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Abstract. Data and knowledge of surface water bodies (SWB), including large lakes andreservoirs (surface water areas > 1 km2), are critical forthe management and sustainability of water resources. However, the existingglobal or national dam datasets have large georeferenced coordinate offsetsfor many reservoirs, and some datasets have not reported reservoirs andlakes separately. In this study, we generated China's surface water bodies,Large Dams, Reservoirs, and Lakes (China-LDRL) dataset by analyzing allavailable Landsat imagery in 2019 (19 338 images) in Google Earth Engine andvery-high spatial resolution imagery in Google Earth Pro. There were∼ 3.52 × 106 yearlong SWB polygons in China for2019, only 0.01 × 106 of them (0.43 %) were of large size(> 1 km2). The areas of these large SWB polygons accountedfor 83.54 % of the total 214.92 × 103 km2 yearlongsurface water area (SWA) in China. We identified 2418 large dams, including624 off-stream dams and 1794 on-stream dams, 2194 large reservoirs (16.35 × 103 km2), and 3051 large lakes (73.38 × 103 km2). In general, most of the dams and reservoirs in Chinawere distributed in South China, East China, and Northeast China, whereasmost of lakes were located in West China, the lower Yangtze River basin, andNortheast China. The provision of the reliable, accurate China-LDRL dataseton large reservoirs/dams and lakes will enhance our understanding of waterresources management and water security in China. The China-LDRL dataset ispublicly available at https://doi.org/10.6084/m9.figshare.16964656.v3 (Wang et al., 2021b). 

Coastal wetlands provide essential ecosystem goods and services but are extremely vulnerable to sea‐level rise, extreme climate, and human activities, especially the coastal wetlands in large river deltas, which are regarded as “natural recorders” of changes in estuarine environments. In addition to the area (loss or gain) and quality (degradation or improvement) of coastal wetlands, the information on coastal wetland structure (e.g., patch size and number) are also major metrics for coastal restoration and biodiversity protection, but remain very limited in China's four major river deltas. In this study, we quantified the spatial–temporal dynamics of total area (TA) and patch number (PN) of coastal wetlands with different sizes in the four deltas and the protected areas (PAs) and assessed the effects of major driving factors during 1984–2020. We also investigated the effectiveness of PAs through the comparison of TA and PN of coastal wetlands before and after the years in which PAs were listed as Ramsar Sites. We found both TA and PN experienced substantial losses in the Liaohe River Delta and Yellow River Delta but recent recoveries in the Yangtze River Delta. The coastal wetlands had a relatively stable and variable trend in TA but had a continually increasing trend in PN in the Pearl River Delta. Furthermore, reduced coastal reclamation, ecological restoration projects, and rapid expansion of invasive plants had great impacts on the coastal wetland structure in various ways. We also found that PAs were effective in halting the decreasing trends in coastal wetland areas and slowing the expansion of reclamation, but the success of PAs is being counteracted by soaring exotic plant invasions. Our findings provide vital information for the government and the public to address increasing challenges of coastal restoration, management, and sustainability in large river deltas.

 

Introduced species may homogenize biotic communities. Whether this homogenization can erase latitudinal patterns of species diversity and composition has not been well studied. We examined this by comparing nematode and microbial communities in stands of nativePhragmites australisand exoticSpartina alterniflorain coastal wetlands across 18° of latitude in China. We found clear latitudinal clines in nematode diversity and functional composition, and in microbial composition, for soils collected from nativeP. australis. These latitudinal patterns were weak or absent for soils collected from nearby stands of the exoticS. alterniflora. Climatic and edaphic variables varied across latitude in similar ways in both community types. InP. australisthere were strong correlations between community structure and environmental variables, whereas inS. alterniflorathese correlations were weak. These results suggest that the invasion ofS. alterniflorainto the Chinese coastal wetlands has caused profound biotic homogenization of soil communities across latitude. We speculate that the variation inP. australisnematode and microbial communities across latitude is primarily driven by geographic variation in plant traits, but that such variation in plant traits is largely lacking for the recently introduced exoticS. alterniflora. These results indicate that widespread exotic species can homogenize nematode communities at large spatial scales.