Vegetation Response to Hydrological Changes in Poyang Lake, China

Abstract

Poyang Lake is the largest freshwater lake and area of alluvial wetlands in China. The vast, seasonally-inundated alluvial plain is internationally recognized for its rare and endangered species which was one of the first to be included in The Ramsar Convention’s List of Wetlands of International Importance. Average lake stage (water level) has declined during both the summer wet season and dryer part of the year since the early 2000s, resulting in significant hydrological and ecological consequences. The purpose of this study is to describe changing spatial patterns for major vegetation types and relate vegetation response to changing hydrological conditions. The results suggest that vegetation patterns have shifted substantially in recent years. Most significant is spread of reed and sedge dominated plant communities to sites 1 m to 2 m lower in elevation. Reed communities that continue to dominate the highest elevations within the lake basin expanded across shallow regions of the lake previously too wet for regeneration. In contrast, sedges cannot tolerate dry conditions, and therefore, declined on higher sites. The dominance of aquatic plant communities doubled in area at low elevation sites in the absence of the severe floods that normally inhibit regeneration. We attributed the variation of vegetation patterns to the great water regime changes. However, lower lake stage has not resulted in a highly-degraded wetland ecosystem. Plant communities will continue to adjust to future long-term changes in lake hydrological conditions. The findings provide an important baseline in monitoring vegetation communities’ shifts in Poyang Lake wetland from which future research can be compared but also for other international tropical wetlands also impacted by similar threats.