Ecological restoration can result in extensive land use transitions which may directly impact on water runoff and sediment loss and thus influence tradeoffs between multiple hydrological and soil ecosystem services. However, quantifying the effect of these transitions on runoff and sediment yields has been a challenge over large spatial scales. This study integrated and synthesized 43 articles and 331 runoff experimental plots in the Loess Plateau of China under natural rainfall to quantify the impacts of land use transitions on (a) runoff and sediment production, (b) runoff and soil loss reduction effectiveness, and (c) the tradeoffs between runoff and soil erosion. The effects of ecological restoration on runoff and sediment yields were quantified using a general mixed linear meta-regression model with a restricted maximum likelihood estimator on overall and individual ecological restoration types. The results showed that artificial grassland, forest, natural grassland, and shrubland had higher runoff and sediment reduction effectiveness. The annual runoff reduction effectiveness of the ecological restoration overall was 72.18% with the effects of artificial grassland, natural grassland, shrubland, and forest at 71.89%, 50.60%, 73.18%, and 73.08%, respectively. The annual sediment reduction effectiveness of the overall ecological restoration was 99.9% without a significant difference among the four land uses associated with ecological recovery. In addition, shrubland and forest significantly reduced sediment yields with relatively high runoff costs. Natural grassland was optimal for balancing water provisioning and soil conservation, and artificial grassland was second to natural grassland in this respect. Meanwhile, newly unmanaged abandoned land and cropland had relative weak functionality with regard to soil and water conservation. The implications of this study’s findings are discussed along with their potential to contribute to an improved understanding of the effects of ecological restoration on water supply and soil retention for the water-limited terrestrial ecosystem at a regional scale.

Climatic extremes have adverse concurrent and lagged effects on terrestrial carbon cycles. Here, a concurrent effect refers to the occurrence of a latent impact during climate extremes, and a lagged effect appears sometime thereafter. Nevertheless, the uncertainties of these extreme drought effects on net carbon uptake and the recovery processes of vegetation in different Tibetan Plateau (TP) ecosystems are poorly understood. In this study, we calculated the Standardised Precipitation–Evapotranspiration Index (SPEI) based on meteorological datasets with an improved spatial resolution, and we adopted the Carnegie–Ames–Stanford approach model to develop a net primary production (NPP) dataset based on multiple datasets across the TP during 1982–2015. On this basis, we quantised the net reduction in vegetation carbon uptake (NRVCU) on the TP, investigated the spatiotemporal variability of the NPP, NRVCU and SPEI, and analysed the NRVCUs that are caused by the concurrent and lagged effects of extreme drought and the recovery times in different ecosystems. According to our results, the Qaidam Basin and most forest regions possessed a significant trend towards drought during 1982–2015 (with Slope of SPEI < 0, P < 0.05), and the highest frequency of extreme drought events was principally distributed in the Qaidam Basin, with three to six events. The annual total net reduction in vegetation carbon uptake on the TP experienced a significant downward trend from 1982 to 2015 (−0.0018 ± 0.0002 PgC year⁻¹, P < 0.001), which was negatively correlated with annual total precipitation and annual mean temperature (P < 0.05). In spatial scale, the NRVCU decrement was widely spread (approximately 55% of grids) with 17.86% of the area displaying significant declining trends (P < 0.05), and the sharpest declining trend (Slope ≤ −2) was mainly concentrated in southeastern TP. For the alpine steppe and alpine meadow ecosystems, the concurrent and lagged effects of extreme drought induced a significant difference in NRVCU (P < 0.05), while forests presented the opposite results. The recovery time comparisons from extreme drought suggest that forests require more time (27.62% of grids ≥ 6 years) to recover their net carbon uptakes compared to grasslands. Therefore, our results emphasise that extreme drought events have stronger lagged effects on forests than on grasslands on the TP. The improved resilience of forests in coping with extreme drought should also be considered in future research.

Land change is a key topic in research on global environmental change, and the restoration of degraded land is the core component of the global Land Degradation Neutrality target under the UN 2030 Agenda for Sustainable Development. In this study, remote-sensing-derived land-use data were used to characterize the land-change processes in China’s Loess Plateau, which is experiencing large-scale ecological restoration. Geographically Weighted Regression was applied to capture the spatiotemporal variations in land change and driving-force relationships. First, we explored land-use change in the Loess Plateau for the period 1990–2015. Grassland, cropland and forestland were dominant land cover in the region, with a total percentage area of 88%. The region experienced dramatic land-use transitions during the study period: degraded grassland and wetland, expansion of cropland and built-up land and weak restoration of forestland during 1990–2000; and increases in grassland, built-up land, forestland and wetland, concurrent with shrinking cropland during 2000–2015. A Geographically Weighted Regression (GWR) analysis revealed altitude to be the common dominant factor associated with the four major land-use types (forestland, grassland, cropland and built-up land). Altitude and slope were found to be positively associated with forestland, while being negatively associated with cropland in the high, steep central region. For both forestland and grassland, temperature and precipitation behaved in a similar manner, with a positive hotspot in the northwest. Altitude, slope and distance to road were all negatively associated with built-up land across the region. The GWR captured the spatial non-stationarity on different socioeconomic driving forces. Spatial heterogeneity and temporal variation of the impact of socioeconomic drivers indicate that the ecological restoration projects positively affected the region’s greening trend with hotspots in the center and west, and also improved farmer well-being. Notably, urban population showed undesired effects, expressed in accelerating grassland degradation in central and western regions for 1990–2000, hindering forestland and grassland restoration in the south during 2000–2015, and highlighting the long-term sustainability of the vegetation restoration progress. Such local results have the potential to provide a methodological contribution (e.g., nesting local-level approaches, i.e., GWR, within land system research) and spatially explicit evidence for context-related and proactive land management (e.g., balancing urbanization and ecological restoration processes and advancing agricultural development and rural welfare improvement).

The concept of the Earth's Critical Zone (CZ)—the near-surface heterogeneous environment of our planet—was originally defined to include the land surface, vegetation canopy, rivers, lakes and shallow seas [ 1]. CZ accommodates interactions among air, water, soil, rock and living organisms, and determines the availability of life-sustaining resources needed for the well-being and sustainability of human society. Therefore, there are new opportunities for integrative studies of the CZ as a key research frontier [ 1, 2] to address the grand challenges of global sustainability in the twenty-first century [ 3].