Synergistic effects of soil microstructure and bacterial EPS on drying rate in emulated soil micromodels
Synergistic effects of soil microstructure and bacterial EPS on drying rate in emulated soil micromodels
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DOI：
10.1016/j.soilbio.2014.12.006
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发表时间：
2015-04-01
影响因子：
9.7
通讯作者：
Shor, Leslie M.
中科院分区：
文献类型：
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作者：
Deng, Jinzi;Orner, Erika P.;Shor, Leslie M.
微生物胞外聚合物(EPS)已被证明能改变土壤水分保持，并在大范围内改善幼苗存活和植物生长。EPS介导的保水机理包括交联聚合物基质的可逆膨胀和促进土壤团聚结构。然而，EPS对保水性的影响从未在孔隙尺度上被直接观察到。在这里，开发了模拟的土壤微观模型，以直接观察物理、化学和生物因素对孔隙尺度水分保持的影响。在本演示中，创建了一个伪2D孔隙结构来表示细砂壤土的物理特征。复制的微型模型最初被不同土壤细菌的悬浮液饱和，并随着时间的推移直接成像孔隙尺度的空气渗透。通过使用定制的恒湿环境室，外部蒸发度保持恒定。填充了高度粘性的苜蓿中华根瘤菌悬浮液的微型模型保持水分的时间大约是物理上相同的填充非粘液性苜蓿中华根瘤菌悬浮液的微型模型的两倍。在六次重复实验中，粘液悬浮液的相对干燥速度从1.1倍到15倍不等。空气渗透的模式相似，但在不同的样本中并不相同。结果表明，孔隙流体EPS和微观模型几何结构共同作用，限制了孔喉的蒸发。微观模型方法的优点包括直接观察孔隙尺度的动态过程，以及系统复制复杂物理结构的能力。这些能力将使用户能够筛选来自不同结构和微生物组成的益处，并建立对微生物栖息地系统整体功能的预测性理解。(C)2014爱思唯尔有限公司。保留所有权利。
Microbial extracellular polymeric substances (EPS) have been shown to alter soil moisture retention and to improve seedling survival and plant growth at the bulk scale. The mechanisms of EPS-mediated water retention include reversible swelling of the cross-linked polymer matrix and the promotion of an aggregated soil structure. However, the effects of EPS on water retention have never been directly observed at the pore scale. Here, emulated soil micromodels were developed to directly observe the effects of physical, chemical, and biological factors on pore-scale water retention. In this demonstration, a pseudo-2D pore structure was created to represent physical features of a fine sandy loam. Replicate micromodels were initially saturated with suspensions of different soil bacteria, and pore-scale air infiltration was directly imaged over time. External evaporativity was held constant through the use of a custom constant-humidity environmental chamber. Micromodels filled with suspensions of highly mucoid Sinorhizobium meliloti retained moisture about twice as long as physically identical micromodels filled with suspensions of non-mucoid S. meliloti. Relative drying rates in six replicate experiments ranged from 1.1 to 15 times slower for mucoid suspensions. Patterns of air infiltration were similar but not identical across replicates. The results suggest that pore fluid EPS and micromodel geometry act together to limit evaporation at pore throats. Advantages of the micromodel approach include direct observation of pore-scale dynamic process, and the ability to systematically replicate complex physical structures. These abilities will enable users to screen benefits from different structures and from microbial compositions, and build predictive understanding of the overall function of microbe-habitat systems. (C) 2014 Elsevier Ltd. All rights reserved.