Study On The Effect Of Soil Microorganism On Biological Soil Crust In The Treatment Of Desert Soil

This paper was conducted to study 4 sand dunes of a testing station of the Chinese Academy of Sciences, namely, fixed sand dune of natural vegetation (Sample 1), unenclosed fixed sand dune of artificial vegetation (Sample 2), enclosed fixed sand dune with artificial vegetation (Sample 3) and moving sand dune (Sample 4), analyzing the amount of microorganism, the average seasonal changes of enzymes activities and soil nutrition in the crust and 3-10cm 10-20cm soil layer in the testing area, as well as the connections between them. The purpose is to provide basic data and theoretical foundation for harnessing desertification by utilizing biological crust. The results are:1. There are seasonal differences in the average amount of microorganism in the crust layer and 0-20cm soil layer. The order in crust layer is: Sample 3> Sample 1> Sample 2> Sample 4; the order in 0-20cm soil layer is: Sample 3> Sample 2> Sample 1> Sample 4. The amount of microorganism in Sample 3 is more than other fixed dunes. In different seasons, the order changes somewhat as to the amount of microorganism in the crust and 0-20cm soil layer of Sample 1,2,3 , but much more than that in Sample 4.2. In a year in Sample 1,2,3, the deeper the layer, the less the amount of microorganism. In Sample 4, the amount is larger in lower layer than in upper layer. The amount of bacteria is larger than that of azotobacter; actinomyceto is less and fungi is the least.3. In Sample 1 and 2, the amount of bacteria in the crust is more in summer and autumn.; the amount of fungi is the least in spring and most in winter; actinomyceto is the most in summer; azotobacter is more in spring and autumn. In Sample 3, the amount of bacteria in the crust layer is the most in spring, lesser in summer, autumn and winter; the amount of fungi is decreasing in spring, summer and autumn, while becomes the most in winter; actinomyceto is the most in spring and least in autumn; azotobacter is more in spring and winter. The movement of the amount of microorganism in the lower soil layer in Sample 1,2,3 is basically consistent with the crust layer, but there is exception. The movement of microorganism in Sample 4 is relatively moderate.4. In Sample1,2,3, the deeper the soil, the weaker the urease,protease,soil enzyme,in a year. However the polyphenol oxidase is just the opposite. In the crust layer, the yearly movement of the enzymes activities is similar to the lower soil layer. In Sample 1,2, protease activities are stronger in autumn and summer. In Sample 3, they are stronger in spring while in Sample 4, stronger in autumn. The soil enzyme activities are stronger in autumn and winter in Sample 1,3, in Sample 2, they are stronger in autumn and summer. In Sample 1,2, the polyphenol oxidase activities are stronger in autumn and winter; in Sample 3, stronger in autumn and summer; in sample 4, stronger in spring and autumn. When moving dunes become fixed, the enzymes activities in the crust layer and lower layer will increase to some extent. urease,protease activities are the strongest in the crust and lower layer of Sample 1, followed by Sample 2 and 3. soil enzyme activities are the strongest in the crust layer and 10-20cm layer in Sample3, followed by Sample 1,2. polyphenol oxidase activities in Sample 1 are the strongest , followed by Sample 2 and 3.5. The content of the total nitrogen, organic substances and the total phosphorus generally becomes less in deeper soil layer, but that of the total potassium shows no difference in different soil layers. In Sample 1,2,3 and 4, the content of total nitrogen is the lowest in summer and relatively higher in spring and autumn; organic substances, the total phosphorus and the total potassium are the highest in autumn and lower in spring and summer in Sample 1,2,3; in Sample 4, the content of organic substances in autumn is the highest while there are no significant differences in the content of the total potassium and the total phosphorus. Nutrition content is increased in fixed dunes, the changes in the content of the total nitrogen in Sample 1 are the most obvious, in which the changes in the crust layer is the greatest; the content of the total nitrogen in the crust layer and the 10-20cm soil layer in Sample 3 also changed a lot. In Sample 1,3, the content of organic substances is increased in the crust layer and the lower soil layer; in Sample 2, the changes are not obvious. The content of the total phosphorus and the total potassium is greatly increased in Sample 1 and 3, but not evident in Sample 2.6. Relative analysis illustrates that: there are some positive relations between the content of nutrition in sand soil and the amount of microorganisms as well as the enzymes activities; there are evidently positive relations between soil microorganisms and the enzymes activities; inside soil microorganisms, the enzymes activities and soil nutrition, there are positive relations too. Moreover, microorganisms, enzymes and nutrition in soil depend and affect each other; they play a decisive role in maintaining the stability of the soil ecosystem.