Dissolved and gaseous nitrogen losses in forests controlled by soil nutrient stoichiometry
Dissolved and gaseous nitrogen losses in forests controlled by soil nutrient stoichiometry
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DOI：
10.1088/1748-9326/ac007b
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发表时间：
2021-05
影响因子：
6.7
通讯作者：
F. Oulehle;C. Goodale;C. Evans;T. Chuman;J. Hruska;P. Krám;T. Navrátil;M. Tesař;A. Ač;O. Urban;Karolina Tahovská
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作者：
F. Oulehle;C. Goodale;C. Evans;T. Chuman;J. Hruska;P. Krám;T. Navrátil;M. Tesař;A. Ač;O. Urban;Karolina Tahovská
全球长期氮沉降到森林可以缓解生态系统氮的限制，对生物多样性、碳固存、土壤和地表水质量以及温室气体排放具有潜在的广泛影响。然而，预测这些后果的能力，需要改善难以测量的N通量的量化，特别是N气体损失和土壤N保留。在这里，我们结合联合收割机一套独特的长期流域N预算在欧洲中部的生态系统15 N数据，揭示在温带森林溶解和气态N通量的根本控制。流淋溶损失的溶解N对应的森林地面的营养化学计量，流N的损失增加生态系统的进展对磷的限制，而土壤中的N储存增加草酸可提取的铁和铝的含量。我们基于15 N储量估算的土壤气体损失平均为2.5 ± 2.2 kg N ha−1 yr−1，占总N沉降的20% ± 14%。气态氮的损失增加与森林地面N：P比和溶解N的损失。我们的气态和溶解态氮损失之间的关系也能够解释以前在热带和亚热带流域测量的基于15N的氮损失率，这表明硝酸盐（NO3 −）丰度驱动的可概括的响应，其中溶解态氮相对于气态氮损失的相对重要性往往随着NO3 −输出的增加而增加。在全球范围内应用这种关系，我们推断目前森林的气态氮流失通量为8.9 Tg N yr−1，占全球森林目前氮沉积的39%。
Global chronic nitrogen (N) deposition to forests can alleviate ecosystem N limitation, with potentially wide ranging consequences for biodiversity, carbon sequestration, soil and surface water quality, and greenhouse gas emissions. However, the ability to predict these consequences requires improved quantification of hard-to-measure N fluxes, particularly N gas loss and soil N retention. Here we combine a unique set of long-term catchment N budgets in the central Europe with ecosystem 15N data to reveal fundamental controls over dissolved and gaseous N fluxes in temperate forests. Stream leaching losses of dissolved N corresponded with nutrient stoichiometry of the forest floor, with stream N losses increasing as ecosystems progress towards phosphorus limitation, while soil N storage increased with oxalate extractable iron and aluminium content. Our estimates of soil gaseous losses based on 15N stocks averaged 2.5 ± 2.2 kg N ha−1 yr−1 and comprised 20% ± 14% of total N deposition. Gaseous N losses increased with forest floor N:P ratio and with dissolved N losses. Our relationship between gaseous and dissolved N losses was also able to explain previous 15N-based N loss rates measured in tropical and subtropical catchments, suggesting a generalisable response driven by nitrate (NO3 −) abundance and in which the relative importance of dissolved N over gaseous N losses tended to increase with increasing NO3 − export. Applying this relationship globally, we extrapolated current gaseous N loss flux from forests to be 8.9 Tg N yr−1, which represent 39% of current N deposition to forests worldwide.