Reconstructing past climatic impacts on hydrologic and soil systems
To formulate rational environmental policies for the future we must understand the past. Linking conditions in modern and ancient systems allows us to assess future and paleoenvironmental responses to climate.
Jay Banner’s laboratory explores: (1) the application of modern hydrologic, geologic and soil conditions, determined by monitoring, to Pleistocene and Holocene mineral deposits in caves (speleothems; Pape et al. 2010); and (2) the impacts of urbanization on streamwater quality through novel tracers (Christian et al., 2011). Speleothems can be precisely dated and incorporate tracers that preserve decadal to millennial-scale records of water quality and quantity (Banner et al., 2007). REU researchers can investigate: (1) the physical and chemical parameters of cave hydrology and meteorology and how speleothems reflect past climate, or (2) the natural and anthropogenic sources of dissolved ions to streams. They will learn methods for low-contamination field and clean-room sampling and mass spectrometer analysis of water, soil, and rock. Speleothem studies in Texas afford a regional analysis of paleorainfall across abrupt climate change events during the late Pleistocene, in a region of particular climate sensitivity (Feng et al., 2014a). Studies on Guam can help define paleorainfall and present aquifer conditions near a growing U.S. military base on a water-limited (although not arid) Pacific island.
Daniel Breecker and Todd Caldwell will mentor students in interdisciplinary projects that combine isotope geochemistry and soil physics. The objective will be to understand soil carbonate (CaCO3) formation and its impact on ecosystem health and resilience. Geographic expansion of carbonate-bearing soils may be a consequence of aridification or an increase in extreme precipitation events. Our results will 1) elucidate the effects of soil CaCO3 accumulation on soil hydrology, pH and organic matter and 2) improve paleoenvironmental reconstructions based on paleosol carbonates. We will grow CaCO3 in experimental ‘sandboxes’ in which temperature, pCO2 and water contents are monitored and manipulated. These data will test models of chemistry and water and gas transport used to simulate soil CaCO3 stability (e.g., Meyer et al., 2014). Temperature, water content, clumped and stable C and O isotope compositions and O2/CO2/Ar will define CaCO3 stability for comparison with models. REU researchers can conduct proof-of-concept experiments, sampling and analysis of soil gases and water, data assessment and interpretation, and dissemination of results.
Tim Shanahan’s group uses organic geochemical and stable isotopic techniques (biomarkers) to reconstruct past climate and environmental changes in a variety of hydrological settings (lacustrine, terrestrial). Shanahan’s REU researchers would be involved in research on sites ranging from the high Arctic to the tropics, and on Holocene to orbital timescales. New studies of Holocene and late-glacial lake deposits and paleowetlands in the southwest US provide local field opportunities and represent an archive of past climate conditions in the southwestern United States that integrates changes in climate, vegetation, fire disturbance and hydrology. Hands-on laboratory experience will involve the extraction and purification of organic compounds for analysis by state-of-the-art GC and HPLC mass spectrometry.
Climate Change Impacts on Ecosystems
Earth’s biological systems are changing in response to shifts in temperature and precipitation patterns and amounts. REU researchers will study the ecological interplay of symbionts, natural and invasive species, and fire with changes or gradients in climate.
Christine Hawkes’ lab will mentor students in plant and microbial responses to climate change and impacts on biogeochemical processes. The soil and plant microbiome are critical to how carbon flows through ecosystems and how this will feed back to climate change through the balance of ecosystem carbon storage vs. loss. In addition, plant symbionts are key mediators of plant drought responses, which are important for maintaining productive agriculture in a drier future. We use a wide array of genes-to-ecosystems approaches to integrate plant and microbial community patterns with biogeochemical processes, ranging from metagenomics to microbial physiological measurements. REU projects on plant, microbial, and carbon cycling responses to water availability can leverage our 10 years of research across a rainfall gradient or our ongoing rainfall manipulation experiments.
Undergraduate students in Shalene Jha’s lab will learn to implement vegetation and insect surveys, use microscopy to study pollen usage, and develop cutting edge spatial mapping methods across rainfall and soil gradients. Two senior honors thesis projects in Jha’s lab are typical of the types of research REU students might undertake. The first developed geospatial-supervised techniques for the classification of human-altered land-use types in central Texas. The second project investigated pollen preferences for native solitary bees across Texas by examining pollen load composition via high-powered microscopy.
Norma Fowler’s research group studies the effects of wildfire and the use of prescribed fires to reduce the risk of wildfires. As the climate of the Western US warms, plant transpiration rates will rise, which by itself will increase drought stress and lower plant moisture content. It is now thought likely that annual rainfall will decrease in this region. Both warming and precipitation decreases will increase the likelihood and intensity of wildfire. REU students may participate in one or both of two projects. (1) A study of recovery trajectories after 2011 wildfires in the Lost Pines region of central Texas. Of particular interest is the post-fire balance between loblolly pine (Pinus taeda), the former dominant, and sand post oak (Quercus margaretta), which may become dominant. (2) A study of prescribed fire to control an invasive grass, King Ranch bluestem (Bothriochloa ischaemum) and reduce the danger of wildfires.
Mathew Leibold’s lab focuses on how communities and ecosystems respond to perturbations and change. We focus especially on pond ecosystems that can be easily studied in the numerous small ponds that serve as water sources for wildlife and livestock and can be replicated in mesocosm experiments. REU student research could focus on the effects of drought and pollutants and interactions with food web structure. We study both short term pollutants that have strong pulsed (but not chronic) effects such as the pesticide chlorpyrifos and chronic inputs of pollutants resistant to biodegradation, such as mercury inputs from precipitation from coal plants. Droughts alter the food webs of these ponds by eliminating fishes and shifting predation to insects with consequent effects on pollutant degradation and retention/accumulation.
Rob Plowes at Brackenridge Field Laboratory (BFL) mentors students either working in the Invasive Species Research Program or on climate related ecological studies at the field station. The Invasive Species lab researches the causes and consequences of biological invasions, and tests opportunities for biological control of pest species applicable to the arid western and southern parts of Texas where climate plays a limiting role in species distributions. In other studies at the BFL field station, we follow several biological systems across time to determine relationships with weather patterns and environmental gradients.
Students working with Kelley Crews conduct research on spatio-temporal scaling of landscape change dynamics and dynamism, specifically resilience, health, and vulnerability of savanna systems. With over fifteen years of experience in the tropics, her research links remote sensing, Geographic Information Systems (GIS), and quantitative landscape ecology with fieldwork (vegetation sampling, carbon sequestration assessments, and household interviews) for environmental analysis of landcover/landuse change. For the last ten years Crews has concentrated her work in the Kalahari of Botswana, with particular attention to the western Kalahari semi-deserts and the Okavango catchment, both of which are extremely vulnerable to climate change impacts and concomitant management / use fluctuations.
Energy-water nexus and infrastructure adaptations
Climate change and increasing demand combine to exert pressure on hydrologic systems, many of which are already regulated for human needs such as drinking water supply, agriculture, energy production and energy use.
Mary Jo Kirisits’ research group will mentor REU students in one of several ongoing drinking-water projects. The first investigates the effect of climate change on water treatment practice at small drinking-water systems. The objective is to develop guidelines for small-system operators to account for temperature changes in their treatment systems. The second project involves rainwater harvesting (where rainwater is collected and treated for potable or non-potable use), which is becoming common practice in semi-arid regions. Our aim is to understand the role of the storage cistern in changing harvested rainwater quality. The third project involves emerging biological drinking water treatment systems and the goal is to decrease the energy and associated greenhouse gas footprint of centralized water treatment.
Lynn Katz and Kerry Kinney are engaged in two research projects focused on the reuse of water in semi-arid regions that are suitable for REU researchers. The first project is on the reuse of water from hydraulic fracking and oil production. This project involves the further development of a patented hydrophobic membrane technology for oil/water separation from produced, frac, oil spill and biofuel production waters. REU students will evaluate the membrane operation for a particular set of waters and operating parameters to support the development of a predictive model for this system. The second project is a collaboration with Pecan Street, a 501(c)(3) research and development organization focused on collecting data on consumer energy and water consumption. Students will be sampling and analyzing rainwater and air conditioning condensate at Pecan Street metered homes to assess the reuse of this water in semi-arid to arid climates.
Michael Webber’s research group analyzes energy and environmental problems at the intersection of engineering, science and public policy. The group emphasizes interdisciplinary issues by recognizing that sustainable solutions must also address environmental and public policy issues. Students in the Webber group complete research on the energy-water nexus, energy systems modeling, and alternative transportation fuels. Each of these topics can be linked to the impact of climate change and its effect on arid regions. As an example, researchers recently investigated the impact that rising water temperatures and water scarcity will have on power plants to maintain cooling performance. Undergraduate students will collaborate closely with mentors, attend group meetings, collect data, complete technical analysis, and possibly work on scientific communication projects such as educational videos.