Assessment Of Thinning Effects On Natural Secondary Forests In The Qinling Mountains

The aim of the study was to find the most available thinning intensity of Pinus tabulaeformis secondary forest in the Qinling Mountains, providing theoretical basis for forestry ecological management. 32 Pinus tabulaeformis plantation stand in Xunyangba, Huoditang and Xinkuang were selected in this study. The thinning intensities included light, medium, heavy and control, respectively. Based on overall analyses of effects of thinning intensities on population structure, productivity, water conservation and species diversity of vegation, single-target and multi-target decisions of different thinning intensities by means of grey situation decision theory was carried out after 4 years of cut. The results of single-target decision indicated that medium thinning intensity showed the most significant effect on optimizing the population structure and increasing the productivity, while heavy thinning intensity showed the most significant effect on improving the water conservation and species diversity of vegetation. However, light thinning did not show positive effects when compared with control group. Moreover, the results of multi-target decision showed that medium thinning was the best thinning intensity for Pinus tabulaeformi secondary forest in the Qinling Mountains. Thin forest on the medium intensity could optimize the population structure to decease competition, increase the productivity, the stability of forest, the water conservation and species diversity of vegetation. 15% thinning intensity was suggested for the Pinus tabulaeformi secondary forest in the Qinling Mountains.Based on overall analyses of population structure, productivity, water conservation and species diversity of vegation for Pinus tabulaeformis secondary forest affter 4 years of thinning, the objective and subjective combination weighting was carried out to synthetical evaluate of thinning effects for Pinus tabulaeformis secondary forest in the Qinling Mountains, mingling degree、biomass、litter storages and shannon-wiener index of shrub were screened as dominant factors. The results showed that, within 36 sampling plots, no one was unhealthy, 22% plots were in sub-health, 67% plots were in healthy state and 12% plots were high quality. According to analyzing the dominant factors, we can receive that improving the mingling degree was the necessary means of promoting development for Pinus tabulaeformis secondary forest; the thinning intensity of Pinus tabulaeformis secondary forest should not be too heavy; eliminating shrub was also not allowed.Study on spatial patterns of species populations can provide many important clues about underlying processes of these patterns formation. Secondary Quercus aliena var. acuteserrata forest populations are representative forsest type in Qinling Mountains. This paper intended to investigate the spatial pattern of Secondary Quercus aliena var. acuteserrata forest, and to provide a basis for managing the natural forest. Two sample plots were established on sunny slope and shady slope respectively to analyze and compare spatial patterns of Quercus aliena var. acuteserrata populations. The pair correlation function and univariate statistics of point pattern were used to analyze spatial distribution of different development stages and habitats, while bivariate statistics was to analyze spatial associations of different stage and different populations on each plot. The change of population spatial pattern and association among different development stage and different populations was compared to explore inherent formation mechanism of spatial patterns. The results show that, spatial distribution patterns and age structure of Quercus aliena var.acuteserrata population were different on sunny and shady slope. The degree of spatial distribution aggregated on shady slope was higher than that on sunny slope; the age structure appeared a reverse ‘J’ type on sunny slope, belonging to growing type, while the population renewaled adverse on shady slope, belonging to declining type. Different development stages with similar distribution pattern on each slope, the population distribution pattern in aggregated, which became random when young trees getting matured. Some differences appeared in the relevance of each development stages on each slope, positive association was observed among each development stages on sunny slope, and negative association was observed among each development stages on shady slope. On sunny slope, the distribution patterns of Quercus aliena var. acuteserrata population were positively associated with Populus davidiana, negatively associated with Bothrocaryum controversum and Carpinusturc zaninowii; On shady slope, the distribution patterns of Quercus aliena var.acuteserrata population were positively associated with Populus davidiana and Toxicodendron vernicifluum, negatively associated with Bothrocaryum controversum, Acer davidii,Carpinusturc zaninowii. In summary, the distribution patterns of Quercus aliena var. acuteserrata population were basically reasonable on sunny slope, intraspecific and interspecific competition were not fierce; the distribution patterns of Quercus aliena var. acuteserrata population were not only influenced by the interspecific competition, but also were restricted by intraspecific competition on shady slope, suggestting that proper thinning could increase light transmittance, as improving the regeneration and stablity of Quercus aliena var. acuteserrata population.Based on overall analyses of population structure, productivity, water conservation and species diversity of vegation for Quercus aliena var. acuteserrata secondary forest affter 3 years of thinning, the objective and subjective combination weighting was carried out to synthetical evaluate of thinning effects for Quercus aliena var.acuteserrata secondary forest on south slope of Qinling Mountains. within 25 sampling plots, no one was unhealthy, 20% plots were in sub-health, 68% plots were in healthy state and 12% plots were high quality.