Our work focuses on using stable isotopes at natural abundance levels to understand carbon and nitrogen cycling in tundra, northern peatlands, and forest ecosystems. We are particularly interested in understanding the importance of mycorrhizal fungi in these systems, both as a carbon sink and as a source for nitrogen. Mycorrhizal fungi are ubiquitous root symbionts that supply most nutrients to forest vegetation, protect tree roots against pathogens, and filter out potentially toxic metals such as aluminum. Mycorrhizal fungi appear heavily affected by atmospheric nitrogen deposition in Europe, and we suspect that the same processes are starting to operate in the northeastern US, with possibly deleterious consequences for forest health, including the uptake of other important nutrients such as calcium. We use culture studies, isotopic tracers, natural abundance measurements, and computer modeling to understand the role of mycorrhizal fungi in terrestrial ecosystems.
Other work has included using isotopic measurements to understand diets of arctic ground squirrels in Alaska and reindeer in Svalbard, the relationship between dietary protein and body protein in mammals, using saprotrophic fungi as integrators of climate change responses in lawns, assessing the carbon sources of 400-million-year old fungi (that happened to be 6 meters tall), and applying tracer isotopes of glucose to understand the main metabolic fluxes during lipid biosynthesis in cultured fungi.
Andrew Ouimette (co-advisor)
Matthew Vadeboncoeur (PhD 2013)
Julee Shamhart (MS 2010)
Claire Hoff (MS 2009)
Kirsty Lloyd (MS 2007)
Janet Chen (postdoctoral associate, 2013-2015)
Francesca Scandellari (postdoctoral associate, 2009-2011)
Samson Gumbo (visiting researcher, Midlands State University (Zimbabwe), 2010)
Mark Matsa and Vongai Nyawo (visiting researchers, Midlands State University, 2012)
Jaturong Kumla (visiting PhD student, Chiang Mai University (Thailand), 2013)
Shin Ugawa (visiting researcher, Kagoshima University (Japan), 2016-2017)
Qingli Liu (visiting researcher, Chinese Academy of Agricultural Sciences (Beijing), 2017-2018)
Uncovering the belowground drivers of weed-crop competition for improved weed management
In a project led by Rich Smith (UNH Department of Natural Resources), we are testing how soil resource pools, crop and weed species-specific abilities to partition soil resources, and mutualistic plant-microbe associations interact to affect weed-crop competition in controlled environments and in field conditions.
Nitrogen synchrony at the crop-soil interface: optimizing root-microbe interactions to minimize environmental N losses
In a project led by Stuart Grandy (UNH Department of Natural Resources), we are examining the biological N mineralization processes driven by interactions among plant roots, arbuscular mycorrhizal fungi, and soil microbes. This project will assess how these processes can be managed to maximize crop N and P nutrition and C sequestration while minimizing environmental N losses.
Controls regulating biological nitrogen fixation in longleaf pine ecosystems: the role of fire and military training
In a project led by Nina Wurzburger (University of Georgia), we are investigating the importance of biological N2 fixation in longleaf pine ecosystems influenced by military training and land management. Our goals are to: 1) reduce uncertainties about the process of N2 fixation, including the role of taxonomic groups of N2‐fixers and soil nutrients in regulating the input of N to ecosystems, and 2) quantify the importance of N2 fixation at the landscape level and determine if these N inputs are sufficient to counteract the loss of N through fire, leaching and volatilization.
We are currently collaborating with numerous researchers on manuscripts stemming from prior or ongoing projects.
Some of them include:
- Shin Ugawa, Kagoshima University, Japan. Incorporating stable isotopes into forest ecosystem models.
- Niles Hasselquist, Swedish Agricultural University (Umeå). Responses of ectomycorrhizal fungi, Scots pine, and soils to long-term nitrogen additions.
- Raisa Makipaa, LUKE, Finland. Field studies of wood decomposition.
- Mark Harmon, Oregon State University. Wood decay fungi in a long-term log decomposition study.
- Ryan Stephens, Andy Ouimette, and Becca Rowe, UNH. Life histories of truffles at Bartlett Experimental Forest, New Hampshire.
Erik Hobbie is a naturalist and hike leader every summer for the Appalachian Mountain Club at its Cold River Camp facility.
Our publication, “Carbon isotopes in the saprotrophic fungus Amanita thiersii reveal increased C3 productivity of Midwestern lawns since 1982” (Journal of Geophysical Research), was profiled in the American Geophysical Union's magazine Eos (April 2017), Science Daily (April 2017) and The Atlantic (May 2017).
Erik Hobbie visited Japan for two weeks in July 2017 and gave lectures at Kagoshima University (home institution of visiting researcher Shin Ugawa), Kyoto University, and the Forestry and Forest Products Research Institute.
PhD student Nate Thorp visited the Department of Energy’s climate change study in northern Minnesota in early September 2017 to collect field samples of mushrooms and vegetation.