Study On Sustainable Forest Resources Controlling Techniques

Sustainablity of forest resources means maintenance of ecological processes and functions. However, complete controlling of ecological processes and functions cannot be realized under present knowledge and technological conditions. Based on the principle that function and structure are closely related, this study focused on forest resources dynamics on respect of both aspatial and spatial structure to realize sustainable management of forest resources. Main contents as follows:First, forest resources dynamics during past 40 years form 1958 to 1998 was analyzed, and the in depth cause of the worsening of resources structure was discussed. The result shows that, the characteristic of the changing trend is, age structure becoming younger, species structure dominating by more secondary forest, and productivity decreasing continuously. Major reason is due to management schemes were not carried out strictly over long time, while excessive and concentrated clear-cut dominated the management practice in order to pursue short-term profit. Forest resources administration and planting was enhanced in recent years, which bring the area of forested land increasing. However, it is still a long-term hard task to increase the forest stock and to improve spices structure and age structure, In order to keep the sustainability of forest resources, it is very urgent to adjust resources structure with scientific approaches and technology.Second, according to principles of sustainable management and other relevant theories, the object structure was deduced from present resources structure. Object structure of plantation forest aimed at even flow of high economic profit should be Normal even age vector. While natural secondary forest, with lagging of stand-age growth, cannot be sustained with Normal even age vector. Its object structure should be a vector of arithmetical progression. Using linear programming technique, structure adjusting optimization models was constructed.Third, landscape structure of both 1958 and 1998 was analyzed quantitatively, andlandscape transfer probability was calculated. On respect of landscape composition, patch types was increased in 1998, but the area ratio of mature and over-mature patch was decreasing strikingly, and conifer patch (belonging to local climatic community) having decreased further. On respect of landscape configuration landscape becoming more fragmentedin 1998, in that number of patches, ratio of small patches, amount of edge increased, and isolation of patches, mean patch size decreased. According to analysis of landscape transfer, land-type transformation is very ideal since area of forested landscape was increased, but species, age and forest stocking transformation were not good.In the end, with G1S spatial database as the basis, using DEM based hydrologic analysis, GIS buffer analysis, topological relationship query and other relevant GIS spatial analysis functions, 3 different spatial harvest pattern were simulated over 9 25-year simulation time steps. In each iteration, harvest area was decided by the linear programing model, and stand development was predicted with a neural network model, then the resulted landscape structure is measured, so as to achieve desired age structure and landscape structure, to realize spatial support decision-making. It is the basis for sustainable forest management to integrate multiple values and functions as management object.