Forest Vegetation's Investigation By Remote Sensing Technique And Assessment In Gansu Province

The paper, uniting other related information, uses "3S" technology ,which is the integration system of RS,GIS and GPS, and TM743 datum to monitor the amount of forest land area and to establish indicator system of sustainable management capacities of forest resources in Gansu province,and combines the principle component analysis(PCA) ,which is used to determine the weight of each indictor,and the multiple target-linear function method,which is used to calculate values of them,to assess sustainable management capacities of forest resources in Gansu province .The results are summarized as follows:1.Using RS,GPS and GIS,TM743 images are interpreted ,the interpretation keys are set up, the amount of forest land area is investigated and the trend of dynamic change of it is analysed. Meanwhile, combined remote sensing and other related information ,the database of forest land in Gansu is worked out.The results indicate that forested land increased and percentage of forest coverage reached 14.21% of region's total area, that the ratio of shelter forest and special forest area to the forest stand area increased while that of timber forest and fuel forest decreased during the period of 1988-1998 ,and show that the structure of land is gradually adjusted and the direction of forestry gradually shifts from "economic property construction" to "ecological environment construction".2.According to inherence dynamic mechanism for sustainability of forest resources and the principle that indictors of sustainable management capacity should respond to basic essential factors of it,which includes economic sustainable capacity, ecological sustainable capacity and social sustainable capacity, the sustainable management indictor system of forest resources in Gansu is set up and 29 dominant indicators are chosen .3.29 indicators' weights are determined by PCA and economic sustainable capacity, ecological sustainable capacity and social sustainable capacity are 0.241,0.562 and 0.197 respectively. Each indictor's weight is objective as drawn from original data.4.Based on numerical characters and ordered multistate characters, sustainable management capacity of forest resources is evaluated.The assessment result is less sustainable management of Gansu province, the comprehensive score of which is 0.314,of each region, the comprehensive score of which is less than 0.6,and of each county except Diebu ,whose comprehensive score is 0.707 and shows that the county is in medium-less sustainable management.5.The change regularity of the sustainable management capacity goes as follows:economic sustainable capacity is higher in the industrial and mining area while lower in the farming area; ecological sustainable capacity is higher in the southeast of Gansu while lower in the middle area and the west area; social sustainable capacity is higher in most urban of region and county where administration departments stay while lower in the farming area.6.The analysis shows that main factors restraining the sustainable management of forest resources ,for Diebu, are that economic and social sustainable capacity of forest resources are poor ,which can be shown from that per capital GDP , per capital net income are low, people's quality is poor and tourism resources have still not been exploited or not enough,for most counties,are that per capital output value of forest, percentage of forest cover ,forest growing stock and investment level are low, that ecological environment factors are unfavorable and that people's quality is poor.7.In the dendrogram obtained by clustering analysis based on block distance of 23 indictors ,87 counties tend to cluster into 4 sections according to the leaps of linkage distance (L.D.=12.523).These results coincide with the capacities of sustainable management.