红碱淖环境变化与遗鸥繁殖地关系研究

红碱淖位于中国候鸟迁徙的主要路线上，是遗鸥（Larus relictus）等珍稀水鸟的重要迁徙停歇地和繁殖地。为了进一步做好遗鸥的保护工作，本研究通过对红碱淖湖心岛和水体面积信息遥感提取和解译、现场调查和采样分析，结合前人的研究成果，分析红碱淖生态环境的变化、遗鸥栖息繁殖的条件、遗鸥繁殖地的变化等，探究了2001年起遗鸥选择红碱淖作为繁殖地的原因。结果显示：1）20世纪80年代以来，随着水面面积萎缩，红碱淖pH、盐度、总氮和总磷等呈上升趋势，不断咸化和富营养化，2003年之后湖内鱼类消失，2016年之后随着水面面积的增大略有改善；2）2001年起遗鸥将红碱淖作为新繁殖地，与红碱淖鱼类产量剧减并逐渐消失密切相关，使豆娘（Ischnura heterosticta）幼虫和摇蚊科（Chironomidae）幼虫等遗鸥食物从牧食压力中解放了出来；3）遗鸥是以动物性食物为主的鸟类，为了减轻幼鸟的觅食压力，通常7月下旬大部分亲鸟先行迁离，散布于沙漠各湖泊间。遗鸥的这一生活习性有利于其及时发现适宜的繁殖地，而红碱淖处于鄂尔多斯遗鸥分布区，具备满足遗鸥筑巢繁殖的条件；4）2001年起红碱淖具备了遗鸥繁殖和生存的条件，可为遗鸥提供适宜的湖心岛和整个繁殖季节主要食物来源，从而被选作繁殖地。这些研究认识较好地解释了遗鸥栖息于沙漠盐碱湖中的原因，可为其生境管理提供技术支撑，对进一步做好遗鸥的保护工作具有重要意义。

Study on the relationship between environmental changes and breeding sites of Larus relictus in Hongjiannao Lake

Hongjiannao Lake(38°59'59″~39°10'01″N, 109°45'16″~109°59'58″E) is located at the main route of migrant birds in China and is the main spot for resting and reproduction of many types of rare waterfowl, such as Larus relictus, at the junction of Shenmu City, Shaanxi Province and Ordos City, Inner Mongolia Autonomous Region. In this study, in order to further improve the protection of Larus relictus, using the Modified Normalized Differential Water Index(MNDWI), 20 Landsat remote sensing images during the breeding period between 1987 and 2006 were used to extract Hongjiannao Lake island area and water area. Secondly, in 2015, 2016, and 2020, we came to Shenmu City, Shaanxi Province Nature Reserve for field research and data collection, and we sampled the water quality and benthic animals in the lake center and lakeside, which the water quality monitoring indicators is including pH, total nitrogen, total phosphorus, permanganate index, total alkalinity, salinity, etc. This research analyzes the changes of the ecological environment of Hongjiannao Lake, breeding conditions, and the change of Larus relictus breeding sites in the past 30 years, and explores why Larus relictus choose Hongjiannao Lake as a breeding site since 2001. The results show that: (1) Since the 1980s, with the shrinkage of water surface area, the pH, salinity, total nitrogen and total phosphorus of Hongjiannao Lake have increased, continuously salinized and eutrophicated. The fish in the lake disappeared after 2003 and improved slightly with the increase of water surface area after 2016; (2) Since 2001, Larus relictus has taken Hongjiannao Lake as a new breeding ground, which is closely related to the sharp decline and gradual disappearance of fish production in Hongjiannao Lake, which has liberated the Larus relictus food such as Ischnura heterosticta larvae and Chironomidae larvae from the grazing pressure; (3) Hongjiannao Lake is located in the distribution area of Larus relictus in Ordos. The parent birds of Larus relictus first moved out and scattered in the distribution area of Larus relictus in late July, which is qualified for the discovery of Hongjiannao Lake; (4) Since 2001, Hongjiannao Lake has had the conditions for the reproduction and survival of Larus relictus, which can provide suitable lake-center island and main food source for the whole breeding season, so it has been selected as a breeding site. These studies can better explain the reasons why Larus relictus inhabits in desert saline-alkaline lakes, which can provide technical support for its habitat management, and are of great significance to further protect Larus relictus.