| The effects of soil improvement of reforest pattern from farmland were important index of pattern selection and effects evaluation. Research of dynamics of soil nutrition during the reforestation would benefit to reveal the intrinsic principals of soil directional improvement in vegetation restoration, and the principals of interaction between plant and soil. This study selected two reforest patterns (pattern 1: Triploid Populus tomentosa+ Lolium multiflorum Lam; pattern 2: Bambusa pervariabilis× Dendrocalamopsis Oldhami) as object ,with th farmland as antitheses to research the patterns' influence to soil nutrient, used two method (conventional method and method of testing balanceable soil solution) to analysis the change of soil nutrition reverse and dynamics of available nutrient in soil solution.1. The analysis result of the soil nutrient background value at the beginning of site investigation under two reforest patterns and farmland showed: the content of soil total N and Hydrolysable N in pattern 1 were conspicuously higher than the other two. The content of SOM and CEC in subsoil in pattern 1 are higher than in the other two. It was because that the content of nutrition returning was abundant and the rate of decomposition of litter was rapid in the forest and grass composite pattern. The content of SOM, soil total N, and Hydrolysable N were lower than in pattern 1. Because the content of nutrition returning was little and the rate of decomposition of bamboo' leaves.The content of soil available P and rapidly available K in subsoil in these two reforested patterns are lower than in farmland. It was because that the reforested patterns' absorption to the soil available nutrition was better. There was another reason that the farmland was fertilized.2. In order to research the different pattern's influence to the soil nutrition after aperiod of site investigation, the study used covariance analysis to avoid the influence of the background value of soil nutrition, and to adjust the annual soil nutrition value in three plots. The result showed: the annual changed value of soil total N, NO3--N, total P, total K, pH, CEC, BSP had no conspicuous difference in there plots. The conspicuous difference of soil Hydrolysable N, NH4+-N, total P, available P, slowly available K, rapidly available K were brought by the influence of different vegetation pattern.3. The content of soil total N, total K, pH, CEC, BSP of soil nutrition background value had not great changes in the period of site investigation, but the content of rapidly available soil nutrition changed a lot. The content of Hydrolysable N, NO3--N, slowly available K descended and the content of rapidly available K and pH value raised. The change of SOM and rapidly available P in differ plot and differ layer were different.4. The result of analysis to the nutrition in soil solution showed: the content of NH4+-N, NO3--N, available P, available K, and pH value had obvious seasonal changes in two years. The content of nutrition in soil solution was high in the season of plant growing, and the pH was low. It was conversely in other season. The content of NH4+-N in soil solution reduced year after year, and the content of NO3-+-N increased. The content of available K in soil solution reduced year by year. The content of available P and pH value had no significant changes. The result of correlate analysis to the pH value and the temperature showed that there are significant correlation between them.Pattern 1 was better than pattern 2 in promoting soil nutrition. The structure of pure bamboo needed regulated to obtain better improving effect.
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