Study On Spatial And Temporal Variability Of Soil Nutrient In The Broad-leaved Mixed Low-quality Forest After Induced Transformation In Daxing’ An Mountains

Clear-cutting were executed in Daxing’an Mountains’broad-leaved mixed low-quality forest with different bandwidth (6m,10m,14m and18m), then induced transformation was performed by planting Mongolica Litv、Pinus koraiensis and Larix gmelinii, and gained the soil nutrient data from2009to2012by field sampling and experimental analysis, then used subjective-objective comprehensive weighting method to determine the weight of each soil nutrient index, and the fuzzy pattern recognition comprehensive evaluation method was carried on the soil nutrients in the early stage after induced transformation, meanwhile, the descriptive statistical analysis was carried on the soil nutrient elements of different plots in different years to explore the spatial and temporal variability of soil nutrient in the low-quality forest after induced transformation in Daxing’an Mountains.When determining the weight of each soil nutrient index, the study adopted analytic hierarchy process method for subjective weighting, and adopted the variation coefficient method for objective weighting, then the subjective and objective weighting results were used for linear combination weighting.The results of subjective and objective comprehensive empowerment were as follows:Available P (0.200)> Total P (0.169)> organic matter (0.145)> Available K (0.142)> Hydrolysis N (0.122)> Total N (0.118)> Total K (0.104), which showed that the P was the main influence factor, especially the soil Available P, its weight was as high as0.200, therefore, the forest managers can apply Phosphate fertilizer properly for Daxing’an Mountains’low quality forests in the future cultivation process, which can improve the soil nutrients effectively.This study adopted the fuzzy pattern recognition method for the comprehensive evaluation of soil nutrients, and obtained the soil nutrient levels characteristic values of every plots in the early stage after induced transformation, the results were as follows:the soil nutrient levels characteristic values of plots before induced transformation was2.910; the soil nutrients level characteristic values of control plots from2010to2012were2.861、2.729and2.864; the soil nutrients level characteristic values of6m induced transformation plots from2010to2012were2.646.2.440and2.649; the soil nutrients level characteristic values of10m induced transformation plots from2010to2012were2.729.2.608and2.271; the soil nutrients level characteristic values of14m induced transformation plots from2010to2012were2.539.2.320and2.271; the soil nutrients level characteristic values of18m induced transformation plots from2010to2012were2.294.2.203and1.857.Through analyzing the soil nutrient spatial and temporal variation of the low-quality forest after induced transformation in Daxing’an Mountains, got the following conclusions:the spatial variation dynamic of different soil nutrient elements in different plots were different in the early stage after induced transformation, but taken together, the soil nutrients after the transformation were higher than before, and in general, with the passage of time after the transformation, the soil nutrient increased year by year; the spatial variation trend of different soil nutrient elements in different years were different after induced transformation, but taken together, the soil nutrients of various transformation plots were higher than that of the control plots, and in general, with the clear-cutting bandwidth increases, the soil nutrient increased; it’s scientific and reasonable by using the fuzzy pattern recognition method for the comprehensive evaluation of soil nutrients, which also has good guide and reference meaning.