Effects Of Vegetation Restoration On Soil Fertility In Northern Sichuan Basin

In this paper, we selected different types of vegetation restoration(Neosinocalamus affinis plantation, tea trees, Camptotheca acuminata plantation, Cryptomeria fortunei plantation and crop land) in Northern seismic disastrous area of Sichuan basin as the research objects to study soil physical properties, chemical properties and biological characteristics and discuss the relationship of different soil fertility indexes. The main results were as follows:(1) After vegetation restoration, soil became tight and heavy due to bulk density increased. Under dry sieving and wet sieving conditions, the content of>0.25cm soil aggregate increased and the composition proportion of soil characteristic micro-aggregates decreased, which contributed to the improvement of soil structure and ability to regulate and control soil fertility. Under dry sieving and wet sieving conditions, the content of>0.25cm soil aggregate, non-capillary pore, capillary pore, total pore space, soil natural moisture content, maximum water-holding capacity, capillary water holding capacity and minimum water holding capacity in different types of vegetation restoration ranked as Neosinocalamus affinis plantation> tea trees> Camptotheca acuminata plantation> Cryptomeria fortunei plantation, while soil bulk density and the composition proportion of soil characteristic micro-aggregates ranked as Neosinocalamus affinis plantation<tea trees<Camptotheca acuminata plantation<Cryptomeria fortunei plantation.(2) After vegetation restoration, the content of soil organic matter, total N, hydrolysis nitrogen and ammonium were all higher than those in crop land. Soil nitrate nitrogen, total mineral nitrogen, available phosphorus and available K were all lower than crop land, which was related to crop-land using chemical fertilizer. Soil organic matter, total N, hydrolysis nitrogen, ammonium, nitrate nitrogen, total mineral nitrogen, available phosphorus and available K under different vegetation restoration types all ranked as Neosinocalamus affinis plantation> tea trees> Camptotheca acuminata plantation> Cryptomeria fortunei plantation. Soil organic matter, total N, hydrolysis nitrogen and ammonium was significantly and positively related with>0.25cm soil aggregate of dry and wet sieving conditions, while was significantly and negatively related with composition proportion of soil characteristic micro-aggregates.(3) After vegetation restoration, the content of soil microbial biomass carbon and its ratio in organic carbon, soil microbial biomass nitrogen and its ratio in total N, bacterium, fungus, actinomyces and total microbe quantity significantly increased and ranked as Neosinocalamus affinis plantation> tea trees> Camptotheca acuminata plantation> Cryptomeria fortunei plantation> crop land. Soil microbial biomass carbon and nitrogen, bacterium, fungus, actinomyces and total microbe quantity were significantly and positively related with total pore space, natural moisture content,>0.25cm soil aggregate of dry and wet sieving conditions, soil organic matter, total N, hydrolysis nitrogen and ammonium, while was significantly and negatively related with composition proportion of soil characteristic micro-aggregates. Soil microbial biomass carbon and nitrogen significantly and positively related with bacterium, fungus, actinomyces and total microbe.(4) After vegetation restoration, the activity of soil invertase, urease and phosphatase significantly increased and ranked as Neosinocalamus affinis plantation> tea trees> Camptotheca acuminata plantation> Cryptomeria fortunei plantation> crop land. The activity of soil invertase, urease and phosphatase were all significantly and positively related with the content of soil organic matter, total N, hydrolysis nitrogen and ammonium, soil microbial biomass carbon and nitrogen, bacterium, fungus, actinomyces and total microbe quantity.Therefore, vegetation restoration and selecting appropriate model played an important role in improving soil physical properties and soil water-holding and water supply capacity and increasing soil nutrient content, soil microbial biomass and microbe quantity and enzymatic activity. The results provided reference for vegetation restoration and improving soil fertility in study area.