University Programs

REU Projects

At the University of Arizona, we are building a program to bridge the gap between laboratory- and field-scale studies by utilizing the unique infrastructure of Biosphere 2. Biosphere 2 offers unique opportunities for the exploration of complex questions in Earth sciences because of its ability to combine varying scales, precise manipulation and fine monitoring in controlled experiments. By building upon the large external scientific network at the University of Arizona in hydrology, geology, geochemistry, ecology, biology, physics, engineering and atmospheric sciences, we are developing a strong multidisciplinary team of researchers who are undertaking the design and deployment of top-notch science to address complex questions in environmental sciences. Projects for 2018 REU students include:


Ecosystem Science, Renewable Energy Production, Food, and Water Sustainability

Greg Barron-Gafford, Department of Geography and Development, and Biosphere 2. External forces (like environmental and human factors) and internal characteristics (like plant ecophysiology) determine where species can live and thrive. This nexus is critical for tackling one of the greatest challenges facing our future - how to simultaneously maximize renewable energy production and food production without degrading the environment. The "Agrivoltaics" installation at B2 blends renewable energy production from solar photovoltaics with agriculture to study the impacts of this novel approach on plant function, water use, and biomass production.


Abiotic Effects and Dynamics of Woody Plant Cover

David Breshears, School of Natural Resources and Environment. Gradients of woody plant cover, which can span from grassland to forest, inspire questions about abiotic effects of woody plants and responses to changes in climate or land use. Projects could include assessments of changes in near-ground microclimate conditions associated with different densities of woody plant cover, spatial variation in dust production as a function of woody plant cover, and/or plant water stress preceding tree mortality along vegetation gradients. Approaches include hemispherical photography and computational assessments of solar radiation regimes, measurements of dust production using a variety of instruments, and/or measurements of plant water stress and related physiological metrics.


Coupling Subsurface Biogeochemistry to Critical Zone Evolution

Jon Chorover, Soil, Water and Environmental Science Dept. Chorover’s lab provides opportunities to investigate (bio)geochemical aspects of the CZO, including work at one of two sites within the UA CZO: Santa Catalina Mountains (AZ) and Jemez River Basin (NM). Students would couple field work and laboratory studies to understand subsurface biogeochemical processes and their interaction with Critical Zone ecohydrology, stream water dynamics, and landform evolution.


Mineral Weathering, Soil Formation and Carbon Sequestration as Influenced by Water Flow and Biota

Katerina Dontsova, Biosphere 2. Projects at B2 would focus on soil formation processes and development of subsurface heterogeneity through hydrologic-geochemical coupling using direct measurement and geochemical modelling: what happens in the basalt covering LEO slopes as a result of water flow and biological activity; what is the role of slope position, water residence time, and microbial activity on total weathering, chemical denudation, formation of high surface-area secondary solids, and accumulation of organic and inorganic carbon.


Microbial Ecology in Semiarid Ecosystems

Rachel Gallery, School of Natural Res. and Environment. Ecological mechanisms controlling maintenance or loss of terrestrial biodiversity may hinge on cryptic interactions among microscopic members of the soil community. REU students would investigate the microbial symbioses of plants in natural and managed ecosystems of the Sonoran Desert. Approaches include environmental metagenomic identification of native plant root microbiomes, quantification of microbial biomass, and potential exoenzyme activity of bacteria, archaea, and fungi in soils. Applied research examines the efficacy of microbial amendments to reduce invasive species encroachment and reverse the trend of declining native plant biodiversity in the US Southwest.


Watershed Hydrobiogeochemistry

Jennifer McIntosh, Department of Hydrology & Atmospheric Sciences. McIntosh, Co-PI on UA’s NSF CZO project, studies surface water-groundwater hydrology and biogeochemistry. Students doing field and lab work would generate chemical and isotopic data to understand hydrologic and biogeochemical processes. Questions include: what is the influence of bedrock geology on chemical and isotopic signature of waters? How do water transit time, flowpaths, and watershed area influence water quality? How do forest fires affect routing and quality of water?


Microbe-mediated Exchange of Trace Gases between Soils and the Atmosphere

Laura Meredith, School of Natural Resources and Environment. Trace gases make up a small fraction of atmospheric composition, yet play a significant role in climate as greenhouse gases (e.g., methane, carbon dioxide) and in microbial metabolism (e.g., hydrogen as a fuel for life). My research focuses on the interactions between microbes in the soils and trace gas cycling. Example research questions at Biosphere 2 include: 1) Do microbial communities rely on trace gas “fuels” such as hydrogen and methane to pioneer harsh, low nutrient environments? 2) Which biomes in Biosphere 2 are greenhouse gas sources and which are sinks, and how is this explained by variations in the soil microbial communities? The student(s) involved in this project will have the opportunity to work with methods in microbial genomics, bioinformatics, and analytical atmospheric chemistry in various biomes and experiments within Biosphere 2.


Developing, Improving, and Testing a Computer-based, Terrestrial Integrated Modeling System (TIMS)

Guo-Yue Niu, Department of Hydrology & Atmospheric Sciences, and Biosphere 2. TIMS focuses specifically on the interaction between hydrological, microbial, geochemical, geomorphological and ecological processes at the Earth’s land surface. TIMS takes advantage of existing state-of-the-art community models (e.g., CATHY and Noah-MP) and couples states and fluxes between the models to study interaction and feedback. TIMS is being developed using an experimentation-model learning cycle, so that new data derived from B2 physical models, e.g., LEO and the rainforest, can help us improve our understanding and parameterizing of fundamental processes.


Interaction of Landscapes, Pedogenesis and Mass Fluxes

Craig Rasmussen, Soil Water and Environmental Sciences Department. Landscape scale variation in chemical and physical weathering has emerged as a key modulator of terrestrial biogeochemistry. In particular, CO2 consumption associated with mineral weathering and the interaction of this process with pedogenesis and erosion appear to be significant factors controlling long-term patterns in atmospheric CO2 concentration. Weathering and mass flux are hypothesized to vary predictably with landscape position and climate forcing. Testing of this hypothesis involves quantifying the mass flux of elements such as Na and Si from soil profiles located at various landscape positions in the Santa Catalina Mountains using field sampling, laboratory analyses, and data synthesis.


Water Transit Time at Catchment Scales

Peter Troch, Department of Hydrology & Atmospheric Sciences, and Biosphere 2 (Science Director). Troch studies catchment scale hydrological processes via advanced measurement, modeling and synthesis to 1) Develop, test, and apply advanced observation methods for hydrological fluxes and states at a range of spatial and temporal scales; 2) Develop hillslope-to-catchment scale hydrological models for water and solute transport; 3) Understand hydrological synthesis at the catchment scale with special attention to extremes; 4) Determine effect of scale on co-evolution of hydrological and geochemical processes. Findings contribute to improved water resources management in light of climate change and other human influences. Students can work on water transit time estimation using stable isotope data from rain and streamflow samples combined with field and lab work including running the laser spec, and mathematical modeling of flow and transport processes at catchment scales using both LEO and CZO watersheds.


Using Satellite Remote Sensing to Assess the Climate Sensitivity of North American Grasslands

William Smith, School of Natural Resources and Environment. Climate change forecasts of warming and increased multi-scale precipitation variability are expected to significantly impact grassland vegetation dynamics. Current evidence suggests that warmer temperatures will increase aridity (irrespective of changes in precipitation) and reduce soil moisture availability, with cascading effects on ecosystem structure and function. Yet, the effects that increased multi-scale precipitation variability will have on the dynamics and resilience of grassland ecosystems, and whether these effects will be magnified by warming, remain largely unknown. The student(s) involved in this project will have the opportunity to work with cutting-edge climate and remote sensing datasets to explore questions aimed at improving our understanding of the climate sensitivity of North American grasslands. Research questions may include: 1) How do the timing and intensity of drought events impact grassland productivity and variability? 2) How is climate change impacting the resilience of grassland ecosystems regionally? 2) Are CO2 fertilization effects changing grassland precipitation sensitivity over time? 4) How is climate change impacting the frequency of disturbance events (e.g., fire) across grassland ecosystems?


Tropical Forest Dynamics and Trace Gas Fluxes

Joost van Haren, Biosphere 2. Tropical forests are among the most dynamic ecosystems in the world, but their responses to climate change are uncertain. B2 provides an opportunity to study tropical ecosystems under future conditions (increased temperature, decreased precipitation); the large enclosure and artificial rainfall allows precise determination of water and carbon movement through the biome. Students use the B2 tropical forest to assess plant, hydrological, and carbon cycling responses to altered temperature and precipitation.


Tracing Water and Carbon Fluxes through Stable Isotope Analysis

Till Volkmann and Peter Troch, Biosphere 2. Stable isotope analysis provides a powerful and increasingly used tool for tracking water and carbon through soils, plants, and atmosphere. By monitoring the small variations in molecular mass of water and carbon dioxide in space and time, we can gain new understanding of interacting water storage and flux-partitioning, biogeochemical weathering, and plant functioning as driven by the environmental conditions. Students would have the opportunity to work with state-of-the-art laser spectroscopic instrumentation for water and carbon dioxide isotope analysis within the framework of the Landscape Evolution Observatory (LEO) at B2. The project would involve experimental work as well as analysis and interpretation of data from unique observational systems in highly-controlled experimental set-ups with the overall goal to obtain new insights into the origin, pathways, and physicochemical reaction processes of water and/or carbon dioxide in the landscape’s atmosphere, subsurface, and discharge conduits.