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Study Region: Upper to Middle Yellow River Basin (UMYRB). Study Focus: Climate, land use, and landscape engineering measures are the main drivers affecting watershed hydrology, yet disentangling their respective contributions over large and complex regions is a great challenge. We combine process modeling techniques and hydrological observations to investigate the temporal changes of streamflow and sediment in the UMYRB during 1971–2016 and the imprints of climate change and anthropogenic activities. New hydrological insights for the region: Long-term statistical analysis shows that streamflow and sediment decreased over time across the basin with an increasing magnitude of reduction from upstream to midstream. Streamflow of UMYRB and sediment in the upstream area have decreased by 37.59 % and 71.86 %, respectively, since their change-point years. Analytical modeling results in the UMYRB demonstrate that 77.30 % of the streamflow reduction was attributed to landscape engineering measures, 16 % to climate change and the remaining 6.70 % to land use change. For sediment reduction, landscape engineering measures appeared to be the sole decisive factor for the upstream (over 126 %), while climate and land use changes positively affected sediment yield. Our study highlights the importance of considering the impacts of multiple factors when evaluating hydrological changes in large basins, and the method we adopted can be valuable elsewhere. Developing process-based methods to quantify the hydrological effects of engineering measures is still a research priority moving forward.

Human activities and climate are two key factors affecting hydrological and soil erosion processes. Understanding their impacts on water discharge and sediment transport is very important for sustainable development of watersheds, particularly in subtropical regions with high precipitation and high sediment loads. We here compared the long-term dynamics of water discharge and sediment transport in four large contiguous watersheds in subtropical China and explored the importance of the main influencing factors including climate, nature endowment such as geology, and human activities. Significant differences have been observed between watersheds in terms of sediment and water discharge (p

Land use and land cover change (LUCC) has yielded significant impacts on ecosystem structure and functions. Gross primary production (GPP), the largest flux in the terrestrial carbon cycle, has been drastically changed by various LUCC activities. However, the indirect impacts of LUCC on GPP (i.e., local environment changes induced by LUCC), particularly those related to landscape dynamics, remain unclear. Here, we explored the relationships between GPP and landscape metrics of forest ecosystems in China along a forest coverage gradient from 2001 to 2019, using an up-to-date GPP dataset derived from Solar-Induced Chlorophyll Fluorescence and a widely used landcover product MCD12Q1. Results showed that forest landscape features (e.g., core area index, CAI) synchronized with GPP spatially as shown by the distribution of their hot/cold spots on correlations. Furthermore, two nonlinear change patterns of GPP and landscape metrics along forest coverage gradient were found. One is a hump-shaped pattern, which indicated that GPP and some landscape features (e.g., annual median GPP, annual change rate of forest composition) peaked in medium (about 70–80%) forest-cover regions. Another is a super-linear curve, revealing the rapid and accelerated growth of some landscape features (e.g., annual median CAI) in high forest-cover regions. Finally, forest coverage affected the sensitivity of GPP to landscape features in a nonlinear fashion, characterized as an inverted ‘hook’ curve peaking in intermediate (around 70%) forest-coverage regions. Our study proposed the optimal landscape regulation hypothesis to explain the nonlinear pattern: forest GPP is most responsive to the landscape pattern regulation at intermediate to low levels of disturbance, implying that forest coverage has various impacts on landscape features; together they affect GPP nonlinearly. Regulating the forest landscape composition and configuration can enhance the performance of forest ecosystems in addition to managing forest coverage. Thus, we recommend the adoption of suitable region-specific forest management practices to improve GPP and other ecosystem services of forest ecosystems via manipulating landscape composition and configuration.

Study region: Surface water bodies in Hunan Province, China. Study focus:: Surface water bodies (WB) are important for agriculture, aquiculture, and aquatic and terrestrial ecosystems, yet monitoring and understanding the spatiotemporal dynamics of water bodies over large areas remain a major challenge. This study used all the available Landsat images and the Google Earth Engine (GEE) to map and analyze annual changes of all water bodies (>0.001 km2) in Hunan Province, China, from 1987 to 2020. New hydrological insights for the region:: A total of 76,928 WBs were detected with a total area of 4181.14 km2 (both were averages during the study period) with an interannual variability of − 117 and − 20.05 km2 year-1, respectively. Surface areas of small (0.001–1 km2), medium (1–50 km2), and large (>50 km2) WBs changed at various rates and directions. The size-abundance relationship of WBs followed the power scaling law with a positive trend in the scaling exponent, implying the fraction of small WB number has decreased over the past three decades. The temporal change of the size-abundance relationship, reflects the strong and dynamic imprints of both human activities and regional climate change. Future research should strive to understand the temporal change of the size-abundance relationship of WBs as it is important for water resources management and estimating the temporal changes of greenhouse gas fluxes from WBs over large areas.