Subsoil Nutrient Responses to Harvesting, Fire, and Elevated CO2.

The effects of forest harvesting (whole-tree vs bole only), fire (prescribed and wildfire), and elevated CO2 on both surface and subsoil chemical changes are reviewed. In most cases, the effects of harvesting and fire on surface soils either 1) reflect changes in surface soils, but are attenuated, or 2) absent in subsoils. Thus, the omission of subsoil data in such cases would not have changed the conclusions reached. The exception to this pattern is elevated CO2, where increases in soil organic C and C:N ratio were seen in subsoils but not in surface soils after 6 years of treatment. Regardless of whether treatment effects on subsoils reflect those in surface soils or not, however, it is essential to include subsoil data on soil chemical concentrations and physical properties (bulk density and percent coarse fragments) when evaluating treatment effects on nutrient budgets.