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Aims <p>Canopy conductance (<i>g</i><sub><i>c</i></sub>) regulates the exchange processes of water, carbon, and energy fluxes in forest ecosystems. Although vapor pressure deficit (<i>VPD</i>) and soil water content (<i>SWC</i>) are the primary drivers of <i>g</i><sub><i>c</i></sub>, how local environmental conditions (e.g., stand structure, climate conditions, and soil properties) collectively shape the responses of <i>g</i><sub><i>c</i></sub> to short-term changes in <i>VPD</i> and <i>SWC</i> on the daily scale remains inadequately quantified.</p> Methods <p>Here we calculated whole-tree <i>g</i><sub><i>c</i></sub> using sap flow data from 72 sites spanning environmental gradients in the SAPFLUXNET database, and analyzed the effects of <i>SWC</i> on the maximum <i>g</i><sub><i>c</i></sub> (<i>G</i><sub><i>cref</i></sub>) and the sensitivity of <i>g</i><sub><i>c</i></sub> to <i>VPD</i> (<i>β</i><sub><i>VPD</i></sub>). We further evaluated how these parameters are influenced by local stand structure, climate conditions, and soil properties.</p> Results <p>Our results reveal that both <i>G</i><sub><i>cref</i></sub> and <i>β</i><sub><i>VPD</i></sub> elevate significantly with the <i>SWC</i>, with the magnitude of these responses varying across ecosystem types, dryness level, and stand density. More importantly, we identify a dynamic hierarchy of environmental controls. Precipitation is the dominant climatic driver during dry periods, whereas temperature becomes more influential during wet periods. Soil properties modulate <i>g</i><sub><i>c</i></sub> by their influences on nutrient availability and soil hydraulic conditions. Crucially, stand structure emerges as the principal regulator of <i>g</i><sub>c</sub> under soil water limitation, surpassing climate variables in explanatory power.</p> Conclusion <p>These findings underscore that incorporating stand structural attributes is essential for accurately modeling <i>g</i><sub>c</sub> and predicting ecosystem responses to soil and atmospheric drought. Our study provides a mechanistic basis for improving forest management strategies under changing climate conditions.</p>

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Stand structure plays a key role in regulating canopy conductance responses to water stress

  • 期刊论文

  • 发表日期：

    2025年12月11日

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  • Ji Zhang,
  • Na Liu,
  • Cicheng Zhang,
  • Xiong Xiao,
  • Xinguang He,
  • Xiuchen Wu

摘要

Aims

Canopy conductance (gc) regulates the exchange processes of water, carbon, and energy fluxes in forest ecosystems. Although vapor pressure deficit (VPD) and soil water content (SWC) are the primary drivers of gc, how local environmental conditions (e.g., stand structure, climate conditions, and soil properties) collectively shape the responses of gc to short-term changes in VPD and SWC on the daily scale remains inadequately quantified.

Methods

Here we calculated whole-tree gc using sap flow data from 72 sites spanning environmental gradients in the SAPFLUXNET database, and analyzed the effects of SWC on the maximum gc (Gcref) and the sensitivity of gc to VPD (βVPD). We further evaluated how these parameters are influenced by local stand structure, climate conditions, and soil properties.

Results

Our results reveal that both Gcref and βVPD elevate significantly with the SWC, with the magnitude of these responses varying across ecosystem types, dryness level, and stand density. More importantly, we identify a dynamic hierarchy of environmental controls. Precipitation is the dominant climatic driver during dry periods, whereas temperature becomes more influential during wet periods. Soil properties modulate gc by their influences on nutrient availability and soil hydraulic conditions. Crucially, stand structure emerges as the principal regulator of gc under soil water limitation, surpassing climate variables in explanatory power.

Conclusion

These findings underscore that incorporating stand structural attributes is essential for accurately modeling gc and predicting ecosystem responses to soil and atmospheric drought. Our study provides a mechanistic basis for improving forest management strategies under changing climate conditions.