Studies On Interaction Between Soil Quality And Vegetation Restoration In Loess Hilly Region

In order to provide a scientific basis to the soil-vegetation system management and ecological construction and to solve the ecological problems of soil conservation and vegetation restoration and answer the basic scientific question of the coupling mechanism between soil quality evolution and vegetation restoration,based on a long-term located experiment,we explored the coupling and mutual effects of soil quality evolution and vegetation property changes in different soil quality background and different restoration methods(natural restoration and artificial restoration)at the same site conditions.Focusing on the interaction between soil quality and vegetation properties in the process of succession.The main conclusions are as follows:1.There was no significant difference in the content of aggregates,the average weight diameter(MWD),soil water content and soil bulk density caused by different vegetation restoration methods after ten years of restoration in soil-vegetation system(P>0.05).In the artificial restoration mode,the content of Macro-aggregates(R0.25)between 0~20cm and 20~40cm soil layers was significant(P <0.05).The effect of artificial restoration method on soil nutrients properties is more obvious.Natural restoration method is better than artificial restoration method to improve soil biological properties after ten years of restoration in soil-vegetation system.2.There were significant differences in vegetation properties between different fertility gradients in 2008 and 2010(P<0.05),compared with no fertilizer treatment,the fertilization treatment could promote the formation of dominant species,reduce the Shannon-Wiener index and Margalef richness index(P<0.05)and increase the community coverage and biomass(P<0.05).3.With the vegetation succession,there was a slow accumulation in soil nutrient,water content and with dramatic changes in available nutrient.Vegetation dominant species have become from annual herbaceous plants to biennial,perennial herbs and shrubs,but its specific succession sequence are different due to different fertility gradient.Artificial fertilization treatment can have an affect on the diversity index change in the process of vegetation succession,and then accelerate its succession process.4.The relationship between soil properties and vegetation community characteristics was different under different restoration methods,fertility gradients and successional stages,the stable association of soil-vegetation interaction is mainly mediated by soil available nutrient and herbaceous coverage.The correlation between soil and plant also has a "threshold effect",When fertility increases,the significance and direction of the correlation between the two are likely to change.Fertilization changed the carbon,nitrogen and phosphorus contents and its stoichiometry characteristic of soil-microbial-plant system to a certain extent,and the response of microbial C/N and microbial C/P was the most sensitive when soil conditions changed.5.Microbes can play a "link effect" in soil-plant nutrition process.The interaction between carbon,nitrogen and phosphorus in Hippophae rhamnoides leaf and soil nutrition is mainly mediated by microbial biomass nitrogen.The interaction between carbon,nitrogen and phosphorus in Caragana intermedia leaf and soil nutrition is mainly mediated by microbial biomass carbon.The indirect effect of organic carbon on microbial biomass nitrogen is the main way to determine carbon,nitrogen and phosphorus in Hippophae rhamnoides leaves,the indirect effect of organic carbon on microbial biomass carbon is the main way to determine the carbon content of Caragana intermedia leaves.The direct effect of microbial biomass carbon,the indirect effect of organic carbon on microbial biomass carbon and the indirect effect of total nitrogen on microbial biomass carbon are the main pathways for determining the nitrogen content of Caragana intermedia leaves.The direct effect of microbial biomass carbon,microbial biomass nitrogen,the indirect effect of total nitrogen on microbial biomass carbon and the indirect effect of microbial biomass carbon on microbial biomass nitrogen are the main pathways to determine phosphorus in Caragana intermedia leaves.