Structure Characteristics and Health Evaluation of Soil in Different Vegetation Restoration Communities

It is of great importance to improve soil structure by restoring vegetation in hilly and mountainous soil erosion districts.This paper makes a careful study of the characteristics of soil structure and its health evaluation in different forest restoration communities in Nuerzhai watershed. The main results are stated in the following.Firstly,the soil bulk density of wasteland-shrub type was the highest among all vegetation types,and that of the plantations was higher than those of the natural and mixed forests.Secondly, the improving effects of vegetation restoration on the soil porosity were better in forest types than in wasteland-shrub type,better in natural forests than in plantations,and better in the soil layer of 0～20 cm depth than in that of 20～40 cm depth.Thirdly,Vernicia fordii and Eucommia ulmoides plantations had the biggest mean weight diameter values of soil aggregates,followed by Pinus massoniana natural forest and Phyllostachys edulis-Cunninghamia lanceolata mixed forest;however,Machilus pingii secondary forest,wasteland-shrub and Cunninghamia lanceolata plantations had the smaller mean weight diameter.And the fractal dimension of soil aggregates in different vegetation communities shows the regularity of Phyllostachys edulis-Cunninghamia lanceolataPinus massonianawasteland-shrub and Machilus pingiiEucommia ulmoidesVernicia fordiiCunninghamia lanceolata.Finally,the result of soil structure and health evaluation by gray incidence analysis demonstrates that the worst soil structure took place in wasteland-shrub but the best in Vernicia fordii plantations.These results could offer some basis and references for vegetation restoration in Nuerzhai watershed and other similar vulnerable eco-regions in China.