The Frey Lab

• Dr. Serita Frey, Associate Professor of Soil Microbial Ecology
• Mel Knorr, Lab Manager
• Sarah Andrews, Ph.D. student
• Alexandra Contosta, Ph.D. student
• Katharine Burnham, B.S. student
• Colleen Kent, B.S. student
• Chelsea Vario, B.S. student
• Alison Grantham

Detailed Description of Research Projects

CAREER: A novel approach to understanding microbial metabolism and soil carbon dynamics (NSF)

Soil carbon storage is determined to a large degree by the balance between plant productivity and organic matter decay. Soil microorganisms are the primary decomposers of organic matter and their metabolism controls how much carbon is lost from the soil and returned to the atmosphere as carbon dioxide. One of the key factors determining the fate of soil carbon is the efficiency with which soil microorganisms convert organic matter to microbial biomass. Despite its importance in determining soil carbon dynamics, little is known about how microbial efficiency responds to environmental change. In this project, calorespirometry is being used to make measurements of microbial efficiency in soils exposed to chronic warming and nitrogen fertilization.

Global change is altering the functioning of terrestrial ecosystems. This project is focusing on two aspects of global change that have particular significance for the northeastern U.S., warming and nitrogen deposition. This project will provide evidence for how warming and nitrogen fertilization interact to influence microbial metabolism and carbon loss from soils, and will provide valuable data for input into global carbon and soil organic matter models. Additionally, a five-year outreach program is being developed for the State of New Hampshire to provide accessible information to the general public on the services that ecosystems provide (e.g., air and water quality), and how global change is impacting the ability of ecosystems to maintain these services. This objective will be accomplished via a website, public service announcements on local National Public Radio stations, posters on public transport systems, and an ecosystems services module for New Hampshire Project Learning Tree, a statewide environmental education program.

Microbial community composition in forest soils exposed to chronic warming and nitrogen deposition (McIntire-Stennis)

The objectives of this project are to determine (1) how soil warming and N additions interact to influence microbial community composition, especially the relative abundance of bacteria and fungi, and (2) if there is a correlation between the fungal:bacterial biomass ratio and the metabolic efficiency of the microbial community in soils exposed to chronic warming and N deposition. We are characterizing the microbial community in samples collected as part of a NSF project described above. Soil samples will be collected from the Soil Warming and Chronic Nitrogen Addition Studies at Harvard Forest in Central Massachusetts and a new soil warming/N addition study that will be established at Harvard Forest to evaluate the interacting effects of warming and increased N availability on the soil microbial community.

Collaborative research on aboveground-belowground interactions: relating plant community composition and diversity to methane cycling in wetland ecosystems (NSF)

This project is being conducted in collaboration with Virginie Bouchard, a plant ecologist at Ohio State University. We are examining how changes in plant community composition and diversity alter the methane (CH 4) cycle in freshwater wetlands. Two hypotheses guide this research:

• Both plant diversity and community composition will be important for determining CH 4 emission due to differences between functional groups in root production. Gross CH 4 flux will be highest in highly productive communities (either high diversity systems or those dominated by the clonal dominant functional group); however, plant communities with high root production will enhance CH 4 oxidation to a relatively greater degree, leading to an overall decrease in CH 4 flux.
• The mechanism driving the diversity-function relationship will be dependent on the makeup of the plant community: a) in plant communities dominated by aggressive species, sampling effect (i.e., species composition) will be the primary mechanism; b) in diverse plant communities, both niche complementarity and sampling effect will be important depending on the function of interest.

We are conducting an observational field study and two controlled mesocosm experiments designed to mimic the structure of natural plant communities. We will also be partnering with the Ohio EPA Wetland Ecology Group to offer an outreach program to wetland professionals to encourage a reevaluation of current practices in wetland conservation, restoration and creation.

Establishment of plant- and microbial-mediated functions in created wetlands: a comparative and mechanistic study to provide guidance for wetland restoration (USDA)

This project is being conducted in collaboration with Virginie Bouchard, a plant ecologist at Ohio State University , and Siobhan Fennessey, a wetlands ecologist at Kenyon College . We are evaluating the ability of created wetlands to develop plant- and microbial-mediated functions associated with the carbon and nitrogen cycles. Natural depressional wetlands function as sinks for C and N, yet the ability of created wetlands to replace natural wetlands in this capacity has been ignored. Ultimately, we seek to provide recommendations for improving the success of wetland mitigation projects. Our objectives are to assess differences between created and natural wetlands for key functions, including plant production, litter decomposition, methane emission, and denitrification; to identify the factors prohibiting these functions in created wetlands; and to develop mitigation recommendations leading to better design of created wetlands. We are completing an across-site field study of created and natural wetlands to assess differences in ecosystem structure and function, conducting controlled lab incubations to address the question of microbial C and N limitation in each wetland type, and developing an ecosystem model that will incorporate all of the functional and structural characteristics of each wetland type and identify the factors driving and/or limiting their development. Current wetland mitigation policy presumes that created wetlands serve as functional surrogates for natural wetlands. This research will improve our understanding of whether and over what time scale key functions become fully developed in created wetlands.