Characterization of coastal wetland soil organic matter: Implications for wetland submergence
Characterization of coastal wetland soil organic matter: Implications for wetland submergence
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沿海湿地土壤有机质的表征：对湿地淹没的影响
DOI：
10.1016/j.scitotenv.2019.04.405
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发表时间：
2019
影响因子：
9.8
通讯作者：
Chambers, Lisa G.
中科院分区：
文献类型：
--
作者：
Steinmuller, Havalend E.;Chambers, Lisa G.
相对海平面的高速率上升会导致沿海湿地淹没，危及湿地内土壤有机质的稳定性。在淹没之后，有机质可以通过矿化作用损失，输出到沿海海洋，或重新埋藏在相邻的潮下带沉积物中。通过结合土壤理化性质，微生物群落丰度，有机碳分馏和稳定同位素特征的措施，本研究的特点是地下SOM在沿海湿地，告知其潜在的命运在改变环境条件下。从美国洛杉矶巴拉塔里亚湾（Barataria Bay）一处目前正经历快速侵蚀和淹没的湿地采集了9个150 cm深的土芯，并将其切成10 cm的间隔。分析每个土壤段，以确定总碳（C），氮（N），磷（P）和稳定同位素（δ 13 C和δ 15 N）含量，以及可提取的铵（NH 4+），硝酸盐（NO3−）和可溶性活性磷（SRP）。在0-10 cm和130-140 cm之间，可提取的NH 4+和SRP浓度分别增加了7倍和11倍。通过定量PCR发现细菌和硫酸盐还原基因的拷贝数随着深度的增加而减少，而古细菌的基因拷贝数没有变化。这项研究还表明，随着深度的增加，不稳定的：难降解的C比只有很小的下降;通过结合δ 15 N数据和不稳定的：难降解的C比，没有观察到C：N比随深度的变化，我们推断深层土壤中存在最低限度加工的有机物质和高养分可用性，挑战了传统的选择性保护理论的适用性，土壤质量随深度下降。随着湿地淹没的进展和土壤暴露于含氧海水中，这种相对不稳定的SOM和生物可利用的N和P存储在深处有可能快速矿化和/或出口到沿海地区。
High rates of relative sea level rise can cause coastal wetland submergence, jeopardizing the stability of soil organic matter (SOM) sequestered within wetlands. Following submergence, SOM can be lost through mineralization, exported into the coastal ocean, or reburied within adjacent subtidal sediments. By combining measures of soil physicochemical properties, microbial community abundance, organic carbon fractionation, and stable isotope signatures, this study characterized subsurface SOM within a coastal wetland to inform its potential fate under altered environmental conditions. Nine soil cores were collected to a depth of 150 cm from a wetland currently experiencing rapid erosion and submergence within Barataria Bay, LA (USA), and were sectioned into 10 cm intervals. Each soil segment was analyzed to determine total carbon (C), nitrogen (N), phosphorus (P), and stable isotope (δ13C and δ15N) content, as well as extractable ammonium (NH4+), nitrate (NO3−), and soluble reactive phosphorus (SRP). Extractable NH4+and SRP concentrations increased 7× and 11×, respectively, between 0–10 cm and 130–140 cm. Through quantitative PCR, number of gene copies of bacteria and sulfate reduction genes were found to decrease with depth while there was no change in number of gene copies of archaea. This study also demonstrated only small decreases in labile: refractory C ratios with depth; by combining δ15N data with labile:refractory C ratios and no observed change in C:N ratios with depth, we inferred the presence of minimally processed organic material within deep soils and high nutrient availability, challenging the applicability of the traditional theory of selective preservation and decreased soil quality with depth. As wetland submergence progresses and soils are exposed to oxygenated seawater, this relatively labile SOM and bioavailable N and P stored at depth has the potential for rapid mineralization and/or export into the coastal zone.