Carbon fluxes, storage and harvest removals through 60Â years of stand development in red pine plantations and mixed hardwood stands in Northern Michigan, USA

The storage and flow of carbon (C) into and out of forests can differ under the influence of dominant tree species because of species-based variation in C production, decomposition, retention, and harvest-based export. Following abandonment of agricultural activities in the first half of the 20th century, many landscapes of the Great Lakes region (USA) were planted to red pine (Pinus resinosa) or naturally regenerated to northern hardwood species including sugar maple (Acer saccharum), red oak (Quercus rubra) and red maple (Acer rubrum). We located eight pairs of adjacent, similarly aged (∼60 yr) stands of planted red pine and naturally regenerated hardwood forests on previous agricultural fields. We found that the hardwood forests stored more C than pine stands (255 vs. 201 Mg C ha−1), with both storing substantially more than an adjacent area maintained as pasture (107 Mg C ha−1). The greater accumulation of C in the hardwood stands occurred mostly in living biomass. No significant differences for soil C (to 1 m depth) were found between forest types, despite significantly higher belowground inputs and aboveground litterfall in hardwood stands. Notably, both forest types had about 18% more soil C than the pasture, with O horizon C accounting for about one-third of the increase under trees. Forest type had no significant effect on estimated amount of exported C despite fairly large differences in projected end uses (solid wood products, land-fills, bioenergy). Using adjacent pasture as our baseline condition, we combined estimated on-site accumulation rates with estimates of exported C, and found that average total C sequestration rates were higher for hardwood (2.9 Mg C ha−1 yr−1) than red pine plots (2.3 Mg C ha−1 yr−1). The modeled potential contribution of exported C to these sequestration rate estimates did not differ between species, but the fate of modeled post-harvest off-site C may exert a large influence on sequestration rate estimates depending on actual displacement actions, including product longevity. These results show that tree species selection has the potential to impact C sequestration rates but effects vary by ecosystem component and could not be predicted from previous species effects studies.