Shane Stoner


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Stoner

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Shane

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0000-0002-6977-4587

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Publications 1 - 8 of 8
  • Reviews and syntheses: The promise of big diverse soil data, moving current practices towards future potential
    Item type: Review Article
    Todd-Brown, Katherine E.O.; Abramoff, Rose Z.; Beem-Miller, Jeffrey; et al. (2022)
    Biogeosciences
    In the age of big data, soil data are more available and richer than ever, but-outside of a few large soil survey resources-they remain largely unusable for informing soil management and understanding Earth system processes beyond the original study. Data science has promised a fully reusable research pipeline where data from past studies are used to contextualize new findings and reanalyzed for new insight. Yet synthesis projects encounter challenges at all steps of the data reuse pipeline, including unavailable data, labor-intensive transcription of datasets, incomplete metadata, and a lack of communication between collaborators. Here, using insights from a diversity of soil, data, and climate scientists, we summarize current practices in soil data synthesis across all stages of database creation: availability, input, harmonization, curation, and publication. We then suggest new soil-focused semantic tools to improve existing data pipelines, such as ontologies, vocabulary lists, and community practices. Our goal is to provide the soil data community with an overview of current practices in soil data and where we need to go to fully leverage big data to solve soil problems in the next century.
  • Beyond bulk: Density fractions explain heterogeneity in global soil carbon abundance and persistence
    Item type: Journal Article
    Heckman, Katherine; Hicks Pries, Caitlin E.; Lawrence, Corey R.; et al. (2021)
    Global Change Biology
    Understanding the controls on the amount and persistence of soil organic carbon (C) is essential for predicting its sensitivity to global change. The response may depend on whether C is unprotected, isolated within aggregates, or protected from decomposition by mineral associations. Here, we present a global synthesis of the relative influence of environmental factors on soil organic C partitioning among pools, abundance in each pool (mg C g−1 soil), and persistence (as approximated by radiocarbon abundance) in relatively unprotected particulate and protected mineral-bound pools. We show that C within particulate and mineral-associated pools consistently differed from one another in degree of persistence and relationship to environmental factors. Soil depth was the best predictor of C abundance and persistence, though it accounted for more variance in persistence. Persistence of all C pools decreased with increasing mean annual temperature (MAT) throughout the soil profile, whereas persistence increased with increasing wetness index (MAP/PET) in subsurface soils (30–176 cm). The relationship of C abundance (mg C g−1 soil) to climate varied among pools and with depth. Mineral-associated C in surface soils (<30 cm) increased more strongly with increasing wetness index than the free particulate C, but both pools showed attenuated responses to the wetness index at depth. Overall, these relationships suggest a strong influence of climate on soil C properties, and a potential loss of soil C from protected pools in areas with decreasing wetness. Relative persistence and abundance of C pools varied significantly among land cover types and soil parent material lithologies. This variability in each pool's relationship to environmental factors suggests that not all soil organic C is equally vulnerable to global change. Therefore, projections of future soil organic C based on patterns and responses of bulk soil organic C may be misleading. © 2021 John Wiley & Sons Ltd.
  • How diverse minerals affect soil organic matter age distribution and chemical composition
    Item type: Other Conference Item
    Stoner, Shane; Sierra, Carlos; Doetterl, Sebastian; et al. (2022)
    EGUsphere
    Soil mineral characteristics have been shown to play a dominant role in stabilizing soil organic matter over medium to long term timescales. However, while great strides have been made (Kleber et al, 2021) toward understanding organic matter stabilization processes, there remain uncertainties about the chemistry, time scales, and age of carbon that is stored on soil minerals. We applied modern thermal analysis methods to investigate soil mineral effects on the thermal stability, chemical composition, and age distribution of soil organic matter. We selected subsoil mineral fractions that contained a single dominant stabilizing pathway (e.g. 2:1 clays, iron oxides, short-range order minerals, crystalline minerals) to isolate effects of individual minerals. We paired thermal fractionation with pyrolysis-GC/MS to describe the relationships of SOM age and chemical composition. Early results show that while certain minerals display heterogeneous thermal stabilities, single mineralogies contain generally narrow age ranges. In addition, organic matter chemistry associated with diverse minerals varies widely and indicates that certain minerals provide higher stability to complex, energy-rich molecules. Associated with this work, we also present novel continuous SOM radiocarbon distributions from thermal fractionation.
  • Reviews and syntheses: The promise of big soil data, moving current practices towards future potential
    Item type: Working Paper
    Todd-Brown, Katherine E. O.; Abramoff, Rose Z.; Beem-Miller, Jeffrey; et al. (2021)
    Biogeosciences Discussions
    In the age of big data, soil data are more available than ever, but -outside of a few large soil survey resources- remain largely unusable for informing soil management and understanding Earth system processes outside of the original study. Data science has promised a fully reusable research pipeline where data from past studies are used to contextualize new findings and reanalyzed for global relevance. Yet synthesis projects encounter challenges at all steps of the data reuse pipeline, including unavailable data, labor-intensive transcription of datasets, incomplete metadata, and a lack of communication between collaborators. Here, using insights from a diversity of soil, data and climate scientists, we summarize current practices in soil data synthesis across all stages of database creation: data discovery, input, harmonization, curation, and publication. We then suggest new soil-focused semantic tools to improve existing data pipelines, such as ontologies, vocabulary lists, and community practices. Our goal is to provide the soil data community with an overview of current practices in soil data and where we need to go to fully leverage big data to solve soil problems in the next century.
  • Fertilization and irrigation effects on the time scale of carbon cycling in New Zealand Pastures
    Item type: Other Conference Item
    Doetterl, Sebastian; Stoner, Shane; Trumbore, Susan; et al. (2019)
    Geophysical Research Abstracts
    Soil organic matter is the largest terrestrial stock of carbon, and agricultural soils have potential to store large amounts of carbon (C), dependent on management practices such as fertilization and irrigation. Soil C is composed of a complex mixture of organic molecules of varying sources, energy contents, and degrees of stabilization, and are cycled at different rates in soils. Thus the “age” of these molecules can be largely variable and widely distributed. Since management practices can modify both the amount of carbon that enters the soils and the rates at which C is cycled, we expect management practices to affect times scales of soil carbon cycling. In this contribution, we present results from a unique set of archived soil samples collected between 1959 and 2008 from a long-term pasture production study in New Zealand. Thirteen subsamples were analyzed for radiocarbon analyses, and a three-pool feedback model was fit to the data, which spans over 60 years. Such highly constrained models can accurately investigate differences in management effects on mean system age (MSA) and mean transit time (MTT). Management effects were observed showing significant differences in MSA and MTT across both irrigation and fertilization trials. In particular, we observed: 1) irrigated pastures have a large fast-cycling pool due to higher productivity in spite of lower system transit times. 2) Frequent irrigation decreases the amount of long-term stable C in pastures. 3) Despite no difference in soil C accumulation, fertilized pastures store C longer than unfertilized pastures. These results suggest a potential paradigm shift toward prioritizing management that promotes long-term storage of C above simple increases in soil C content, which could lead to more effective methods of addressing rising atmospheric C. Results from this study could be applied to systems that are lacking spatio-temporal resolution present here.
  • Radiocarbon constraints on carbon cycling in plants and soils
    Item type: Other Conference Item
    Trumbore, Susan; Sierra, Carlos; Hoyt, Alison; et al. (2021)
    EGUsphere
    Tracing ‘bomb’ radiocarbon produced by atmospheric testing of atomic weapons through vegetation and soils provides information of the dynamics of terrestrial carbon cycling on timescales of years to centuries. Processes operating on these timescales are of interest because they regulate key functions in long-lived plants and regulate the potential for increasing soil carbon storage. However, the multiple pathways taken by carbon transiting ecosystems from photosynthesis to respiration and decomposition complicate the quantitative interpretation of radiocarbon observations. In the 14Constraint project, we are exploring how to optimize measurements of radiocarbon as well as to improve their interpretation by providing constraints for comparison with models. This talk will focus on efforts to synthesize global radiocarbon measurements of mean age and transit time, and suggest ways forward to improve process-level understanding.
  • Relating mineral-organic matter stabilization mechanisms to carbon quality and age distributions using ramped thermal analysis
    Item type: Journal Article
    Stoner, Shane; Trumbore, Susan E.; González-Pérez, José A.; et al. (2023)
    Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences
    Organic carbon (OC) association with soil minerals stabilizes OC on timescales reflecting the strength of mineral-C interactions. We applied ramped thermal oxidation to subsoil B horizons with different mineral-C associations to separate OC according to increasing temperature of oxidation, i.e. thermal activation energy. Generally, OC released at lower temperatures was richer in bioavailable forms like polysaccharides, while OC released at higher temperatures was more aromatic. Organic carbon associated with pedogenic oxides was released at lower temperatures and had a narrow range of 14 C content. By contrast, N-rich compounds were released at higher temperatures from samples with 2: 1 clays and short-range ordered (SRO) amorphous minerals. Temperatures of release overlapped for SRO minerals and crystalline oxides, although the mean age of OC released was older for the SRO. In soils with more mixed mineralogy, the added presence of older OC released at temperatures greater than 450°C from clays resulted in a broader distribution of OC ages within the sample, especially for soils rich in 2: 1 layer expandable clays such as smectite. While pedogenic setting affects mineral stability and absolute OC age, mineralogy controls the structure of OC age distribution within a sample, which may provide insight into model structures and OC dynamics under changing conditions. This article is part of the Theo Murphy meeting issue 'Radiocarbon in the Anthropocene'.
  • Quantifying Relevant Time Scales of Soil Carbon Cycling Through Long-Term Modeling and Novel Fractionation Techniques
    Item type: Doctoral Thesis
    Stoner, Shane (2023)
    Globally, soil organic carbon (C) is a large, diverse, and dynamic pool. The complex mechanisms that control the timescales of C persistence in soil are still not fully understood. Quantifying the sensitivity of soil C pools to climate and land use change is critical for predictions of future ecosystem response. More comprehensive understanding requires a set of methods to characterize C persistence in the context of soil processes. By combining laboratory methods and models that describe soil C dynamics with radiocarbon (14C), a powerful tracer, this thesis seeks to broaden knowledge of controls on soil organic matter (SOM) dynamics. In Chapter 1, I provide a general introduction to the challenges and uncertainties facing soil C science under changing climate. I then describe current methods for separating SOM along functional boundaries that determine its persistence and describe how various soil minerals act as strong controls on SOM cycling, as well as a recent thermal analysis method for resolving the ages of C in various soil “pools”. Applications of 14C and soil C modeling are laid out as powerful tools for tracing biogeochemical processes and testing hypotheses. Finally, the conceptual framework and research questions of this thesis are described. To begin addressing these research questions, in Chapter 2 I analyze long-term soil archives at the Winchmore Irrigation Research Station in New Zealand. Two-pool soil models are constrained with nearly 60 years of annual SOC and 13 discrete 14C measurements over the duration of the experiment. Two experimental pasture production trials were investigated: an irrigation trial and a phosphorus fertilizer trial, each with respective controls and two levels of treatment. Previous analysis had shown that intensification of management increased pasture production, and thus C inputs, but C concentrations in soil had increased at a consistent rate in all trials over the course of the experiment. By applying 14C constraints and calculations of C transit times in each system, I observe that greater inputs were more rapidly respired so that the time to respire 50% of inputs decreased from 6 - 7 years to about 4 years, and that consistent storage of 0.18 to 0.22 T ha-1 yr-1 of C was stabilized in all trials over longer timescales. Management did not influence the processes causing long-term C accumulation in these topsoils. In Chapter 3, I adapt and develop a laboratory method for separating SOM into pools with diverse controls on C persistence. Thermal fractionation is a relatively new method that applies ramped heating as a proxy for increasing activation energy input to break SOM bonds. The resulting profiles of C release describe thermal stability as a proxy for biogeochemical stability in soil. In addition, discrete 14C measurements associated with pools of C released across temperature reveal the age of C “fractions” with varying stability. To test the capacity of this method to capture the range of 14C contents in SOM, I thermally fractionate bulk soils as well as component density and chemical residue fractions. All samples released older C at higher temperatures. In topsoil, free and occluded particulate SOM fractions were found to be young (0 - ~100 years) and fairly homogenous in 14C content while mineral-associated SOM, containing 85% of total C, contained both recent (post- 1950) and centuries-old C. However, the mineral-associated fraction in subsoil was much older and more homogeneous in age. Results confirm that soil mineral characteristics have strong effects on persistence, and that thermal fractionation can be an effective tool for precisely resolving SOM age structure. Due to overlapping activation energies and varying 14C contents between density fractions, I recommend removing particulate SOM from mineral-associated SOM prior to thermal fractionation. In Chapter 4 I expand my investigation of soil mineral effects on SOM persistence across a broader set of soil types. Specifically, from subsoil B horizons where minerals play a more dominant role than in topsoils. Mineralogies are classified by the minerals that act as dominant controls on C dynamics in each soil, including metal oxides, primary minerals, clays, and quartz sand. Mineral-associated SOM fractions were thermally fractionated to highlight mineral effects on thermal stability and 14C age distribution. I found that soils without 2:1 layer clays showed mostly similar, relatively low thermal stability, while 2:1 clay-bearing soils showed a distinct C pool that was more thermally stable. I observed that 14C contents varied less in samples without 2:1 clay, while those with 2:1 clay minerals had similar pools of younger and older C relative to the average. I concluded that the age structure of SOM bound to soil minerals is dependent on the clay-sized minerals present. The assessment of soil C age structure was combined with an analysis of SOM chemistry in each thermal fraction using pyrolysis gas chromatography / mass spectrometry (py-GC/MS) to identify the influence of minerals and SOM chemistry on persistence. Soils with limited stabilization capacity released only labile (recently added/sequestered) polysaccharides and (older, more resilient) aromatic compounds. Highly diverse SOM was found in soils containing amorphous “short- range order” (SRO) non-crystalline oxides. Nitrogen-bearing C, known to form strong SOM-mineral bonds, was detected in soils containing SRO minerals and 2:1 clays, the latter of which corresponded to high activation energy and older C ages. I concluded that the absolute age of soil C is determined by the factors controlling soil processes, but soil minerals influence the range of cycling timescales and type of C that can persist in soil. In Chapter 5, the fundamental aspects of the previous three science chapters are discussed in the context of how the presented findings help to answer overarching research questions. I introduce future avenues of research to further our knowledge of C dynamics and persistence in soil and suggest a “proof-of-concept” approach that builds on laboratory and modeling methods advanced in this thesis to bridge the gap between laboratory “fractions” and model “pools”. By interpolating 14C and C data collected during thermal fractionation, one can estimate continuous, mass- weighted distributions of 14C that can be compared with, and potentially act as a constraint on, model outputs. Refinement of this method is an important step forward in conceptualizing, characterizing, and calculating SOM dynamics. Further advancement of these tools will serve to predict the amount and rate at which soil C responds to global change in coming decades and centuries.
Publications 1 - 8 of 8