Fossil fuel carbon emissions from silviculture: Impacts on net carbon sequestration in forests

Increasing concentrations of CO2 in the atmosphere have increased the value of sequestration and storage of C in forests. To maximize the value of this forest function, land managers require accounting systems to track the C stored in forests and in wood and fiber products. Accounting frameworks and data for quantifying C in forests and in wood and fiber products are generally available. In contrast, C emitted from fossil fuels utilized for silvicultural activities such as site preparation or fertilization, which are designed to increase C sequestration, have not been accounted for. The fossil fuel C emissions associated with silvicultural activities must be systematically evaluated to ensure that a net positive C balance results from activities ranging from planting to harvesting. The necessary data for evaluation are compiled from existing information. Utilizing the data, total C emissions from silvicultural activities for an intensive fiber farming operation of southern pine on a 25-year rotation is estimated to be <3 Mg C ha−1. Increased C sequestration in soil or wood and fiber products in response to silvicultural treatments is simulated for 100 years to compare to the fossil fuel C emissions from silvicultural activities. The comparison demonstrates that the expected gains in C accumulation in soils of 16 Mg ha−1 over 100 years or gains due to increased harvest for paper products, also ∼16 Mg ha−1, could each individually be largely balanced by silvicultural C emissions. On the other hand, C storage in wood products due to accelerated growth of trees to a saw log category might exceed the incurred C emissions by 3-fold (i.e., 35 Mg ha−1). If the combined C sequestration benefits from soil C accumulation, increased C storage in paper products, and storage in saw timber products could be captured these would outweigh the fossil fuel C emissions due to increased silvicultural activities.