Effects of extreme drought on landscape pattern of Dongting Lake wetland, China

• 30 m is the best landscape grain size for researching extreme drought in DL wetland. • Extreme drought has caused grass to expand into mudflats in Dongting Lake. • In landscape metrics, it caused significant changes in IJI, CONTAG, SIDI, etc. • In class metrics, it caused significant changes in CA, MPS, AI. • It caused a significant decrease in landscape heterogeneity. With the change of global climate, extreme weather is happening more and more frequently. As a typical extreme weather, extreme drought seriously endangers the safety of wetland ecosystem. In this study, remote sensing technology was used to compare the landscape pattern of Dongting Lake (DL, the second largest freshwater lake in China) wetland in normal year, drought year and wet year, to reveal the influence of extreme drought/wetness on landscape pattern. The results showed that extreme drought caused the expanding of grass to mudflat. On landscape metrics, extreme drought caused significant changes in IJI, CONTAG, ED, SIDI, SHDI, SHEI, landscape diversity and landscape heterogeneity decreased significantly; on class metrics, extreme drought caused significant changes in CA, MPS, AI, the degree of fragmentation is reduced and the landscape connectivity is enhanced. These changes will affect various migratory birds living in the DL wetland. Additionally, we also discovered that, in contrast to extreme drought, extreme wetness has a relatively minor influence on the DL wetland, and their impacts on landscape fragmentation are contrary.