Using contemporary and historical data to establish baseline carbon storage in mature, unmanaged pine-hardwood stands of the Midsouth

Background/Question/Methods Carbon (C) sequestration is an increasingly important aspect of forest management in North America.  The forests of the southeastern United States are the largest wood producing region in the world, and have been intensively managed for most of the last century, increasingly so during the last three decades.  The logging of the original forests of this region, coupled with the increasing conversion of natural-origin stands to loblolly pine (Pinus taeda) plantations, makes it difficult to establish baseline data on C storage.  However, there are still a number of unmanaged, mature pine-hardwood stands of natural origin in the Midsouth region that can provide this information.  Furthermore, it is also possible to estimate presettlement C storage levels using a variety of historical sources of information.  Applying allometric equations to detailed, diameter-based stand tables, live tree biomass (aboveground + belowground) was estimated from data collected on both contemporary and historic examples of mature, unmanaged, pine-dominated forests.  Biomass quantities were then converted to C totals using a standard conversion factor of 0.5.

Results/Conclusions This work found between 112 and 159 metric tons of C per hectare (mTC/ha, n = 6 stands) in modern-day examples of mature, unmanaged, pine-dominated forests.  Old descriptions of the virgin pine-hardwood forests of the Midsouth are less reliable, but suggest that the presettlement forests of this region averaged ~54 mTC/ha (range = 27 to 85 mTC/ha, n = 7 stands).  During this historic period, individual loblolly pines may have reached 183 cm in DBH in this area, yielding perhaps as much as 16 mTC of live biomass.  This research supports the observation that historical pine-dominated stands of the Midsouth were less well stocked than those currently observed. It is likely that presettlement disturbance regimes, primarily fire, limited overall C storage in this region.  C storage patterns also differ, with historic stands being more influenced by very large individual trees, rather than an abundance of small-diameter pine and hardwood.