Abstract:

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 terms 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 km²), while maize land vegetation had the largest decrease (622.2 km²). 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%).

Key words: coastal wetland, ecosystem, landscape fragmentation, Liaohe Delta, vegetation map, vegetation structure