Indy Burke, Global Change Effects on Nitrogen Cycling Along a Temperature Gradient in the US Central Grasslands

important ecosystem services, such as soil carbon storage and forage for livestock grazing. Grasslands are both water and nitrogen limited, making rates of plant growth and decomposition slow. Because of this, these ecosystems may be particularly vulnerable to the effects of global change (e.g., warming and nitrogen deposition). Grasslands exist across a range of climates, which could further complicate the response of these systems to global change. For example, we hypothesize that a site with a historically cooler climate may be less adapted to rising temperatures and will lose more soil carbon because of elevated rates of decomposition. However, we have a more limited understanding of how the nitrogen cycle in grasslands may shift in response to global change across different climates. This project investigates the role of historical temperature in influencing nitrogen cycle shifts in response to future warming and nitrogen deposition in grassland ecosystems. We have six field sites set up along a latitudinal gradient on the western edge of the US Central Grasslands. Field sites are in Texas, New Mexico, Colorado, Wyoming, and Montana. Each site receives roughly the same amount of mean annual precipitation and has similar soil characteristics and vegetation. However, these sites span a large temperature gradient, with the Texas site having a mean annual temperature of 25℃ _and the Montana site having a mean annual temperature of 2.5℃. Last year, a doctoral student in the School of the Environment established an experiment where each site has plots with control, warmed, elevated nitrogen, and warmed + elevated nitrogen treatments. For this project, the undergraduate researcher will accompany this doctoral student in the field and estimate rates of net nitrogen mineralization across treatments along the gradient. The student would place ion exchange resins at the start of the growing season at each site, which would estimate changes in inorganic nitrogen levels under the different treatments. These results could have important implications for understanding how global change may affect nutrient limitation and ecosystem function in grasslands across large spatial scales. Applicants should be comfortable working outside for extended periods of time and flexible to changing conditions. This project would provide an opportunity to travel around the American West, interact with important stakeholders (i.e., environmental nonprofits, federal agencies, private landowners), and gain valuable field research experience in ecosystem ecology.

Locations: Marfa, TX; Milnesand, NM; Lamar, CO; Nunn, CO; Bill, WY; Sun Prairie, MT

Liza Comita, Insect Herbivory and Tropical Rainforest Recovery

Description: The Comita Lab is looking for an enthusiastic undergraduate student to join our research project on the role of natural enemies in the recovery of tropical rainforests in Panama. This field project will be part of a large research study investigating the effect of insects and fungi on tree community assembly during the secondary succession of tropical rainforests. The student will measure variation in insect herbivory on seedlings in a field experiment at seven forest sites within the Panama Canal watershed. These forest sites represent different stages of forest recovery after human disturbance (10, 50, 70, 100 years since agricultural abandonment). In each site, the student will conduct an observational measurement of the amount of insect herbivory in existing vegetation plots that either exclude or include insects. The results of this project will help promote our understanding of whether herbivory varies with forest successional age and across plant species and how such variation may affect the seedling community during forest recovery. The student will work alongside our local field crew and with a postdoc and students from the lab, who will guide and support the student in conducting their research. Nonetheless, a certain degree of independence is expected, and field work will take place under challenging conditions (heat, insect bites, walking through dense forest understory). During the eight weeks of the SURES internship the student will be able to visit and explore different tropical forest sites, to develop an understanding of experimental design for field studies, to work with an international team, and to gain experience with ecological field methods. We will support the student during data analysis and writing and encourage the student to use the results of this project (on their own or in combination with results from additional measurements) to prepare and/or contribute to a scientific publication. The student will be based on Barro Colorado Island in Panama, a research station run by the Smithsonian Tropical Research Institute. Living and working at the research station offers a fantastic opportunity to interact with researchers from all over the world working on many different topics. This is a stimulating place to develop ideas for future research and a fantastic opportunity to get research experience in one of the most diverse ecosystems on Earth.

Location: Panama 

Jenn Coughlan, Finding the Genes Underlying Climate Resiliency in a Widespread Herb 

Description: Current climate models predict more extreme and variable temperature and precipitation regimes, and hotter, more extreme droughts are a leading cause of widespread forest mortality. Despite their central role in plant ecological adaptation, potential variation in complex physiological processes such as drought tolerance are rarely surveyed at a population level. Furthermore, we know very little about either the genetic basis or potential plasticity of plant drought tolerance. This is problematic, because if and how species will adapt to climate change depends in large part on the amount and distribution of genetic variation for ecologically relevant traits. We seek a motivated undergraduate to help us bridge global ecology and evolutionary genetics by exploring the genetic architecture and within-species variation of plant drought tolerance, a trait that is predicted to be a key factor in determining a species climate using a widespread herb that is also an emerging “model system” for plant ecological adaptation and evolutionary genetics. Tasks will include helping to set up, monitor, and organize a large-scale common garden experiment, measure several phenological, morphological, and physiological traits, as well as the potential for DNA extractions and molecular work.

Location: New Haven, CT

William Lauenroth, Examining the Effects of Altered Precipitation on Phenology and Productivity in Big Sagebrush Plant Communities

Description: Shifts in regional weather patterns caused by climate change are straining plant communities. Dryland plant communities are particularly sensitive to shifts in precipitation due to their dependence on soil water availability. Interannual fluctuation of precipitation patterns can have immediate impacts on the productivity and composition of dryland plant communities. Herbivory complicates this response and, even though drylands are resistant to low levels of grazing, livestock densities can exceed the resistance threshold of local plant communities. This can lead to herbivore-induced compositional shifts and, in some cases, shifts to a low productivity state. Livestock grazing also may interact with climate change shaping the response of dryland plant communities. Despite this possibility, there are few experimental designs that examine the individual and interactive effects of variable grazing pressure and projected shifts in precipitation. To address this gap our study focuses on intermountain big sagebrush (Artemisia tridentata Nutt.) plant communities in the southern most portion of the Greater Yellowstone ecosystem. This area is a crucial migration pathway for mule deer (Odocoileus hemionus) and pronghorn (Antilocapra americana), while providing large stretches of habitat for sage grouse (Centrocercus urophasianus) and a host of other wildlife. It also serves as important summer and spring forage for cattle ranching operations in the basin. Big sagebrush plant communities are resistant to short-term climatic fluctuations but begin to experience phenological and demographic shifts after multiple years of treatment (e.g. drought and irrigation). We are currently simulating predicted increases in spring precipitation with targeted water additions over a grazing intensity gradient around livestock water points (wells) to test whether regional climate futures and grazing management decisions interact and impact the stability of big sagebrush plant communities threatening an important forage source for animals migrating through the GYE and livestock, a large economic component of the region. This design addresses two objectives. (1) To understand how livestock grazing and regional climate change in dryland plant communities effect phenology and species interactions of a dryland plant community. (2) To address the consequences of livestock grazing and climate change on productivity and the timing/quality of forage. The student selected for this project will gain experience sampling plant communities, NDVI and soil moisture. The student will have the ability to design their own project that answers a question related to the study topic. We have multiple years of camera trapping, climate, and plant composition data available for analysis.

Location: Pinedale, Wyoming 

Xuhui Lee, Temperate Forest Ecology Using Drones and Ground Surveys

Description: We are initiating a long-term study of temperate liana (woody vine) impacts on tree growth, carbon storage, and other forest metrics using high resolution drone imagery and lidar, ground surveys, and weather sensors. We anticipate tangential studies on methods and procedures for drone-based forest surveys, particularly at Yale Myers Forest in Connecticut. We will be conducting surveys and setting up liana removal experiments this summer (May–July 2024), starting with training and methods testing at Yale Myers, before traveling to West Virginia, Virginia, and the Coastal Plain of Maryland (location TBD). Field work will consist of traveling to and briefly scouting 4–5 proposed sites, mapping these sites with a multispectral camera and lidar, establishing field inventory plots (~20 15-m circular plots), conducting tree and liana censuses (ID, measurement), and finally conducting a random treatment of lianas (cutting all lianas on half of plots with liana presence). Students with an interest in forestry, forest ecology, botany, sampling methods, remote sensing, image classification, and/or GIS are encouraged to apply. There is potential for student assistants to be co-author on publications and receive additional training in remote sensing (image processing, analysis, and presentation) from this project.

Locations: Yale Myers Forest, remote Appalachia sites (near Parsons, WV), and Delmarva Penninsula (near Chestertown MD)

Martha Muñoz, Discovering the Physiological Diversity of Carribean Rain Frogs

Description: Ongoing climate change presents an existential threat to biodiversity, but these threats are especially pronounced in amphibians (e.g., frogs and salamanders). As wet-skinned ectotherms, amphibians are highly vulnerable to changes in both temperature and moisture. Rain frogs (Genus Eleutherodactylus) are highly diverse, with dozens of endemic species found across the Caribbean. Yet, we know very little about the natural history and ecophysiology of these species, which are critical pieces of information needed for forecasting the vulnerability of these frogs under global change. The YIBS SURES student(s) will participate in an ongoing research project on the ecology and evolution of Eleutherodactylus frogs. First, students will join an expedition to the Dominican Republic where they will participate in field work on these frogs. They will collect ecological, behavioral, and environmental data while working in several natural preserves across the country. They will assist with physiological assays on the frogs, including estimation of water loss rates, metabolic rates, and heat tolerance. Then, they will come back to the lab at Yale, where they will learn how to extract and sequence DNA so that a phylogenetic tree for the Eleutherodactylus frogs can be built. Students will learn how to perform phylogenetic analyses. Through this project, the students will develop field, laboratory, analytical, and programming skills.

Locations: Dominican Republic and New Haven, CT

Alan Rooney, Defining the Pattern of Paleozoic Oceanic Anoxic Events (OAEs)

Description: The co-evolution of Earth and life are recorded in the biological and geochemical history of our planet. Major perturbations in the Earth system are recorded as extinction/biodiversity crises and these events typically coincide with major upheavals in the geochemical cycles of the ocean-atmosphere-biosphere system. More than two dozen of these combined biogeochemical events have been identified from the Phanerozoic (the past 540 million years) record, typified by major positive excursions in the d13C record of the ocean-atmosphere system, and they have become the central foci of how geoscientists study the evolution of the Earth-Life system. A nearly identical relationship between biotic crisis, major positive carbon isotope excursions, metal toxicity, and expansion of anoxic to dysoxic environments has been documented from several such events. Unfortunately, these events are often investigated on an event-by-event basis and potential similarities between events remain under-evaluated. The primary objective of this proposal is to determine if enhanced deposition of critical elements is a consistent feature of major Paleozoic biogeochemical events. The second major objective is to evaluate the cause(s) of perturbations in marine elemental cycling. For example, was enhanced deposition of critical elements primarily driven by external inputs to the ocean (e.g., volcanism), or by enhanced delivery to the sediment column via productivity or enhanced redox scavenging. Answers to these questions will allow us to address our third, and perhaps most fundamental question, which is: What role, if any, perturbations in major- and trace-element cycling played in each biogeochemical event. This fellowship will dovetail into this large, multi-institute proposal and will interact with both PIs and visit labs at Yale to learn clean-lab and mass spec techniques as they assist with this project. Clean-lab chemistry skills acquired will be applicable to both academic and industry jobs. Overall, this will provide opportunities to independently design experiments, implement, and prepare geochemical samples for analyses. Carry out isotope analysis in the Yale Clean Lab facilities, compile, analyze, and interpret scientific data/results related to Earth history. Log and sample archived geological rock core based on distinct sedimentological characteristics and stratigraphic framework.

Locations: Iowa City, IA and New Haven, CT

Jessica Thompson, Analysis of Animal Bones from African Stone Age Archaeological Sites

Description: The Malawi Ancient Lifeways and Peoples Project (MALAPP) is a paleoarchaeology/ paleoecology project based in Malawi, southern-central Africa. The central research aims are to reconstruct ancient environments and hunter-gatherer behavior in the region over the last 30,000 years, as the last Ice Age cycle gave way to present environmental conditions. The project involves identification and analysis of subfossil (old, but not all the way fossilized) animal bones from archaeological sites in northern Malawi. The sites contain records of human occupation and environmental change (documented by artifacts, fossils, and occasionally also human skeletal remains), and have yielded some of the most ancient human DNA in Africa. Applicants can view more information and videos/images and media about the field sites and previous research results here: https://campuspress.yale.edu/jcthompson/malawi-ancient-lifeways-and-peoples-project/

In this project, the student will learn how to identify animal bones from archaeological sites, and learn how to collect data from them that can be used to answer the question: How did these bones get to the sites, and what can they tell us about ancient human behavior? The fossils are the property of the Malawi government and must be returned in excellent condition after their study. Therefore, the student should be ready and excited to undertake an authentic research experience on a real research collection, under the supervision of Dr. Jessica Thompson, who is an expert in human evolution and the analysis of archaeological animal remains. They should be prepared to do a variety of tasks in the Yale Paleoarchaeology Lab, including the preparation of bones for analysis, entry of data into databases, and curation of physical specimens after analysis is complete.

Location: This project is based entirely at the Paleoarchaeology Laboratory in New Haven, CT. 

David Vasseur, Validating a New Measure of Extinction Risk 

Description: Forecasting the risk of warming and temperature variability on species is of paramount importance. Recent work in my lab has developed a new measure of extinction risk that uses thermal performance curves (relationships between ambient temperature and fitness or a fitness proxy) to determine two key quantities that regulate extinction risk: the mean population growth rate and the variance of population growth rate. For any species that has a documented thermal performance curve, we can use this measure to assess its likelihood of extinction in current, historical, or future environments. YIBS SURES student(s) will take a central role in two key projects. The first project will use laboratory experiments to assess the utility of this extinction risk measure. Briefly, we will grow replicate populations of aquatic microbes (mainly rotifers and ciliates) across a range of different temperatures and subject them to different amounts of thermal variation. We will compare observed extinctions to our forecasted risk to validate its utility. In a second project, we will scour the literature for experiments that have examined the effects of temperature on population growth and extinction risk and use these sources as an addition means of evaluating the utility of our risk estimate. This project will allow students to develop basic laboratory skills for culturing and assaying microbial populations through to the statistical analysis of experimental and literature-based experimental data. Students will also develop the quantitative skills (analysis, programming, etc.) needed to generate risk forecasts for species.

Michelle Wong, Plant Root Exudates in Northeastern Temperate Forests 

Description: Forests play a critical role in the global carbon cycle by sequestering approximately one-third of anthropogenic carbon emissions from fossil fuels and land-use change annually. However, global change drivers – such as rising atmospheric carbon dioxide levels and warming – may be altering the carbon cycle balance in many northeastern forests. Specifically, indirect evidence suggests that more carbon is moving through plant roots and into soils as root exudates, potentially leading to soil carbon losses through increased microbial activity. The quantity of root exudates released by plants remains the largest unknown carbon flux in forests, and it is unclear what factors control the flux of root exudates. To address this large knowledge gap, the undergraduate fellow will have the opportunity to: 1) conduct a greenhouse experiment testing elevated carbon dioxide, nutrient availability, and warming on plant root exudate fluxes, and 2) participate in a two-weeks field campaign at Hubbard Brook Experimental Forest in New Hampshire with a larger team measuring root exudates. The undergraduate fellow can contribute to taking care of the plants in the greenhouse and assist with developing methods to capture and quantify root exudates and microbial enzyme activity in the greenhouse and the field. In summary, the undergraduate fellow will be able to carve out their research question of interest; learn lab, field, and project management skills; conduct data analysis and interpretation; and collaborate with a larger team.

Location: New Haven, CT and Hubbard Brook, NH 

How to apply

The application process for 2024 will open on February 6th, 2024. Applications are due no later than March 4th, 2024 at 11:59 PM (Eastern). For any questions or concerns regarding the application process contact yuji.torikai@yale.edu