The Evaluation Of The Oak Natural Secondary Forest In Baotianman National-level Nature Reserve

The confirmation of indicators of the forest resource evaluation will be provide the basis for the forest resource management, forest macroeconomic policy and the establishment of criteria and indexes of the forest sustainable development. According to the objective of evaluation and the characteristics of the indicator, the thesis selects stand density, stand diameter distribution, the site quality, productivity and biodiversity as indicators to evaluate forest quality, and taking the oak natural secondary forest in Baotianman National-level Nature Reserve as the research object, according to the survey data of 32 temporary standard samples and analytic trees, analyzes and evaluates in detail the forest quality of the oak natural secondary forest in Baotianman National-level Nature Reserve.The evaluation of the stand density. Through analyzing comparatively each indexes of stand density, the thesis chooses the density index to carry on the evaluation of density to the oak natural secondary forest, gets the density equation of this stand, then put the key diameter of the oak natural secondary forest into it and we get the stand density of the oak natural secondary forest, it is 2,505trees/hm~2.The study on the stand diameter distribution. First, By the help of the forstat2.0 which is a statistics software invented by the Chinese forestry academy of science, the thesis uses five probability distribution functions and the main formula of three characteristics of diameter distribution to carry on the fitting and calculation to the community of the main trees diameter distribution, gets the fitting result of five probability distribution functions. Then, uses the BP neural network model which established in the thesis to carry on the fitting again, gets the fitting result of BP Neural network model. Comparing with these fitting results, we can know: the error of the BP Neural network model is smaller, the precision is higher, and the fitting effect is better. It is proved that this BP neural network model has a strong outreach capacity and can be used as the effective simulation technology of diameter distribution.From three characteristics of diameter distribution (skewness, kurtosis, change coefficient), we can see that the trees of the middle and little diameter is in the most in the oak natural secondary forest; the diameter distribution curves of var.btecipetiolata Nakai, P.strobilacea Sieb.et, L.obtusiloba Bl. are relatively flat, they show that the separated degree of the diameter bands are very big. The diameter distribution curves of the other four trees are sharp, and their separated degree of diameter bands are small and concentrated. The change coefficient of T.chinensis is the biggest one, which shows that the range of the diameter distribution is very large, Q.aliena Bl. is the second, and the other trees are very small, which show that their ranges of the diameter distribution are...