Forest phenology directly reacts to global climate change, potentially regulating greenhouse gas fluxes between ecosystems and the atmosphere. To explore this phenomenon in two plain poplar (Populus spp.) forests in eastern China, we measured CO₂ fluxes and phenology at the canopy scale based on the eddy covariance and PhenoCam technology. From 2019 to 2022, poplars in a high-speed wind site (HWS) experienced shorter maturity durations (108 ± 4.9 days vs. 152 ± 1.2 days) and an earlier date of foliar senescence (day of year: 223.8 ± 2.5 vs. 259.5 ± 0.9) than those in the low-speed wind site (LWS). The annual net CO₂ uptake in the HWS (689.65 ± 105.15 g C·m⁻²·year⁻¹) was approximately 2.4 times higher than that in the LWS (285.65 ± 81.37 g C·m⁻²·year⁻¹). Our results indicate that environmental changes like wind stress alter forest phenology that can dynamically regulate ecosystem respiration and gross primary production.