Physical Protection in Aggregates and Organo-Mineral Associations Contribute to Carbon Stabilization at the Transition Zone of Seasonally Saturated Wetlands
Physical Protection in Aggregates and Organo-Mineral Associations Contribute to Carbon Stabilization at the Transition Zone of Seasonally Saturated Wetlands
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DOI：
10.1007/s13157-022-01557-3
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发表时间：
2021-03
期刊：
影响因子：
2
通讯作者：
A. Kottkamp;C. N. Jones;M. Palmer;K. Tully
中科院分区：
文献类型：
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作者：
A. Kottkamp;C. N. Jones;M. Palmer;K. Tully
由于缺氧条件抑制了土壤有机碳（SOC）的流失，湿地在全球范围内储存了大量的SOC。然而，存储的SOC可能变得容易分解的气候和土地利用变化改变湿地水文。季节性饱和的湿地经历波动的水文条件，可以促进已知的稳定陆地SOC的物理化学机制。因此，这些湿地可能是重要的SOC存储在土壤尺度。本研究探讨了理化稳定的SOC在五个季节性饱和湿地的水文梯度，从经常饱和的盆地边缘很少饱和的高地。在每个湿地，我们监测水位，并收集土壤样品，从顶部两个矿物层在5个样带点，以量化的物理保护SOC的聚集体和有机无机协会之间的SOC和铁（Fe）。正如预期的那样，从10-50厘米的SOC浓度和SOC库存下降，从经常饱和的土壤，很少饱和的土壤横断面。然而，从0-10厘米SOC股票增加沿着这一梯度，表明分散SOC动态整个土壤剖面。大部分的SOC与大团聚体在整个样带，这表明大团聚体很可能在物理上保护湿地SOC在季节性干旱。相比之下，整个样带中与铁相关的有机碳含量较低，但在全年饱和度最高的过渡区观察到了适度的铁积累（5 mg Fe g− 1土壤）。我们的研究结果表明，SOC稳定发生在大团聚体内的物理保护，并在较小程度上，有机矿物协会在干燥期间和周围的季节性饱和湿地。由于气候情景预测了许多湿地的干湿循环加剧，因此了解SOC稳定性对于预测未来变化的脆弱性至关重要。
Wetlands store significant soil organic carbon (SOC) globally due to anoxic conditions that suppress SOC loss. However, stored SOC may become vulnerable to decomposition where climate and land use change alter wetland hydrology. Seasonally saturated wetlands experience fluctuating hydrologic conditions that could promote physicochemical mechanisms known to stabilize terrestrial SOC. These wetlands are therefore likely to be important for SOC storage at the landscape-scale. This study examined physicochemical stabilization of SOC within five seasonally saturated wetlands across a hydrologic gradient from the frequently saturated basin edge to the rarely saturated upland. At each wetland, we monitored water level and collected soil samples from the top two mineral horizons across five transect points to quantify physical protection of SOC in aggregates and organo-mineral associations between SOC and iron (Fe). As expected, both SOC concentrations and SOC stocks from 10–50 cm decreased across the transect from frequently saturated soils to rarely saturated soils. However, SOC stocks from 0–10 cm increased along this gradient, indicating diverging SOC dynamics throughout the soil profile. The majority of SOC was associated with macroaggregates across the transect, suggesting that macroaggregates are likely to physically protect wetland SOC during seasonal drying. By contrast, Fe-associated SOC was low across the transect, though modest accumulations of Fe (5 mg Fe g−1soil) were observed in the transition zone where saturation was most dynamic throughout the year. Our results suggest that SOC stabilization occurs via physical protection within macroaggregates and, to a lesser extent, organo-mineral associations during dry periods in and around seasonally saturated wetlands. As climate scenarios predict intensified wet and dry cycles in many wetlands, understanding SOC stabilization is critical to predicting vulnerability to future change.