Name: soil lysimeter excavation for coupled hydrological, geochemical, and microbiological investigations
Uploaded: 2016-09-11T15:00:00
Description: Watch this Scientific Journal Video about Soil Lysimeter Excavation for Coupled Hydrological, Geochemical, and Microbiological Investigations at JoVE.com

We thank Ty P.A. Ferr&#233;, 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.

1. Devise a Sampling Matrix to Ensure Systematic and Comprehensive Sampling of Lysimeter
<ol>
	<li>Divide lysimeter into voxels of fixed length, width, and depth.
	<ol>
		<li>Use a Euclidean space coordinate system and divide the total distance along each direction (X, Y and Z) into an adequate number of equally spaced intervals. Consider discarding the soil near the walls of the lysimeter to avoid boundary effects. 
		NOTE: A buffer of 5 cm along the four walls is adopted in this experiment to avoid boundary effe...

<ol>
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P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Landscape+evolution+(A+Review).">Landscape evolution (A Review).</a> Proc. Natl. Acad. Sci. U. S. A. 79, 4477-4486 (1982).</li><li>Temme, A., Montgomery, D. R., Bierman, P. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Predicting+the+effect+of+changing+climate+on+landscapes+with+computer+based+landscape+evolution+models.">Predicting the effect of changing climate on landscapes with computer based landscape evolution models.</a> Key Concepts in Geomorphology. , (2013).</li><li>Troch, P. 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M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Contributions+of+atmospheric+CO+and+hydrogen+uptake+to+microbial+dynamics+on+recent+Hawaiian+volcanic+deposits.">Contributions of atmospheric CO and hydrogen uptake to microbial dynamics on recent Hawaiian volcanic deposits.</a> Appl. Environ. Microbiol. 69 (7), 4067-4075 (2003).</li><li>Meyer, W. S., Barrs, H. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Roots+in+irrigated+clay+soils:+Measurement+techniques+and+responses+to+rootzone+conditions.">Roots in irrigated clay soils: Measurement techniques and responses to rootzone conditions.</a> Irrig. Sci. 12 (3), 125-134 (1991).</li><li>Graham, C. B., Woods, R. A., McDonnell, J. 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Landscape evolution is the cumulative effect of hydrological, geochemical, and biological processes12. These processes control flow and transport of water and elements, and biogeochemical reactions in evolving landscapes. However, capturing the interactions simultaneously requires precisely coordinated experimental design and sampling. Additionally, studying incipient landscape evolution is difficult in natural systems, with limited capabilities to identify &#34;time zero&#34; conditions. Literature reports on...

Soil and landscape dynamics are shaped by the complex interaction of physical, chemical, and biological processes1. Water flow, geochemical weathering, and biological activity shape the overall development of the landscape into a stable ecosystem2,3. While surface changes are the most conspicuous features of landscape4, understanding cumulative effects of hydrological, geochemical, and microbiological processes in the subsurface region is crucial to understanding the underlying forces that shape a landscape2. Future climate perturbation scenarios further confound the predictability and pattern of landscape evolution5. It thus becomes a challenge to link small-scale processes to their large-scale manifestation on the landscape-scale6. Traditional short-run laboratory experiments or experiments in natural landscapes with unknown initial conditions and time-variable forcing fall short in capturing the intrinsic heterogeneity of landscape evolution. Also, due to strong nonlinear coupling, it is difficult to predict biogeochemical changes from hydrological modeling in heterogeneous systems7. Here, we describe a novel experimental method to excavate a fully controlled and monitored soil hillslope with known initial conditions. Our excavation and sampling procedure is aimed at capturing the developing heterogeneity of the hillslope along its length and depth, with the goal of providing a comprehensive dataset to investigate hydro-bio-geochemical interactions and their impact on soil formation processes.
Hydrologic systems found in nature are far from being static in time, with changes in hydrological responses taking place over a wide range of spatial and temporal scales3. The spatial structure of flow pathways along landscapes determines the rate, extent and distribution of geochemical reactions and biological colonization that drive weathering, the transport and precipitation of solutes and sediments, and the further development of soil structure. Thus, incorporating knowledge from pedology, geophysics, and ecology into theories and experimental designs to assess hydrologic processes and improve hydrologic predictions has been suggested8,9. Landscape evolution is also impacted by subsurface biogeochemical processes in conjunction with water dynamics, elemental migration during soil development, and by mineralogical transformations brought about by reaction of mineral surfaces with air, water, and microorganisms10. Consequently, it is important to study development of geochemical hotspots within an evolving landscape. Additionally, it is critical to relate geochemical weathering patterns to hydrological process and microbiological signatures during incipient soil formation in order to understand the dynamics of complex landscape development. The specific processes of soil genesis are governed by the combined influence of climate, biological inputs, relief and time on a specific parent material. This experiment was designed to address heterogeneities in the weathering of parent material governed by hydrological and geochemical variations associated with relief (including slope and depth) and the associated variability in microbial activity that is driven by environmental gradients (i.e., redox potential) under conditions where parent material, climate and time are held constant. With respect to microbial activity, soil microorganisms are critical components and have a profound impact on landscape stability11. They play a crucial role in soil structure, biogeochemical cycling of nutrients, and plant growth. Therefore, it is necessary to understand the significance of these organisms as drivers of weathering, soil genesis, and landscape formation processes, while simultaneously identifying the reciprocal effects of hydrological flow-paths and geochemical weathering on microbial community structure and diversity. This can be achieved by studying spatial heterogeneity of microbial community diversity over an evolving landscape whose hydrological and geochemical characteristics are also being studied in parallel.
Here, we present an excavation procedure of a soil lysimeter, operationally named miniLEO, designed to mimic the large-scale zero-order basin models of the Landscape Evolution Observatory (LEO) housed at Biosphere 2 (University of Arizona). The miniLEO was developed to identify small-scale landscape evolution patterns arising from cumulative heterogeneous hydro-bio-geochemical processes. It is a lysimeter 2-m in length, 0.5-m in width, and 1-m in height, and slope of 10&#176; (Figure 1). Additionally, the walls of the lysimeter are insulated and coated with non-biodegradable two-part epoxy primer and an aggregate filled aliphatic urethane coat to avoid potential contamination or leaching of metals from the lysimeter frame into the soil. The lysimeter was filled with crushed basalt rock that was extracted from a deposit of late Pleistocene tephra associated with Merriam Crater in northern Arizona. The loaded basalt material was identical to the material used in the much larger LEO experiments. The mineral composition, particle size distribution, and hydraulic properties are described by Pangle et al.12. The downslope seepage face was lined with a perforated plastic screen (0.002-m diameter pores, 14% porosity). The system is fitted with sensors such as water content and temperature sensors, two types of water potential sensors, soil-water samplers, hydraulic weight balance, electrical conductivity probes, and pressure transducers to determine water table height. The lysimeter was irrigated for 18 months prior to the excavation.
The excavation was meticulous in its approach and was aimed at answering two broad questions: (1) what hydrological, geochemical, and microbial signatures can be observed across the length and depth of the slope with respect to simulated rainfall conditions and (2) whether relationships and feedbacks between hydro-bio-geochemical processes occurring on the hillslope can be deduced from the individual signatures. Alongside the experimental setup and excavation procedure, we present representative data and suggestions on how to apply similar excavation protocols for researchers interested in studying coupled earth-system dynamics and/or soil development processes.

<table border="0" cellpadding="0" cellspacing="0" width="1632">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Measuring tape</td>
			<td style="width:71px;">Any</td>
			<td style="width:153px;">Any</td>
			<td style="width:1192px;">Preventing cross-contamination of samples&#160; is crucial. Therefore, it is helpful to have multiple putty knives to isolate voxel boundary.</td>
		</tr>
		<tr height="60">
			<td height="60" style="height:60px;width:216px;">Brilliant Blue dye</td>
			<td style="width:71px;">Waldeck GmBH &#38;Co&#160;</td>
			<td style="width:153px;">B0770</td>
			<td>Rulers can be used to draw grids. The sampling strategy can be modified based on individual experiments.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Soil Corer</td>
			<td style="width:71px;">AMS</td>
			<td style="width:153px;">56975</td>
			<td>Any commercially manufactured Brilliant Blue dye can be used.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">75% Ethanol</td>
			<td style="width:71px;">Any</td>
			<td style="width:153px;">Any</td>
			<td>A Nikon D90 camera and 50mm lens were used for photography. Any high resolution camera and lens can be used for this purpose.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Spray Bottle</td>
			<td style="width:71px;">Any&#160;</td>
			<td style="width:153px;">Any</td>
			<td>Use of dye and color card is subjective to individual experiments and/or research questions.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Spatula</td>
			<td style="width:71px;">Any&#160;</td>
			<td style="width:153px;">Any</td>
			<td>Gardening gloves may be used if handling of corer becomes tedious.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Gloves</td>
			<td style="width:71px;">Any&#160;</td>
			<td style="width:153px;">Any</td>
			<td>Ensure microbiology samples are kept in ice during sampling and frozen as soon as possible.</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:216px;">KimWipes</td>
			<td style="width:71px;">KimTech Science</td>
			<td style="width:153px;">Any</td>
			<td>Water can be used to wash soil corer, prior to sanitizing with ethanol.</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:216px;">Sterile Sample bags</td>
			<td style="width:71px;">Fisher Scientific&#160;</td>
			<td style="width:153px;">Whirl-Pak 4 OZ. 24 OZ</td>
			<td>Keep buckets and dustpans handy to facilitate removal of waste soil.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Color Card</td>
			<td style="width:71px;">Any</td>
			<td style="width:153px;">Any</td>
			<td>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.</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:216px;">X-ray Fluoresce Spectrophotmeter</td>
			<td style="width:71px;">XRF, OLYMPUS</td>
			<td style="width:153px;">DS-2000 Delta XRF</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Polypropylene cores</td>
			<td style="width:71px;">Any</td>
			<td style="width:153px;">Any</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Metal cores&#160;</td>
			<td style="width:71px;">Any&#160;</td>
			<td style="width:153px;">Any</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Caps for polypropylene cores</td>
			<td style="width:71px;">Any</td>
			<td style="width:153px;">Any</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Hammer</td>
			<td style="width:71px;">Any&#160;</td>
			<td style="width:153px;">Any</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Plastic putty knives</td>
			<td style="width:71px;">Any&#160;</td>
			<td style="width:153px;">Any</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Face masks</td>
			<td style="width:71px;">Any&#160;</td>
			<td style="width:153px;">Any</td>
			<td></td>
		</tr>
	</tbody>
</table>

soil lysimeter excavation for coupled hydrological, geochemical, and microbiological investigations

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.

The dimensions of voxels ensured collection of samples for hydrological, geochemical, and microbiological measurements. The excavation procedure yielded 324 cores for microbiological analysis, 972 pXRF data points, 324 geochemical sample bags, 180 Ksat samples (128 vertical and 52 horizontal), and 311 bulk density samples. Preferential flow of Brilliant Blue dye was also observed to a depth of 30 cm below the surface. A representative set of 81 samples from a single vertical slice of the ...

Watch this Scientific Journal Video about Soil Lysimeter Excavation for Coupled Hydrological, Geochemical, and Microbiological Investigations at JoVE.com

Soil Lysimeter Excavation for Coupled Hydrological, Geochemical, and Microbiological Investigations

This study presents an excavation method for investigating subsurface hydrological, geochemical, and microbiological heterogeneity of a soil lysimeter. The lysimeter simulates an artificial hillslope which was initially under homogeneous condition and had been subjected to approximately 5,000 mm of water over eight cycles of irrigation in an 18-month period.

Studying co-evolution of hydrological and biogeochemical processes in the subsurface of natural landscapes can enhance the understanding of coupled ...

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Design and Operation of a Continuous 13C and 15N Labeling Chamber for Uniform or Differential, Metabolic and Structural, Plant Isotope Labeling

Design and Operation of a Continuous 13C and 15N Labeling Chamber for Uniform or Differential, Metabolic and Structural, Plant Isotope Labeling

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Integrated Field Lysimetry and Porewater Sampling for Evaluation of Chemical Mobility in Soils and Established Vegetation

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Protocols for Quantifying Transferable Pesticide Residues in Turfgrass Systems

Plant canopies in established turfgrass systems can intercept an appreciable amount of sprayed pesticides, which can be transferred through various routes ...

Nanopore DNA Sequencing for Metagenomic Soil Analysis

This article describes the steps for construction of a DNA library from soil, preparation and use of the nanopore flow cell, and analysis of the DNA ...

Measuring and Mapping Patterns of Soil Erosion and Deposition Related to Soil Carbonate Concentrations Under Agricultural Management

Spatial patterns of soil erosion and deposition can be inferred from differences in ground elevation mapped at appropriate time increments. Such changes ...

Wastewater Irrigation Impacts on Soil Hydraulic Conductivity: Coupled Field Sampling and Laboratory Determination of Saturated Hydraulic Conductivity

Since the early 1960s, an alternative wastewater discharge practice at The Pennsylvania State University has been researched and its impacts monitored. ...

Use of Principal Components for Scaling Up Topographic Models to Map Soil Redistribution and Soil Organic Carbon

Landscape topography is a critical factor affecting soil formation and plays an important role in determining soil properties on the earth surface, as it ...

Combined Size and Density Fractionation of Soils for Investigations of Organo-Mineral Interactions

Combined size and density fractionation (CSDF) is a method used to physically separate soil into fractions differing in particle size and mineralogy. CSDF ...