Study Of Near-natural Modification To The Plants In Small Mountain Town Of Southwest

Our country is very mountainous,with more then half of the towns loated on the hills and mountains. Yunnan Province is in low latitudes,and the town population accounts for 45.2 percent of the whole province's population. The geographical position is extremely bad, and the terrains and landforms are complex and varied. Recently,Economic development around the frequent increase in the urban population, accelerated urbanization, blind development, coupled with the fragile mountain environment of the basin, made the environment worse, and d towns isaster-proned. Deforestation, cultivation on steep slopes, land use and other long-term transition of human disturbance account for the severe vegetation degradation. Among study area, all the plant types are essential for water and soil conservation. Therefore, the accelerated recovery of forest vegetation is not only the need for environmental protection, but also the ecological benefits of forests.Near nature modification plays a significant role in adjusting structure,improving species composition and promoting evolution to natural forest for artificial forest of Pinus yunnanensis.Based on the state and analysis of the social, economy ,main plant types and the rusults of Naturalness Evaluation,this paper set out the goals of Near nature modification,and took the modification of artificial forest of Pinus yunnanensis as an example.Firstly, according to the status and characteristics of Yipinglang Town, and the factors of altitude,age,direction,and position of plant distribution, the town was divided into three ecological areas, the areas of ecology-protective forest,landscape-economy forest and farm-produce forest.Then, the Naturalness Evaluating Index System of Pinus yunnanensis forest was constructed,based on the proach of analytic hierarchy process, and six different Pinus yunnanensis communities were evaluated according to the natural composition index system in Yipinglang Forest Farm in Yunnan Province. According to selection through sensitivity analyzing and calculating of weight values of evaluation indexes, the evaluation system was constructed which in eleven indexes belonging to three aspects of soil characteristic, community construction and succession state. Based on analysis of the results, the six of different Pinus yunnanensis forestry was divided into four grades,and different management measures were given.It reflected the near natural state of Pinus yunnanensis forest objectively.In the last,taking the example of artificial forest of Pinus yunnanensis, based on analysis of artificial forest plot,near-natural modification plot after 4 yr and secondary forest of the same age plot of Pinus yunnanensis, this paper analysed the preliminary results and existential problems of Near Nature Modification of artificial Pinus yunnanensis forest.The results showed that the density and the important value of artificial forest of Pinus yunnanensis were both reduced.In shrub layer, the renewal kinds were more abundant and the forestry diversity were increased whereas in herb layer changed little.On the whole,It accelerated to chang to uneven aged-mixed tiered forest and evolut to nature forest structure.