Sensitivity analysis of variables correlated to soil organic matter in Chinese fir plantations

To ascertain the key control factors of soil organic matter (SOM) and provide theory to reveal its changing mechanism，effects of correlated variables on SOM content in Chinese fir plantations were studied with path analysis and sensitivity analysis in Dagang Mountain of Jiangxi Province，eastern China. Results showed that SOM content was affected by the variables in different ways and intensities，indirectly but strongly by alkali-hydrolyzable nitrogen content and soil density，and directly by total porosity，readily available potassium，and the number of bacteria and fungi. Available phosphorus content and the number of actinomycetes had the least effect on SOM content. The sensitivity of variables correlated to SOM content was in the order of alkali-hydrolyzable nitrogen contentthe number of fungithe number of bacteriaavailable phosphorus content the number of actinomycetestotal porosityreadily available potassiumsoil density. Soil alkali-hydrolyzable nitrogen content and the number of bacteria and fungi had higher importance and sensitivity，and determined most variation of SOM content. The smaller analysis error indicats that path analysis and sensitivity analysis are feasible in studying the relation between SOM content and soil-correlated variables.