Theory of soil polarization in planted pure forests and its application in loess plateau of China
A new concept of “soil polarization was proposed to describe the deviation of soil properties of planted pure forest from its original equilibrium status toward an extreme condition due to long-term growth or continuous planting of a single tree species, which has unique biological and ecological characteristics and results in selective nutrient absorption and special environmental effects. A number of descriptive indices including Width of anti-polarization (W), Resistance to polarization (R), Polarization (P) and Ratio of polarization/resistance to polarization (I=P/R) were also proposed and the degree of soil polarization was classified into 5 grades as conserve stable (Ⅰ), light polarization (Ⅱ), moderate polarization(Ⅲ), strong or serious polarization (Ⅳ) and very strong orserious polarization (Ⅴ) according to the indices of P and I. Through applying this theory in the semi-humid loess hilly region of loess plateau of China, the results indicated that soil polarization reached the level of moderate or higher （Pa＞0.10）in almost all pure forests that were examined and showed following soil trends. Pinus tabulaeformis forest depleted nutrients and trace element content. Larix principis-rupprechtii forest increased trace element content but depleted nutrients. Platycladus orientalis forest increased C and N content and improved biological properties. Pinus armandii forest improved physical properties, but depleted nutrients and caused deterioration in biological properties. Robinia pseudoacacia forest increased nutrients and improved biological properties, but decreased trace element content and caused deterioration in physical properties. Populus simonii forest decreased nutrients and trace element content and caused deterioration in biological and physical properties. Betula platyphylla forest improved physical properties and increased trace element content, but depleted nutrients. Quercus liaotungensis forest increased trace element content. When comparing the level of soil polarization to the capacity of resistance to polarization of forest, it indicated more than moderate level of soil polarization (Ia >0.40) for the followings: physical properties in P. simonii forest; physical, chemical properties, and trace element content in P. orientalis forest; all soil properties in L. principis-rupprechtii, R. pseudoacacia and B. platyphylla forests.
continuous planting planted pure forest soil degradation soil polarization
Zengwen LIU Caihong MI Qian LI Kai CHEN
College of Resources and Environment, Northwest A & F University, Yangling, Shaanxi Province 712100, China
国际会议
西安
英文
1057-1061
2010-10-11（万方平台首次上网日期，不代表论文的发表时间）