黄河口湿地植被时空变化及其影响因素

Temporal and Spatial Variation of Wetland Vegetation in the Yellow River(Huanghe)Mouth and Its Influencing Factors

本文基于1999—2021年Landsat系列卫星遥感影像数据,以黄河口湿地植被作为研究对象,对比了清8叶瓣和废弃清水沟叶瓣的植被时空变化特征,结果表明:湿地植被发育过程中呈现了显著阶段性和空间差异性变化,整个研究区域的植被覆盖面积经历了先波动变化后快速上升的趋势,其中显著变化区域主要集中在现行河口区,而废弃河口的变化相对稳定,在空间分布上,植被主要从河道两侧扩散到现行河口潮间带区域。2012—2021年现行河口区的植被类型中互花米草的面积显著增加,其面积增加了7倍以上,碱蓬的面积变化经历了先稳定后减小的过程,在2021年其面积仅为12.2 km 2,芦苇和柽柳经历了缓慢增加和波动性减小,其总体面积略有增加,光滩的面积及其所占比例均呈现出先减小后增加的特征。黄河改道与河口摆动和调水调沙工程加快了造陆速率,给植被带来栖息空间和生长条件,而互花米草的入侵和快速扩散虽然增加了植被覆盖面积,但也改变了本地的生态系统,极大地限制了碱蓬的生长和扩散,影响了河口湿地的健康发展。

Based on Landsat satellite remote sensing data from 1999 to 2021,we studied the temporal and spatial variation of the wetland vegetation.The results showed that:The whole study area experienced a rapid increase in NDVI value after a fluctuating period during 1999—2011.Among them,the change of NDVI in the active river mouth was the most significant.The NDVI increased slowly from 1999 to 2012 with the average value of 0.24,and it jumped by 70.8%to 0.42 during 2012—2021 in the active river mouth.In comparison,of the NDVI in the abandoned river mouth was relatively stable.Spatially,vegetation coverage area extended from the both sides of the river channel to the intertidal zone during 1999—2021.The vegetation types in the Yellow River mouth can be divided into bare flat,Suaeda salsa,Spartina alterniflora,Phragmites australis and Tamarix chinensis.The area of S.alterniflora increased significantly by over 7 times,from 5.5 km 2 in 2012 to 42.5 km 2 in 2021.The area of Suaeda was basically stable during 1999—2012 and then decreased by 42.2%from 2012 to 2021 Area of P.australis and Tamarix experienced a slow increase during 1999—2012 and a decrease with fluctuation after 2012,and their total area increased slightly from 1999 to 2021.Both the area and its proportion of the bare flat decreased during the first period and then increased after 2012.Diversion of the Yellow River deltaic channel and the water-sediment regulation scheme changed the land-building rate,brought habitat space and growth conditions for vegetation.The invasion and rapid extention of S.alterniflora increased the vegetation coverage,but also changed the local ecosystem,greatly limiting the growth and extent of Suaeda.