Research projects

Plant competition, invasion, and nutrient retention in coastal wetands

Bill Currie is working with collaborator Deborah Goldberg and her student Emily Farrer and postdoc Radka Wildova to understand the linkages among plant community change and nutrient cycling in Great Lakes coastal wetlands. When cattails (Typha spp.) invade native marshes, the ecosystem is essentially converted to a different stable state in which production is higher, nutrient cycling is higher, and plant diversity is reduced.

This research is in a pilot stage; funding has not yet been obtained to pursue this actively. We have submitted grant proposals to NSF, NASA, and USDA.

Carbon balance, community dynamics, and nutrient cycling in temperate forests

A continuing theme in Bill Currie's research has been to understand carbon cycling processes and controls on the balance (source or sink) or carbon in forests. He has published journal articles on the C in downed woody debris as related to land use history (Currie and Nadelhoffer 2002), controls on C storage in the forest floor and mineral soil (Yanai et al. 2003, Currie et al. 2003, Johnston et al. 2004), production and movement of dissolved organic carbon in forest soils (Currie et al 1996), decomposition of foliage, roots, and wood (Currie and Aber 1997, Parton et al. 2007), energy flows related to carbon flows in forests (Currie 2003), and C storage related to forest production through nutrient cycling (Magill et al. 2004, Chastain et al. 2006).

We are developing new field and modeling research at the University of Michigan Biological Station to understand dynamics in the forest carbon balance as a linked set of community and biogeochemical processes. One of the goals is to combine field observations, ecosystem modeling, and ecosystem theory to gain a greater insight into how fine-scale processes integrate to produce ecosystem-level sources or sinks of carbon in forests and how those change over time as a forest develops.

Spatial mapping of forest trees ("stem maps") will help us to include realistic community dynamics in forest ecosystem models. Stem mapping is being conducted by students Alicia Lindauer-Thompson, Elissa Chasen, Elizabeth Haber, and Claire Otwell. These students are being partially supported on a grant from the U.S. Forest Service.

Land cover change, exurban development, and landscape-scale carbon balance

Bill Currie is collaborating in a group project led by Dan Brown, the SLUCE project (Spatial Land Use Change and Ecological effects), involving SNRE and the Center for the Study of Complex Systems at Michigan, among others. Southeastern Michigan is providing a testbed for the development of an integrated suite of approaches to understand and simulate the driving processes and ecological effects of sprawl, or exurban development. This research combines agent-based models of human behavior, GIS and remote sensing analysis, fieldwork on soils and vegetation, and ecosystem modeling and scaling of carbon balance.

To pursue this work, we recently received a 4-year grant from the National Science Foundation, Coupled Natural and Human Systems (CNH) Program. Graduate students Meghan Hutchins and Lauren Lesch are conducting field work this summer to interview landowners and physically measure and sample the soiland vegetation in residential lots. Graduate Student Peter Gamberg is conducting GIS work for site selection based on soils and topography and is helping to trace the history of each lot back to the 1950s using aerial photography. Graduate student Ari Kahan last year completed some preliminary analyses using GIS, aerial photography, and fieldwork to trace both the histories of patches of residential land and to study the effects of housing density on soil C and N and plant community diversity.

Forest nitrogen cycling and C-N interactions studied using large-scale 15N tracers

In the northeastern US and in other regions worldwide, terrestrial ecosystems are becoming more nitrogen-rich through elevated N in rainfall. If forests can store and cycle the N they can decrease its entry in to aquatic ecosystems and they can potentially store more C from the atmosphere.

Bill Currie is collaborating with Adrien Finzi from Boston University, Kirsten Hofmockel from Michigan, and others to study ecosystem-scale C-N interactions under artificially elevated CO2 treatments at the Duke Forest in North Carolina. The research uses field applications of isotopically enriched 15N tracers interpreted with the ecosystem model TRACE that Dr. Currie developed in collaboration with Knute Nadelhoffer and John Aber. Previously, this model was used to interpret isotope cycling in artificially N-enriched forest stands at the Harvard Forest in Massachusetts. These studies were funded by the National Science Foundation.

Integrating forest ecology, economics, and C storage in forest management decision making

Graduate student Alicia Lindauer-Thompson is finishing her MS thesis that uses a combination of modeling, GIS, and field research to address how a goal of storing atmospheric carbon could alter decision-making processes for forest management. Bill Currie also recently collaborated with Rupert Seidl and Manfred Lexer at the University of Natural Resources and Applied Life Sciences in Vienna in a study that used a model of forest dynamics and C storage to forecast the economics of forest products against valuation of C sequestration.

Both of these projects were partially funded by the US Forest Service.

Control of agricultural nutrient runoff in the Raisin River Watershed

Graduate student Nic Enstice is working on a MS thesis focusing on assessing both the acceptability, to farmers and other stakeholders, and the effectiveness of "best management practices" (BMPs) to control agricultural nutrient runoff into streams in the Raisin River Watershed (Southeastern Michigan). He is assessing acceptability of BMPs through a stakeholder survey and their effectiveness by applying survey results as scenarios driving a watershed-scale hydrogeochemical model in collaboration with postdoc Nate Bosch in Dave Allan's research group.

Nic Enstice is supported by the Doris Duke Charitable Foundation.

Appalachian mineland reclamation as a land use / land cover change driving watershed ecosystem processes

Strip mining has been a widespread practice in Appalachia for decades, although since 1977 the law requires soils to be replaced and land to be contoured and vegetated, largely to protect stream water quality. Bill Currie collaborated with Lou Pitelka, Keith Eshleman, Mark Castro, Jeff Simmons and others at the University of Maryland Center for Environmental Science (UMCES) and several Appalachian colleges to develop a long-term paired-watershed study. The study compared a reclaimed mine watershed with a forested watershed in western Maryland. Two of Dr. Currie's graduate students, Molly Ramsey and Madhura Kulkarni (at right), completed MS theses studying wetland patches, plant biodiversity, and ecosystem nutrient cycling processes by conducting fieldwork in these paired watersheds.

This research was funded by the Andrew W. Mellon Foundation.

Global climatic controls on plant litter decomposition and N release: the LIDET study

Rates of leaf litter decomposition are a key ecosystem process that controls rates of C storage and release in ecosystems both directly, through C loss or stabilization, and indirectly through nutrient cycling. Global biogeochemical models make use of generalized relationships that express climate interactions with litter quality in controlling these rates. Bill Currie collaborated in LIDET (Long-Term Integrated Decomposition Experiment), a 10 year field study to test the limits of these climate-litter relationships. Plant litter was field incubated across climates: temperate forest litter in the arctic, arctic litter in the tropics, wet tropical litter in deserts, and so on. This project was led by Mark Harmon at Oregon State and also involved Bill Parton and Indy Burke at Colorado State, Whendee Silver at UC Berkeley, Steve Hart at Northern Arizona, along with dozens of other collaborators.

This research was funded by the National Science Foundation.