis vary with seasons in a year , showing the maximum in autumn , fewer in spring and the minimum in summer or winter, that among the three kinds of microorganisms, namely bacteria, actinomycetes and fungi, Soil microbial numbers in all lands are all follow the order: Bacteria>Actinomycetes>Fungi. In all samples, bacteria coverde 92.83⁹5.45% of the total amount of microorganisms, actinomycetes about 4.17⁶.66%, fungi only 0.38⁰.50%. The results showed that microbes there were mainly concentrated in the 0²0 cm soil layer and their quantity rapidly decreased with the increase of soil depth ; The numbers of soil microbes of the same group varied greatly in soil with a depth of 0⁶0cm, among which aerobic bacteria was 0.31 × 10⁶ 14.39×10⁶cell·g^-1 , actinomyces 0.06×10⁶⁰.79×10⁶cell·g^-1, fung 0.06×10⁶⁰.79×10⁶ cell·g^-1, and anaerobe 0.05×10⁶³.22×10⁶cell·g^-1. Total microbial numbers in 0²0cm was more than that in the other soil layers, the vertical distribution of total microbial number was:0²0cm>20⁴0cm>40⁶0cm, which decreased along with soil depths. Comparing to C. glauca second growth land and Farming land , the number of soilmicrobes in Eucalyptus grandis plantation is larger than C. glauca second growth land . With the insemination of Eucalyptus grandis, the activity of soil microbes becomes more active, and the amount of soil microbes becomes more larger . The Simpson index of the bacteria physiological groups is 0.806, and the Shannon-Wiener index of the bacteria physiological groups is 1.709.The Eucalyptus grandis plantation as a kind of tree for the Cropland Conversion to Forest and Grassland (CCFG) has a good ecological and economic benefit.With the traditional culturing approaches, the dominant of microorganisms was researched. The dominant population of bacterial physiological groups was the genus of Aerobic nitrogen fixing bacteria > Rhizobia ^ Ammonifying bacteria > Organic phosphorus-decomposing bacteria in Eucalyptus grandis plantation, that of actinomycetes was Genus Streptomyces (over 90% ) and the dominant fungal genera were Penicillium and Aspergillus.The total amount of microorganisms was 18.07*106 cell-g"1 in rhizosphere of Eucalyptus grandis. Soil microbial numbers in rhizosphere of Eucalyptus grandis followed the order: B acteria > Actinomycetes > Fu ngi.