Carbon sequestration potential in operational loblolly pine plantations

Forests store a large amount of carbon, and managing this storage has been proposed as a potential tool for moderating global climate change. However, many of the models currently in use for this purpose take a simplistic view of the system, assuming stationarity of soil carbon pools. Here we report the differences between net primary productivity (NPP, the annual increase in vegetation biomass) and net ecosystem productivity (NEP, the annual change in total ecosystem carbon), which differ by heterotrophic respiration (Rh, annual loss of ecosystem carbon from debris and soil). We evaluate a set of 12 young operational loblolly pine plantations distributed throughout SE-US for their differences in NPP and NEP, and explore the implications and uncertainties for the region in general. The preliminary results indicate sensitivity of Rh to broadly applied silvicultural treatments (fertilization and competition control), as well as to drought episodes, resulting in decoupling between NPP and NEP. Although the magnitude of these responses is small, they are consistent across a broad region and may potentially have a significant modulating influence on the region's carbon sequestration potential.