The Dynamic Characteristic And Its Application In Close-to-nature Forest Management Of Pinus Yunnanensis Community

Pinus yunnanensis forest is one of main forest types with 52% area of total woodland and 32% timber volume of total forests volume, respectively, in Yunnan province. However, the 80% of P. yunnanensis forest is pure stand with simple structure and low species diversity that resulted in aggravating of diseases and pests damage and reducing of community stability. The problems of pure forest mentioned above have happened in developed countries, and they have put forward corresponding silviculture system and technical measure to solve the problems based on long-term study. The economically efficient way of solving pure forest problems was approaching-nature forest management and establishing continuous cover forest system, which have been proved in practice. The former study of P. yunnanensis was focused on genetic improvement, forest protection, exploitation and utilization of non-timber resources, silviculture and so on, the basic study of approaching-nature forest management of pure stand has not been reported. In order to provide some basic information for approaching-nature forest management of the pure forests, this study presented silvicultural regimes and technical parameters of approaching-nature forest management based on plot investigation and community dynamic analysis. The space-time dynamic of plant community and population of P. yunnanensis were studied with the methods of spatial sere substituting for time sere, plots arranged with age and general. According to experimental data on the dynamics of community structure, stand quantity was compared before and after close-to-nature cutting. The main results were as follows:In the woodlands of similar site quality, the results of comparative study show that species richness, forest structure, forest quality, the maintenance of soil fertility and other capabilities in natural mixed forests were significantly better than artificial pure forest. Therefore, the natural mixed forest has incomparable superiority in the production and ecological functions continually display. Evidently, artificial pure forest transformed into uneven aged mixed forest is not only necessary, but is feasible also.The space-time dynamic of plant community and population showed that from the chine to the valley, the abundance of species increased gradually, and the type of community transformed was from coniferous forests to ever-green forest. According to space-time dynamic studies, with the population age increased, on the ridgeline, the number and structure of population had been remained by gap regeneration, the community would be dominated only by Pinus yunnanensis. On the middle slope, the number and biomass of population maintained in a certain level, the community would be needle-leaf and broad-leafed mixed forest finally. On the valley, the number and biomass of population rapidly declined almost approaching to zero, and structure of population was declined, the community would be the evergreen broad-leafed stand finally.Based on the above findings, the community type, mixed proportion, reserved density of target trees and the essential technical parameter of nature-approximating modification had been proposed in the study. In the chine, the object type of forests was composed of entire P. yunnanensis. In the upper slope, the mixed proportion of P. yunnanensis and broadleaf would be a ratio of 8 to 2 or 7 to 3. In the mid-slope, the mixed proportion of P. yunnanensis and broadleaf would be a ratio of 6 to 4 or 5 to 5. In the lower slope, the mixed proportion of P. yunnanensis and broadleaf would be a ratio of 2 to 8 or entire broadleaf. The choice of mixed species may imitate species form natural forests, which might be composed of Alnus nepalensis, C. delavayi, C. glaucoides, Quercus aliena, Castanopsis delavayi. It was unsuited to confirm target trees in initial stage of stand formation. The reserved density of target trees was 250-300 and 150-200 stem.hm-2 in the phases of stand formation and stabilization.According to the above technical parameters, nature-approximating modification had been proposed and conducted through logging design of controlling single tree goal growth in the fields. Comparing before and after the logging, the results showed that: the status and the function of the pine in canopy were reduced and witch of broad-leaved trees were increased, the straightness of the pine population and the plant species diversity in regenerations and herbaceous were improved by approaching-nature cutting. Meanwhile, approaching-nature cutting was feasible in economy. Therefore, the nature-approximating modification of P. yunnanensis was accordant with naturally successional direction. Furthermore, the population succession, community stability, diversity and quality of forestry will be improved...