Spatiotemporal variations and underlying mechanism of the floodplain wetlands in the meandering Yellow River in arid and semi-arid regions

Floodplain wetlands in the arid and semi-arid regions are highly threatened by complex changing environments. In order to better understand the response of wetland landscape patterns to floodplain hydro-geomorphology and landuse changes in drylands, this study aims to explore the spatiotemporal variation and underlying mechanisms of the floodplain wetland landscape patterns of the Yellow River in the arid and semi-arid region during 1973-2014. Based on the time-series Landsat observations, land use and hydrological data, the directional distribution, connectivity indicators, as well as univariate and multivariate linear regressions were used to analyze the trends and variations of wetland landscape pattern changes and their relationship with floodplain hydro-geomorphology and land use changes. Our results showed that the floodplain wetlands became more fragmented during 1973-2014, characterized by a decrease (6756 ha) in the total wetland patch area and an increase (353) in the number of patches. The center point of the wetlands in the whole study area migrated from the southwestern to northeastern part (0.8 km in the east direction and 1.7 km in the north direction). The greatest migration of the center point of wetlands occurred during the combined operation of the Longliu reservoirs, indicating that the decreasing frequency of large floods and unstable channel resulted in the fragmentation and migration of the overall wetlands. In addition, the operation of dam augmented the influence of hydro-geomorphology on the wetlands. Ice flooding benefed the formation of new wetlands and accelerated the migration of the overall wetlands. Land use changes due to the practice of various protection policies did not pose impact on the spatiotemporal changes of wetlands. Thus, a better understanding of the wetland landscape pattern changes in unstable floodplains requires considering both the floodplain hydro-geomorphology and land use changes, which is supportive to sustainable river floodplain management.