Temporal And Spatial Variation Analysis Of The Elevation Of Alpine Timberline In Guangdong Province In The Past50Years

As a special form of ecological crisscross belt, alpine timberline has become theresearch focus in recent years because of its high sensitivity to the climate change.By researching the dynamic changes of tree species, vegetation pattern orelevation of timberline, it helps not only unveiling the regional response to globalclimate change in history, also helps providing necessary information and dataaccumulation for further research on response of timberline to climate change.In this thesis, we estimate the elevation of timberline distribution in GuangdongProvince based on research methods such as GIS, regression analysis, after overviewof domestic and overseas researchers of timberline.Then this thesis obtains the change characteristics of timberline in50years byresearching the effect of topographic factors to the timberline elevation based onregional statistics analytical models, after the overlaying analysis of regionaltimberline data. And it also unveils the correlation between timberline elevation andthe location factor quantitatively. The research contents and conclusion shown asfollows:(1) Grasslands Patch Extraction based on SPOT5data: interpretation of SPOT5data in2008using ENVI4.7.Extract grasslands patches by visual interpretation and interactive interpretationand convert it into vector data. Then process the layer mosaic in ArcGIS9.3to get themap of grassland distribution in research area. The area of grassland in2008wasapproximately181.4km~2, as covering0.14%of mountain area in Guangdong.(2) Grasslands Distribution and the Relationship between its Dynamic Changeand Topographic Factors: calculate the grasslands distribution and its relationshipwith topographic factors by improved topographic distribution index, landscapepatch fragmentation index and change rate of land use.From the aspects of grasslands distribution, the grassland distribution rategenerally increases as the increasing of elevation and slope degree and then decreaseat the specific elevation and slope degree.The main distribution of grassland is the area with slope degree of30°-55°andthe elevation of800m-1600m, and the slope direction differentiation is small. In23years from1985to2008, the grassland area decreased by17.91km~2, it appears morefrequently decreasing at the elevation of1150m-1250m. (3) Timberline elevation and its dynamic change: Overlay the grassland layerwith mountain map of Guangdong province, and then merge these data layer toobtain the grassland distribution on each mountain.Overlay this result to DEM data of research area, calculate the mode ofgrassland elevation on each mountain as the timberline elevation.By comparing the timberline from three periods, the timberline in Guangdongprovince rises in different rates and it was fatter after1985.(4) Topography variation of timberline: Overall, the timberline elevationdecrease both way as increase and decrease on slope, and the peak value appears atthe slope degree of50°.On the other hands, timberline elevation is lower on the shady slope than theSunny slope.(5) Spatial distribution characteristic of timberline altitude: There is somecertain characteristic of timberline elevation distribution in Guangdong province.Overall, the timberline elevation increases as the latitude increases.In the east-west direction, the timberline elevation decrease both way as increaseand decrease on slope, and the peak value appears at the longitude degree of113°E,but not as obvious as it changes with changing of latitude.In the vertical direction, the timberline elevation increases as the height of itsmountain increases. But via partial correlation analysis, we can find that timberlineelevation in Guangdong is positively correlated with location factor.