1988–2006年辽河三角洲植被结构的变化

Transformation of vegetation structure in China’s Liaohe Delta during 1988–2006

在人类干扰和气候波动的影响下,辽河三角洲的植被结构发生了显著变化。该文研究了辽河三角洲植被结构的变化,对于保护该地区生态系统、促使其健康发展具有重要意义。研究区域包括了整个辽河三角洲。资料来源主要是1988年和2006年的TM(Landsat Thematic Mapper)遥感图像。采用数字化、制作植被图和叠加分析等方法研究探讨了辽河三角洲植被结构的特点,以及植被的空间分布转移和面积变化。结果显示,以双台子河口为中心,4大植被类型(自然湿地植被、人工湿地植被、人工旱地植被和自然旱地植被)大体上构成半环状分布格局。从整体上看,从1988年至2006年,植被结构仍然保持半环状的空间格局。但是,主要植被类型的空间分布趋于集中,形成了比较大的斑块,而不是离散、破碎的。从植被类型间相互转化的情况看,几乎所有植被类型的空间分布和面积都有明显改变。在绝对面积上,水稻(Oryzasativa)田、玉米(Zeamays)地和滨海芦苇(Phragmitesaustralis)湿地是辽河三角洲3个面积最大的植被类型。水稻田是面积增加最多的植被类型,增加977.1km2;而玉米地是面积减少最多的植被类型,减少622.2km2。在面积变化幅度上,水稻田、玉米地和滨海芦苇湿地的变化幅度分别为33.2%、–16.1%、–23.2%。面积减少幅度最大的植被类型是草地,–77.9%;面积增加幅度最大的植被类型是翅碱蓬(Suaedaheteroptera)盐化草甸,212.1%。

Aims An obvious transformation of vegetation structure in the Liaohe Delta has resulted from climatic fluctuation and human disturbance. We focus on the transformation of vegetation structure with the objective of contributing to management for maintaining a healthy ecosystem. Methods The study area included the entire Liaohe Delta, and data sources came from Landsat Thematic Mapper （TM） imagery in 1988 and 2006. The methods of digitizing, mapping vegetation and overlay analysis were used to explore structural characteristics, changed distributions and transformed areas of vegetation. Important findings The vegetation pattern consisted of a semi-ring of four main vegetation types （natural wetland, constructed wetland, constructed dryland and natural dryland vegetation） encircling the estuary of Shuangtaizi River. In terms of this macrostructure, the vegetation pattern did not change greatly, and the main vegetation types tended to aggregate rather than fragment as relatively large vegetation landscapes came into being from 1988 to 2006. However, almost all vegetation types changed in spatial distribution and area. In terlns of vegetation area, the main vegetation types were rice （Oryza sativa） land, maize （Zea mays） land and coastal wetland reed. Rice land vegetation had the largest increase in area （977.1 km^2）, while maize land vegetation had the largest decrease （622.2 km^2）. The transforming percentages among vegetation types were 33.2%, -16.1% and -23.2% for rice land, maize land and coastal wetland reed, respectively. The meadow had the maximal decrease （-77.9%）, while the community of salt meadow seepweed （Suaeda hetroptera） had the maximal increase （212.1%）.