Research On Dynamic Changes Of Soil Microorganisms, Soil Enzymes And Soil Nutrition In Different Grazing Intensities In Stipa Breviflora Desert Steppe Of Inner Mongolia

This paper was conducted to study three regions at different grazing itensities in Stipa breviflora desert steppe of Inner Mongolia. Three different constituents were analyzed, including seasonal fluctuation of the main kinds of soil microorganisms,soil enzymes activities and soil nutrition in grassland ecosystem, the effects on them in different grazing rates and the relationship among them .The theoratical base was provide by results, the results could be summaried as follows: 1. The relationship among the numbers of the soil microorganisms was bacteria > azotobacter > actinomyceto > fungi, and the numbers of microorganisms were higher in the 0-10cm soil layer than that in the 10-20cm soil layer. 2. The numbers of soil microorganisms,soil enzymes activities and content of soil nutrition fluctuated in different patterns. according to seasonal changes. In a year, the total numbers of microorganisms was highest in spring and lowest in winter. The numbers of bacteria,azotobacter and fungi were highest in spring. The numbers of actinomyceto were highest in nongrazing and heavy grazing regions in antumn, but highest in light grazing region in summer, and lowest in winter;Urease activity was highest in spring and lowest in summer. Catalase and polyphenol oxidase activities were different according to the grazing regions, highest in nongrazing in spring and light grazing regions, but highest in heavy grazing region in autumn. Protease activity was highest in sping and lowest in winter;The total nitrogen(total N)content was highest in nongrazing region in summer, but higher in light and heavy grazing regions and lowest in summer. The total carbon (total C) and the total phosphorus (total P) were highest in autumn and lower in winter and spring. The total potassium (total K) was highest in nongrazing region in autumn and stabilized in other seasons , but higher in winter and spring and lowest in heavy grazing and light grazing regions in summer. 3. Different effects were shown on soil microorganisms,soil enzymes activities and soil nutrition with different grazing intensities. The numbers of microorganisms and the content of total N,total P,total K increased under nongrazing and 0.67-0.83 sheep/hm2 stocking rate of grazing intensities. At the same time, protease activity increased very prominently, urease and catalase activities also have little improve under 0.67-0.83 sheep/hm2 stocking rate. Nongrazing can maintain polyphenol oxidase activity higher. Under 2-2.5 sheep/hm2 stocking rate of grazing intensity, the numbers of total microorganisms,bacteria,actinomyceto,fungi had incresed prominently,while the numbers of azotobacter increased significantly in spring and autumn, decreased slightly in summer. The urease activity incresed remarkbly and Catalase ,polyphenol oxidase and protease activities were inhibited. Meanwhile, the total N and the total K content decreased, the effects on the total P and total C were little markable. In conclusion, nongrazing and moderate grazing were helpful to improve the soil fertilization. But over grazig had decreased the soil fertilization. 4. The correlation analysis showed that the numbers of soil microorganisms and soil enzymes activities were closely related to soil nutrient content, these indicate the soil microorganisms are a very important index during evaluating soil quality. Moreover, microorganisms ,enzymes and nutrition in soil ecosystem depended and affeced together.