A perspective on soil carbon resource impacts.
Importance of Spruce Systems
Red spruce and hemlock stands are important for a multitude of reasons including habitat for Cheat Mountain Salamanders and Northern Flying Squirrels, timber production, recreational aesthetics, and carbon sequestration for global warming mitigation. Current and past documentation of Organic horizon (O-horizon) surface layers up to a meter thick in spruce stands shows that these systems can tie up a lot of carbon.
These soils also collect dark-colored carbon in subsurface spodic horizons (Bh or Bhs horizons) where carbon is moved lower in the soil through a leached zone and then deposited usually anywhere from 20 cm all the way down to meters deep depending on the amount of horizon development (e.g. left). This potential for the combination of surface and subsurface carbon storage offers a lot of potential for sequestration efforts in areas that lost spruce historically (e.g. right). We suspect many of these sites may have lost the carbon rich spodic horizons from Spodosol soils as has been observed in similar areas in other parts of the U.S. (Barret and Schaetzl, 1998), and thus restoring spruce could potentially re-form these horizons and pull carbon back out of the atmosphere.
Many studies have looked at the history of red spruce (Picea rubens) in the central Appalachians. Most agree that the spruce stands seen currently are a small fraction of what existed before 1800 due to vast logging and resulting fires (Adams et al., 2010; Hopkins, 1899; Pielke, 1981; Rollins et al., 2010). In most areas where spruce was harvested, northern hardwood forest has recolonized (see pictures on right) and we suspect that much carbon has been lost in these areas due to erosion after harvest, disturbance-related fire, and resulting changes in energy and carbon inputs. However, there are still more continuous spruce stands along the highest ridges and to a lesser degree in other parts of high elevation areas of the central Appalachians. Rockier and sandier high ridge areas that currently have spruce show a well documented relationship with Spodosol soils with high levels of organic matter and low nutrient contents (Flegel, 1998). However, other mountain sideslope areas in siltier soils have little documentation of Spodosols despite the existence of isolated yet significant spruce stands. Our recent investigations have documented the presence of Spodosol in these areas and we are looking at this data for guidance in future management efforts for these forests. We hypothesize that much of these areas that are now in hardwood could be restored to spruce and that this shift could potentially resequester large amounts of carbon lost because of past harvest and burning.