Journal Paper Digests

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Journal Paper Digests 2017 #27

  • Developing a molecular picture of soil organic matter-mineral interactions by quantifying organo-mineral binding
  • Geolokit: An interactive tool for visualising and exploring geoscientific data in Google Earth
  • Automated delineation and characterization of drumlins using a localized contour tree approach
  • Measuring land-use and land-cover change using the US department of agriculture’s cropland data layer: Cautions and recommendations.
  • Is demineralization with dilute hydrofluoric acid a viable method for isolating mineral stabilized soil organic matter?
  • Decrease of soil organic matter stabilization with increasing inputs: Mechanisms and controls
  • Statistics, Scoring Functions, and Regional Analysis of a Comprehensive Soil Health Database

Developing a molecular picture of soil organic matter-mineral interactions by quantifying organo-mineral binding

Authors: Newcomb, CJ; Qafoku, NP; Grate, JW; Bailey, VL; De Yoreo, JJ

Source: NATURE COMMUNICATIONS, 8 396-396; AUG 30 2017

Abstract: Long residence times of soil organic matter have been attributed to reactive mineral surface sites that sorb organic species and cause inaccessibility due to physical isolation and chemical stabilization at the organic-mineral interface. Instrumentation for probing this interface is limited. As a result, much of the micron-and molecular-scale knowledge about organic-mineral interactions remains largely qualitative. Here we report the use of force spectroscopy to directly measure the binding between organic ligands with known chemical functionalities and soil minerals in aqueous environments. By systematically studying the role of organic functional group chemistry with model minerals, we demonstrate that chemistry of both the organic ligand and mineral contribute to values of binding free energy and that changes in pH and ionic strength produce significant differences in binding energies. These direct measurements of molecular binding provide mechanistic insights into organo-mineral interactions, which could potentially inform land-carbon models that explicitly include mineral-bound C pools.

Geolokit: An interactive tool for visualising and exploring geoscientific data in Google Earth

Authors: Triantafyllou, A; Watlet, A; Bastin, C

Source: INTERNATIONAL JOURNAL OF APPLIED EARTH OBSERVATION AND GEOINFORMATION, 62 39-46; OCT 2017

Abstract: Virtual globes have been developed to showcase different types of data combining a digital elevation model and basemaps of high resolution satellite imagery. Hence, they became a standard to share spatial data and information, although they suffer from a lack of toolboxes dedicated to the formatting of large geoscientific dataset. From this perspective, we developed Geolokit: a free and lightweight software that allows geoscientists - and every scientist working with spatial data to import their data (e.g., sample collections, structural geology, cross-sections, field pictures, georeferenced maps), to handle and to transcribe them to Keyhole Markup Language (KML) files. KML files are then automatically opened in the Google Earth virtual globe and the spatial data accessed and shared. Geolokit comes with a large number of dedicated tools that can process and display: (i) multi-points data, (ii) scattered data interpolations, (iii) structural geology features in 2D and 3D, (iv) rose diagrams, stereonets and dip-plunge polar histograms, (v) cross-sections and oriented rasters, (vi) georeferenced field pictures, (vii) georeferenced maps and projected gridding.Therefore, together with Geolokit, Google Earth becomes not only a powerful georeferenced data viewer but also a stand-alone work platform. The toolbox (available online at https://protect-au.mimecast.com/s/aYDOBJiAr3QgF2?domain=geolokit.org) is written in Python, a high-level, cross-platform programming language and is accessible through a graphical user interface, designed to run in parallel with Google Earth, through a workflow that requires no additional third party software. Geolokit features are demonstrated in this paper using typical datasets gathered from two case studies illustrating its applicability at multiple scales of investigation: a petro-structural investigation of the Ile d’Yeu orthogneissic unit (Western France) and data collection of the Mariana oceanic subduction zone (Western Pacific).

Automated delineation and characterization of drumlins using a localized contour tree approach

Authors: Wang, SJ; Wu, QS; Ward, D

Source: INTERNATIONAL JOURNAL OF APPLIED EARTH OBSERVATION AND GEOINFORMATION, 62 144-156; OCT 2017

Abstract: Drumlins are ubiquitous landforms in previously glaciated regions, formed through a series of complex sub glacial processes operating underneath the paleo-ice sheets. Accurate delineation and characterization of drumlins are essential for understanding the formation mechanism of drumlins as well as the flow behaviors and basal conditions of paleo-ice sheets. Automated mapping of drumlins is particularly important for examining the distribution patterns of drumlins across large spatial scales. This paper presents an automated vector-based approach to mapping drumlins from high-resolution light detection and ranging (LiDAR) data. The rationale is to extract a set of concentric contours by building localized contour trees and establishing topological relationships. This automated method can overcome the shortcomings of previously manual and automated methods for mapping drumlins, for instance, the azimuthal biases during the generation of shaded relief images. A case study was carried out over a portion of the New York Drumlin Field. Overall 1181 drumlins were identified from the LiDAR-derived DEM across the study region, which had been underestimated in previous literature. The delineation results were visually and statistically compared to the manual digitization results. The morphology of drumlins was characterized by quantifying the length, width, elongation ratio, height, area, and volume. Statistical and spatial analyses were conducted to examine the distribution pattern and spatial variability of drumlin size and form. The drumlins and the morphologic characteristics exhibit significant spatial clustering rather than randomly distributed patterns. The form of drumlins varies from ovoid to spindle shapes towards the downstream direction of paleo ice flows, along with the decrease in width, area, and volume. This observation is in line with previous studies, which may be explained by the variations in sediment thickness and/or the velocity increases of ice flows towards ice front.

Measuring land-use and land-cover change using the US department of agriculture’s cropland data layer: Cautions and recommendations

Authors: Lark, TJ; Mueller, RM; Johnson, DM; Gibbs, HK

Source: INTERNATIONAL JOURNAL OF APPLIED EARTH OBSERVATION AND GEOINFORMATION, 62 224-235; OCT 2017

Abstract: Monitoring agricultural land is important for understanding and managing food production, environmental conservation efforts, and climate change. The United States Department of Agriculture’s Cropland Data Layer (CDL), an annual satellite imagery-derived land cover map, has been increasingly used for this application since complete coverage of the conterminous United States became available in 2008. However, the CDL is designed and produced with the intent of mapping annual land cover rather than tracking changes over time, and as a result certain precautions are needed in multi-year change analyses to minimize error and misapplication. We highlight scenarios that require special considerations, suggest solutions to key challenges, and propose a set of recommended good practices and general guidelines for CDL-based land change estimation. We also characterize a problematic issue of crop area underestimation bias within the CDL that needs to be accounted for and corrected when calculating changes to crop and cropland areas. When used appropriately and in conjunction with related information, the CDL is a valuable and effective tool for detecting diverse trends in agriculture. By explicitly discussing the methods and techniques for post-classification measurement of land-cover and land-use change using the CDL, we aim to further stimulate the discourse and continued development of suitable methodologies. Recommendations generated here are intended specifically for the CDL but may be broadly applicable to additional remotely-sensed land cover datasets including the National Land Cover Database (NLCD), Moderate Resolution Imaging Spectroradiometer (MODIS)-based land cover products, and other regional, national, and global land cover classification maps.

Is demineralization with dilute hydrofluoric acid a viable method for isolating mineral stabilized soil organic matter?

Authors: Sanderman, J; Farrell, M; Macreadie, PI; Hayes, M; McGowan, J; Baldock, J

Source: GEODERMA, 304 4-11; SI OCT 15 2017

Abstract: Hydrofluoric acid (HF) is a powerful tool in the investigation of soil organic matter (SOM) due to its ability to dissolve minerals but not break the chemical bonds of organic matter. These properties make the use of HF a common pretreatment step for removing paramagnetic interferences and concentrating carbon prior to solid-state C-13 NMR spectroscopy with the working assumption that any SOM lost during HF treatment will not bias the resulting NMR spectra. Hydrofluoric acid is also used to isolate a mineral-stabilized OM fraction with the working assumption that most mineral-stabilized OM is primarily low molecular weight compounds bound to mineral surfaces and when the minerals are dissolved in HF, the OM bound to these surfaces will be lost to solution. The working assumptions behind these two uses of HF dissolution appear to be contradictory. To address this apparent conundrum, we treated a number of simple organic compounds, soil and sediment samples with HF in 2 and 10% concentrations and tracked C and N loss as well as chemical shifts observed in solid-state 13C NMR spectra. For the soil and sediment samples there were inconsistent C and N losses but no difference in loss between the 2% and 10% HF concentrations. There were no obvious soil properties that could explain the differences in C or N loss. Overall, there were significant shifts in NMR-observable organic chemistry after treatment with both 2 and 10% HF with anoxic fine grained sediments under a seagrass meadow exhibiting strong preferential loss of O-alkyl C while terrestrial soils generally lost OM with more of a mixed chemical character. For many samples, the degree of selective loss was enough to significantly bias the interpretation of OM composition. Given the lack of ability to explain the large differences in C loss between samples with observed soil properties, this study suggests that caution should be used when interpreting HF-soluble C to indicate a mineral-stabilized fraction without considering the soil physicochemical environment and putative mechanisms for organo-mineral associations in that particular soil. (C) 2017 Elsevier B.V. All rights reserved.

Decrease of soil organic matter stabilization with increasing inputs: Mechanisms and controls

Authors: Shahbaz, M; Kuzyakov, Y; Heitkamp, F

Source: GEODERMA, 304 76-82; SI OCT 15 2017

Abstract: Crop residue addition is a way to increase soil organic matter (SOM) level in croplands. However, organic matter input and SOM stocks are not linearly related. Consequently, adding high amounts of residues, such as straw, may increase SOM to only a small extent, and an alternative use of the residues may be justified. The objective of this study was to test how the level and type (above- or belowground) of residue addition affect SOM stabilization. We hypothesise that (1) root residues will be mineralised slower than leaf and stalk residues, (2) soil aggregate formation will increase with high additions, and (3) wheat residue addition will induce positive priming, with the magnitude depending on the residue level and type. Homogeneously C-13-labelled wheat residues (leaves, stalks, roots) were added to a silt-loam soil at levels of 1.40 and 5.04 g DM kg(-1) and CO2 release and delta C-13 signature were measured over 64 days at 20 degrees C. Water-stable macroaggregates (> 250 mu m), microaggregates (53-250 mu m) and silt plus clay size fractions (< 53 mu m) were separated and C-13 incorporation from residue was quantified in each fraction after 64 days. Aggregate formation generally increased with added residue amount, but the proportion of residues occluded within aggregates decreased with increasing addition level. The occlusion of residues from aboveground biomass was more reduced with addition level than that of roots. Residue mineralisation increased with the addition level, but this increase was less for roots compared to stalks and leaves. Priming effects were similar between residue types and mainly depended on the added amount: SOM mineralisation increased by 50% and 90% at low and high addition levels, respectively. We conclude that the proportion of residues physically protected within aggregates decreases and priming effects increase with increasing C input leading to decreasing rate of long-term C stabilization within SOM by increasing residue addition.

Statistics, Scoring Functions, and Regional Analysis of a Comprehensive Soil Health Database

Authors: Fine, AK; van Es, HM; Schindelbeck, RR

Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL, 81 (3):589-601; MAY-JUN 2017

Abstract: Soil health (SH) refers to the ability of a soil to function and provide ecosystem services. The Comprehensive Assessment of Soil Health (CASH) is an approach that measures 15 physical, biological, and chemical soil indicators, which are interpreted through scoring functions. This study reports on the SH status of 5767 samples from the Mid-Atlantic, Midwest, and Northeast regions of the USA as evaluated using CASH. Descriptive statistics and ANOVAs of subdatasets by region and soil textural group for SH indicators, in addition to correlation coefficients, principal component (PC) analysis, and best subsets regression (BSR) were performed. From these analyses, new CASH scoring functions were developed. Separate scoring functions by textural group (fine, medium, coarse) were necessary for Wet Aggregate Stability (WAS), Available Water Capacity (AWS), Organic Matter (OM), Active Carbon (AC), and Protein. Differences existed among regions, especially for WAS, OM, Protein, and Respiration (Resp), where the Midwest had relatively lower mean values compared to the Mid-Atlantic and Northeast. Biological properties and WAS showed moderately strong correlations (r = 0.58-0.78) and the highest loadings for the first two PCs. BSR results using the overall soil quality index as the response variable indicated that AC accounts for 45% of the variation, with additional predictability from Penetration Resistance, Resp, and WAS (68%). These four indicators are suggested for simplified SH tests. We conclude that the CASH approach can be successfully applied to evaluate the health status of soils with differing pedogenetic histories.

Sydney Institute of Agriculture World Soil Day SOILinar

The world was in massive celebration on December 5. If you were wondering what all of that was about, it was because it was World Soil Da...… Continue reading

Journal Paper Digests

Published on November 20, 2017