Study On Soil Microorganism And Soil Enzyme Activity Of Different Vegetation Restoration In The Upper Reaches Of Jialingjiang River

This dissertation studied on the five resume modes of degraded ecosystem in the observation station of the upper reaches of Jailingjiang River; they are Robinia pseudo acacia, burned mark shrub, mixed stands of Pinus elliottii and Robinia pseudoacacia, Pinus elliottii, Cyclobalanopsis glauca and selected a serious degenerate area as the controlled site. The results show:1. The bulk density of five sites are all lower than that of control site, among them, the lowest one is Pinus elliottii. On the aspect of the capillary porosity and total porosity, burned shrub is the highest, Robinia pseudoacacia and Pinus elliottii are the lowest. Cyclobalanopsis glauca is the highest on the non-capillary porosity, and the control site is the lowest. On the other hand, the burned mark shrub is the highest and Robinia pseudoacacia is the lowest on the max moisture capacity, capillary capacity and field capacity. Cyclobalanopsis glauca is the highest on the soil aerate degree.2. According to the content of organic matter, total nitrogen , hydrolysable nitrogen and the rate of C/N, the five modes are all higher than the control site and the Cyclobalanopsis glauca and the burned site are significantly higher than others. Among them, the content of organic matter, total nitrogen under ground 0-15cm is higher than that in the 15-30cm soil layer. The 0-15cm shows the highest evidence in autumn and winter, and lowest in summer. Soil water content in burned shrubs site is higher than that in other sites, and the Cyclobalanopsis glauca shows the lowest level and no remarkable seasonal dynamics.3. The soil microorganism shows an significantly increase after the restoration of the degraded ecosystem. Such as the burned shrub sites has the highest amount of Bacteria and Actinomyces, while the Pinus elliottii represents the lowest signal. Pure broadleaf(Cyclobalanopsis glauca and Robinia pseudoacacia) manifest the highest amount ofFungi, while the burned shrubs site is the lowest on the index. The soil microorganism represents the significant seasonal dynamics, Bacteria and Actinomyces are remarkably high in autumn and lower in summer and winter. Fungi are significantly higher in summer and lower in summer. The three kinds of soil microorganisms in the controlled site all represent no significant seasonal diversification.4. Among the five types of restoration mode of vegetation, both the activity of Urease and Invertase are higher than that of control sites, and that in the mixed stands of Pinus elliottii and Robinia pseudoacacia are lower than other modes. The activity of Urease is highest in the burned shrub sites, the activity of Invertase is highest in Cyclobalanopsis glauca and burned shrub sites. However, the activity of Catalase is highest in control sites. The soil enzyme activity represents the significantly seasonal dynamics and varying in different forest sites. Urease and Invertase are higher in autumn, and Catalase increased from spring, and reaches the highest value in winter. Furthermore the activity of Urease and Invertase shows the trend of degression with the depth of soil layer, while the activity of Catalase increases with the depth of soil layer which opposed to the plumb distribution orderliness of the total activity of soil biology.5. Soil respiration intensity of five modes is significantly stronger than that of control sites, and the strongest is Cyclobalanopsis glauca, the feeblest is mixed stands of Pinus elliottii and Robinia pseudoacacia. In addition, the respiration intensity of the five models are all strongest in summer, autumn is the subordination, and the feeblest is in winter.6. The model of total microbes and three soil enzyme activities were drawn as the following formula:Yj = 4.619 + 349.833 Aj- 7.555 A2- 0.822 A3 (R=0.842)Y2 = - 0.374 + 2.505 B, + 0.024 B2 - 0.027 B3 - 0.006 B4 (R=0.942)Y3 = 74.412 - 38.88 C, + 3.87 C2- 1.656 C3 (R=0.893)Y4 = 1.412 - 0.777 D, + 0.078 D2+ 0.055 D3- 0.011 D4- 0.0055 D5 (R-0.955)7. Except Pinus elliottii The ratio of nitrogen translation of four modes is more higher than control site. The ratio of translation in Cyclobalanopsis glauca^ Robinia pseudoacacia and the mixed stands is summer > spring> autumn > winter; and burned shrub is spring > summer, autumn > winter; the seasonal dynamics of Pinus elliottii and control site is notsignificant. The positive correlation between the ratio of nitrogen translation and Urease^ Invertase is significant at the 0.01 level, and minus correlation between the ratio of nitrogen translation and Catalase is significant at the 0.01 level too. Otherwise, the ratio of nitrogen translation and Bacteria ^ Actinomyces has positive correlation, but the coefficient is not significant.8. It shows that the soil nutrient of the burned shrubs sites is the highest, the amount of soil microorganism is the largest, the activity of Urease and Invertase is the strongest, the structure of soil is the best. It demonstrates that the vegetation of natural restoration can cover the ground speedy and can control the loss of water and soil efficiently. But this vegetation is merely ruderal community and shrubs community with inefficient economic benefit. Constructing the arbor-shrub-grass mixed forest is the ideal mode of the soil and water conservation, however all the indexes of the mixed forest referring in this dissertation represent the inefficiency in soil and water conservation because of the influence of human being such as cutting and browsing. And it demonstrated that the influence of human being (including positive and negative effects)is the essential factors of the restoration in degraded ecosystem. Consequently, referring to the restoration of vegetations in the upper reaches of Jailingjiang River, it is reasonable of give priority to forestation by manpower, and introduce broadleaf and local species, cultivating the conifer-broad mixed forest. Besides that assisted with prevent the cattle's grazing management.