Subtropical and tropical wetlands play a prominent role in the global carbon (C) cycle; yet factors that influence their C fluxes remain uncertain. We collected measurements from a temporarily flooded subtropical wetland over 3 years to investigate environmental drivers impacting CO₂ and CH₄ fluxes. The wetland was a sink of CO₂ (−469 to −380 g C‐CO₂ · m⁻² · year⁻¹) and a source of CH₄ (25.1 to 32.1 g C‐CH₄ · m⁻² · year⁻¹) to the atmosphere. Dry season CH₄ emissions represented 41 to 49% of the annual budget, reflecting the importance of continuous CH₄ flux measurements. Gross primary productivity (GPP) increased with temperature and radiation, and the influence of VPD on GPP varied with soil inundation. Higher water tables decreased R_eco and increased GPP, and a higher GPP in turn lead to enhanced R_eco likely through enhancements of GPP on autotrophic respiration. This suggests that the impact of the water table on R_eco depends on the cancelling effects of hydrology and GPP. Emissions of CH₄ increased with soil temperature, water table, and GPP until soils were inundated at which point temperature and GPP became the main drivers. Water table and temperature influenced GPP and CH₄ fluxes, and increases in GPP directly enhanced CH₄ emissions. In addition to impacting C fluxes directly through water table depth, hydrology also determined the hierarchy of the dominance of factors controlling C fluxes and their response. The positive climate forcing of subtropical wetlands may be dictated by plant‐mediated and climate interactions, with hydrological factors playing a major role in determining the greenhouse gas sink or source strength of subtropical wetlands.

中文翻译：

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临时淹没的亚热带湿地中CO2和CH4动态的季节性控制

亚热带和热带湿地在全球碳（C）循环中起着重要作用。然而，影响其碳通量的因素仍然不确定。我们在3年的时间里从临时淹没的亚热带湿地收集了测量数据，以研究影响CO ₂和CH ₄通量的环境驱动因素。湿地是CO ₂的汇（-469至-380 g C-CO ₂ ·m ^-2 ·年^-1）和CH ₄的来源（25.1至32.1 g C-CH ₄ ·m ^-2 ·年^{- 1}）进入大气。旱季CH ₄排放量占年度预算的41％至49％，反映了连续CH的重要性_4个磁通量测量。总初级生产力（GPP）随温度和辐射的增加而增加，VPD对GPP的影响随土壤淹没而变化。较高的地下水位会降低R _eco并增加GPP，而较高的GPP反过来可能会通过增强GPP的自养呼吸来提高R _eco。这表明地下水位对R _eco的影响取决于水文和GPP的抵消作用。CH _4的排放量随土壤温度，地下水位和GPP的增加而增加，直到土壤被淹没时，GPP才成为主要驱动力。地下水位和温度影响GPP和CH ₄通量和GPP的增加直接增加了CH ₄排放。除了直接通过地下水位深度影响碳通量外，水文学还确定了控制碳通量及其响应的主导因素层次。亚热带湿地的正向气候强迫可能由植物介导和气候相互作用决定，水文因素在确定亚热带湿地的温室气体汇或源强度中起着重要作用。