The Study On Soil Microbial Community Of Forest Soil In Black Soil Region

In order to systematically understand the distribution characteristics on soil microbial communities in typical black soil region of northeastern China, the method of Biolog ECO-microplate culture and dilution-plate method were employed to study several types of forest soil including undisturbed typical black soil (the Populus davidiana natural secondary forest), different kinds of soil and water conservation forests and different forest ages of Larch(Larix gmelini) plantations by measuring and analyzing soil microorganisms quantity, Richness index, Shannon-Weiner index, Simpson index and McIntosh index. The results showed that:1. The quantity of soil microorganism, bacteria and fungi of soil depth (0-150cm) of undisturbed typical black soil decreased with soil depth increasing and achieved maximum value of4.10×106cfu (Coromy Forming Unit)·g-1dry soil,4.05×106cfu·g-1dry soil and5.04×104cfu·g-1dry soil for0-10cm soil depth, respectively. The number of actinomycetes presented a unimodal curve relationship with the increase of soil depth and the maximum in30-50cm soil depth with0.94x104cfu·g-1dry soil. The average well color development (AWCD), richness index. Shannon-Weiner diversity index. Simpson diversity index were and Mclntosh index were decreased gradually with soil depth increasing, varying from0.09-1.21.0-27.0.46-3.17.0.33-0.95, and0.09-8.19. respectively (168h). The carbon sources with higher utilization efficiency or utilization intensity by soil microbes were amino acids, carboxylic acids and polymers. Above all. this result would provide more important primitive characteristics of microbial features in the degradation and restoration process of the quality of the soil habitat scientifically.2. Soil microbial population was the maximum in summer, fewer in spring, and the minimum in autumn of surface soil (0-10cm) of undisturbed typical black soil (the Populus davidiana natural secondary forest). The quantity of soil microorganism, bacteria, fungi and actinomycetes was4.76-16.44×106cfu (Coromy Forming Unit)·g-1dry soil.4.68-16.19×106cfu·g-1dry soil,4.29-10.07×104cfu·g-1dry soil and3.97-14.96×104cfu·g-1dry soil, respectively. The peak value of the average well color development (AWCD) was found in summer followed by spring and autumn in consequence, varying from0.81to1.21(168h). The microbial functional diversity was significantly higher in summer than in spring and autumn(p <0.05) and showed no significant difference in spring and autumn.3. The broadleaved forest (Poplar and Manchurian Ash) may have the higher soil microorganisms quantity than coniferous forest (Larch and Scots Pine) for surface soil (0-10cm) for four kinds of soil and water conservation forests. The peak value of the average well color development (AWCD), Richness index, McIntosh index, Shannon-Weiner index and Simpson index was found in Poplar followed by Manchurian Ash, Larch, Scots Pine in consequence, varying from0.11-0.62,.4-22,1.46-5.21,1.37-3.00and0.62-0.94, respectively (144h). The carbon sources with higher utilization efficiency or utilization intensity by soil microbes were polymers for different forest types, and amino acids and carboxylic acids for broadleaved forest in addition to polymers also. The significant relationships were observed between the metabolic diversity of microbial communities and soil physical and chemical properties. We concluded that broadleaved forest may have the more functional diversity of soil microbial community than coniferous forest. The results presented in this paper could provide theoretical basis and reference for soil and water conservation forest construction in typical black soil region.4.The quantity of soil microorganism, bacteria and fungi of Larch plantations (21-,30-,40-, and52-year-old) increased gradually with forest age increasing, but the number of actinomycetes decreased with that in surface soil (0-10cm); the quantity of soil microorganism in lower layers (10-20cm) showed higher values than in surface soil. The average well color development (AWCD), richness index, Shannon-Weiner index, Simpson index, and McIntosh index increased gradually with forest age increasing, varying0.41-1.40and0.20-0.69,12-25and6-14,2.55-3.12and1.83-2.62.0.89-0.95and0.76-0.91,4.22-9.49and2.52-6.18for0-10cm and10-20cm soil depth, respectively (168h). Sensitive carbon source to cause the microbial metabolic differences were carbohydrates, polymers and amines for soil of0-10cm, and carboxylic acids for10-20cm in addition to carbohydrates and amines also. The significant relationships were observed between the metabolic diversity of microbial communities and soil physical and chemical properties. We concluded that functional diversity of soil microbial community in the larch plantation increases gradually with the increase of forest age and soil microbial functional diversity can be improved by implementing plantation vegetations recovery. The results presented in this paper could further suggest a reference for revealing transmutation of soil quality under plantations of black soil region.