Factors Driving Wetland Herbs Distribution Range of Lake-Terrestrial Ecotone in Tibet, China

Abstract Background: Lake is a critical part of Tibet's hydrological cycle, the lake-terrestrial ecotone is the most sensitive area in the water and terrestrial ecosystem. For the ecological protection and maintenance of the lakeside zone, defining the upper boundary of the lake-terrestrial ecotone is a key issue that needs to be solved urgently. However, the ecological characteristics of lake-terrestrial ecotone made it diffcult to delimit. Wetland herbs are characteristic plants of the radiant belt toward the land of the lake-terrestrial ecotone, and their distribution range can be used to reflect the upper boundary of the lake-terrestrial ecotone. We took Baksum Lake, Yambdroktso, Namtso, Siling Co as examples, based on the spatial structure of the lake-terrestrial ecotone, used the moving split-window technology (MSWT) delimited the range of wetland herbs.Results:The results of MSWT showed the distribution range of wetland herbs in each lake-terrestrial ecotone with the natural-wetland type sampling line of Baksum Lake, Yambdroktso, Namtso, Siling Co was 51m, 56m, 33~53m, 19~31m. DCA showed number of wetland herbs species,BK1＞YT1=NT1＞NT2＞SC1=SC2. PCA, RDA showed SMO, pH, SSC, and soil nutrient content had obvious correlation with distribution range. Conclusion:MSWT was a feasible method to delimit the distribution range of wetland herbs. SMO, pH, SSC, and soil nutrient content were all-important environmental factors affect the wetland herbs distribution range of the four lakes, however, the SMO was the most important factor. Besides, compare with the lakes in the lower Yangtze Plain,the high-density population distribution,high-intensitive human activity invaded the plants' growth area, resulting in a smaller distribution range.