Stand-Density Effects on Aboveground Carbon Dynamics in Secondary Pinus and Quercus Forests of Central USA

Abstract

Abstract Temperate forests play an important role in the sequestration and storage of carbon. We evaluated the long-term effects of manipulating stand density on aboveground live tree carbon dynamics and volume production for separate pine (Pinus spp.) and oak (Quercus spp.) forests of central USA. For both species groups, stand-level carbon storage in standing live trees was greatest without management, with unthinned pine plateauing around 100 Mg/ha of carbon at approximately 50 years old and the oak stands increasing to around 100 Mg/ha of carbon by about 80 years old. In the pine stands, stand-level carbon sequestration was greatest in stands that were thinned but maintained fully stocked conditions. Consequently, the gross carbon that accumulated during the study period, which included standing carbon in live trees and carbon from trees that were harvested or otherwise died, was maximized when stand stocking was maintained at an average of around 80% stocking during the study period. These results were compatible with the production of sawtimber volume, which was greatest for stands that were maintained in fully stocked but not overstocked conditions. Our results demonstrate that thinning can be a forest management strategy to achieve multiple objectives, including those for carbon management and sawtimber production. Study Implications: Our results support stand-density management (i.e., thinning) as a forestry practice compatible with carbon objectives and more traditional objectives of timber production. Aboveground carbon stored in live trees was greatest without thinning, but gross production and sequestration rates were greatest when stand density was maintained in fully stocked but not overstocked conditions. Active forest management during stand development can provide managers with the flexibility to address multiple objectives and may be used with other carbon management practices such as extended rotations or continuous canopy cover, particularly in the central and northeastern United States where forests are generally aging uniformly throughout the region.