Complex Drivers of Riparian Soil Oxygen Variability Revealed Using Self‐Organizing Maps
Complex Drivers of Riparian Soil Oxygen Variability Revealed Using Self‐Organizing Maps
复制标题
DOI：
10.1029/2022wr034022
复制
发表时间：
2021-12
影响因子：
5.4
通讯作者：
B. Lancellotti;Kristen L. Underwood;J. Perdrial;C. Adair;A. Schroth;E. Roy
中科院分区：
文献类型：
--
作者：
B. Lancellotti;Kristen L. Underwood;J. Perdrial;C. Adair;A. Schroth;E. Roy
氧气 (O2) 调节土壤还原氧化过程，从而调节生物地球化学循环。准确表征土壤 O2 变化的困难促使人们使用土壤湿度作为 O2 的代表，因为 O2 扩散到土壤水中的速度比在土壤空气中慢得多。单独使用土壤湿度作为 O2 的替代测量值可能会导致 O2 估算不准确。例如，在土壤呼吸速率较低的凉爽月份，O2 可能会保持较高水平。我们使用机器学习技术“自组织图”分析了高频传感器数据（例如土壤湿度、二氧化碳、气相土壤孔隙 O2），以查明与对比 O2 状态相关的土壤条件套件。在佛蒙特州北部的两个河岸地点，我们发现氧气水平随季节和土壤湿度变化。例如，47% 的低 O2 水平与潮湿和凉爽的土壤条件有关，而 32% 与干燥和温暖的条件有关。相比之下，大多数（62%）高氧气条件发生在干燥和温暖的条件下。高土壤湿度并不总是导致低 O2，因为 38% 的高 O2 值发生在潮湿和凉爽的条件下。我们的结果凸显了仅根据含水量预测土壤 O2 的挑战，因为土壤和水文条件的可变组合可能会使含水量和 O2 之间的关系变得复杂。这表明仅依靠土壤湿度来估计 O2 的基于过程的生态系统和反硝化模型可能需要结合其他地点和气候特定的驱动因素来准确预测土壤 O2。
Oxygen (O2) regulates soil reduction‐oxidation processes and therefore modulates biogeochemical cycles. The difficulties associated with accurately characterizing soil O2 variability have prompted the use of soil moisture as a proxy for O2, as O2 diffusion into soil water is much slower than in soil air. The use of soil moisture alone as a proxy measurement for O2 could result in inaccurate O2 estimations. For example, O2 may remain high during cool months when soil respiration rates are low. We analyzed high‐frequency sensor data (e.g., soil moisture, CO2, gas‐phase soil pore O2) with a machine learning technique, the Self‐Organizing Map, to pinpoint suites of soil conditions associated with contrasting O2 regimes. At two riparian sites in northern Vermont, we found that O2 levels varied seasonally, and with soil moisture. For example, 47% of low O2 levels were associated with wet and cool soil conditions, whereas 32% were associated with dry and warm conditions. Contrastingly, the majority (62%) of high O2 conditions occurred under dry and warm conditions. High soil moisture levels did not always lead to low O2, as 38% of high O2 values occurred under wet and cool conditions. Our results highlight challenges with predicting soil O2 solely based on water content, as variable combinations of soil and hydrologic conditions can complicate the relationship between water content and O2. This indicates that process‐based ecosystem and denitrification models that rely solely on soil moisture to estimate O2 may need to incorporate other site and climate‐specific drivers to accurately predict soil O2.