Grant A. Harris fellowship (2014 recipients)


  • 2014 recipients

  • Troy Magney
    Troy Magney, University of Idaho
    Response of the photochemical reflectance index (PRI) to environmental stressor conditions for improved prediction of grain yield in wheat

    Ground-based remote sensing techniques have recently garnered wide interest from the agricultural community as a tool to track crop performance with high temporal (daily) and spatial resolution. To cope with a projected increase in temperature and periods of drought worldwide, growers and scientists could benefit from more readily available information about daily crop performance. A better understanding of crop response to environmental stress conditions using ground-based remote sensing platforms that collect and process data in real-time could lead to a more rapid and efficient method for targeting site-specific management practices at local scales; and further, provide valuable information for scaling plant reflectance spectra from the plot to the landscape scale via airborne and satellite sensors.

    One technique for gathering site-specific information on crop performance is via remotely sensed vegetation indices (VIs) such as the photochemical reflectance index (PRI). My work seeks to advance the understanding and interpretation of the PRI as a remote indicator of plant stress with specific application to improving our understanding of how different environmental stress conditions may impact grain quality and quantity.

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  • Michael Santiago

    Michael Santiago, Cornell University
    Microtensiometer to continuously monitor water potential in plants

    Water potential (Ψ) is the best measure of a plant’s hydration relative to growth and product yield/quality. Unfortunately, directly measuring Ψ in plant tissue is only possible through labor-intensive, destructive methods such as the leaf pressure bomb and stem psychrometer. A common alternative is to use ‘set-and-forget’ soil tensiometers to measure soil water potential (Ψsoil) as a proxy for plant water potential (Ψplant), but this method is unreliable for plants with high hydraulic resistance (e.g., vines and woody species) where often Ψplant << Ψsoil.

    Although very accurate and simple to use, tensiometers also have two drawbacks: they are large and bulky, and tend to cavitate in even slightly dry soils. My project involves using MEMS technology to develop a miniature tensiometer (microtensiometer) that overcomes these drawbacks and thus can be embedded in plant stems to directly measure Ψplant, is easily mass-manufactured, is stable for months, and communicates digitally.

    Now that we have a functional prototype, I will use the AquaLab 4TE dew point water activity meter to produce solutions of specific activity to test, calibrate, and characterize the microtensiometer. My intent is to improve the design of this sensor so it can be used in the field to, for instance, continuously monitor and control Ψplant in vineyards, and consistently produce high-quality wine grapes with an exact flavor/aroma profile.

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  • Melissa Stewart

    Melissa Stewart, University of Colorado at Boulder

    Physical modeling of the thermo-hydro-mechanical response of soil-geosynthetic interaction in thermally active reinforced soil systems

    Reinforced soil structures such as mechanically-stabilized earth (MSE) walls are a widely accepted method for grade separation in civil engineering, not only to allow more room for roads along highways but also to be more efficient in how space is used on private building sites. Traditional design of these structures calls for a select type of backfill which is free-draining to combat pore water pressures from developing in the system. These select backfills are not usually found on-site or readily available and can therefore be cost-prohibitive for some projects. Poorly-draining, marginal backfills such as silts and clays, which can be found on-site, have been used in some projects, though there are still some concerns over pore water pressure developing in the reinforced zone since the soils are not free draining.

    A novel method for controlling pore water pressure is to incorporate heat exchangers to cause thermally driven water vapor flow out of the reinforced zone. While this method has been shown to increase the strength of soils, it could have a negative effect on the geosynthetics, which are typically made of polymers that are susceptible to thermal changes. The objective of this research is to quantify the effects of temperature changes on the complex interaction between unsaturated, compacted soils and geosynthetics. In particular, the thermally induced water flow away from the heat exchangers will lead to changes in soil-geosynthetic interaction. A better understanding of changes in thermal properties and how these systems function is instrumental in determining the feasibility of thermally active reinforced earth structures.

    For this project, METER 5TM moisture probes will be used to evaluate changes in volumetric water content and temperature at discrete locations within a geosynthetic-reinforced soil layer during heat injection. Additionally, a METER KD2 Pro system will be used to determine non-isothermal relationships between the thermal properties of the soil and the degree of saturation. This set of instrumentation will be used to evaluate quantifying coupled heat transfer and water flow processes and related effects on the efficiency of geothermal heat in unsaturated soil deposits over time.

  • Kathleen Quigley

    Kathleen Quigley, Wake Forest University
    Modeling soil-plant-animal feedbacks to understand “hotspot” persistence in Serengeti National Park

    Physical and chemical properties of soils play a key role in mediating plant-herbivore interactions yet are often completely overlooked by ecologists. Serengeti “hotspots” are temporally stable swards of fast-growing, nutrient-rich grasses which attract populations of resident herbivores (zebra, gazelles) and generate heterogeneity within the ecosystem. Researchers have long been fascinated with hotspots but remain unable to explain the creation, maintenance, and spatial distribution of these unique microhabitats.

    I will compare heavily grazed hotspots to neighboring non-hotspot sites and observe how specific soil characteristics vary with grazing intensity. I am especially interested in how the presence of grazers influences soil water potential and, ultimately, plant community composition and herbivore dynamics. Installing METER MPS-6 sensors and Em50 data loggers will allow me to monitor spatiotemporal variation in water potential in relation to grazing intensity. These data will serve as an integral component of a structural equation model (SEM) to provide a comprehensive mechanistic explanation for the persistence of Serengeti hotspots.

  • Manuel Helbig

    Manuel Helbig, Université de Montréal
    Impacts of degrading permafrost on vegetation productivity and thermal and moisture regimes of soils in boreal forest landscapes

    Boreal forest at the southern limit of the permafrost zone is especially vulnerable to a projected warmer climate. Widespread permafrost disappearance has been observed in northwestern Canada causing ground surface subsidence and a decline in forest cover. The resulting fragmented landscape is characterized by a high degree of spatial heterogeneity of soil thermal and moisture conditions as well as vegetation types.

    Boreal forests in the Taiga Plains in northwestern Canada store a large amount of frozen soil organic carbon. Current soil thaw exposes this organic carbon to microbial decomposition but might also increase carbon uptake through increased plant productivity. A better understanding of the magnitude and dynamics of these carbon fluxes is important to assess potential feedbacks on the global climate.

    In my doctoral research, I am using the eddy covariance technique and flux footprint models to study how the net exchanges of carbon, water, and heat between the land surface and the atmosphere are influenced by rapidly degrading permafrost. METER instrumentation allows continuous monitoring of vegetation status of the dominating land cover types and concurrent land cover type-specific monitoring of thermal and moisture dynamics. This information is essential to analyze integrated net ecosystem carbon dioxide exchange and its component fluxes gross ecosystem productivity and ecosystem respiration and to upscale these fluxes to regional scales.

  • Rebecca Lloyd

    Rebecca Lloyd, University of Montana

    Hydrological and ecological recovery after road removal: Influence of treatment design on ecosystem services

    Despite the millions of dollars invested in the removal and restoration of legacy forest roads on public lands, there is considerable uncertainty among managers about the most effective road decommissioning method—particularly for promoting recovery of high value ecosystem services such as quantity and quality of water, nutrient cycling, and forest productivity.  At the core of management uncertainty is a dearth of research related to understanding the mechanisms of recovery for coupled above- and below-ground hydrological and ecological processes.

    Because of the extensive road decommissioning and restoration efforts ongoing on the Nez Perce-Clearwater National Forest in north central Idaho, I have the opportunity to:

    1. Increase understanding of the role of soil, vegetation, and ecohydrological properties for restoring ecosystem function
    2. Assess whether recovery of soils, vegetation, and ecohydrological properties and functions vary with road removal method
    3. Develop integrated production functions to quantify how road removal may enhance ecosystem services, specifically quantity and quality of water and net primary productivity

    Location of Research: Lochsa Drainage, Nez Perce-Clearwater National Forest, Idaho County, ID.

  • Melanie Stock

    Melanie Stock, University of Wisconsin–Madison
    A winter water balance to investigate nutrient transport from manure during freeze/thaw events

    Phosphorus losses in agricultural runoff are a major environmental concern and thus are a key focus in manure management. Nutrient transport is sensitive to winter weather and the complex conditions of frozen soils, but as winter runoff generation and process-oriented information is limited, models and subsequent management guidelines are often not supported by data.

    To investigate winter nutrient transport on manured fields, my objectives include quantifying a water balance to elucidate the underlying freeze/thaw mechanisms that control soil infiltration potential. Soil permeability will be tested in till versus no till corn fields with fall versus late-winter manure applications and unmanured controls. I will monitor runoff volume and nutrient load, snow, frost, soil moisture, and temperature.

    Sublimation will be measured with VP-3 and DS-2 sensors and vertical soil water fluxes will be measured with MPS-2 water potential sensors. Data will inform prediction tools that evaluate nutrient loss from agroecosystems and improve agricultural sustainability by balancing environmental and economic viability.