Fine Extraction And Change Analysis Of Mountain Altitudinal Zone On The Northern Slope Of Tianshan Bogda

As one of the most active and important components of the earth's surface,vegetation is an important part of the terrestrial ecosystem,which provides basises for the sustainable development of ecosystem.And the mountainous region have concentrated environmental gradient,less human interference,and highly heterogeneous habitats,which reflects biodiversity and landscape diversity.With the global warming,the mountain ecosystem is undergoing profound changes.Bogda heritage site,the most typically mountain altitudinal zone on the north slope of Tianshan Mountain,is a representative of the mountain altitudinal zone in the global temperate arid region,and its changes of vegetation cover is sensitive to global climate change.On the time scale of 30 years,the land use/cover classification information of the research area in 1989,1997,2004 and 2016 were analyzed by using remote sensing images,and the "DEM-NDVI-classification information" scatter plot was established to extract the mountain altitudinal zone of Bogda.At the same time,the spatial and temporal variation of the 1985-2016 temperature and precipitation in Bogda heritage site was extracted,combining with NDVI spatial autocorrelation analysis to explore the response characteristics of the mountain altitudinal zone and vegetation cover in Bogda.The following conclusions are drawn:(1)the remote sensing image visual interpretation bank of vegetation classifications & mountain vertical zones of Bogda heritage site was set up to describe the image features and extraction features of each land class.According to this,the corresponding relationship between vegetation classifications and mountain vertical zones was established.The Desert Steppe corresponds to the Temperate Desert Steppe Zone,the Grassland is corresponds to the Mountain Steppe Zone and the Mountain Meadow Zone,the Woodland is corresponds to the Mountain Coniferous Forest Zone,the Bare Land is corresponds to the Alpine Cushion Vegetation Zone,and the Glaciers and Permanent Snow is corresponds to the Alpine Snow-Ice Zone.(2)The "DEM-NDVI-classification information" scatter plot showed the change characteristics of both NDVI and land use classification with increasing altitude in Bogda,the NDVI was in an inverted U-shape and the land use classification displayed agglomeration effect in a fixed altitude range.The correlation between DEM and NDVI showed an upward trend year by year,and R2 were 0.73,0.71,0.74 and 0.76,respectively.(3)The spatial autocorrelation of NDVI in 1989,1997,2004 and 2016 increased year by year.NDVI was highly dependent on the elevation change,and the spatial aggregation model was very similar to the distribution characteristics of the vegetation zone.At the same time,the average value of NDVI in Bogda heritage site were obviously rising,and the average NDVI of four year were 0.362,0.365,0.368 and 0.423.And the annual average temperature and annual precipitation in the Bogda heritage site are increasing in 1985-2016,the temperature increased about 1-2?,and the precipitation increased about 20 mm.(4)The attribution analysis of mountain altitudinal zone changes was obtained by combining both the climate data(temperature and precipitation)and NDVI.The results indicated that: The Temperate Desert Steppe Zone,shrinking downward about 93 m of its upper boundary,was the most sensitive to climate changes;the range of Mountain Coniferous Forest Zone expanded to the upper and lower in 49m;the Mountain Meadow Zone monolithic moved up about 20 m with an unchanged span;the Alpine Snow-Ice Zone,retreating upward about 54 m of its lower boundary,was affected by global warming.