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，需实现对土壤痕量气体通量沿土壤肥力自然梯度与气候特征梯度变化的预测。我们在巴拿马的五个样点对低地森林土壤的痕量气体通量进行了定量测定，该研究覆盖了正交的降水与土壤肥力梯度。2010—2012年间，我们采用带通风口的动态采样箱（仅用于一氧化氮（NO）测定）或带固定基座的静态采样箱，每月对土壤痕量气体通量开展观测：其中一氧化氮的观测时长为1年，二氧化碳（CO₂）、甲烷（CH₄）、一氧化二氮（N₂O）的观测时长为2年。五个样点的年通量范围分别为：8.0~10.2 Mg CO₂-C、−2.0~−0.3 kg CH₄-C、0.4~1.3 kg N₂O-N 以及 −0.82~−0.03 kg NO-N ha⁻¹ yr⁻¹。土壤CO₂排放通量在各站点间无显著差异，但在站点内呈现明显的季节差异，且随土壤湿度呈现抛物线型变化模式。所有样点均为CH₄的汇；样点内部的通量主要受土壤湿度调控，而样点间的通量与土壤肥力综合指数呈正相关。土壤N₂O通量在整个观测期内均处于较低水平，但最高排放出现在降水中等、土壤氮有效性较高的样点。所有样点的土壤表面NO通量均表现为净负值，其中在靠近巴拿马城的低降水样点中，负通量幅度最大；这可能源于人为源排放导致的环境高NO浓度。本研究强调了短期（气候因素）与长期（土壤及站点特征）因素在预测土壤痕量气体通量中的重要性。