1973-2018年青海湖岸线动态变化

青海湖独特的地理位置使得其不仅对环湖周边区域气候起着天然调节器的作用，而且还拥有丰富的湖岸线资源，准确、及时地掌握青海湖岸线动态变化对保护沿湖生态环境有重要意义.因此本文基于1973-2018年Landsat MSS/TM/OLI遥感影像和1961-2017年实测水位资料，对青海湖岸线动态变化及对鸟类栖息地的影响进行研究，同时结合面积、水位及气象数据讨论了影响岸线变化的主要因素.研究表明：1）近45年来青海湖岸线发生变化最大的区域是东岸的沙岛，西岸的鸟岛、铁布卡湾及北岸沙柳河入口区域.尤其自2004年以来，鸟岛地区岸线后退距离最大（5.52 km），鸟类栖息地扩张约97.94 km²，为鸟类提供了较好的栖息环境.（2）1973-2018年青海湖岸线长度以0.88 km/a的速率逐渐延长.1997年之前岸线长度呈较为平稳的上升趋势，1997-2004年呈波动下降趋势，2004年之后呈剧烈波动增加趋势，岸线曲折性也表现出相同的变化趋势.（3）总体上岸线长度和曲折性受水位和面积的影响并不显著，但在不同的水位情况下，二者对青海湖动态变化做出不同的响应.尤其当水位小于3193.3 m或面积小于4249.3 km²时，岸线曲折性会随着水位和面积变化呈现相同的变化趋势，而水位高于3193.3 m时，岸线曲折性一直在增加，且水位上升速率越大则曲折性年际变化越大.（4）1973-2004年间青海湖水位下降和土地沙漠化是造成湖岸线变化的直接成因，人类活动及草场退化加速了湖泊岸线的变迁.2004年之后，随着青海湖水位回升与面积扩张，岸线逐渐后退，尤其在2017-2018年岸线后退距离最大.

Dynamic change of Lake Qinghai shoreline from 1973 to 2018

The unique geographical location of Lake Qinghai not only plays a role as a natural regulator for the climate around the lake, but also has abundant resources on the shoreline. Accurate and timely grasp of the shoreline dynamic changes of Lake Qinghai is of great significance to protect the ecological environment along the lake. Based on Landsat MSS/TM/OLI remote sensing images from 1973 to 2018 and water level data from 1961 to 2017, this paper studied the changes of shoreline and its impact on bird habitats. At the same time, the main factors affecting shoreline changes were discussed in combination with area, water level and meteorological data. The main conclusions are as follows:(1) In the past 45 years, the areas with the greatest changes in the shoreline of Lake Qinghai have been the Lake Shadao on the east coast, the Bird Island on the west coast, the Tiebuka Bay and the entrance to the Shaliu River on the north coast. Especially since 2004, the shoreline in the Bird Island had the largest retreat distance (5.52 km) and bird habitat expansion was about 97.94 km², which provided a better habitat for birds. (2) The length of the Lake Qinghai shoreline gradually extended at a rate of 0.88 km/a from 1973 to 2018. Before 1997, the length of the shoreline showed a relatively steady upward trend. Then, it showed a fluctuating downward trend from 1997 to 2004. After 2004, it showed a sharp increase in volatility, and the shoreline tortuosity also showed the same trend. (3) The overall shoreline length and tortuosity were not significantly affected by water level and area, but they responded differently to the dynamic changes of Lake Qinghai under different water levels. Especially when the water level was less than 3193.3 m or the area was less than 4249.3 km², the tortuosity of the shoreline showed the same trend with the change of water level and area. While the water level was higher than 3193.3 m, the tortuosity of the shoreline had been increasing, and the greater the rate of water level rise, the greater the annual variation of tortuosity. (4) The water level decline and land desertification of Lake Qinghai from 1973 to 2004 were the direct causes of lakeshore changes. Human activities and grassland degradation accelerated the change of lake shoreline. After 2004, as the water level of Lake Qinghai rebounded and the area expanded, the coastline gradually receded, especially during 2017-2018.