The characteristics of greenhouse gas emissions from tobacco fields at different elevations in mountainous areas and their temperature and moisture sensitivity

Greenhouse gas (GHG) emissions are a significant driver of global climate change. Their temperature and moisture sensitivities can be influenced by environmental changes along altitudinal gradients, but the sensitivities in tobacco fields remain unclear. Here, we monitored GHG fluxes using the static chamber and gas chromatography at 10 sites between 800 and 1200 m a.s.l. in Enshi, Hubei, during the tobacco-growing season. Seasonal cumulative emissions were calculated by interpolation between consecutive sampling dates. To interpret controls, soil temperature and soil water content were recorded concurrently, temperature sensitivity was expressed as Q₁₀ from an exponential fit, and moisture sensitivity was quantified from the flux–moisture slope. Tobacco fields are agronomically distinct from cereal systems in fertilizer timing and residue handling; therefore, understanding how elevation reshapes microclimate and thereby flux sensitivities can improve emission estimation for mountainous specialty crops. (1) CO₂ flux decreased significantly with elevation, and the cumulative CO₂ emissions were negatively correlated with elevation (R² = 0.47, P< 0.05). This pattern is consistent with cooler soils and lower microbial and root respiration at higher sites during the monitoring window, suggesting that thermal constraints dominate seasonal CO₂ budgets under otherwise comparable management. (2) CH₄, as a sink, exhibited a nonlinear (quadratic) pattern; its cumulative values were significantly correlated with elevation (R² = 0.45, P<0.05). The strengthening of the CH₄ sink along parts of the gradient is likely linked to better aeration and enhanced methanotrophy under lower temperatures and moderate moisture, although site-specific soil texture may modulate this response. (3) Instantaneous N₂O fluxes did not differ significantly among elevations, whereas seasonal cumulative N₂O emissions decreased with elevation (R² = 0.65, P< 0.01). This indicates that while short-term pulses are spatially heterogeneous, the integrated seasonal budget is still governed by elevation-driven microclimate, potentially via moisture constraints on nitrification–denitrification pathways. (4) The temperature sensitivity (Q₁₀) of CO₂ was lowest at mid-elevation, and its moisture sensitivity was negatively related to elevation. In contrast, the temperature sensitivity of CH₄ peaked at mid-elevation, and its moisture sensitivity increased with elevation. For N₂O, temperature sensitivity decreased with elevation, while moisture sensitivity increased. Overall, elevation indirectly regulates GHG emissions in mountainous tobacco fields by altering soil temperature and water content, thereby informing refined estimation and management of GHG emissions in mountainous tobacco fields. Practically, moderation of midday soil temperature at lower elevations (e.g., mulching or optimized canopy shading) may curb respiration-driven CO₂ losses, whereas careful moisture regulation at higher elevations may help suppress N₂O without weakening the CH₄ sink. Our findings support incorporating elevation-dependent sensitivity functions into regional inventories for tobacco-growing regions and motivate future work covering non-growing periods and diurnal cycles to close annual budgets.