Effect of increasing of water level during the middle of dry season on landscape pattern of the two largest freshwater lakes of China

Abstract

The hydrologic conditions of global wetlands are dramatically changed, and its ecological responses attract the great attention around the world. In recent decades, the water level of the middle of dry season had a tendency of significant increase in Dongting Lake and Poyang Lake (DL and PL, the two largest freshwater lake of China). Landscape pattern is sensitive to the local environmental changes and anthropogenic activity, and could influence the progresses and function of ecosystems. In this study, the landscape pattern between middle of dry season with increased water level (DIW) and that with normal water level (DNW) were compared to reveal the influence of the increasing of water level during the middle of dry season on landscape pattern of DL and PL. The results revealed that the increasing of water level during the middle of dry season caused expanding of deep water (cover increased from 14.40% to 18.36% of the total lake) to shallow water zone and expanding of shallow water (from 6.41% to 10.12%) to mudflat zone in DL; while it caused expanding of deep water (from 24.17% to 46.00%) to shallow water, sand, mudflat and grass zone and expanding of shallow water (from 12.18% to 19.51%) to sand, mudflat and grass zone in PL. In landscape metrics, it caused significant increase of the LPI in PL. In class metrics, it caused the some significant changes of landscape pattern indices (such as TA, LPI, MPS, AMPFDI, MNN and IJI) of the lakes. It had greater effects on the landscape pattern of PL than that of DL. And these changes of landscape pattern would affect birds, fish and mammals.