An estimated 35 percent of the global terrestrial carbon is stored in soil and biotic carbon pools, such as forests. These pools can store or release carbon. Because forests store immense amounts of carbon, forest management is becoming part of efforts to increase carbon sequestration and mitigate greenhouse gas emissions.
Long-term research from the USDA Forest Service provides insights on carbon and nitrogen pools and fluxes in forests. In 1991, Jennifer Knoepp and her colleagues installed five plots on reference watersheds at the Coweeta Hydrologic Laboratory, NC. The plots were located along an elevation gradient and represent four common forest communities: mixed oak-pine, mixed oak, cove hardwood, and northern hardwoods. For 20 years, the scientists monitored:
- Forest productivity and biomass;
- Carbon and nitrogen in leaves, needles, and wood on the forest floor;
- Carbon and nitrogen in organic soil and surface mineral soil; and
- Relationships between carbon and nitrogen fluxes and soil temperatures in the growing season soil, as well as precipitation.
The results indicate that plant productivity is sensitive to short-term changes in climate, while belowground processes do not respond on annual time scales.
The researchers found similar patterns across a gradient in vegetation community, temperature, and precipitation. This suggests that changes in climate would eventually alter forest ecosystem carbon and nitrogen pools and cycling.