土壤蒸渗仪开挖加之水文，地球化学和微生物调查
Summary
这项研究提出调查地下的水文，地球化学和土壤蒸渗仪的微生物异质性挖掘方法。在蒸渗仪模拟人工坡面它最初是均匀的条件下，并在18个月内曾受到近5000毫米的水灌溉超过8个周期。
Abstract
Studying co-evolution of hydrological and biogeochemical processes in the subsurface of natural landscapes can enhance the understanding of coupled Earth-system processes. Such knowledge is imperative in improving predictions of hydro-biogeochemical cycles, especially under climate change scenarios. We present an experimental method, designed to capture sub-surface heterogeneity of an initially homogeneous soil system. This method is based on destructive sampling of a soil lysimeter designed to simulate a small-scale hillslope. A weighing lysimeter of one cubic meter capacity was divided into sections (voxels) and was excavated layer-by-layer, with sub samples being collected from each voxel. The excavation procedure was aimed at detecting the incipient heterogeneity of the system by focusing on the spatial assessment of hydrological, geochemical, and microbiological properties of the soil. Representative results of a few physicochemical variables tested show the development of heterogeneity. Additional work to test interactions between hydrological, geochemical, and microbiological signatures is planned to interpret the observed patterns. Our study also demonstrates the possibility of carrying out similar excavations in order to observe and quantify different aspects of soil-development under varying environmental conditions and scale.
Introduction
土壤和景观动态由物理，化学的复杂的相互作用，和生物过程1型。水流量，地球化学风化和生物活性塑造景观的整体发展成一个稳定的生态系统中2,3。虽然表面的变化都在地下区域景观4的最显着的特征，水文地球化学的认识累积效应，和微生物方法是了解潜在力量塑造景观2至关重要。未来气候情景摄惊慌失措进一步进化景观5的可预见性和模式。因此，它成为对景观尺度6小规模的过程链接到他们大型的表现是一个挑战。传统的短期实验室实验或与未知的初始条件和时间变化迫使功亏一篑捕捉个自然景观实验Ë固有景观演变的异质性。另外，由于强非线性耦合，它是很难预测在异构系统7从水文模拟生物地球化学的变化。在这里，我们描述了一种新的实验方法来挖掘已知初始条件完全控制和监测土坡。我们的挖掘和取样程序的目的是捕获沿其长度和深度的坡面的显影异质性，以提供全面的数据集来调查水力生物地球化学相互作用以及它们对土壤形成过程的影响的目的。
在自然界中发现水文系统远远不是静态的时间，在发生了大范围的空间和时间尺度3的水文响应变化。沿着风景流动通道的空间结构决定的速度，程度和地球化学反应和生物殖民化推动的分布风化，运输和溶质和沉积物的沉淀，和土壤结构的进一步发展。因此，结合从土壤学，地球物理和生态知识转化为理论和实验设计，评估水文过程，提高水文预测已建议8,9。景观演变也由地下的生物地球化学过程与水动力学，土壤发育过程中元素的迁移，并结合由空气，水矿物表面和微生物10的反应所带来的矿物转变的影响。因此，为一个变化的领域内研究地球化学热点的发展是重要的。此外，关键是为了了解复杂的景观发展的动态初始土壤形成过程中涉及的地球化学风化图案，水文过程和微生物的签名。土壤发生的具体过程管辖由气候，生物输入，浮雕和时间上的特定母材的综合影响。该实验的目的是要解决的条件，其中下在母材通过用浮雕（包括斜率和深度）相关的水文和地球化学变化支配风化的非均质性，并是受环境梯度（ 即 ，氧化还原电位）驱动在微生物活性相关的变异母体材料，气候和时间保持不变。对于微生物的活性，土壤中的微生物是重要组成部分，而且对景观稳定性11深远的影响。它们在土壤结构，营养元素的生物地球化学循环和植物生长至关重要的作用。因此，有必要了解这些生物体如风化司机，土壤发生，和景观形成过程的重要性，同时识别的水文流动路径和地球化学我们的倒数效果athering对微生物群落结构和多样性。这可以通过在一个不断发展的景观的水文地球化学特征也正在研究并行研究微生物群落多样性的空间异质性来实现。
在这里，我们提出了一个土壤蒸渗仪，操作上名为miniLEO，设计模仿设在生物圈2号（亚利桑那大学）的景观演变天文台（LEO）的大型零阶盆地模型的挖掘过程。该miniLEO目的是为了查明从累计异构水文生物地球化学过程所产生的小规模的景观演化模式。它是一个蒸渗2米长，0.5米宽，并在高度1米，以及10°的斜面（ 图1）。此外，蒸渗的壁是绝缘的，涂有非生物降解的两部分组成的环氧底漆和骨料填充脂族氨基甲酸酯涂层，以避免潜在的污染或浸出从蒸渗帧到土壤中的金属。在蒸渗仪中弥漫着被从火山口梅里亚姆在亚利桑那州北部关联晚更新世火山灰的存款中提取碎玄武岩。加载的玄武岩材料是相同的大得多的LEO实验中使用的材料。矿物组合物，粒度分布，和液压属性由潘高等人 12所述。下坡渗水面带小孔的塑料屏幕（0.002米直径的孔，14％的孔隙率）的衬里。该系统配有传感器，例如水含量和温度传感器，两种类型的水势传感器，土壤 – 水取样，液压重量平衡，导电性的探针，以及压力传感器，以确定水位高度。在蒸渗仪被用于灌溉前的开挖18个月。
此次发掘是在方法上细致，旨在回答两大问题：（1）什么水文，地球化学和微生物的签名可以在斜坡的长度和深度可以观察到相对于模拟降雨条件和（2）是否水力生物地球化学过程之间的关系，并反馈的坡面发生可以从推断个人签名。除了实验装置和发掘过程中，我们提出了关于如何申请类似的发掘协议兴趣研究加之地球系统动力学和/或土壤发展进程的研究人员具有代表性的数据和建议。
Protocol
Representative Results
Discussion
景观进化是水文，地球化学和生物过程12的累积效应。这些过程控制流量以及水和元件运输，并在不断发展的景观生物地球化学反应。然而，捕捉交互同时要求精确协调的实验设计和抽样。此外，研究早期景观演化是自然系统困难，用有限的能力来识别“零时间”的条件。文献报道其进行测量植物根系密度23，而灌溉和挖掘基于现场的办法是由Graham等 24和 安德?…
Declarações
The authors have nothing to disclose.
Acknowledgements
We thank Ty P.A. Ferré, Till Volkman, Edwin Donker, Mauricio Vera for helping us during the excavation, and Triffon J. Tatarin, Manpreet Sahnan and Edward Hunt for their help in sample analysis. This work was carried out at Biosphere 2, University of Arizona and funded by National Science Foundation grant EAR_1344552 and Honors Research Program of Biosphere 2.
Materials
| Measuring tape | Any | Any | Preventing cross-contamination of samples is crucial. Therefore, it is helpful to have multiple putty knives to isolate voxel boundary. |
| Brilliant Blue dye | Waldeck GmBH &Co | B0770 | Rulers can be used to draw grids. The sampling strategy can be modified based on individual experiments. |
| Soil Corer | AMS | 56975 | Any commercially manufactured Brilliant Blue dye can be used. |
| 75% Ethanol | Any | Any | A Nikon D90 camera and 50mm lens were used for photography. Any high resolution camera and lens can be used for this purpose. |
| Spray Bottle | Any | Any | Use of dye and color card is subjective to individual experiments and/or research questions. |
| Spatula | Any | Any | Gardening gloves may be used if handling of corer becomes tedious. |
| Gloves | Any | Any | Ensure microbiology samples are kept in ice during sampling and frozen as soon as possible. |
| KimWipes | KimTech Science | Any | Water can be used to wash soil corer, prior to sanitizing with ethanol. |
| Sterile Sample bags | Fisher Scientific | Whirl-Pak 4 OZ. 24 OZ | Keep buckets and dustpans handy to facilitate removal of waste soil. |
| Color Card | Any | Any | The original design of miniLEO has various sensors embedded in the lysimeter. Such sensors may or may not be necessary based on the scope of individual experimental design. |
| X-ray Fluoresce Spectrophotmeter | XRF, OLYMPUS | DS-2000 Delta XRF | |
| Polypropylene cores | Any | Any | |
| Metal cores | Any | Any | |
| Caps for polypropylene cores | Any | Any | |
| Hammer | Any | Any | |
| Plastic putty knives | Any | Any | |
| Face masks | Any | Any |
Referências
- Brady, N. C., Weil, R. R. . The nature and properties of soils. , (2008).
- Chorover, J., Kretzschmar, R., Garica-Pichel, F., Sparks, D. L. Soil biogeochemicial processes within the critical zone. Elements. 3, 321-326 (2007).
- Troch, P. A., et al. Catchment coevolution: A useful framework for improving predictions of hydrological change?. Water Resour. Res. 6, 1-20 (2015).
- Sharp, R. P. Landscape evolution (A Review). Proc. Natl. Acad. Sci. U. S. A. 79, 4477-4486 (1982).
- Temme, A., Montgomery, D. R., Bierman, P. R. Predicting the effect of changing climate on landscapes with computer based landscape evolution models. Key Concepts in Geomorphology. , (2013).
- Troch, P. A., et al. Dealing with Landscape Heterogeneity in Watershed Hydrology: A Review of Recent Progress toward New Hydrological Theory. Geogr. Compass. 3, 375-392 (2009).
- Wang, Y., et al. Dissecting the Hydrobiogeochemical Box. in Am. Geophys. Union Fall Meet. , (2015).
- Lin, H., et al. Hydropedology: Synergistic integration of pedology and hydrology. Water Resour. Res. 42 (5), W05301 (2006).
- Band, L. E., et al. Ecohydrological flow networks in the subsurface. Ecohydrology. 7, 1073-1078 (2014).
- Churchman, G. j., Lowe, D. . Handbook of Soil Science Properties and Process. 1, (2012).
- van der Heijden, M. G. A., Bardgett, R. D., van Straalen, N. M. The unseen majority: soil microbes as drivers of plant diversity and productivity in terrestrial ecosystems. Ecol. Lett. 11 (3), 296-310 (2008).
- Pangle, L. a., et al. The Landscape Evolution Observatory: A large-scale controllable infrastructure to study coupled Earth-surface processes. Geomorphology. 244, 190-203 (2015).
- . . User Manual: Delta Famiy Handheld XRF Analyzers. , (2013).
- Valentìn-Vargas, A., Root, R. A., Neilson, J. W., Chorover, J., Maier, R. M. Environmental factors influencing the structural dynamics of soil microbial communities during assisted phytostabilization of acid-generating mine tailings: A mesocosm experiment. Sci Total Environ. 500-501, 314-324 (2014).
- JoVE Science Education Database. . Essentials of Environmental Microbiology. Culturing and Enumerating Bacteria from Soil Samples. , (2016).
- JoVE Science Education Database. . Essentials of Environmental Microbiology: Quantifying Environmental Microorganisms and Viruses Using qPCR. , (2016).
- Sengupta, A., Dick, W. A. Bacterial community diversity in soil under two tillage practices as determined by pyrosequencing. Microb. Ecol. 70, 853-859 (2015).
- Caporaso, J. G., et al. Correspondence – QIIME allows analysis of high- throughput community sequencing data. Nat. Publ. Gr. 7, 335-336 (2010).
- Hall, G. E. M., Vaive, J. E., Beer, R., Hoashi, M. Selective leaches revisited, with emphasis on the amorphous Fe oxyhydroxide phase extraction. J. Geochemical Explor. 56, 59-78 (1996).
- Grossman, R. B., Reinsch, T. G., Dane, J. H., Topp, G. C. Bulk density and linear extensibility. Methods of Soil Analysis. Part 4-Physical Methods. , 201-228 (2002).
- Reynolds, W. D., Elrick, D. E., Youngs, E. G., Amoozegar, A., Bootlink, H. W. G., Bouma, J., Dane, J. H., Topp, G. C. Saturated and field-saturated water flow parameters. Methods of Soil Analysis, Part 4-Physical Methods. , 802-816 (2002).
- King, G. M. Contributions of atmospheric CO and hydrogen uptake to microbial dynamics on recent Hawaiian volcanic deposits. Appl. Environ. Microbiol. 69 (7), 4067-4075 (2003).
- Meyer, W. S., Barrs, H. D. Roots in irrigated clay soils: Measurement techniques and responses to rootzone conditions. Irrig. Sci. 12 (3), 125-134 (1991).
- Graham, C. B., Woods, R. A., McDonnell, J. J. Hillslope threshold response to rainfall: (1) A field based forensic approach. J. Hydrol. 393 (1-2), 65-76 (2010).
- Anderson, A. E., Weiler, M., Alila, Y., Hudson, R. O. Dye staining and excavation of a lateral preferential flow network. Hydrol. Earth Syst. Sci. Discuss. 5 (2), 1043-1065 (2008).
- Gleeson, T., Paszkowski, D. Perceptions of scale in hydrology: what do you mean by regional scale?. Hydrol. Sci. J. 00, 1-9 (2013).
- Molins, S., Trebotich, D., Steefel, C. I., Shen, C. An investigation of the effect of pore scale flow on average geochemical reaction rates using direct numerical simulation. Water Resour. Res. 48, W03527 (2012).
- Fierer, N., Lennon, J. T. The generation and maintenance of diversity in microbial communities. Am. J. Bot. 98 (3), 439-448 (2011).
- Niu, G. Y., Pasetto, D., Scudeler, C., Paniconi, C., Putti, M., Troch, P. A. Analysis of an extreme rainfall-runoff event at the Landscape Evolution Observatory by means of a three-dimensional physically-based hydrologic model. Hydrol. Earth Syst. Sci. Discuss. 10, 12615-12641 (2013).
- Marteinsson, V., et al. Microbial colonization in diverse surface soil types in Surtsey and diversity analysis of its subsurface microbiota. Biogeosciences. 12, 1191-1203 (2015).
- Orcutt, B. N., Sylvan, J. B., Rogers, D. R., Delaney, J., Lee, R. W., Girguis, P. R. Carbon fixation by basalt-hosted microbial communities. Front. Microbiol. 6, 00904 (2015).
- Wu, L., Jacobson, A. D., Chen, H. C., Hausner, M. Characterization of elemental release during microbe-basalt interactions at T=28°C. Geochim. Cosmochim. Acta. 71, 2224-2239 (2007).
