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《Acta Ecologica Sinica》 2001-08
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The assessment of forest ecosystem biodiversity by remote sensing

GUO Zhong-Wei,LI Dian Mo, GAN Ya-Ling (Institute of Zoology, Chinese Academy of Sciences, Beijing 100080)  
Forest biodiversity refers to either the biological diversity within species, between species, and of ecosystems, and means not only species diversity but also the variation in ecological structures, functions and processes. Their assessment involves potentially enormous work, and any methods that can be time-saving for data collecting are therefore of interest. Remote sensing represents such a method although it has been under-utilized in the studies of forest biodiversity. \;Remote sensing operates from the species to the global scale. The grain, the smallest unit in landscape ecology, is defined by the pixel size or the scale-dependent resolution of photographs. The major benefit of remote sensing is the total coverage of extended areas, which assures easy assessment of structural parameters in a synoptic way, derivation of geographically correct models of the landscape, visualization of the area, and documentation of all visible information. Remote sensing thus has the potential to provide a range of different data for biodiversity studies. \;A number of different remote sensing technologies are available and the required resolution of the end product determines which will be the most appropriate. Photography, which will use the film as data carrier, and digital optical images are the two main technologies used to derive information. As film normally provides a better spatial resolution than digital data, film is mostly used for applications with high requirements for detailed textural information, while digital data often provide better spectral information. In addition, there are some promising remote sensing technologies, which might also provide very interesting information for the assessment of biodiversity. One such is the use of lasers, which supply information on the height and form of the ground surface and the different vegetation layers. Others include thermal remote sensing and radar. Photographs and digital optical images, the most frequently used forms of remote sensing in ecology, are provided from three different platforms: terrestrial, airborne and spaceborne. Terrestrial photography enables the assessment of sections of landscapes, single species, or parts of species, at large scales and from an earth-bounded perspective. While airborne and spaceborne remote sensing technologies allow a synoptic view from a bird's-eye perspective, mostly at scales of 1:1000 upwards. Airborne and spaceborne remote sensing enable the assessment of species, habitats and landscapes. The importance of each technology is dependent on the information being sought.\;Remote sensing is normally considered as referring to airborne or spaceborne technologies. Airborne remote sensing methods may be either aerial photography or digital airborne scanner data, while spaceborne remote sensing methods refer mainly to digital satellite data. Radar and lasers might provide information about the internal structure of forest stands. Existing earth observation satellites provide data which are suitable for the assessment of between habitat, landscape and regional to global diversity information. The spatial scales for the studies are in general smaller than those provided by aerial photography and three-dimensional data are not usually accessible. \;Forests occur within the context of the landscape. They are embedded within a landscape consisting not only of forests but also of a variety of other habitats. The overall effect is one of a mosaic of different habitats. These habitats vary in size, shape, composition and persistence. The degree of habitat fragmentation plays a decisive role affecting the viabilities of both plant and animal populations in the remaining fragments. The degree of fragmentation appears to influence important ecosystem processes. AVHRR has been used to lookat land cover richness,vegetation richness and vegetation clustering,while high resolu- tion satellites can provide more detailed spatial information.The investigation of structure diversity at a landscape level implies the selection of a spatial resolution
【Fund】: 国家自然科学基金重大研究 (3 9893 3 60 );; 青年科学家小组 (C2 9990 83 )资助项目;; World Bank的 BRIM(Biodiversity Research and Information Management)项目;; NASA Earth Observation System Interdisci- plinary Science Program的资助
【CateGory Index】: S718.5
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