Effect of Litter Decomposition on Soil Polarization in Three Typical Planted Pure Coniferous Forests in Loess Plateau, China.

Soil polarization is a new concept which describes 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 single tree species. It is thought to be one fundamental obstacle of the development of forest. In order to investigate the effect of litter decomposition on soil polarization of planted forests in the hilly area of Loess Plateau, China, humus soil and litter (leaf litter and fine roots) were sampled in three typical coniferous forests, and 4 treatments as "soil +leaf litter" "soil + roots" "soil+ leaf litter + roots" and CK were set for laboratory incubation experiment in this research. The results showed that polarizations of different properties were variable, in both direction and degree, after the incubation with litters. Based on analyzing the polarization ratios by PCA (principal component analysis) method, the results of comprehensive soil properties is showed as follows: both of leaf litter and roots resulted in negative polarization in the Platycladus orientalis and Larix principis-rupprechtii forest soil, conversely, as for the Pinus tabulaeformis forest soil, both of leaf litter and roots resulted in positive polarization. When leaf litter and roots mixed-together with the soil, the interaction sequence is P. tabulaeformis (2.329)P. orientalis(-0.916)L. principis-rupprechtii (-1.413). In general, P. tabulaeformis litter is more beneficial for soil properties than the other two plants after incubation. [ABSTRACT FROM AUTHOR]