Vegetation Coverage’s Variations Surrounding Thermokarst Lake In Beilu River Basin Along The Qinghai-Tibet Railways

Under the influence of the global warming and human activities, the thermal melting disaster within the Qinghai Tibet engineering corridor is really serious. The thermokarst lake is one of the most typical hazards, an important indicator of the permafrost degradation. The development of the thermokarst lake along Tibet Railway poses a threat to the stability of the railway roadbed. The Qinghai Tibet Plateau ecosystem is very delicate. we studied the variety of thermokarst lake and the surrounding vegetation along the Qinghai Tibet railway to provide guidance for the Qinghai Tibet railway project and the surrounding ecological protection.In this paper, we chose three thermokarst lakes in the beilu river basin along Qinghai-Tibet railway as study area. By means of remote sensing, based on MATLAB,ENVI, ARCGIS software platform, we extract the edge of the thermokarst lake,calculate the surrounding vegetation coverage and establish the buffer and finally we got some surrounding vegetation coverage change characteristicsof the thermokarst lakes, the main conclusions are as follows:(1) The traditional Canny edge detection algorithm improved by adding wavelet smoothing detected lakes’ edge, Compared with software MATLAB’s own algorithm, the result detected by the new algorithm is more accurate;(2) The thermokarst lakes’ area has increased and expanded to the railway with different rate.(3) Thermokarst lake has a negative influence on vegetation coverage and the influence on vegetation coverage has certain range;(4)The reduction level of vegetation coverage has less to do with area of the thermokarst lake, but has more correlation with expansion rate of the thermokarst lake.The development of the new lake or pit where the vegetation coverage showed a sharp decline phenomenon proved this conclusion. Relevant literature showed that thethermokarst Lake pit is caused by soil excavation for building the Qinghai-Tibet Railway;(5) in the effective distance that vegetation can be influenced, degradation degreeof vegetation closed to the thermokarst lake is more serious, in addition to the influence of thethermokarst lake, it may also be related to vegetation types.