Study On Appropriate Crown Density Of Stand Based On Geomatics

Forestry is an important part of the national economy, whereas the forest is the main body of forestry management. Soil and water conservation and prevention of soil erosion is one of important eco-efficiency in forest ecosystems. Stand crown density is an important indicator which reflects stand density, and its values directly affects the stand conditions of overall biomass, thereby affects the capacity of forest soil and water conservation. It's significant to analyze the relationship between forest canopy density and soil erosion and furthermore determine reasonable and appropriate forest canopy density. This study was conducted in the Yongan City of Fujian Province. TM and ETM+ fusion image of Yongan City in 2003, DEM data and the database of Forest survey datum and Forest Resources Inventory were used by the Geomatics. Based on the thematic information extraction of forest resources in Yongan City, with the goal of prevent soil erosion ,this study determined the appropriate forest canopy density of different tree species in order to provide technical support and theoretical basis for different stand management, forest resources survey, ecological forest construction, water and soil conservation and forest ecological research. The main conclusions are as follows:(1) Based on the spectral characteristics, the selection of the appropriate threshold and the use of hierarchical classification method, supervised classification method and visual interpretation of human-computer interaction and so on, this study has extracted the thematic information of land use types and forest resources types of Yongan City in 2003. The result shows that classification accuracy of the woodland, fir forest, pine forest and broad-leaved forest is 93.15﹪, 89.66﹪, 86.81﹪and 85.54﹪respectively.(2) Based on sample information of Forest Resources Inventory of Yongan City in 2003, referring to the related literature ,this paper has set up 20 estimation factors, and then carries out factors optimization and establishes a estimation model of forest canopy density with ridge estimation methods and consequently achieves inversion of stand canopy density of Yongan City in 2003. The inversion accuracy is up to85.58﹪after testing which used the data on the outside of model.(3) According to the facts of Yongan City and the Universal Soil Loss Equation, this study constructs the suitable soil erosion model, and then get the factors (R, K, LS, C) diagrams by calculating, finally overlie each factor map with the modeling functions of ERDAS software. It achieves a quantitative estimation of soil erosion of Yongan City in 2003 and provides a data infrastructure for researching the relationship between forest canopy density and soil erosion.(4) To prevent soil erosion, Chinese fir forest, pine forest, broad-leaved forest as the main study object, composition of the different levels of slope aspect and gradient as the prerequisite conditions, this study extracts the information of canopy density locations and amount of soil erosion and studies the relationship between them by generating random samples, and then establishes polynomial equations to determine the most appropriate forest canopy of the various stands under different conditions, and at the same time analyzes the results in accordance with the actual conditions in Yongan City. It puts forward the appropriate forest canopy density which is to prevent soil erosion in Yongan City, the value range of the fir forest, pine forest, broad-leaved forest and the general is 0.70～0.78, 0.72～0.80, 0.66～0.74 and 0.70～0.78, respectively.