Data from: Soil trace gas fluxes along orthogonal precipitation and soil fertility gradients in tropical lowland forests of Panama

Tropical lowland forest soils are significant sources and sinks of trace gases. In order to model soil trace gas flux for future climate scenarios, it is necessary to be able to predict changes in soil trace gas fluxes along natural gradients of soil fertility and climatic characteristics. We quantified trace gas fluxes in lowland forest soils at five locations in Panama, which encompassed orthogonal precipitation and soil fertility gradients. Soil trace gas fluxes were measured monthly for 1 (NO) or 2 (CO2, CH4, N2O) years (2010–2012) using vented dynamic (for NO only) or static chambers with permanent bases. Across the five sites, annual fluxes ranged from 8.0 to 10.2 Mg CO2-C, −2.0 to −0.3 kg CH4-C, 0.4 to 1.3 kg N2O-N and −0.82 to −0.03 kg NO-N ha−1 yr−1. Soil CO2 emissions did not differ across sites, but they did exhibit clear seasonal differences and a parabolic pattern with soil moisture across sites. All sites were CH4 sinks; within-site fluxes were largely controlled by soil moisture, whereas fluxes across sites were positively correlated with an integrated index of soil fertility. Soil N2O fluxes were low throughout the measurement years, but the highest emissions occurred at a mid-precipitation site with high soil N availability. Net negative NO fluxes at the soil surface occurred at all sites, with the most negative fluxes at the low-precipitation site closest to Panama City; this was likely due to high ambient NO concentrations from anthropogenic sources. Our study highlights the importance of both short-term (climatic) and long-term (soil and site characteristics) factors in predicting soil trace gas fluxes.热带低地森林土壤是痕量气体的重要源与汇。为针对未来气候情景构建土壤痕量气体通量模型，需依据土壤肥力与气候特征的自然梯度，预测土壤痕量气体通量的变化。我们对巴拿马5处低地森林土壤的痕量气体通量进行了定量测定，这些样地覆盖了正交的降水与土壤肥力梯度。我们采用通风动态箱（仅用于一氧化氮（NO）检测）或带永久基座的静态箱，于2010至2012年间每月测定土壤痕量气体通量：其中NO的测定时长为1年，二氧化碳（CO₂）、甲烷（CH₄）及一氧化二氮（N₂O）的测定时长为2年。5个样地的年通量范围如下：二氧化碳碳通量为8.0~10.2 Mg CO₂-C，甲烷碳通量为-2.0~-0.3 kg CH₄-C，一氧化二氮的氮通量为0.4~1.3 kg N₂O-N，一氧化氮的氮通量为-0.82~-0.03 kg NO-N，单位均为kg·ha⁻¹·yr⁻¹。各站点的土壤CO₂排放通量无显著差异，但均表现出明显的季节变化特征，且随土壤湿度呈现抛物线型变化趋势。所有样地均为甲烷汇；样地内部的甲烷通量主要受土壤湿度调控，而样地间的通量差异则与土壤肥力综合指数呈正相关。整个监测周期内，各站点的土壤一氧化二氮通量均处于较低水平，但最高排放通量出现在降水中等且土壤氮有效性较高的样地。所有样地的土壤表面一氧化氮净通量均为负值，其中距离巴拿马城最近的低降水样地的一氧化氮净负通量绝对值最大；这一现象可能源于人为源排放的高浓度大气一氧化氮。本研究强调了短期（气候因素）与长期（土壤及样地特征）两类因素在预测土壤痕量气体通量中的重要性。