Study On The Assessment And Remote Sensing Classification Technique Of Shrub In Tibet

As an important part of forest in Tibet, shrub plays an irreplaceable role in regional ecological security maintenance and regional economic and social development. However, shrub has been limited both in forestry production and scientific research because of the incorrect understanding and less attention for a long time. In this paper, based on the review of shrub population and community characteristics, spatial structure and distribution of shrub, as well as remote sensing classification techniques, the research was carried out as following by taking the shrub in Tibet which accorded with the special regulation of national as the research object: (â…°) the community characteristics of shrub in Tibet were analyzed; (â…±) the populations niche of shrub in Tibet were measured, and the adaptability and interspecific competitions of shrub populations were studied; (â…²) the spatial structure of shrub types was studied through the landscape pattern analysis, spatial autocorrelation analysis, and spatial scaling effects analysis; (â…³) interactional relationship between environmental factors and distribution of shrub was analyzed, and the spatial distribution of shrub types was studied; (â…´) the remote sensing classification technique of shrub in Tibet was discussed, including the process of assistant classification based on spatial distribution characteristics and re-classification based on spectral characteristics.The inventory was carried out and the community characteristics were analyzed. The results show that, the main family compositions of shrub in Tibet are Rosaceae, Papilionaceae and Ericaceae. Species composition in shrub communities is single, and species richness and diversity are at low level. Dominant species in the communities occupy a main proportion, and as a result, stable original or secondary communities with single dominant specie are dominated. Mostly, the coverage of the shrub communities is larger than 0.4, and it is remarkable different in districts and shrub types. Being affected by the plateau environment and shrub species ecology characteristic, the tree height distributes between 0.1 m and 6.0 m, and the ground diameter distributes between 1 cm and 5 cm. The power function curves of H-D of some shrub types show prominent relativity.Niche breadth and overlap indexes were measured at the environmental space including altitude, aspect, position and slope. The result shows that the environmental adaptability is different among environmental factors through the measurement of the population niche characteristics from the four-dimensional environment space. The populations show flexible width to different environmental factors, and it makes the habitat resources useable for each species from different aspects. The comparison of environmental adaptability could be carried out by the quantitative measurement of niche breadth. After a long period of natural selection, the stable symbiosis relationships have been set up with less interspecific competition in shrub communities. The comparison of symbiotic relationship could be studied by the quantitative measurement of niche overlap.The spatial structure of shrub in Tibet was quantitative studied based on the principles and methods of landscape ecology. The patch-size distributions of the shrub types are subject to anti-J shape. Generally, the area of shrub occupies 4.6% of the whole landscape, and the patch number accounts for 54.8%. And, the pattern characteristics of typical shrub types are different in patch shape and size, and positive correlation was showed to the spatial autocorrelation. Scale effect is evident between different spatial extent, and it showed strong sensitivity to scale in patch-size, landscape mosaic, patch shape and landscape diversity index.The interactional relationship between environmental factors and distribution of shrub was analyzed by multiple correspondence analyses. The spatial distribution of shrub is mainly affected by the regional factors, including the terrain, precipitation, light condition, etc. The results show that the most important factor that effects the distribution is the longitude, latitude and altitude, which are from the large-scale region which due to the terrain of Tibet that gradually upheaval from southeast to northwest. At the niche level, the distribution of shrub is usually affected by factors'combination, such as slope aspect, position, slope, etc.Because of the large size of shrub patch and pure stand mostly, it is helpful to the remote sensing classification of shrub types. With assistant classification based on the spatial distribution characteristics and re-classification based on the spectral characteristics, the classification results of shrub types were drawn. The accuracy of assistant classification based on the spatial distribution characteristics is 86.24%, which could meet the requirements of forestry production, and the accuracy is 70.64% based on the spectral characteristics classification. Hippophae L. and Tamarix L. can be identify accurately by using of technical processes image data, other shrub types could be classified to types or type groups depend on the precision request.