Print PageAlthough the woody debris pool is currently a carbon sink in temperate forests, it could change to a source in the next 100 years in response to soil warming from global climate change. Fine woody debris typically takes years to decompose. It is unclear, however, how soil warming will alter decomposition in temperate forests or how debris size and quality differentially alter patterns of decomposition. To look at the effect of soil warming on the woody debris decomposition of varying size and quality, we placed fine woody debris of two size classes (2 x 20 cm and 4 x 40 cm) and four species (Acer saccharum, Betula lenta, Quercus rubra and Tsuga canadensis) in a soil warming and ambient area at Harvard Forest in central Massachusetts. We collected the debris once a year for two years and measured mass loss and lignin concentration from the debris collected.
Results/Conclusions
We found that warming increased mass loss for all species and size classes over two years (by as much as 30%), but that more recalcitrant and larger debris decomposed much more slowly. Surprisingly, lignin degradation did not follow the same trends as mass loss. Lignin loss from the most lignin-rich species, T. canadensis, was highest despite the fact that it decomposed the slowest. Prior research has demonstrated that soil warming increases soil respiration and decreases carbon stores belowground, and our results indicated that soil warming will also increase decomposition of woody debris. Faster decomposition of species with higher quality wood, such as Acer and Betula, will further increase carbon dioxide released into the atmosphere. Future models and policy efforts must account for this change.
