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Article ; Online: Observations of a Coniferous Forest at 9.6 and 17.2 GHz

Aaron Thompson / Richard Kelly

Remote Sensing, Vol 11, Iss 1, p

Implications for SWE Retrievals

2018 Volume 6

Abstract: UWScat, a ground-based Ku- and X-band scatterometer, was used to compare forested and non-forested landscapes in a terrestrial snow accumulation environment as part of the NASA SnowEx17 field campaign. Field observations from Trail Valley Creek, ... ...

Abstract	UWScat, a ground-based Ku- and X-band scatterometer, was used to compare forested and non-forested landscapes in a terrestrial snow accumulation environment as part of the NASA SnowEx17 field campaign. Field observations from Trail Valley Creek, Northwest Territories; Tobermory, Ontario; and the Canadian Snow and Ice Experiment (CASIX) campaign in Churchill, Manitoba, were also included. Limited sensitivity to snow was observed at 9.6 GHz, while the forest canopy attenuated the signal from sub-canopy snow at 17.2 GHz. Forested landscapes were distinguishable using the volume scattering component of the Freeman⁻Durden three-component decomposition model by applying a threshold in which values ≥50% indicated forested landscape. It is suggested that the volume scattering component of the decomposition can be used in current snow water equivalent (SWE) retrieval algorithms in place of the forest cover fraction ( FF ), which is an optical surrogate for microwave scattering and relies on ancillary data. The performance of the volume scattering component of the decomposition was similar to that of FF when used in a retrieval scheme. The primary benefit of this method is that it provides a current, real-time estimate of the forest state, it automatically accounts for the incidence angle and canopy structure, and it provides coincident information on the forest canopy without the use of ancillary data or modeling, which is especially important in remote regions. Additionally, it enables the estimation of forest canopy transmissivity without ancillary data. This study also demonstrates the use of these frequencies in a forest canopy application, and the use of the Freeman⁻Durden three-component decomposition on scatterometer observations in a terrestrial snow accumulation environment.
Keywords	radar scatterometer ; snow ; SWE retrieval ; Freeman-Durden 3-component decomposition ; Science ; Q
Subject code	910
Language	English
Publishing date	2018-12-01T00:00:00Z
Publisher	MDPI AG
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Why Do Sustainable Ventures Fail to Attract Management Talent?

Neil Aaron Thompson / Roosje Eijkemans

Sustainability, Vol 10, Iss 11, p

2018 Volume 4319

Abstract: Entrepreneurship is widely recognized to play a crucial role in transitioning societies towards sustainability, yet sustainable ventures often have difficulty in attracting talented management employees that are necessary to scale their sustainable ... ...

Abstract	Entrepreneurship is widely recognized to play a crucial role in transitioning societies towards sustainability, yet sustainable ventures often have difficulty in attracting talented management employees that are necessary to scale their sustainable opportunities. This study examined 19 qualitative interviews with three interview groups (human resource managers of sustainable ventures, recently hired employees at sustainable ventures, and management professionals looking for employment opportunities) to explain the impediments of attracting management talent and what competitive advantages sustainable ventures may have in the labour market. We discuss how these findings have theoretical and practical implications for scholars and sustainable entrepreneurs by drawing out a number of ways that sustainable ventures may attract management professionals.
Keywords	sustainable entrepreneurship ; human resources ; management professionals ; competitive advantage ; Environmental effects of industries and plants ; TD194-195 ; Renewable energy sources ; TJ807-830 ; Environmental sciences ; GE1-350
Language	English
Publishing date	2018-11-01T00:00:00Z
Publisher	MDPI AG
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Sensitivity of Ku- and X-Band Radar Observations to Seasonal Snow in Ontario, Canada

Aaron Thompson / Richard Kelly / Joshua King

Canadian Journal of Remote Sensing, Vol 45, Iss 6, Pp 829-

2019 Volume 846

Abstract: Radar scatterometer observations at 17.2 GHz and 9.6 GHz were made of the snow cover in mid-latitude agricultural fields, using the University of Waterloo scatterometer, to determine the sensitivity of the frequency-dependent radar response to snow water ...

Abstract	Radar scatterometer observations at 17.2 GHz and 9.6 GHz were made of the snow cover in mid-latitude agricultural fields, using the University of Waterloo scatterometer, to determine the sensitivity of the frequency-dependent radar response to snow water equivalent. Observations were made in alfalfa fields near Maryhill, Ontario during the 2013–2014 and 2014–2015 winter seasons. Additional observations in the 2014–2015 season were made at Englehart, Ontario. The natural snowpack was scanned using polarimetric observations throughout the season as snow accumulated. Conditions typical of the mid-latitude snow environment, including non-frozen ground, snow melt, freezing rain, and agricultural vegetation were observed to confound the relationship between backscatter and SWE or snow depth. With these special cases removed from the analysis, the strongest relationship is observed at 17.2 GHz where VV-polarized backscatter increased linearly by 0.35 dB/cm SWE. Further, the backscatter increases linearly by 0.10 dB/cm of snow depth. Relationships at 9.6 GHz are weaker. These findings are unique. They highlight the suitability and challenges of radar remote sensing for estimating snow accumulation in a mid-latitude environment and demonstrate the use of polarization signatures for identifying the effects of short vegetation prevalent in this environment.
Keywords	Environmental sciences ; GE1-350 ; Technology ; T
Subject code	551 ; 910
Language	English
Publishing date	2019-11-01T00:00:00Z
Publisher	Taylor & Francis Group
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Iron-mediated organic matter decomposition in humid soils can counteract protection

Chunmei Chen / Steven J. Hall / Elizabeth Coward / Aaron Thompson

Nature Communications, Vol 11, Iss 1, Pp 1-

2020 Volume 13

Abstract: Reactive iron minerals protect vast amounts of terrestrial carbon from decomposition and release as CO2. Here the authors show that reactive iron alone does not provide sufficient protection except under strict oxic conditions—instead, iron itself ... ...

Abstract	Reactive iron minerals protect vast amounts of terrestrial carbon from decomposition and release as CO2. Here the authors show that reactive iron alone does not provide sufficient protection except under strict oxic conditions—instead, iron itself promotes carbon decomposition.
Keywords	Science ; Q
Language	English
Publishing date	2020-05-01T00:00:00Z
Publisher	Nature Publishing Group
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Iron-mediated organic matter decomposition in humid soils can counteract protection

Chunmei Chen / Steven J. Hall / Elizabeth Coward / Aaron Thompson

Nature Communications, Vol 11, Iss 1, Pp 1-

2020 Volume 13

Abstract	Reactive iron minerals protect vast amounts of terrestrial carbon from decomposition and release as CO2. Here the authors show that reactive iron alone does not provide sufficient protection except under strict oxic conditions—instead, iron itself promotes carbon decomposition.
Keywords	Science ; Q
Language	English
Publishing date	2020-05-01T00:00:00Z
Publisher	Nature Portfolio
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: The “wing-heeled” traveler

Taylor Kain / Jordan Weinstein / Aaron Thompson / Andrea K. Boggild

Tropical Diseases, Travel Medicine and Vaccines, Vol 6, Iss 1, Pp 1-

2020 Volume 6

Abstract: Abstract Intoxication syndromes may be travel acquired, and are related to intentional or accidental inhalational or percutaneous exposures or ingestions. Due to their myriad clinical presentations, initial differential diagnosis of such intoxications in ...

Abstract	Abstract Intoxication syndromes may be travel acquired, and are related to intentional or accidental inhalational or percutaneous exposures or ingestions. Due to their myriad clinical presentations, initial differential diagnosis of such intoxications in returned travelers is broad, and typically requires detailed history and laboratory investigations to disentangle. We herein use a case-based clinical problem solving approach to illumination of a mercury intoxication syndrome, which presented in a 48-year-old VFR traveler to Guyana. Common clinical presentations, differential diagnoses, laboratory investigations, and therapeutic interventions are discussed.
Keywords	Ciguatera fish poisoning ; Heavy metal intoxication ; Nephropathy ; Neuropathy ; Skin bleaching ; Arctic medicine. Tropical medicine ; RC955-962
Language	English
Publishing date	2020-02-01T00:00:00Z
Publisher	BMC
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article: Ferrous Iron Oxidation under Varying pO2 Levels: The Effect of Fe(III)/Al(III) Oxide Minerals and Organic Matter

Chen, Chunmei / Aaron Thompson

Environmental science & technology. 2018 Jan. 16, v. 52, no. 2

2018

Abstract: Abiotic Fe(II) oxidation by O2 commonly occurs in the presence of mineral sorbents and organic matter (OM) in soils and sediments; however, this tertiary system has rarely been studied. Therefore, we examined the impacts of mineral surfaces (goethite and ...

Abstract	Abiotic Fe(II) oxidation by O2 commonly occurs in the presence of mineral sorbents and organic matter (OM) in soils and sediments; however, this tertiary system has rarely been studied. Therefore, we examined the impacts of mineral surfaces (goethite and γ-Al2O3) and organic matter [Suwannee River fulvic acid (SRFA)] on Fe(II) oxidation rates and the resulting Fe(III) (oxyhydr)oxides under 21 and 1% pO2 at pH 6. We tracked Fe dynamics by adding 57Fe(II) to 56Fe-labeled goethite and γ-Al2O3 and characterized the resulting solids using 57Fe Mössbauer spectroscopy. We found Fe(II) oxidation was slower at low pO2 and resulted in higher-crystallinity Fe(III) phases. Relative to oxidation of Fe(II)(aq) alone, both goethite and γ-Al2O3 surfaces increased Fe(II) oxidation rates regardless of pO2 levels, with goethite being the stronger catalyst. Goethite surfaces promoted the formation of crystalline goethite, while γ-Al2O3 favored nano/small particle or disordered goethite and some lepidocrocite; oxidation of Fe(II)aq alone favored lepidocrocite. SRFA reduced oxidation rates in all treatments except the mineral-free systems at 21% pO2, and SRFA decreased Fe(III) phase crystallinity, facilitating low-crystalline ferrihydrite in the absence of mineral sorbents, low-crystalline lepidocrocite in the presence of γ-Al2O3, but either crystalline goethite or ferrihydrite when goethite was present. This work highlights that the oxidation rate, the types of mineral surfaces, and OM control Fe(III) precipitate composition.
Keywords	aluminum oxide ; catalysts ; crystal structure ; environmental science ; ferrihydrite ; fulvic acids ; goethite ; iron ; lepidocrocite ; oxidation ; oxygen ; pH ; rivers ; sediments ; soil ; sorbents ; spectroscopy
Language	English
Dates of publication	2018-0116
Size	p. 597-606.
Publishing place	American Chemical Society
Document type	Article
ISSN	1520-5851
DOI	10.1021/acs.est.7b05102
Database	NAL-Catalogue (AGRICOLA)

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Article ; Online: Transient O2 pulses direct Fe crystallinity and Fe(III)-reducer gene expression within a soil microbiome

Jared Lee Wilmoth / Mary Ann Moran / Aaron Thompson

Microbiome, Vol 6, Iss 1, Pp 1-

2018 Volume 14

Abstract: Abstract Background Many environments contain redox transition zones, where transient oxygenation events can modulate anaerobic reactions that influence the cycling of iron (Fe) and carbon (C) on a global scale. In predominantly anoxic soils, this ... ...

Abstract	Abstract Background Many environments contain redox transition zones, where transient oxygenation events can modulate anaerobic reactions that influence the cycling of iron (Fe) and carbon (C) on a global scale. In predominantly anoxic soils, this biogeochemical cycling depends on Fe mineral composition and the activity of mixed Fe(III)-reducer populations that may be altered by periodic pulses of molecular oxygen (O2). Methods We repeatedly exposed anoxic (4% H2:96% N2) suspensions of soil from the Luquillo Critical Zone Observatory to 1.05 × 102, 1.05 × 103, and 1.05 × 104 mmol O2 kg−1 soil h−1 during pulsed oxygenation treatments. Metatranscriptomic analysis and 57Fe Mössbauer spectroscopy were used to investigate changes in Fe(III)-reducer gene expression and Fe(III) crystallinity, respectively. Results Slow oxygenation resulted in soil Fe-(oxyhydr)oxides of higher crystallinity (38.1 ± 1.1% of total Fe) compared to fast oxygenation (30.6 ± 1.5%, P < 0.001). Transcripts binning to the genomes of Fe(III)-reducers Anaeromyxobacter, Geobacter, and Pelosinus indicated significant differences in extracellular electron transport (e.g., multiheme cytochrome c, multicopper oxidase, and type-IV pilin gene expression), adhesion/contact (e.g., S-layer, adhesin, and flagellin gene expression), and selective microbial competition (e.g., bacteriocin gene expression) between the slow and fast oxygenation treatments during microbial Fe(III) reduction. These data also suggest that diverse Fe(III)-reducer functions, including cytochrome-dependent extracellular electron transport, are associated with type-III fibronectin domains. Additionally, the metatranscriptomic data indicate that Methanobacterium was significantly more active in the reduction of CO2 to CH4 and in the expression of class(III) signal peptide/type-IV pilin genes following repeated fast oxygenation compared to slow oxygenation. Conclusions This study demonstrates that specific Fe(III)-reduction mechanisms in mixed Fe(III)-reducer populations are uniquely ...
Keywords	Soil microbiome ; Redox cycling ; Microbial Fe(III) reduction ; C cycling ; Metatranscriptomics ; Mössbauer spectroscopy ; Microbial ecology ; QR100-130
Subject code	500
Language	English
Publishing date	2018-10-01T00:00:00Z
Publisher	BMC
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article: Faster redox fluctuations can lead to higher iron reduction rates in humid forest soils

Barcellos, Diego / K. Taylor Cyle / Aaron Thompson

Biogeochemistry. 2018 Feb., v. 137, no. 3

2018

Abstract: Iron (Fe) minerals play an important role in carbon (C) and nutrient dynamics in redox fluctuating soils. We explored how the frequency of redox oscillations influence Fe reduction rates and C content in Puerto Rican soils. We hypothesized that iron ... ...

Abstract	Iron (Fe) minerals play an important role in carbon (C) and nutrient dynamics in redox fluctuating soils. We explored how the frequency of redox oscillations influence Fe reduction rates and C content in Puerto Rican soils. We hypothesized that iron reduction rates would be faster during short oscillation periods than in longer oscillation periods. Surface soils from an upland valley in a humid tropical forest were exposed to systematic redox oscillations over 49 days. The oxidation events were triggered by the introduction of air (21% O₂), maintaining the time ratio under oxic or anoxic conditions at 1:6 (τₒₓ/τₐₙₒₓ). After pre-conditioning the soil to fluctuating redox conditions for 1 month, we imposed 280- and 70-h (or 11.67- and 2.5-day) redox oscillations, measuring Feᴵᴵ every few days. We found that by the end of the experiment, Fe reduction rates were higher in the short oscillation period (τₒₓ = 10 h, τₐₙₒₓ = 60 h) than in the long oscillation period (τₒₓ = 40 h, τₐₙₒₓ = 240 h). Carbon and nitrogen loss however was similar for both treatments. These results suggest the characteristics of redox fluctuations can alter rates of Fe reduction and potentially influence ecosystem processes that depend on iron behavior.
Keywords	air ; anaerobic conditions ; biogeochemistry ; carbon ; chemical reduction ; ecosystems ; forest soils ; highlands ; iron ; minerals ; nitrogen ; oxidation ; oxygen ; tropical forests
Language	English
Dates of publication	2018-02
Size	p. 367-378.
Publishing place	Springer International Publishing
Document type	Article
ZDB-ID	1478541-9
ISSN	1573-515X ; 0168-2563
ISSN (online)	1573-515X
ISSN	0168-2563
DOI	10.1007/s10533-018-0427-0
Database	NAL-Catalogue (AGRICOLA)

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Article: Order from disorder: do soil organic matter composition and turnover co-vary with iron phase crystallinity?

Hall, Steven J / Asmeret A. Berhe / Aaron Thompson

Biogeochemistry. 2018 Aug., v. 140, no. 1

2018

Abstract: Soil organic matter (SOM) often increases with the abundance of short-range-ordered iron (SRO Fe) mineral phases at local to global scales, implying a protective role for SRO Fe. However, less is known about how Fe phase composition and crystal order ... ...

Abstract	Soil organic matter (SOM) often increases with the abundance of short-range-ordered iron (SRO Fe) mineral phases at local to global scales, implying a protective role for SRO Fe. However, less is known about how Fe phase composition and crystal order relate to SOM composition and turnover, which could be linked to redox alteration of Fe phases. We tested the hypothesis that the composition and turnover of mineral-associated SOM co-varied with Fe phase crystallinity and abundance across a well-characterized catena in the Luquillo Experimental Forest, Puerto Rico, using dense fractions from 30 A and B horizon soil samples. The δ¹³C and δ¹⁵N values of dense fractions were strongly and positively correlated (R² = 0.75), indicating microbial transformation of plant residues with lower δ¹³C and δ¹⁵N values. However, comparisons of dense fraction isotope ratios with roots and particulate matter suggested a greater contribution of plant versus microbial biomass to dense fraction SOM in valleys than ridges. Similarly, diffuse reflectance infrared Fourier transform spectroscopy indicated that SOM functional groups varied significantly along the catena. These trends in dense fraction SOM composition, as well as ∆¹⁴C values indicative of turnover rates, were significantly related to Fe phase crystallinity and abundance quantified with selective extractions. Mössbauer spectroscopy conducted on independent bulk soil samples indicated that nanoscale ordered Fe oxyhydroxide phases (nano-goethite, ferrihydrite, and/or very-SRO Fe with high substitutions) dominated (66–94%) total Fe at all positions and depths, with minor additional contributions from hematite, silicate and adsorbed Feᴵᴵ, and ilmenite. An additional phase that could represent organic-Feᴵᴵᴵ complexes or aluminosilicate-bearing Feᴵᴵᴵ was most abundant in valley soils (17–26% of total Fe). Overall, dense fraction samples with increasingly disordered Fe phases were significantly associated with increasingly plant-derived and faster-cycling SOM, while samples with relatively more-crystalline Fe phases tended towards slower-cycling SOM with a greater microbial component. Our data suggest that counter to prevailing thought, increased SRO Fe phase abundance in dynamic redox environments could facilitate transient accumulation of litter derivatives while not necessarily promoting long-term C stabilization.
Keywords	B horizons ; Fourier transform infrared spectroscopy ; carbon ; catenas ; crystal structure ; ferrihydrite ; hematite ; iron ; iron oxyhydroxides ; microbial biomass ; moieties ; nitrogen ; particulates ; plant residues ; protective effect ; roots ; silicates ; soil organic matter ; soil sampling ; stable isotopes ; valleys ; Puerto Rico
Language	English
Dates of publication	2018-08
Size	p. 93-110.
Publishing place	Springer International Publishing
Document type	Article
ZDB-ID	1478541-9
ISSN	1573-515X ; 0168-2563
ISSN (online)	1573-515X
ISSN	0168-2563
DOI	10.1007/s10533-018-0476-4
Database	NAL-Catalogue (AGRICOLA)

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