Evaluation Model Of Soil Fertility Of Natural Secondary Forest In Daxingan Mountains

In this paper,different mathematical models are used to evaluate the soil fertility of the experimental plots under different transformation modes.Organic matter,total nitrogen,total potassium,total phosphorus,hydrolyzed nitrogen,available phosphorus and available potassium are selected as evaluation indicators.These seven indicators can reflect the actual situation of soil fertility.Firstly,the fuzzy comprehensive evaluation model based on analytic hierarchy process is used to evaluate soil fertility.In the process of building the model,the weight of each index is determined by analytic hierarchy process.The highest score of soil fertility in S7 sample plot has been obtained by solving the model,which indicated that when the thinning intensity is 42.01%,it is beneficial to improve the soil quality in the experimental area,which is consistent with the actual conclusion,and also proved the feasibility of the fuzzy comprehensive rating model.Secondly,the comprehensive evaluation model of grey relational analysis is used to evaluate soil fertility,and the evaluation results are generally consistent with the results of fuzzy comprehensive evaluation.And the grey correlation curve is used to analyze the degree of closeness between the indicators,which further prove the rationality of the evaluation indicators selected in this paper.Finally,the comprehensive evaluation model of principal component analysis has been used to evaluate the soil fertility of the experimental plots.The cumulative contribution rate of the first five principal components has reached 90.454%.Therefore,the first five principal components have been extracted and the comprehensive evaluation function F has been constructed to obtain the comprehensive evaluation results.In the evaluation process of the model,the relative importance rankings of seven indicators have been obtained,which are effective phosphorus,total nitrogen,total phosphorus,total potassium,hydrolyzed nitrogen,available potassium and organic matter.The results of the three comprehensive evaluation models are the highest in S7 plots with thinning intensity of 42.01%.It shows that 42.01%thinning intensity is the bestter transformation model in the experimental area,which is consistent with the conclusion that moderate thinning intensity is beneficial to improving soil condition.The first two evaluation models are feasible to apply in this study and based on the synthesis of principal component analysis.The combined evaluation model did not achieve high accuracy.