A Simulation System Of Disturbance Affects On Structure And Process Of Secondary Forest In Northeast China

Forest dynamic simulation is a significant approach of acquiring quantitative information in forest succession and a vital method of verifying various disturbance hypotheses. In order to predict dynamic changes of secondary forest in different disturbances, an integrative disturbance simulation system describing the process of structure changes of secondary forest was established on the development platform of Visual Studio by using C# language, Access database and ArcGIS Engine. The system comprised terrain and meteorological data pre-process module, vegetation dynamic simulation module (including disturbance) and results analysis module. Based on CFDM, the model structure was improved, parameters were optimized and a disturbance module for studying dynamic response of secondary forest to disturbances was integrated in the system. Taking the catchment of Zhangjiagou as study area, the dynamics of secondary forest without disturbance was firstly simulated in this study, and then, dynamic response processes of secondary forest to three predetermined disturbance scenarios were discussed respectively. Results showed that:1) In natural simulation, the secondary forest, composed of major broadleaved tree species such as Fraxinus mandshurica,Acer tegmenlosum,Tilia amurensis, could complete succession and regeneration smoothly and then stayed in a long and relative steady subclimax status without Korean pine(Pinus koraiensis); the original climax dominant species. The verification result showed that, numbers of trees and time dependant variations of volume for secondary forest coincided with characteristics of trees and succession regulation of forest; spatial and temporal distribution of species composition and community structure of secondary forest was similar to the practical distribution; the simulated age structure of species conformed to ecological strategy.2) In different disturbance simulations, singe and wide-range disturbance is not the determinants of destroying secondary forest in different disturbances. Period selection is the key point in clear cutting disturbance. The best disturbance period appeared between 60 and 80 years for each cutting strip. In selection cutting, the maximum of total cutting of multi-disturbances appeared in the scheme of initial cutting diameter at breast height of 10cm and disturbance period of 20 years. Under this disturbance scenario, forest density was maintained in a moderate level and the optimum of light illumination under the forest canopy produced biomass increasing sharply. Potential distribution regulation of natural vegetation, restoration and reconstruction regulation of vegetation after disturbance on landscape level were revealed and the disturbance influences on landscape structure and process of secondary forest were explored by simulating different disturbances conditions.