Yajun Wang

Forest management influences key ecosystem services essential for societal well-being. However, how these human management activities affect forest resilience under different environmental conditions remains poorly understood. This study investigates how different forest management practices interact with biophysical factors and explores their joint effect on forest resilience globally during 2001–2015. To address this gap, we develop a framework that integrates Critical Slowing Down theory, satellite-based vegetation indices, and machine learning. Results show that natural forests without management exhibit the highest resilience among all forest management types, followed by natural forests with management and planted forests. Overall, forest management practices weaken resilience prominently under intensive anthropogenic pressures. However, specific biophysical conditions can reverse this pattern. Planted forests show higher resilience than natural forests when the ratio of precipitation to potential evapotranspiration exceeds 1.5 in wet climates, whereas natural forests remain more resilient in drier climates below this threshold. This threshold reflects the point where water availability becomes sufficient to compensate for the detrimental effects originating from human pressures. Cold temperatures, dense vegetation, and high soil fertility may further enhance the resilience of managed forests to levels typical of natural forests.

The Pearl River Delta (PRD) is among the world’s most intricate delta systems, shaped by the dynamic interaction of upstream runoff and downstream tidal dynamics. However, the mechanisms underlying river-tide connectivity within such complex networks remains insufficiently understood, particularly the nonlinear feedback loops and spatiotemporal lag effects governing water level dynamics. This study employs an information-theoretic framework to investigate water level connectivity in the PRD, integrating relative mutual information (RMI) and relative transfer entropy (RTE) to quantify synchrony, causality, and directional information flow among hydrological variables. Results highlight the dominant role of upstream river discharge on water level synchrony in the Xijiang and Beijiang River systems, while downstream tidal dynamics exert greater causal effects in the Pearl River’s mainstream and coastal distributary regions. Since the 1990s, human activities, such as dam construction and channel dredging, have attenuated the influence of river discharge while leaving tidal impacts largely unchanged. Seasonal analysis reveals that that upstream river discharge predominantly governs water level connectivity during the flood season, whereas downstream tidal forcing becomes more prominent in the dry season, with spring tides amplifying these effects across both seasons. The study further shows spatiotemporal heterogeneity in connectivity, highlighting nonlinear feedback mechanisms and lag effects across subsystems. These insights underscore the adaptability and resilience of the PRD under both natural and anthropogenic pressures. By providing a novel perspective on deltaic process dynamics, this study contributes to the theoretical foundation for sustainable management and resilience planning in the PRD.

Stratification and mixing of the water column is an important dynamic process in the estuary, which plays a significant role in the estuarine circulation, mass transport and energy exchange. Based on the multi-station synchronous observation data from 26 February to 6 March in 2011 during dry season in the North Channel of the Changjiang Estuary, the Richardson number, the Simpson number and the potential energy anomaly of water were calculated to analyze the tidal variation of the mixing and stratification processes. The roles of the depth-mean straining, longitudinal advection, non-mean straining and tidal stirring in the processes of mixing and stratification of the water column were analyzed by calculating the contribution terms of the time-derivative of potential energy anomaly. The results show that the mixing and stratification of the water column in the North Channel have significant spatiotemporal variation. Stability of the stratification gradually decreases from neap tide to spring tide. In the reaches of salt wedge migration, permanent stratification develops during neap and mean tide, with stability increasing on the flood and decreasing on the ebb, which is dominated by longitudinal advection. During spring tide, periodic stratification develops, with development of stratification on the flood and its breakdown on the ebb, which is dominated by longitudinal advection and tidal stirring. In the main reaches of saltwater intrusion, permanent stratification develops during neap tide, with stability increasing on the ebb and decreasing on the flood, which is dominated by depth-mean tidal straining. During mean and spring tide, periodic stratification occurs, with development of stratification on the ebb and its breakdown on the flood, which is controlled by depth-mean tidal straining and assisted by tidal stirring. In the North Channel, tidal advection is the main stratifying agent in the salt wedge migration reaches, and tidal straining is the main stratifying agent in the main reaches of saltwater intrusion.