Soil Fertility Quality Of Different Stands In The Low Mountains And Hills Of Changbai Mountain Region,Northeast China

Preservation and improvement of forest soil fertility quality is the basic task for forest health. In the twenty-first century, to achieve forest management shift from wood production to ecological civilization construction, evaluation of soil fertility quality under different forest stands in each region is particularly important. Soil fertility under four main stand types (natural Korean larch forest, Korean larch plantation, natural mixed coniferous and broad-leaved forest and natural mixed broad-leaved forest) was studied and evaluatedin a representative region of Jincang forest farm, Jilin Province. Analysis and comparison of soil physico-chemical properties, descriptive statistical analysis, variance analysis and correlation analysis were made in different stand density of natural Korean larch forest, different stand age of Korean larch plantations, different elevation of natural mixed coniferous and broad-leaved forest and natural mixed broad-leaved forest, respectively. Soil fertility of these stands in the study area was further assessed with clustering analysis and principal component analysis. In order to provide data support for speeding up the forest management shift from wood production to ecological civilization construction. The results were showed as the followings:(1) With the increase of soil depth, soil bulk density and soil pH increased, but soil water content and nutrients content decreased with different degrees in diverse forest stands.(2) Soil physico-chemical properties were closely related to each other. Soil water contenthad very significant positive correlations with soil organic matter and total K, but very significant negative correlations with total N, total P and available P. Soil pH had significant negative correlations withtotal N, total K and rapidly available K. Very significant negative correlations were found between soil bulk density and soil water content, soil organic matter, total N, total P and rapidly available K. There are diverse degrees of relationships between soil nutrient contents.(3) With the increase of stand density of natural Korean larch forest, the soil fertility quality decreased. Thinning could improve soil physico-chemical properties, and thus controlling thinning intensity with long-term and located observations issuggested to improve the general fertility quality of natural Korean larch forest.(4) Stand age had significant effects on soil fertility quality of Korean larch plantations. The results showed that soil fertility of Korean larch plantation in the decreasing order of middle-age forest>young forest>mature forest>nearly mature forest. Therefore, adjusting stand density of young forest and middle-age forest, controlling cutting intensity and replanting of nearly mature forest and mature forest with long-term located observations are suggested to improve the general soil fertility condition of Korean larch plantations.(5) Soil spatialvariation degree of natural mixed coniferous and broad-leaved forest and natural mixed broad-leaved forest were decreased with increasing elevation. The soil fertility quality assessment showed soil fertility of natural mixed coniferous and broad-leaved forest in the decreasing order of middle elevation forest>low elevation forest>high elevation forest, and that of natural mixed broad-leaved forest in the decreasing order of low elevation forest>middle elevation forest> high elevation forest.(6) Types of forest stands had significant effects on soil fertility quality.The soil fertility assessment in different forest types showed that soil fertility of four main stand typesin the decreasing order of natural mixed coniferous and broad-leaved forest> natural Korean larch forest>Korean larch plantation> natural mixed broad-leaved forest. Therefore, close-to-nature afforestation, timely enrichment and regeneration, mixed coniferous and broad-leaved forest constructionare suggested to improve the general fertility quality of main stand types in the study area.(7) Soil organic matter, total N, total P, total K, available P and rapidly available K of surface soil (0～20cm) in the study area were divided into five levels with clustering analysis.