Headwater wetlands intercept, store, and transform nitrogen inputs from the landscape. However, uncertainties in rate estimates for processes such as denitrification in surface and subsurface soils hinder our ability to quantitatively predict the downstream water quality benefits of these headwater systems. We measured nitrogen pools and fluxes from surface (0 to 10 cm) and subsurface soils (~ 50 cm) of six headwater wetlands of low and high ecological condition (based on anthropogenic stressors) across three hydric soil types (Atkins, Holly, Udifluvent-Dystrochrept Complex). We quantified net nitrification (− 0.027 to 0.113 mg N kg soil⁻¹ day⁻¹), net ammonification (− 0.159 to 1.683 mg N kg soil⁻¹ day⁻¹), and potential denitrification rates (0.12 to 17.05 mg N kg soil⁻¹ day⁻¹) in surface soils during the fall. We also quantified potential denitrification rates in subsurface soils at 4 of the 6 sites in fall and spring (0.005 to 0.177 mg N kg soil⁻¹ day¹). Potential denitrification rates in surface soils varied with soil type, and rates were positively correlated with ground cover and the percentage of time the water level was between 0 and 10 cm below the surface. Potential denitrification rates of subsurface soil did not vary between condition groups or seasons; however, nitrous oxide yield was higher in the spring compared to the fall. At the plot scale, potential denitrification rates in surface soils were correlated with ammonification rates, and rates in subsurface soils were correlated with conductivity and ammonium levels. This work demonstrates the variability in surface and subsurface soil nitrogen cycling and highlights the need to investigate nutrient dynamics at multiple soil depths to accurately quantify the role of headwater wetlands in nitrogen removal at regional scales where soil properties are highly variable.

源头湿地拦截，存储和转化景观中的氮输入。但是，表层和地下土壤反硝化等过程的速率估算不确定性妨碍了我们定量预测这些上游水源系统对下游水质的影响的能力。我们测量了三种水力土壤类型（阿特金斯，霍利，Udifluvent-a）的六个低生态环境和高生态环境（基于人为压力源）的源头湿地的表层土壤（0至10厘米）和地下土壤（约50厘米）的氮库和通量。 Dystrochrept复合体）。我们量化了净硝化作用（− 0.027至0.113 mg N千克土壤^-1 天^-1），净氨化作用（− 0.159至1.683 mg N kg土壤^-1 天^-1），以及秋季期间表层土壤中潜在的反硝化率（0.12至17.05 mg N kg土壤^-1天^-1）。我们还对秋季和春季的6个地点中的4个地点的地下土壤中的潜在反硝化率进行了定量（0.005至0.177 mg N kg土壤^-1 天¹）。地表土壤中潜在的反硝化率随土壤类型而变化，且与土壤覆盖率和水位在表层以下0至10 cm之间的时间百分比呈正相关。在不同的条件组或季节之间，地下土壤的潜在反硝化率没有变化；然而，春季的一氧化二氮产量比秋季高。在样地尺度上，表层土壤中的潜在反硝化速率与氨化速率相关，而表层土壤中的潜在反硝化速率与电导率和铵水平相关。