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<p>Drought impacts vegetation physiology, canopy structure and agricultural productivity via immediate and time-aggregated water deficits. However, how river basin features regulate the spatial heterogeneity of these lagged and cumulative effects remains poorly understood. Here, we investigate the responses of solar-induced chlorophyll fluorescence (SIF), gross primary productivity (GPP), and leaf area index (LAI) to lagged and cumulative drought effects across China’s Loess Plateau and Qin-Ba Mountains. We further explore their spatial stratified heterogeneity. These regions encompass vital ecological barriers, sensitive agropastoral ecotones, and extensive dryland farming areas. We found that basin-scale hydrothermal conditions (precipitation, temperature, and soil moisture patterns) significantly constrained this spatial heterogeneity. Physiological metrics (SIF) generally exhibited shorter lagged time (4–5 months) compared to canopy structural metrics (GPP and LAI, 10–11 months). This contrast indicates a distinct functional decoupling. Spatially, this response was structured by basin order and topography. In the arid, first-order basins of the Loess Plateau, limited precipitation prolongs soil moisture deficits, amplifying cumulative impacts on GPP and LAI. Conversely, in the humid, higher-order basins (second- to fourth-order) of the Qin-Ba Mountains, greater soil moisture buffering capacity delayed drought propagation, producing longer SIF lagged time. Notably, high-elevation basins exhibited extended cumulative effects on LAI, suggesting a potential hydrological mismatch in which vigorous canopy growth increases water demand vulnerability. These findings reveal the critical role of basin characteristics in regulating drought propagation, providing valuable ecological implications for assessing ecosystem vulnerability and informing basin-specific water resource planning under a changing climate.</p> Graphical Abstract <p></p> <p>This graphical abstract illustrates how basin hydrothermal conditions shape the spatial heterogeneity of drought impacts on vegetation across the Loess Plateau and Qin-Ba Mountains. The 3D landscape depicts how river basin hierarchies, topography, and hydrothermal factors jointly modulate vegetation responses. It highlights the functional decoupling between instantaneous physiological responses (SIF) and long-term canopy structural adjustments (GPP, LAI) under drought stress, ultimately emphasizing the critical role of basin features in mediating regional ecohydrological vulnerability.</p>

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Basin Hydrothermal Modulation Decouples Lagged and Cumulative Drought Responses of Vegetation Physiology and Structure

  • 期刊论文

  • 发表日期：

    2026年6月2日

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  • Yu Zhang,
  • Xiaohong Liu,
  • Yixue Hong,
  • Lixin Wang,
  • Liangju Zhao,
  • Zhaohui Luo

摘要

Drought impacts vegetation physiology, canopy structure and agricultural productivity via immediate and time-aggregated water deficits. However, how river basin features regulate the spatial heterogeneity of these lagged and cumulative effects remains poorly understood. Here, we investigate the responses of solar-induced chlorophyll fluorescence (SIF), gross primary productivity (GPP), and leaf area index (LAI) to lagged and cumulative drought effects across China’s Loess Plateau and Qin-Ba Mountains. We further explore their spatial stratified heterogeneity. These regions encompass vital ecological barriers, sensitive agropastoral ecotones, and extensive dryland farming areas. We found that basin-scale hydrothermal conditions (precipitation, temperature, and soil moisture patterns) significantly constrained this spatial heterogeneity. Physiological metrics (SIF) generally exhibited shorter lagged time (4–5 months) compared to canopy structural metrics (GPP and LAI, 10–11 months). This contrast indicates a distinct functional decoupling. Spatially, this response was structured by basin order and topography. In the arid, first-order basins of the Loess Plateau, limited precipitation prolongs soil moisture deficits, amplifying cumulative impacts on GPP and LAI. Conversely, in the humid, higher-order basins (second- to fourth-order) of the Qin-Ba Mountains, greater soil moisture buffering capacity delayed drought propagation, producing longer SIF lagged time. Notably, high-elevation basins exhibited extended cumulative effects on LAI, suggesting a potential hydrological mismatch in which vigorous canopy growth increases water demand vulnerability. These findings reveal the critical role of basin characteristics in regulating drought propagation, providing valuable ecological implications for assessing ecosystem vulnerability and informing basin-specific water resource planning under a changing climate.

Graphical Abstract

This graphical abstract illustrates how basin hydrothermal conditions shape the spatial heterogeneity of drought impacts on vegetation across the Loess Plateau and Qin-Ba Mountains. The 3D landscape depicts how river basin hierarchies, topography, and hydrothermal factors jointly modulate vegetation responses. It highlights the functional decoupling between instantaneous physiological responses (SIF) and long-term canopy structural adjustments (GPP, LAI) under drought stress, ultimately emphasizing the critical role of basin features in mediating regional ecohydrological vulnerability.