<学位論文要旨>リモートセンシングデータによる森林資源の評価 : 山火事跡地と松枯れ状況の事例研究を通して
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There is a huge quantity of forest resources on the earth. Vast forest regions, however, exist only in specific areas. Many small scale forests are distributed broadly in various places. Topographically steep remote areas make a quantitative forest resources evaluation quite difficult. Without remote sensing methods, it takes tremendous amount of cost, labor, and time to obtain an adequate evaluation of forest resources. Thanks to the contemporary remote sensing technology, we can make an access to necessary objective information needed for a forest resources assessment : the changes of damaged lands, the extent of forest destruction, and the quantity of resources. Remote sensing techniques for forest investigation using satellite data are in practical use nowadays. One of the major advantages of remote sensing technique is an easy access to periodical monitoring, extensive data and simultaneous observation. Among many forest fires occurred in Daxinganling, China, the one took place on May 6,1987 (hereafter 5.6 Large Forest Fire) caused the largest damage in the area of 13.2×10^5ha. It has been pointed out by Tans et al. (1990), Houghton et al. (1995), and Nakane&Lee (1995), that not only tropical forests but also forests in the Temperate Zone, the Subarctic and Subantarctic Zone are contributing greatly to the preservation of global environment. Therefore, 5.6 Large Forest Fire should not be overlooked. Data with respect to the extent of damaged area, lost biomass and vegetation recovery are of great ecological importance. Moreover the data bear sociological significance since they relate deeply to the problems of global environment. The 5.6 Large Forest Fire was studied under GPS (Global Positioning System) on the basis of field survey data, in which the damage extent for each type of vegetation was estimated with reference to NOAA/AVHRR data. The recovery of vegetation in extensive forest fire sites was measured quantitatively basing on the observation of vegetation cover changes over time. The changes in vegetation quantity were estimated by analyzing regularized vegetation indexed NOAA data. The large forest fire occurred in Daxinganling, China on May 6,1987,which lasted for over one month. It caused a great damage to the forest (c. a. 1,330,000ha; 121°53′∿125°00′E, 52°32′∿53°32′N). Images of the entire burnt area were extracted from NOAA/AVHRR data obtained in 1988 and 1996,respectively. When performing spot investigation on ground was conducted 2 times in 1988 and 1996. A topographic correction was made in forest fire region's data of Daxinanling based on a topographical map of 1 : 1,000,000. The vegetation in the forest fire regions was classified into twelve categories : Larix sp., Larix gmelinii, Pinus sylvestris, Betula eramanii, Pinus sylvestris var. mongolica, Populus Davidiana, Betula plaryphylla, Grass, Shrub, Urban and others, Cloud and recovery area. In terms of the maximum likelihood method, the vegetation types in the burnt area called Tahe were classified with an accuracy of over 94% and 100% in 1988 and 1996,respectively. Based on the satellite information and ground survey data, the pixels of the study area (13.3×10^5ha) in 1996 were classified into the following six types : conifers (6.0×10^6ha), hardwood (1.3×10^5ha), shrubs (1.9×10^5ha), mixture forest (1.8×10^5ha), grass (1.1×10^5ha), others (1.2×10^5ha). Correlating the volume of timber to the vegetation index (NDVI) calculated using the NOAA/AVHRR data, the volume of timber in each pixel was estimated and mapped for each forest type (conifer and hardwood) together with the degree of damage. The average timber volume of conifersand hardwood in the burnt areas were 166m^3ha^<-1>, 37m^3ha^<-1> in 1988; and 469m^3ha^<-1>, 179 m^3ha^<-1> in 1996. The satellite data and ground survey data suggested that the vegetation was almost fully recovered. Therefore we see here that a healthy forest ecosystem can b
- 2000-12-28
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- リモートセンシングデータによる森林資源の評価 : 山火事跡地と松枯れ状況の事例研究を通して