The Forest Health Assessment Study Based On GIS In Jiangle Forest Farm

In this paper which research object was Jiangle Forest Farm in Fujian Sanming City, the forest health assessment methods and techniques based on spatial data were studied. The main contents are as follows:Firstly, the forest dominant function in studied area were determined based on its forest resources’ characteristics and social demand analysis. The ArcGIS platform’s forest dominant function divided indicators and thresholds were proposed based on combination of qualitative and quantitative, then the dominant function types of Jiangle forest subcompartment were divided and9forest management types were proposed.The results show that, Plantation, Water and Soil Conservation Forest, Water Conservation Forest and River-bank Protection Forest were major in Jiangle National Forest Farm and forest dominant function types division became more scientific, intuitive and simple by GIS technology.Secondly, combined the qualitative with quantitative, the forest health assessment indicator system based on GIS were constructed from the aspects of Ecological Performance, Stability and Productivity; To determine weights, firstly the default weights were obtained by analytic hierarchy process; next modified weights were obtained by improved entropy weight; then the final indicators’weights were obtained by weighting the two types of weights.The results show that, improved entropy weight method can avoid super large weights and weights be in the opposite direction with the preset, thus playing to its strengths within a limited range.Thirdly, in the health assessment of the forest witch dominant functions were different, the indicators were unchanged and the thresholds were different. That is the generic assessment model formula:FHI=k1[Slope]+k2[Soil Thickness]+k3[Tree Vigor]+k4[Tree Species Composition Index]+k5[Origin]+k6[Community Structure]+k7[Canopy Density]+k8[Elevation]+k9[Dominant Tree Species]+k10[Aspect]+k11[Distance to Firebreak]+k12[Accumulation per hectare]+k13[Accessibility]+k14[Average DBHJ; Where ki is the weight of each index, i=1,2,......,14.The weights (k1-k14) of the forest which dominant function was Wood Production were:0.0535、0.0798、0.0397、0.0470、0.0486、0.0791、0.0428、0.0364、0.0854、0.0266、0.0211、0.1682、0.0898、 0.1820;The health of the forests, witch dominant functions were Water and Soil Conservation Forest, Water Conservation Forest and River-bank Protection, all performs in ecology, and in this study these three were unified into Water and Soil Conservation Function. The index weights are:0.1071、0.1596、0.0794、0.0939、0.0486、0.0791、0.0428、0.0364、0.0854、0.0266、0.0211、0.0841、0.0449、0.0910.Results show that, to the subcompartments of four class (high-quality, healthy, sub healthy and unhealthy), the number in the whole forest farm were155、736、217、46respectively, area ratio were12.93%,63.18%,20.68%,3.21%; the number of Wood Production leading forest were48、383、164、18, area ratio were7.54%、61.51%、27.74%、3.21%; the number of Water and Soil Conservation leading forest were107、353、53、28, area ratio were19.71%、65.28%、11.79%、3.22%. In general, the health of Water and Soil Conservation leading forest was better.Besides, analyzing image data by ERDAS; processing spatial information factor, managing database and getting visual results by ArcGIS, improved the indicators operability and reduced the uncertainty of traditional qualitative evaluation, thus making assessment more scientific, efficient and intuitive.