山区不同海拔植烟土壤温室气体排放特征及其温湿度敏感性研究

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

  • 摘要: 温室气体(GHG)排放是全球气候变化的重要驱动因素, 其温湿度敏感性受到由海拔梯度变化引起的环境因素的影响, 明确温室气体温湿度敏感性是准确评估和预测其排放的关键。植烟土壤的农艺措施和施肥结构虽异于一般农田, 但其温室气体排放特征和温湿度敏感性并不明确。本研究选取湖北恩施地区海拔800~1200 m 范围内10个烟田采样点, 采用静态箱–气相色谱法现场监测温室气体通量, 并通过插值法计算累积排放量。结果表明: 1) CO2通量随海拔升高显著下降, 且CO2累积排放量与海拔呈显著负相关(R2=0.47, P<0.05); 2) CH4作为汇, 其通量呈非线性(二次)变化, 且累积CH4排放量与海拔显著相关(R2=0.45, P<0.05); 3)尽管N2O瞬时通量在各海拔间无显著差异, 但其累积排放量随海拔显著降低(R2=0.65, P<0.01); 4) CO2的温度敏感性(Q10)在中海拔区域最低, 而其湿度敏感性与海拔呈显著负相关; 相反, CH4的温度敏感性在中海拔区域达到峰值, 其湿度敏感性与海拔呈显著正相关; N2O的温度敏感性与海拔显著负相关, 而湿度敏感性则显著正相关。总体来看, 随着海拔的升高, 不同海拔植烟土壤温度和湿度发生变化并间接影响温室气体排放, 对区域碳循环具有重要调控作用。本研究为山区烟田温室气体排放的精细估算和减排管理提供了坚实的科学依据。

     

    Abstract: 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.

     

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