Ephemeral microbial responses to pulses of bioavailable carbon in oxic and anoxic salt marsh soils
Ephemeral microbial responses to pulses of bioavailable carbon in oxic and anoxic salt marsh soils
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DOI：
10.1016/j.soilbio.2023.109157
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发表时间：
2023-08
影响因子：
9.7
通讯作者：
A. Spivak;A. Pinsonneault;C. Hintz;J. Brandes;J. Megonigal
中科院分区：
文献类型：
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作者：
A. Spivak;A. Pinsonneault;C. Hintz;J. Brandes;J. Megonigal
盐沼草类的根有助于土壤的形成，但也通过释放生物可利用的碳分泌物和氧气来影响分解。解开渗出物和氧气分解的影响是困难的，在外地，但沼泽碳模型和预测全球变化扰动的影响是必不可少的。我们测试了脉冲，模拟渗出物如何影响好氧和缺氧条件下的土壤代谢，以及碳和氧的可用性是否促进现有有机物质的矿化（即，启动）。我们在流通式反应器中进行了实验室实验，每周添加碳脉冲84天，然后在低碳条件下饥饿。在缺氧和好氧条件下，耗氧和硫化物的产生受到抑制，并在分泌物脉冲后1- 5天之间分别减慢21 ± 10%和55 ± 8%。呼吸率紧随其后，脉冲之间随着时间的推移而增加，这表明微生物利用并可能适应斑块资源。饥饿导致耗氧量和硫化物产量下降28%和78%，在好氧和缺氧处理。脉搏后耗氧量的较小下降可能表明更容易获得二次碳源，硫酸盐还原剂更依赖于渗出物。土壤有机碳不可能是次要来源，因为孔隙水溶解的无机碳δ 13 C值在通过反应器的过程中没有变化，尽管供应的海水和沼泽土壤之间的差异为1.26 ‰。氧消耗率的解释是复杂的非呼吸氧化还原无机化合物和可能显着的石自养。渗出脉冲引起快速和短暂的呼吸反应，特别是在缺氧，但非呼吸氧化还原化合物掩盖了我们的实验系统中的氧气供应的影响。尽管如此，更大的有氧呼吸速率表明，氧气供应有更大的潜力，以调节沿海湿地比根分泌物的碳矿化。
Roots of salt marsh grasses contribute to soil building but also affect decomposition by releasing bioavailable carbon exudates and oxygen. Disentangling exudate and oxygen effects on decomposition is difficult in the field but essential for marsh carbon models and predicting the impacts of global change disturbances. We tested how pulsed, simulated exudates affect soil metabolism under oxic and anoxic conditions, and whether carbon and oxygen availability facilitate mineralization of existing organic matter (i.e., priming). We conducted a laboratory experiment in flow-through reactors, adding carbon pulses weekly for 84 days and then following starvation under low carbon conditions. Oxygen consumption and sulfide production were inhibited under anoxic and oxic conditions and slowed by 21 ± 10% and 55 ± 8%, respectively, between 1- and 5- days following exudate pulses. Respiration rates immediately following and between pulses increased over time, suggesting that microbes capitalize on and may acclimate to patchy resources. Starvation caused oxygen consumption and sulfide production to fall 28% and 78% in oxic and anoxic treatments. Smaller decreases in oxygen consumption following pulses could suggest greater access to secondary carbon sources and that sulfate reducers were more reliant on exudates. Soil organic carbon was not the likely secondary source because porewater dissolved inorganic carbon δ13C values did not change during transit through the reactors, despite a ∼26‰ difference between the supplied seawater and marsh soil. Interpretation of oxygen consumption rates is complicated by non-respiratory oxidation of reduced inorganic compounds and possibly significant lithoautotrophy. Exudate pulses elicited rapid and ephemeral respiratory responses, particularly under anoxia, but non-respiratory oxidation of reduced compounds obscured the impact of oxygen availability in our experimental system. Despite this, greater aerobic respiration rates suggest that oxygen availability has more potential to regulate carbon mineralization in coastal wetlands than root exudates.