Effects Of Soil Biological Crust On Biological Characters Under Different Vegetations In The Loess Hilly Region

In order to study the biological effects of soil biological crust and the distribution of soil microorganisms and enzymes activities in the area of Pianguan in Shanxi province, the quantity of soil microorganisms( bacteria, actinomycetes, fungi ) and activities of 4 enzymes( catalase, sucrase, urease, alkaline phaosphatase ) are examined under the vegetation of Pinus sylvestris var. mongolica, grassland, Caragana microphylla, Pinus tabulaeformis and fallow land at 3 defferent period respectively, the results show that:1. The quantity of soil microorganisms among different vegetations is significantly different. In 5 vegetations, the total number of microorganisms,bacteria,actinomycetes and fungi are the highest at P. tabulaeformis, the total number of microorganisms and bacteria are lowest at abandoned land, actinomycetes and fungi are lowest at grassland and C. microphylla, respectively. The total number of microorganisms and bacteria are decreasing with the fallow period, actinomycetes and fungi have no relationship with abandoned period, the total number of microorganisms and bacteria tend to increase with the P. tabulaeformis planting years, actinomycetes have no relationship with planting years.2. The quantity of soil microorganisms associat with the types of soil biological crust, the quantity of soil microorganisms of Under-crust soil is significantly higher than Non-crust soil in almost all plots. The order of the quantity of bacteria and the totle microorganism is: Medium thickness crust>Thin crust>Thick crust>Non-crust, the change of actinomycetes and fungi under different types of crust are irregular.3. The quantity of soil microorganisms indicate a negative relation with the depth of the soil. The total number of microorganisms and bacteria show a significant difference with different level of soil depth, however, the actinomycetes and fungi show only within some level of soil depth.4. The variation of soil enzymes activities is different, however, it is highest in P. tabulaeformis and lowest in abandoned land, and it shows a negative relation and a positive relation with the fallow period and the planting years of the P. tabulaeformis, respectively.5. The soil enzymes activities of Under-crust soil is higher than Non-crust soil in all plots, however, it shows irregular tend in soil under different types of crust. Urease and Alkaline phaosphatase: Medium thickness crust>Thin crust>Thick crust>Non-crust, the difference between these is almost significant, the changing of Catalase and Sucrase shows regular trend only in some plots.6. Activities of all the 4 soil enzymes shows a negative relation with the depth of the soil, and shows significant difference at most of vegetation conditions.