CAREER: Detecting warming impacts on carbon accumulation across a climate transect of Michigan peatlands

Hope College, Holland MI

Investigators

Abstract

This CAREER project will investigate how increases in temperature will affect the carbon (C) cycle in peatlands. Peatlands are wetland ecosystems that naturally store C due to very slow decomposition of plant material, and thus now store a massive amount of C as organic matter. How the C cycle in these peatlands will change as climate warms is unknown. Michigan is positioned at the southern end of the range of boreal (northern) peatlands, which means that Michigan peatlands will be among the first to be affected by warming. This project will establish a climate transect of peatlands to help predict how future warming will affect the C stored in these ecosystems. The transect contains seven sites, from Portage in the south to Newberry in Michigan’s Upper Peninsula. The sites span 5°C in average temperature, which is approximately equivalent to the warming expected over the next century. The project will exploit these natural differences in temperature to determine how C cycle processes in peatlands will change with warming. In addition, a new course for first-year undergraduate students will be developed, centered around a field trip to sites on the peatland transect in the week before the start of classes, to train and inspire the next generation of environmental scientists. The net C balance of the peatland ecosystem is determined by the net balance of C inputs (from plant growth) and C losses (through microbial decomposition of organic matter). Predicting future changes in the C balance has proved difficult because both of these fluxes are expected to increase with warming. C losses will be evaluated by measuring carbon dioxide and methane emissions from the soil, as well as litter bag decomposition experiments. Changes in C inputs via plant growth will be mediated by nitrogen (N) availability, due to the strong N limitation of peatland ecosystems. Therefore, the temperature sensitivity of N mineralization will be assessed in field measurements across the transect. Finally, the effects of warming on net C accumulation will be assessed using a geochemical approach, taking advantage of the 1°C of warming that Michigan has already experienced. The long-term accumulation rate will be compared to the recent accumulation rate, using computer modeling to account for organic matter included in the recent rate that is still undergoing aerobic decomposition. This will allow direct testing of the hypothesis that warming has already begun to slow down peat accumulation in marginal peatlands at the southern edge of their climate window. Together, these approaches will provide a complete picture of how C inputs and losses from peatlands will change in response to the warming expected over the coming decades. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.