Response Of Soil Quality And Its Evaluation Affected By Vegetation Restoration In The Agro-pastoral Transitional Zone

The agro-pastoral transition zone of northern Shaanxi Provence has become one of themost serious desertification regions in China because of its fragile ecological environment andintensive human acativities. The vegetation reconstruction effect in severely degradedecosystem depends on formation and development, evolution situation of the soil environment.The response process, speed and direction were different due to different vegetation types ordifferent stages of reconstruction. Therefore, to analyze the difference of the soil environmentresponse because of different vegetation restoration types and recovery phase was the key toselect scientific the vegetation recovery mode. This research set Yu Yang in the northernShaanxi as study area and the desertification soil in this area as study object. To study the soilquality in the region of different stages of vegetation restoration, vegetation types throughfield investigation and laboratory measurement. The main research results as follow:(1) In the reversal of soil desertification process of vegetation restoration, from shiftingsandy land to fixed sandy land, following the producing and development of the soil crustlayer, soil particle composition had a trend of refinement, soil pH declined a little, organicmatter and available nutrient content gradually increased, soil organic carbon and carbonmanagement index increased appreciably. For the same soil profile, the changed of upper soilcontent was bigger than the lower layer soil. The positive development of soil mainly embodiedin the increasing of soil fine particles material.(2) Vegetation recovery after thirty years could significantly improve the quality of soilenvironment. But the effect benefits between different vegetation types were various. The bestimprovement effect was shrub land in the study region. Comparing with the shifting sandyland, the desertification soil of ten kinds of vegetation restoration about thirty years, and itssoil texture had a tendency to refine, soil bulk density reduced, soil total porosity increased,soil nutrients, organic carbon and carbon management index had a obvious rising trend. Soilquality had a difference due to a variety of vegetation types. Salix and Caragana were in theascendant among all the vegetation types.(3) Soil environmental quality improved gradually along with the vegetation agesincreasing. The soil quality stopped rising and even appeared a small decreasing between thirty and fifty years after vegetation restoration. Between zero and thirty years aftervegetation restoration, soil particle composition was sand content gradually reducing, silt andclay content increasing and the soil nutrients and soil organic carbon content showed anincreasing trend. After thirty years of vegetation restoration, soil quality increase slowly andeven showed a small decrease trend because of the tree growth aging.(4) On the basis of selecting sixteen soil quality evaluation indexes, through thecomprehensive effect score soil quality factors and the coordination relationship among qualityfactors to evaluate the soil quality benefition. Applying the principal component analysis andcorrelation analysis studied the soil quality of ten kinds of vegetation types about thirty yearsafter vegetation restoration. The results showed that the highest soil quality comprehensivescore was salix, the second were Caragana and elm. The correlation coefficient order of soilquality factors among three vegetation communities was shrub land, grassland, arbor land.The shrub land had higher coordination between quality factors than arbor land.