Carbon cycling and accumulation in grasslands: effects of restoration of abandoned croplands
Human activities are altering the Earth's atmosphere, concentrating greenhouse (i.e. CO 2) and other gases created by fossil fuel burning and land use changes (mainly deforestation and natural ecosystem conversion to agriculture). This rise in CO 2 levels has the potential to cause global warming, changes in global and regional climate patterns and sea level rises. The impact of these environmental changes can be mitigated if CO 2 accumulation in the atmosphere is slowed or stopped. Strategies to reduce emissions at source points can be coupled with storage of carbon in terrestrial ecosystems and oceans. Terrestrial ecosystems have the potential to remove and sequester part of the 7GtC that is emitted annually into the atmosphere by increasing photosynthetic carbon gain over respiratory carbon losses. Edmonds et al. (1997) estimated that atmospheric carbon sequestration in agricultural soils alone (1.8-2.2 Gt/year) would "buy" 35 years for the major technological adjustments needed in the world's energy production to take place with potential savings of at least $100 million for the U.S. economy. This will be in addition to other significant added benefits such as improved soil and water quality, maintenance of better wildlife habitats, reduced soil erosion and decreased nutrient loss. However, estimating the potential for increasing carbon sequestration in terrestrial ecosystems is difficult because of a lack of mechanistic understanding on controls of the flow of carbon from plants to soils and to the atmosphere.
The aim of this project is to gain information on ecosystem processes that determine carbon cycling in restored grasslands from croplands in order to couple restoration practices with guidelines focused to enhance the natural carbon cycle. We will focus on tallgrass prairie restoration from cropland at FermiLab NERP (Batavia, IL), which has a chronosequence of restoration plots on soils that were cultivated for more than 100 years. Plots have been established almost every year since 1975. Prairie plots are dominated by C 4 grasses in the summer and the degree of dominance is larger as plots become older. Because C 3 and C 4 photosynthetic pathways discriminate differently against 13CO 2, the isotopic signatures for C 3 ( 13C of -28‰) and C 4 ( 13C of -12‰) can be used to track C 3 and C 4 carbon dynamics in ecosystem respiration and stored carbon since 1975. Our main objectives are:
- To increase understanding on the restored ecosystem structure and function directed toward carbon allocation and partitioning, plant growth and soil carbon accumulation.
- To improve the measurements of gross carbon fluxes and dynamic carbon inventories through the development of new stable isotope nondestructive belowground techniques .
- To evaluate to what extent does ecosystem respiration control sequestration of atmospheric carbon in grasslands ecosystems
- To identify the components of ecosystem respiration that exert the greatest leverage in determining the direction and magnitude of C sequestration.
This project is in collaboration with Argonne National Lab, Fermi Lab and is realted to the CSiTE (Carbon Sequestration in Terrestrial Ecosystems) Network.