Bamboo culm and soil carbon flux synchronous measurement system: a continuous monitoring technique incorporating flow adaptive algorithms

To address the limitations of existing open-path chambers in terms of continuous monitoring stability and dynamic response capability, this study developed a synchronous measurement system (ACM) for bamboo culm and soil carbon fluxes, integrating an ambient air stabilization unit and a concentration-feedback adaptive control algorithm (log-PI control). Based on the open-path gas-exchange chamber principle, the system dynamically and stably regulates the CO₂ concentration inside the chamber, effectively suppressing high-frequency noise and reducing systematic errors, thus enabling long-term, high-frequency reliable monitoring. Using a Lei bamboo ( Phyllostachys praecox ) stand as the test object, a 22-day comparative observation (10 February – 3 March 2026) was conducted at Zhejiang A&F University. The results showed that the daily mean CO₂ flux from bamboo culms was 0.079 ± 0.018 µmol m⁻² s⁻¹, and that from soil was 1.196 ± 0.145 µmol m⁻² s⁻¹. The outlier proportions of the ACM system (Fb 0.1%, Fs 0.2%) were significantly lower than those of the conventional fixed-flow system (NCM) and the non-steady-state intermittent monitoring system (NSM), indicating more robust measurements. This system provides a reliable technical approach for carbon flux studies in bamboo forest ecosystems and holds promise for application to stems of other woody plants, thereby improving the accuracy of terrestrial carbon cycle assessments.