Study On Soil Microorganism And Soil Enzyme Activity Of Different Vegetation In The Mountain Forests-the Arid Valley Ecotone In The Upper Reach Of Minjiang River

This dissertation studied on five resume modes of degraded ecosystem in the mountain forests-the arid valley ecotone of the upper reach of Minjiang River, they are young forest, broad-leaved mixed forest, shrub, theropencedrymion and secondary forest, Systematically studied the variations and changes in laws of soil microorganisms and soil enzyme activity under different vegetation, discussed the restoration of vegetation effect on soil microorganisms and soil enzyme activity, for understanding and evaluation of the mountain forests-the arid valley ecotone of the upper reach of Minjiang River vegetation restoration of the adjustment mechanism, and enrich Ecotone ecological theory of evolution. The results show:1. The number of soil microorganisms in the mountain forests-the arid valley ecotone of the upper reach of Minjiang River is very prominence. The relation with the quantity between hetero rophic microorganisms is that:bacterial>actinomyceto>fungi, the relation with the quantity between physiological groups of microorganisms is that:ammonifiers> azotobacteria>cellulose decomposing bacteria. The most number of fungi is in theropence-drymion, shrub have the most number of bacterial and actinomyceto. With the increase of the elevation, the numbers of fungi, bacteria, actinomyceto, ammonifiers and azotobacteria after the first increase is reducing, while the numbers of Cellulose-decomposing bacteria increases gradually. The number of soil microbial significant change with the seasons, except the number of fungi in shrub after the first increased is gradually decreased after the summer, other vegetation the number of fungi were highest in autumn, The other three quarters is lower; bacterial was highest in summer; except young forest, actinomy- ceto showed the highest in summer, then gradually decreased, the lowest in winter in other vegetation.2. Both the activity of urease and catalase is highest in the shrub sites, the activity of invertase is hightest in the theropencedrymion sites, the activity of protease is hightest in the secondary forest sites. The soil activity of enzyme represents the significantly seasonal dynamics, urease and invertase are higher in autumn, catalase inconsistent with the seasonal variation, and protease decreased from spring to summer, and then increased gradually.3. The pH is greatest in lower altitude (young forest) and with the increase in altitude to reduce, besides young forest the value of its upper (0-10cm) is small than the lower (10-20cm). The soil bulk density under different vegetation types is around 0.96～1.39 g.cm-3 in the study area, soil bulk density in broad-leaved mixed forest is the largest, shrub is the smallest and with soil depth the soil bulk increased. The soil porosity in shrub is the best, broad-leaved mixed worst, and surface layer is better than the lower. With the increase in altitude and vegetation restoration, the content of soil nutrient have a marked increase in the study area, secondary forest have the highest content of organic carbon, total nitrogen, available nitrogen and available phosphorus; shrub have the highest content of total phosphorus; broad-leaved mixed forest have the highest contest of total potassium and available potassium; young forest vegetation recovery time is short, soil nutrient content is at the lowest level.4. Among the five types of restoration mode of vegetation in mountain forests-the arid valley ecotone, the content of soil nutrients, the amount of microorganism and the activity of enzyme have evident gradient. They decrease rapidly with increasing soil depth. Among they have a significant correlation5. The correlation analysis among the amount of microorganism, the activity of enzyme and the content of soil nutrients shows, the minus correlation between the pH and the amount of microorganism,the activity of enzyme. The activity of protease and soil bulk density has positive correlation, the amount of microorganism,the other activity of enzyme and soil bulk density has minus correlation. Otherwise, the amount of microor-ganism,the activity of enzyme were positively correlated with soil nutrients. Thus it can be seen that between the amount of microorganism,the activity of enzyme and soil nutrients has close relationship. Soil microorganisms and the activities of enzyme decreased with altitude are directly related to soil nutrient loss. The amount of microorganism,the activity of enzyme can be used as indicators of soil fertility, and could reflect the extent of vegeta-tion restoration in dry valley.Vegetation recovery with the return of a lot of litter and vegetation on wind erosion and dust interception effect, soil fertility and soil biological activity gradually improved. It provides a theoretical basis on dry valley area to promote vegetation gradually from top to bottom, to improve the effectiveness of vegetation. In the mountain forests-the arid valley ecotone, shrub has most barbed shrub plants, reducing the interference of the animal, so the recovery is better than other vegetation types. Show that in the mountain forests-the arid valley ecotone vegetation restoration process, make the block management is the important measures in vegetation restoration...