Soil NH3 emissions across an aridity, soil pH, and N deposition gradient in southern California
Soil NH3 emissions across an aridity, soil pH, and N deposition gradient in southern California
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DOI：
10.1525/elementa.2022.00123
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发表时间：
2023
期刊：
影响因子：
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通讯作者：
Alexander H. Krichels;Peter M. Homyak;E. Aronson;J. Sickman;Jon K. Botthoff;Aral C. Greene;Holly M. Andrews;Hannah B Shulman;S. Piper;G. D. Jenerette
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文献类型：
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作者：
Alexander H. Krichels;Peter M. Homyak;E. Aronson;J. Sickman;Jon K. Botthoff;Aral C. Greene;Holly M. Andrews;Hannah B Shulman;S. Piper;G. D. Jenerette
土壤氨 (NH3) 排放量很少包含在生态系统养分预算中；然而，它们可能代表了生态系统氮（N）损失的重要途径，特别是在水文氮损失相对较小的干旱地区。为了描述多种因素如何影响土壤 NH3 排放，我们测量了 6 个旱地沿土壤 pH 值、大气氮沉降和降雨梯度的 NH3 损失。我们还向土壤中添加了铵 (NH4+)，以确定氮的可用性是否会限制排放，并在实验润湿后使用土壤室中的被动采样器测量了 NH3 排放。由于 NH3 的挥发对 pH 值敏感，我们假设在碱性土壤中 NH3 排放量会更高，并且随着 NH4+ 可用性的增加而增加。与这一假设一致，平均土壤NH3排放量与平均场地pH值呈正相关（R2 = 0.88，P = 0.004），在最不干旱和最酸性的场地范围为0.77 ± 0.81 µg N-NH3 m−2 h−1，在最干旱和最碱性的场地范围为24.2 ± 16.0 µg N-NH3 m−2 h−1。润湿土壤的同时添加 NH4+ 会增加碱性和中酸性土壤的 NH3 排放（F1,35 = 14.7，P < 0.001），这表明即使 pH 值低于 NH3 挥发的最佳值，高氮利用率也能刺激 NH3 排放。因此，pH 值和氮的可用性均可作为对 NH3 排放的直接控制，表明这些氮的损失可能会限制干旱生态系统中氮的积累量。
Soil ammonia (NH3) emissions are seldom included in ecosystem nutrient budgets; however, they may represent substantial pathways for ecosystem nitrogen (N) loss, especially in arid regions where hydrologic N losses are comparatively small. To characterize how multiple factors affect soil NH3 emissions, we measured NH3 losses from 6 dryland sites along a gradient in soil pH, atmospheric N deposition, and rainfall. We also enriched soils with ammonium (NH4+), to determine whether N availability would limit emissions, and measured NH3 emissions with passive samplers in soil chambers following experimental wetting. Because the volatilization of NH3 is sensitive to pH, we hypothesized that NH3 emissions would be higher in more alkaline soils and that they would increase with increasing NH4+ availability. Consistent with this hypothesis, average soil NH3 emissions were positively correlated with average site pH (R2 = 0.88, P = 0.004), ranging between 0.77 ± 0.81 µg N-NH3 m−2 h−1 at the least arid and most acidic site and 24.2 ± 16.0 µg N-NH3 m−2 h−1 at the most arid and alkaline site. Wetting soils while simultaneously adding NH4+ increased NH3 emissions from alkaline and moderately acidic soils (F1,35 = 14.7, P < 0.001), suggesting that high N availability can stimulate NH3 emissions even when pH is less than optimal for NH3 volatilization. Thus, both pH and N availability act as proximate controls over NH3 emissions suggesting that these N losses may limit how much N accumulates in arid ecosystems.