Canopy-Wind-Induced Pressure Fluctuations Drive Soil CO2 Transport in Forest Ecosystems

Although accurate quantification of forest soil CO2 emissions is critical for improving global carbon cycle models, traditional chamber and gradient methods often underestimate fluxes under windy conditions. Based on long-term field observations in a subtropical maple forest, we quantified the interaction between canopy-level winds and soil pore air pressure fluctuations in regulating vertical CO2 profiles. The results demonstrate that canopy winds, rather than subcanopy airflow, dominate deep soil CO2 dynamics, with stronger explanatory power for concentration variability. The observed “wind-pumping effect” operates through soil pressure fluctuations rather than direct wind speed, thereby enhancing advective CO2 transport. Soil pore air pressure accounted for 33%–48% of CO2 variation, far exceeding the influence of near-surface winds. These findings highlight that, even in dense forests with negligible understory airflow, canopy turbulence significantly alters soil–atmosphere carbon exchange. We conclude that integrating soil pore air pressure into flux calculation models is essential for reducing underestimation bias and improving the accuracy of forest carbon cycle assessments.