Study On Gene Of Forest Subcompartment Extraction And Forest Site Evaluation Based On Gis

In forest production,Subcompartment is the object of forest management, and is smallest plot cell of forest production and construction. Site gene is an important element in Subcompartment investigation. Using GIS technology extract Subcompartment's gene, computer can simulate person to survey, calculate each Subcompartment of gene automatically, which provide a viable technical solutions for solving practical forest production problems.Evaluation of forest site is a basic task in forest production,which is the foundation of the scientific forest development, management and forest harvest predictable.Combining site evaluation studies and GIS technology, through analysis, with a small number of sample data in the GIS environment, Estimate the site index of subcompartment rapidly, Evaluation of forest site is systematism and incorporate can come true,accord with forest production's the actual needs.In this paper, the data of forest resources survey as the main source of information,fengshushan forestry centre is the object in Jingdezhen of Jiangxi Province,At these basis, extracting forest site and evaluating the forest site. The main content of establishing spatial database about forest resources; extrating elevation, topography, slope, aspect base on DEM,choosing the good extraction way; and using GIS technology and the geologic method predict the site index of Chinese fir and Masson pine. The main conclusions are as follows:(1) Analysing principle of extraction to subcompartment's elevation based on the DEM,and using zonal statistics belong to geographical information system software ArcGIS9.2 to caculate the average elevation, topography for subcompartment.(2) Choosing 46 subcompartments in sanbao and nanshan to extract slope by three ways,which are average slope,median slope,center slope, Compared with on the spot investigation value,results showed that the average slope of accurate rate is 80.4%, and the actual investigation of is most similar. The median slope of the accuracy of 73.9%,the center slope of the accuracy is less than 50 percent.the average slope is better than other ways because of smoothing on the mutation of terrain, which makes the average slope way to calculate value stabilized,but the center slope way to calculate value is stochastic,accuracy is relatively poor.Therefore,in the practical application,the best way is average slope to calculate slope in subcompartment, secondly choosing median slope way.(3) Choosing 46 subcompartments in sanbao and nanshan to extract aspect by three ways,which are average aspect, probability aspect,aspect by the highest and lowest in subcompartment point,Compared with on the spot investigation value,The results show that the probability aspect of accurate rate is 87.0%, and the actual investigation is the most similar. Average aspect of the accuracy is 71.7%, the aspect by the highest and lowest in subcompartment point of the aspect accurately calculated rate is 56.5%. This is different the best gradient algorithm between slope and aspect, the reason that aspect is a vector data, it is a direction, and the statistical probability aspect of the largest number as the direction of the subcompartment's aspect is more reasonable. Caculating aspect by the highest and lowest in subcompartment point, the accuracy is poor like center aspect way.Therefore, in the practical application, the best way is probability aspect to calculate aspect in subcompartment.(4) The site index about Chinese fir and Masson pine of spatial variability law have been in the study area. The site index of Chinese fir's ratios of nugget value to sill value [C0/(C0+C1)] are 66.15%, The site index of Masson pine's ratios of nugget value to sill value are 39.41%, Chinese fir>Masson pine. The value of the nugget and sill ratio is between 25% and 75%, Blong to a moderate degree of spatial correlation, and the status of Masson pine for the space-related degree is better than Chinese fir. Compared with their range, site of spatial autocorrelation (spatial scales),Masson pine>Chinese fir.(5) On the basis of the study area after analysis of sample, site index data distribution of the Chinese fir and Masson pine be gridded with the kriging method, through cross-validation analysis, the absolute value of average errors and Average Standard Errors of Chinese fir and Masson pine are very close to zero, root mean errors and mean errors also are relatively small, Root Mean Standardized Errors are close to one,these show that the effection about predicability is very good,demonstrating the Kriging method is agonic estimation.(6) Drawing map about site index distribution in study area of Chinese fir and Masson pine.Through the map analysis to identify the appropriate areas of Chinese fir and Masson pine,provided some basis information in order to get scientific afforestation and reasonable management after analysis of its reasons.