REU Projects 2014

2014 project list:

Plant diversity and ecology (2 students) - Jason Sexton, UC Merced

Methane biogeochemistry and microbial ecology in high elevation lakes (1-2 students) - Michael Beman, UC Merced

Mammal diversity in Yosemite National Park (1-2 students) - Jessica Blois, UC Merced;  Sarah Stock, Yosemite National Park Service

Hydrology in high elevation meadowsTeamrat Ghezzehei, UC Merced

Effects of water and wildfire on soil organic matter and greenhouse gas emissions - Asmeret Berhe, UC Merced

Wildfire impacts on Forest Ecosystems: the 2013 Rim FireStephen Hart, UC Merced and Gus Smith, Yosemite National Park Service

Assessing mercury in lake fish - Ninnette Daniele, Yosemite National Park Service; Travis Espinoza, Yosemite National Park Service 


Plant diversity and ecology

The successful applicants will work on one of these two projects, please indicate a preference.

The California Sierra Nevada is one of the most diverse temperate mountain ranges in the world, yet little is know about how this diversity is responding to rapid environmental change. This summer two students will research:

1) How plant populations are performing in a variety of environmentally challenging conditions, including understanding population attributes at extreme warm and cold elevation limits of species ranges.

2) Additionally, populations will be examined inside and outside of post-burned areas, including the unprecedentedly large Rim Fire of 2013.

Taken together, these projects will inform our understanding of the health of native plant populations and establish a base line with which future studies can compare. 


Lakes are an important source of the potent greenhouse methane gas to the atmosphere, yet a large and highly variable proportion of methane produced in lake sediments is oxidized by microorganisms within the water column. Microbial activity therefore mitigates methane flux, but the factors regulating this important ecosystem service - and the microbial communities involved - are poorly understood. This project will involve measurements of methane fluxes and oxidation, as well as analysis of microbial functional genes and community composition, in high elevation lakes in Yosemite.
The successful applicants will work on one of these two projects, please indicate a preference.
1) Influence of the Rim Fire on Great Gray Owl prey. 
The Rim Fire burned tens of thousands of acres within Yosemite and many more outside the park boundaries. One species that occurs in this area that may have been strongly affected by the fire is the Great Gray Owl. Since the fire burned much of the vegetation, it could have strongly influenced the prey base for the owls. The literature reports that their prey is composed almost entirely of pocket gophers and voles. However analysis of Great Gray Owl pellets has not been thoroughly conducted in recent times for the Sierra Nevada. Furthermore, the prey composition in the pellets could vary through time and space. The REU intern would be responsible for characterizing differences and similarities in Great Gray Owl prey in burned and unburned areas using owl pellets to determine what the owls are eating and how the RIM Fire influenced their diet. 
2) Assessing the fidelity of raptor pellets for inferring small mammal populations in Yosemite National Park.
A recent project assessed the small mammal community living in and around Yosemite to determine whether and how species ranges had shifted due to recent climate change (here). This project will connect changes in small mammal populations inferred from trapping with small mammal populations in the recent surface bone records. The REU intern will collect raptor pellets from the ground below raptor roosts at different elevations through the park, identify the mammals (and other animals) in the pellets, and document how much agreement there is between the live and dead small mammal community.
Hydro-ecological implications of buried volcanic ash (tephra) in meadows of Yosemite.

The most recent volcanic eruptions in the Mono-Inyo chain of craters in the Sierra Nevada, which occurred ~760 and ~1200 years ago, commenced with violent pyroclastic eruptions of pumice that was later carried by wind and deposited over large areas. Today, layers of pumiceous fragments (tephra) are visible in meadow topsoils of the southern Sierra Nevada from Yosemite National Park south to the Kern River drainage. In contrast to the overlying (younger) and underlying (older) meadow soils, the tephra layer has very low organic matter content  and is made up of coarser particles. Consequently, the ability of the tephra to retain moisture against desiccation (by evaporation, drainage, and/or plant uptake) is significantly lower. We established arrays of buried sensors and gas wells in Dana Meadows to analyze the effect of the tephra on the moisture dynamics and associated ecological functioning of meadows. The project provides opportunity for undergraduate students to participate in field acquisition of soil moisture, soil water potential, and temperature from multiple arrays of buried sensors using electronic data-loggers, collection of gas samples, and analysis of gas and soil samples in the lab. 


Effects of water and wildfire on soil organic matter and greenhouse gas emissions.

The successful applicant will work on one of these two projects, please indicate a preference.

1) Soil water storage near the crest of the Sierra Nevada Mountains.

This project investigates how extreme changes in inter-annual precipitation affect soil water storage in high elevation meadows and its implications on soil organic matter dynamics (changes in carbon and nitrogen storage and chemical composition). In this study we have set up transects along hydrologic gradients in two meadows and have been monitoring green house fluxes on the surface or soil and at three different depths in the soil profile. 

2) The role of the Rim Fire on soil organic matter.

This project investigates the role of the Rim Fire on soil organic matter (especially on carbon and nitrogen) amount, composition, and erosion from fire affected hill slopes in Yosemite. In this study we will determine the amount of pyrogenic carbon that was deposited on the soil surface from the latest fire and its resultant fate in the landscape.

Wildfire impacts on Forest Ecosystems: the 2013 Rim Fire

The Rim Fire of 2013 was the largest fire in the recorded history of the Sierra Nevada, burning 257,314 acres and tens of thousands of acres in portions of Yosemite National Park. The student researcher will work on an interdisciplinary project evaluating the impacts of this conflagration on forested watersheds in Yosemite and surrounding areas. Specific tasks may include evaluation of fire effects on forest structure and fuels, soil ecology nutrient cycling, and water quality.

Assessing mercury in lake fish

Mercury pollution is pervasive in the environment, even in pristine areas of the Sierra Nevada.  In Yosemite National Park, mercury is transported through the atmosphere and in to the environment.  Aquatic environments and fish are especially important in accumulating methylmercury, which can be harmful when ingested at high levels.  By dissecting trout gut contents and examining ear stones and scales, the student will evaluate how trout diet and age may contribute to methylmercury burden in lake fish.