Although I use firewood at home for heat, and manage a woodlot, I have never been a particularly aggressive advocate of biomass fuels as a major part of any large scale climate initiative. The potential to do real ecological damage by heavier harvests, shorter rotations, and so on seemed fairly obvious. And the various calculations of carbon cycling within biomass land-use areas, including forests and arable systems, seemed a little too simple to be true. At the very least, I wondered if the natural nitrogen cycle could keep up with the large forest biomass harvesting increases that already result from the search for carbon-neutral fuel.
It turns out that more complete knowledge is emerging. A recent study from a Canadian university looked at the carbon cycle in forest lands just a little east of here in Nova Scotia.
They discovered a substantial dip in soil carbon within a few years of harvest.
Bottom line: Maine land managers providing product to our rapidly expanding pellet mills will need to have, at the very least, some kind of average numbers for the carbon chemistry of their soils, including the deeper mineral layers, and they will need to relate these numbers to the overall areas under management, and perhaps to keep set-aside areas, to rationally claim carbon neutrality for fuel sources. When soil carbon is taken into account, longer rotations will likely be needed to achieve carbon neutrality.
Some further study will be required to apply the results of these initial studies to typical pellet forests in Maine, which have a greater proportion of hardwoods than the study areas used in the original work.
Here's the news article, from EnvironmentalResearchWeb.
Here are a couple of the related papers:
Diochon, A., L. Kellman (2009) Physical fractionation of soil organic matter: Destabilization of deep soil carbon following harvesting of a temperate coniferous forest, J. Geophys. Res., 114, G01016, doi:10.1029/2008JG000844.
Diochon, A. L. Kellman and H. Beltrami (2009) Looking deeper: an investigation of soil carbon losses following harvesting from a managed northeastern red spruce (Picea rubens Sarg.) forest chronosequence, Forest Ecology and Management, 257, 2, 31 January 2009, Pages 413-420, doi:10.1016/j.foreco.2008.09.015.