Projections of forest contributions to global carbon cycles

Forests cover 42 percent of the Northern United States, and collectively they store 13 billion tons of carbon in live trees (29 percent), roots (6 percent), forest floor (9 percent), dead trees (6 percent), and soils (50 percent). About half the biomass of a live tree (dry weight basis) is sequestered carbon (Woodall et al. 2011) - not the largest but the most dynamic source of sequestered forest carbon over time. Through photosynthesis, live trees emit oxygen in exchange for the carbon dioxide that they pull from the atmosphere, storing the carbon in wood above ground and roots below ground as they grow. Dead trees and down logs are also reservoirs of stored carbon, which is released back into the atmosphere slowly through decomposition or rapidly through combustion (McKinley 2011, Woodall et al. 2011).