Distribution of carbon in longleaf pine ecosystems

Background/Question/Methods

Restoration of longleaf pine ecosystems on military installations for protection of threatened and endangered species and for multiple ecosystem services such as carbon sequestration is a priority of military installations in the southeastern United States.  Sustainably managing longleaf pine ecosystems for carbon sequestration requires information at the ecosystem level on how forest management practices impact carbon pools.  A five year study funded by the Strategic Environmental Research and Development Program in the Department of Defense was initiated to: (1) model the forest carbon cycle of longleaf pine ecosystems using measurements made on three military installations in the southeastern U.S. representing longleaf pine’s historical range, (2) elucidate sources and sinks of carbon and changes through time, and (3) determine the contribution of ecological forest management to carbon offsets.  To support model calibration and validation, we are quantifying carbon in above- and belowground plant biomass, decaying stumps, soils, forest floor litter, and detritus.  In 2012, we completed measurements of carbon pools in five longleaf pine forests at Fort Benning, Georgia varying in age from 5 to 87 years.

Results/Conclusions

Above and belowground tree biomass was measured in 5, 12, 21, 64, and 87-year-old longleaf pine forests and data were used to develop allometric relationships. A strong linear relationship between total aboveground tree biomass and the product of stem diameter and height was observed. Carbon in aboveground biomass of longleaf pine trees ranged from 0.9 Mg C ha^-1 in the 5-year-old forest to 72.6 Mg C ha^-1 in the 87-year-old forest.  Total aboveground carbon in all pools ranged from 3.4 Mg C ha^-1 in the 5-year-old forest to 76.4 Mg C ha^-1 in the 87-year-old forest.  Longleaf pine aboveground biomass represented more than 70% of total aboveground carbon in forests above 12 years of age. Carbon in the groundcover layer ranged from 0.03- 0.72 Mg C ha^-1 and was 21% of total C in the youngest forest but dropped to less than 1% in older forests.  Soil carbon to a 1.0 m depth ranged from 52.3 Mg C ha^-1 in the 21-year-old forest to 84.4 Mg C ha^-1 in the 64-year-old forest.  Results will be used to parameterize carbon cycling models for management of plantation and natural uneven-aged longleaf pine forests.