Response of Deep Soil Carbon Pools to Forest Management Treatments in a Highly Productive Andisol.

Soil contains more carbon than the atmosphere and plant biomass combined. Consequently, it is the most important long-term sink for carbon within terrestrial ecosystems. An understanding of the potential to induce carbon sequestration in soils through management is crucial in light of increasing anthropogenic CO₂ emissions. Nevertheless, soil has historically been under-represented in carbon cycling research, especially in regards to subsurface (>30 cm) layers and processes. Research on the effects of forest management practices on deep soil carbon has been particularly lacking. In order to study the effects of various biomass removal and vegetation control treatments on deep soil carbon, soil samples were obtained from 8 depth intervals reaching a depth of 3 meters from the Fall River Long-term Soil Productivity Site in western Washington. Soils at this site are Andisols of the Boistfort series. Treatments were installed 15 years previously in a randomized complete block design with four replicates. Results indicate that there is no statistically significant difference in soil carbon between treatments. These results suggest the stability of soil carbon pools at Fall River and indicate that more intensive management practices may not deplete carbon pools at this site. However, 58% of the soil carbon pool is located below 30 cm, which suggests that previous research may be significantly underestimating soil carbon pools. This underestimation may influence current understanding of global carbon cycling and limit the accuracy of climate models. It also highlights the importance of quantifying deep soil carbon pools and understanding the processes that control them.