Loss-on-ignition (LOI) has been widely used to estimate soil organic carbon (OC) content for coastal wetland soils, owing to recent interest in ‘blue carbon’ systems. Comparatively less attention has been paid to soil nutrient retention, specifically total nitrogen (TN), despite being a historically limited resource that influences C cycling and aquatic ecosystem health. A single conversion equation is available to estimate soil TN content from LOI, derived from salt marshes. This study investigated the utility of creating TN conversion equations from LOI data for application in mangrove soils to improve global understanding of their role in TN interception and sequestration. A dataset of 1275 mangrove soil samples from 17 regions in the western hemisphere was used to create one general equation, two equations pertaining to sedimentary settings, and equations for each of seven coastal environmental settings (CES) that differed in mineral sediment provision, geomorphology, and hydrology. Soil mean LOI and TN ranged from respective lows of 9.5% and 0.18% in terrigenous estuaries to respective highs of 51.4% and 1.25% in carbonate estuaries. The ability of LOI to predict TN in mangrove soils was strong, with an R for the general equation of 0.88, and several regional equations exceeding 0.90. Total N represented between 1.1 and 3.7% of LOI. Differences in equations were minimal between mangrove soils and a previous equation for salt marsh soils, and between carbonate and terrigenous sedimentary settings. Significant differences were observed among CES. Deltas had the lowest TN:LOI (0.014), followed by terrigenous estuaries and open coasts (0.017 and 0.019, respectively). Terrigenous lagoons, carbonate estuaries, and carbonate open coasts had the highest TN:LOI (0.024 for all three). The study provides a decision tree to select an appropriate approach for estimating TN content of mangrove soils, offering an important tool for improving the understanding of the role of coastal wetlands in global TN sequestration.

中文翻译：

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利用烧失量估算红树林土壤的总氮含量


由于最近对“蓝碳”系统的兴趣，烧失量（LOI）已被广泛用于估算沿海湿地土壤的有机碳（OC）含量。尽管土壤养分保留，特别是总氮（TN）历来是影响碳循环和水生生态系统健康的有限资源，但人们对土壤养分保留的关注相对较少。可使用单一转换方程根据盐沼的 LOI 估算土壤总氮含量。本研究调查了从 LOI 数据创建总氮转换方程在红树林土壤中的应用的效用，以提高全球对其在总氮截留和封存中作用的理解。使用来自西半球 17 个地区的 1275 个红树林土壤样本的数据集创建了一个一般方程、两个与沉积环境有关的方程以及七个沿海环境环境 (CES) 中每一个的方程，这些环境在矿物沉积物供应、地貌、和水文学。土壤平均LOI和TN的范围从陆源河口的最低值9.5%和0.18%到碳酸盐河口的最高值51.4%和1.25%。 LOI对红树林土壤TN的预测能力较强，一般方程的R值为0.88，多个区域方程的R值超过0.90。总 N 占 LOI 的 1.1% 至 3.7%。红树林土壤和之前的盐沼土壤方程之间以及碳酸盐和陆源沉积环境之间的方程差异很小。 CES 之间观察到显着差异。三角洲的 TN:LOI 最低（0.014），其次是陆源河口和开放海岸（分别为 0.017 和 0.019）。陆源泻湖、碳酸盐河口和碳酸盐开放海岸的 TN:LOI 最高（0.024 对于所有三个）。该研究提供了一个决策树来选择合适的方法来估计红树林土壤的总氮含量，为增进对沿海湿地在全球总氮固存中的作用的理解提供了重要工具。