Study On Vegetation And Soil Characters At Different Ecological Restoration Stages In Eroded Degradation Area Of Shale

1 For different man-made disturbing degree on shale area in Shizigou catchment,Yichang, China, the vegetation have gone throughout a series of ecological successionstages, including eroded bad land, shrub stage, shrub-tree stage, conifer forest stage,broad-leaved mixed forest stage during the course of the vegetation restoration. Byusing the method of space instead of time, dynamic characteristics of vegetationcommunities in their different restoration were studied, including species compositionand structure, species diversity, overground biomass, changes of soil nutrient contentand soil physical properties. Moreover, changing rules of vegetation and soil atdifferent restoration stages were analyzed in Shizigou catchment. The results were asfollowing:(1) Totally, species diversity increased gradually with the development of communitysuccession. Shannon-wiener index increased gradually with the succession ofvegetation community. Species richness of conifer forest was 15 and more than that ofbroad-leaved mixed forest. Evenness index was the highest in broad-leaved mixedforest, and eroded bad land take second place in evenness index. So, species diversitycould not be regarded as a unique index for measuring the effect of ecologicalrestoration in vegetation. However, the reasons resulted in change of species diversityshould be further studied.(2) Overground biomass increased gradually with the development of vegetationcommunity succession. Overground biomass of shrub stage, shrub-tree stage, coniferforest stage, broad-leaved mixed forest stage was 5.2,8.94,20.12,23.38 times as thatof eroded bad land respectively. These results indicated that vegetation communityproductivity increased gradually.(3) With the development of community succession, soil total nitrogen, availablenitrogen and organic matter content increased gradually; total phosphorus content andavailable phosphorus content decreased gradually and later increased. However, soilpotassium content reduced gradually during vegetation restoration. Soil bulk densitydecreased gradually from 1.51g/cm~3 at eroded bad land stage to 1.31g/cm~3 atbroad-leaved mixed forest stage. Soil stone (＞2mm) content decreased gradually whichwas 79.69% at eroded bad land and 14.45% at broad-leaved mixed forest stagerespectively. The experiment of soil water evaporation showed that the vegetationrestoration could increase the capacity of holding water. (4) There was only weathering crumb of mother rock and no big aggregate formingat the first stage of vegetation restoration. With the vegetation community succession,soil aggregate content increased gradually. Dry sieving aggregation (＞4mm) contentrespectively was 0%,0%,37.87%,58.69% and 79.56% from eroded bad land stage tobroad-leaved mixed forest stage, and dry sieving aggregation (＞2mm) content was 0%,13.59%,64.92%,72.25% and 91.98%. Furthermore, water stable aggregate (＞0.25mm)increased respectively 59.38%,63.58%,63.88% and 78.80% than that of eroded badland.2 By typical artificial forests of different restoration time, the author studiedvegetation coverage, soil layer depth, soil organic matter content, soil aggregate contentin vegetation communities. The results were as following:(1) By artificial forestation measure on eroded bad land in the shale area, vegetationcoverage increased from 25% to 60% and overground biomass increased from2.21t/hm~2 to 10.18t/hm~2 with the development of restoration in artificial forests.(2) When the restoration time continued, both average soil layer depth and organicmatter content increased, however stone (＞2mm) content decreased. Soil organic mattercontent in 6 years artificial forest was 220% as that in 1 year artificial forest. Moreover,average soil layer depth changed from 0.1cm to 2.6cm. Stone (＞2mm) in 6 yearsartificial forest was fewer 21% than that in 1 year artificial forest. Artificial forestationmeasure on eroded bad land in shale area indicated its effect of ecological restoration inShizigou catchment, Yichang, China. In summary, these results indicated that artificialforestation measure on eroded bad land in shale area could ensure positive ecosystemsuccession.