关键词: 遥感, 博格达, 山地垂直带, DEM, NDVI

Abstract:

The mountain altitudinal zone in Bogda Natural Heritage Site, one of the most typical representatives in the northern slope of Mount Tianshan, reflects the distribution characteristics and change rules of vegetation in the temperate desert region. To obtain the characteristics of the vegetation distribution, several steps have been designed and implemented. Firstly, the Landsat images were classified by supervised classifier for producing land cover classification results. Secondly, the vegetation coverage characteristics in Bogda Natural Heritage Site were described by a special scatterplot which integrated the land cover classification with the Normalized Difference Vegetation Index (NDVI) and Digital Elevation Model (DEM). Thirdly, the quantity ratios of each land cover type were calculated in different altitude ranges using the window-sliding method, and the boundary altitudes of two adjacent zones were identified based on the thresholding analysis of the quantity ratios. Lastly, the attribution analysis of vertical vegetation zone changes was conducted by combing the climate data (temperature and precipitation) and NDVI. The results indicated that: (1) the DEM-NDVI-Land Cover Classification Scatterplot showed the change characteristics of both NDVI and land cover classification with increasing altitude in Bogda: the NDVI changed in an inverted U-shape and the land cover classification displayed agglomeration effect in a fixed altitude range. (2) in 1989 and 2016, the upper and lower boundary altitudes of the bottom-up six vegetation zones were 1278, 1784, 2706, 3272, 3636 and 1185 m, 1759, 2730, 3293, 3690, respectively. (3) during the period of 1989-2016, the mountain altitudinal zones have an obvious response to the rising of the temperature and rainfall. The Temperate Desert Steppe Zone, shrinking downward about 93 m of its upper boundary, was the most sensitive one to the climate changes. The range of Mountain Coniferous Forest Zone expanded by 49 m to both upper and lower directions. The Mountain Meadow Zone monolithic moved up about 20m with an unchanged span, and the Alpine Snow-Ice Zone, retreating upward about 54m of its lower boundary, was affected by the global warming.

Key words: remote sensing, Bogda, vertical vegetation zone, DEM, NDVI