| As one of the most important afforestation tree species in the warm temperature humid and semi-humid climatic region in china, the study concerning soil quality and its management was valuable to the sustainable manage of Pinus tabulaeformis stands. In 2000, four different thinning intensities treatments were carried out on 9-year-old stands in the IV site condition in WangJiapu of Yanqing Country, Beijing. In 2005, the growth of the arbor, the coverage, diversity and biomass of forest undergrowth, the physiochemical properties as well as enzymes of soil were analyzed and compared. Based on those, undergrowth and soil were evaluated comprehensively by Principal Components Analysis (PCA).The results are as follows. The stands manipulated by thinning were better than CK on all the growth indicators, and the stand which the thinning intensity was 53.75% was the best of all. The life-form spectrum also can be affected by thinning intensity. Meanwhile, the composition of the mesophytes of shrub layers with the decline of the thinning intensity. Compared with CK, both the rate of substituted species and biomass among undergrowth were accelerated by the rise of thinning intensity. The values of diversity indices, however, were enhanced greatest when the crown shade was between 80% and 87%.The soil physicochemical properties decreased with increasing soil depth except pH. And the soil physicochemical properties were highest in the layer A, followed by in the layers B and C. The five soil enzymes were affected so differently by thinning intensities that alkaline phosphatase, catalase, urease, invertase and polyphenol oxidase were decreased. The soil enzymes in the layer A were enhanced distinctly compared with in the layers B and C. Soil physicochemical properties and soil enzymes were affected differently in different season. Generally, when the stands with initial density of 8000 trees·hm-2 grows up to 9 years old, the reasonable thinning intensity should be about 48.75%.
|
PDF Full Text Request