Exploring interactions in water-related ecosystem services nexus in Loess Plateau

Nonlinear responses of coupled socioecological systems to land use and climate changes in the Yangtze river basin

The intensification of land use and climate change threatens watershed sustainability. These external disturbances drive complex interactions among components within watershed socio-ecological systems (SESs). Understanding how SESs respond to these changes is crucial for developing effective integrated watershed management strategies. Nevertheless, the nonlinear responses of these systems to such changes remain poorly understood. To fill this gap, this study proposes a network analysis method focusing on the Yangtze River Basin to construct an SES network comprising six dimensions, revealing the response of coupled relationships among network elements to climate and land-use change. The results showed that changes in land-use dynamics (LUD) and the standardized precipitation evapotranspiration index (SPEI) altered the link count and importance of network nodes, with notable shifts in vegetation and landscape nodes. Importantly, a strong nonlinear response of the LUD and SPEI to the coupled relationship between SES elements was observed, and critical thresholds were identified for all network attributes. Furthermore, compared to the SPEI threshold, the LUD threshold was stable at 0.24, demonstrating stronger robustness. This study provides a new perspective for understanding watershed SESs, and has important implications for sustainable ecosystem management and planning.

Fluctuations of continuous soil moisture evaporation under different rainfall conditions during the growing period of the non-monsoon season, the eastern Loess Plateau

Soil moisture is an important link between material and energy exchange between the land and atmosphere, and its evaporation loss is crucial to sustainable development of agriculture. Based on observations of long-term stable isotopes of soil moisture in the eastern Loess Plateau (ECLP) during the non-rainy season growing period, this study systematically explored soil water evaporation loss at different soil depths using the Craig-Gordon model and revealed the internal relationship between soil evaporation loss and environmental elements. Main findings included: (1) The soil moisture content showed a gradual decreasing trend, with a weak soil moisture δ18O fluctuation appearing in April, whereas a stronger fluctuation was observed in June. (2) A significant vertical spatial heterogeneity was observed in soil moisture δ18O of each soil layer. Enriched soil moisture δ18O values appeared in the 0-20 cm soil layer, and the minimum value appeared in the 40-60 cm soil layer. (3) A significant spatial and temporal heterogeneity was observed in the soil moisture evaporation loss fraction (f) (0-23.35%), with weaker values at the beginning of the study period and larger values between mid-late May and mid-June. The largest soil evaporation loss was observed in the 0-20 cm soil layer (average value of 8.97%), a fluctuating decreasing trend appeared with increasing soil depth. (4) Regional soil moisture evaporation loss was positively correlated with regional air temperature (T) and potential evapotranspiration (ET0) and negatively correlated with soil water content (SWC) and relative humidity (RH). The correlation between soil moisture evaporation loss and environmental elements gradually weakened with increasing soil depth. (5) The environmentally driven model of continuous evaporation of soil moisture was suitable for larger amounts, especially for the surface soil layers. The results of this study have important implications for water resource management, ecosystem stability, and sustainable regional agriculture in the ECLP.

Multi-objective ecological restoration priority in China: Cost-benefit optimization in different ecological performance regimes based on planetary boundaries

In the context of the "United Nations Decade on Ecosystem Restoration", optimizing spatiotemporal arrangements for ecological restoration is an important approach to enhancing overall socioecological benefits for sustainable development. However, against the background of ecological degradation caused by the human use of most natural resources at levels that have approached or exceeded the safe and sustainable boundaries of ecosystems, it is key to explain how to optimize ecological restoration by classified management and optimal total benefits. In response to these issues, we combined spatial heterogeneity and temporal dynamics at the national scale in China to construct five ecological performance regimes defined by indicators that use planetary boundaries and ecological pressures which served as the basis for prioritizing ecological restoration areas and implementing zoning control. By integrating habitat conservation, biodiversity, water supply, and restoration cost constraints, seven ecological restoration scenarios were simulated to optimize the spatial layout of ecological restoration projects (ERPs). The results indicated that the provinces with unsustainable freshwater use, climate change, and land use accounted for more than 25%, 66.7%, and 25%, respectively, of the total area. Only 30% of the provinces experienced a decrease in environmental pressure. Based on the ecological performance regimes, ERP sites spanning the past 20 years were identified, and more than 50% of the priority areas were clustered in regime areas with increased ecological stress. As the restoration area targets doubled (40%) from the baseline (20%), a multi-objective scenario presents a trade-off between expanded ERPs in areas with highly beneficial effects and minimal restoration costs. In conclusion, a reasonable classification and management regime is the basis for targeted restoration. Coordinating multiple objectives and costs in ecological restoration is the key to maximizing socio-ecological benefits. Our study offered new perspectives on systematic and sustainable planning for ecological restoration.