Study Of Watershed-Scaled Vegetation Dynamic Model

Forest ecosystem is the most complex ecosystem on the earth especially theconfiguration arrangement and function behavior, because of the long life spanwhose dynamic is difficult to observe, so the study of structure and function on itbecame the key problem. More and more attention has been paid on the functionsand processes in landscape ecology field, ecological model, especially the use offorest dynamic models has become the indispensability tools on these field,however, these models are built on the stand and pitch scales, can not effectivelyopen out the landscape scaled ecological processes. How can we achievevegetation dynamic modeling on heterogeneity scales has became the hotspotnow. In this project we developed the individual-based landscape scaledvegetation dynamic models, the model included two parts biological growth andenvironmental impacts on growth, preferably settled the problems that standscaled ecological processes transferred to landscape-scaled. The model employsthe GIS technologies and absorbed the latest gap model headways, described theindividual tree physiological processes and spatial distribution patterns. Throughthe use of individual-based watershed-scaled forest dynamic model found thatthis model can perfectly show out natural secondary forest dynamic and thechange processes of forest structures.The result shows that: the distribution of some species has distinctterritorial, most of Quercus mongolica distributed on the ridge; Fraxinusmandshurica distributed in the valley and humid places; other species aredistributed under restrict of topography and soil moisture all over the hill. In theprophase of modeling, the number of every species are big, but along with themodeling process began to decline gradually, the decline rate are different amongevery species, intolerant tree species decline rate rapider than shade-tolerant treespecies. When the eco-system is about to the stable phases the structure of everyspecies age, number are process structure, can sustainable exist and keep the eco-system stable. At succession prophase Populus davidiana, Betula platyphylla,Populus ussuriensis has higher breast-height area, with the succession processgradually declines, when it comes to 200 years the area of Populus davidiana,Betula platyphylla at breast height goes to stable, and Populus ussuriensis goeson decline. In the earlier 200 years the area of Fraxinus mandshurica at breast-height gradually raise, when it reach to. the maximum gradually decline a little and keep stable. The other species, because of the high number in the successioninitial stage of young trees and middle-aged trees, with the succession processdeath increases, but with the increase of ages, diameter at breast also increase, thearea at breast-height changes slow.In develop on this model, the most difficult issue is the collection ofparameters. A lot of reports in research area were retrieved for estimation of theparameters. The simulation results in zhangjiagou showed that application of thismodel is satisfied. However the area simulated should not more than 300hm~2 dueto limitation of computer hardwares. Finally, model validation issues arediscussed, and it is found that some parameters still remain to be determinedaccurately.