A Study On The Ecological Effects And Operation Technology Of Slective Cutting Of Natural Mixed Stand Of Conifer And Broad-leaved Trees

The natural mixed forests of coniferous and broadleaf have complicated structure, various species, and prominent ecological function. But they divide into competence demonstrate that can't be constant in view and stand. So, they need adopting the management tactics with rational science badly. Slective cutting of natural mixed forests of coniferous and broadleaf is most reasonable type of management according to the actual conditions of different areas and stands. Selective cutting can make full use of tree grow potentiality and forest productivity, increase species diversity and improve resistance against diseases of forest. It is favorable for the rational circulation of nutriment. It can reduce the brokenness intensity of forest, improve the protect efficiency of forest and form the harmonious view. As selective cutting is accord with the natural law, it was received more and more attention by ecologists, biologists, forestry scholars and logging scholars.The sample plots of the dynamically study on selective cutting and upgrade of natural forest were selected in Dayuan logging camps located in Jian'ou city, Fujian province. The experimental stands were developed selective cutting of different intensity (low intensity 13.0%; middle intensity 29.1%; high intensity 45.8%; over-high intensity 67.1%) in August, 1996, and non-cuting and clear cutting were compared(natural regeneration after cutting). Follow-up investigation was surved and analyzed again in July, 2006. Vegetations were investigated in the way of standard sample plots, forest litters were collected and soil sections were examined before and after selective cutting. The vegetation, litter nutrient content and physical and chemical properties of soil were analyzed by conventional methods. The effects of different intensity selective cutting on the stand structure, species diversity, saplings and seedlings, stand volume growth, litter nutrient content, physical and chemical properties of soil et al, were researched after selective cutting 10 years. On this basis, the choices and definitions of the technological factors of selective cutting of natual forests, logging equipments, and types of technology in selective cutting areas are discussed. The comprehensive evaluation and selection of optimum model are also calculated. The aim is to provide theoretical basis of ecological logging and suitable operating systems for sustainable management of natural mixed forests of coniferous and broadleaf in mountain region.The quantitative analysis shows that the impacts on the stand structure, species diversity litter nutrient content and physical and chemical properties of soil, etc by different intensities selective cutting are different. The more intensity of cutting, the more changes of stand structure; the cutting operation results in adverse influences, particularly the serious damage to the forest canopy caused by selective cutting of high intensity. But the rational selective cutting (low intensity and middle intensity) benefits the restoration and maintenance of species during a long time. Biomass of forest litter and total nutrient contents generally reduced with the cutting intensity increasing after selective cutting of different intensity 10 years.After low and meddle intensity selective cutting 10 years, the bulk density of soil and the damage rate of soil structure decreased, while the maximal saturated water retention of soil and the total porosity of soil increased. As for organic matter in soil, total N, hydrolytic N and total P increased, but total K, available K and available P reduced. That is to say, the soil aggregate stability, soil moisture property, soil porosity and soil nutrient were basically recovered and partly improved in 10 years. After high and over-high intensity selective cutting 10 years, the bulk density of soil and the damage rate of soil structure increased, while the saturated water retention of soil and the total porosity of soil decreased. The content of soil nutrient generally decreased. The soil aggregate, soil moisture property and porosity, and soil nutrient were not recovered after 10 years. With the selective cutting intensity increasing, the destruction has deteriorated.Five different operational models used in natual forests cutting area were evaluated comprehensively by using comprehensive evaluation method from two aspects of economic and ecologic benefits. The results show that under certain operation conditions, the selective cutting operation of middle intensity with manual skidding is the optimum model for cutting area operation. The second best comprehensive benefit is achieved in the selective cutting operation of low intensity with manual skidding. The other models are list from large to small comprehensive benefit as the selective cutting operation of high intensity with manual skidding, the selective cutting operation of over-high intensity with manual skidding and the clear cutting operation with manual skidding. The scientific basis was offered to the production decision department of the forestry branch for choosing the operation mod in natural forest cutting rationally.