Abstract:

Desertification is a major ecological and environmental trouble that constrains global sustainable development. Effective mitigation of desertification hinges upon a comprehensive understanding of the interactions between sparse vegetation and wind blow in arid and semi-arid regions. Current research on the windbreak mechanisms of sparse vegetation has not yet to establish a systematic framework of the entire process from static morphological traits, wind-induced dynamic responses to flow field modifications, thereby hindering the integration of multi-scale interactions. Therefore, this review takes the conceptual chain of “static morphology-dynamic response-aerodynamic effect-windbreak mechanism” as the main line, and systematically synthesizes the windbreak mechanisms of sparse vegetation. Regarding static morphological structure, the windbreak efficacy of vegetation is predominantly regulated by structural attributes such as porosity, geometry, flexibility, and phenophase characteristics. The optimal porosity threshold for wind protection varies with the vegetation type. Plant geometric architecture modulates the flow field by altering airflow pathways, regulating aerodynamic drag, and redistributing shear stress. Flexibility further optimizes windbreak function, collectively shaping the spatial heterogeneity of wind protection. In terms of wind-induced dynamic responses, vegetation adapts to wind loading primarily through two pathways: swaying and morphological reconfiguration. Swaying characteristics are predominantly governed by morphological structure, with natural frequency and damping ratio serving as key quantitative parameters for characterizing dynamic responses. Morphological reconfiguration achieves dynamic drag reduction adaptation through streamlining and a decrease in windward area. Regarding aerodynamic effects, these effects represent the pivotal link in wind flow modulation by vegetation. The drag coefficient is a core physical parameter for quantifying the wind resistance effect, directly reflecting the capacity of vegetation to dissipate airflow kinetic energy. In contrast to rigid vegetation models, the drag coefficient of flexible vegetation exhibits a decreasing trend with increasing wind speed. Furthermore, the nonlinear relationship between drag coefficient and porosity is due to the coupling effect of multiple physical processes. In studies of static windbreak mechanisms, models for flow recovery in the lee side have evolved from empirical formulations to coupled mechanistic-statistical models, significantly enhancing predictive accuracy and physical interpretability. Dynamic windbreak mechanisms primarily encompass two pathways: morphological reconfiguration coupled with aerodynamic load regulation, and structural flexibilization coupled with energy dissipation. However, existing research on dynamic mechanisms predominantly focuses on trees, whereas investigations into the dynamic responses of shrubs, which are widely distributed in arid and semi-arid regions, remain remarkably limited. Targeted studies are urgently needed to address this knowledge gap. In summary, the windbreak process of sparse vegetation fundamentally represents a concurrent, multi-scale, dynamically interactive physical continuum. In the future, it is necessary to conduct systematic research on the multidimensional coupling of “static morphology-mechanical properties-aerodynamic effects-flow field modulation-windbreak function”, aiming to construct a comprehensive theoretical framework describing the entire windbreak process for sparse vegetation. Critical challenges include overcoming the mathematical representation bottlenecks in fluid-structure interactions of natural flexible vegetation, deeply elucidating the mechanisms of vegetation-wind interactions, and advancing the theoretical development of multi-physics coupling. Addressing these challenges will provide a robust scientific foundation for desertification control, the optimization of eco-friendly windbreak engineering, and ecological restoration in arid and semi-arid regions.

Key words: desertification, sparse vegetation, windbreak mechanism, static structure, dynamic response, aerodynamic effect