Northern typical forested swamp soil CO₂ efflux dynamics

Aims This study examines soil CO₂-flux responses to micro-environmental temperature and aims to clarify microclimatic controls over soil CO₂-emission dynamics in northern forested swamps. Location: Forested swamps in Laojieji Forest Farm of the Zhangguangcai Range, northern China. Methods Five forest-swamp types were investigated. Soil CO₂ fluxes were monitored at 10-day intervals from May 2023 to May 2024 using the static dark-chamber gas-chromatography method, together with synchronous observations of soil properties and micro-environmental temperature. One-way ANOVA with Tukey’s HSD test was used to compare CO₂-emission patterns and statistically examine inter-community differences in soil physicochemical and micro-climatic parameters. Scatter-plot fitting and backward stepwise multivariate regression based on multi-window antecedent-temperature indices were adopted for unraveling driving mechanisms and microclimate feedbacks. Results Annual mean soil CO₂ fluxes ranged 122.09–235.18 mg·m − 2 ·h − 1 , with growing-season fluxes of 234.21–469.99 mg·m − 2 ·h − 1 and non-growing-season fluxes of 51.07–77.57 mg·m − 2 ·h − 1 . Shrub swamps produced the highest CO₂ efflux and alder swamps the lowest. Most communities showed bimodal intra-annual flux dynamics, while silver-birch swamp followed a unimodal pattern peaking in June–July (G > C > L ≈ B > M). Significant inter-type differences existed in daily maximum and accumulated micro-environmental temperatures, but not in daily mean and minimum temperatures. Scatter-plot fitting revealed positive trends between all antecedent-temperature metrics and soil CO₂ efflux; mean and accumulated temperatures yielded stronger fitting performance (R 2 > 0.7). One-day antecedent air temperature dominated annual-scale flux variation, and temperature-CO₂ coupling displayed pronounced seasonal and community-specific divergence. Conclusion Soil CO₂ efflux shows scale-dependent lagged response to antecedent micro-environmental air temperature. Both the coupling strength and optimal lag-window are modulated by seasonal thermal regimes and plant-community properties: strong short-term lag coupling occurs under freeze–thaw cold conditions, while such coupling breaks down in warm summer periods; in addition, optimal thermal lag responses differ across swamp communities within the growing season.