WHOLE-TREE-HARVESTING EFFECTS ON SOIL-NITROGEN AND CARBON

Soil pools of N and C were estimated quantitatively before, and 3 years after, whole-tree harvesting in a northern hardwood forest in New Hampshire, U.S.A. to determine whether cutting would reduce or redistribute these pools within soil compartments. Concentrations and pool sizes of N and C were measured by excavating 120 pits, 0.71×0.71 m, by horizon (forest floor) or depth strata (mineral soil) on a 23-ha watershed. No detectable changes were observed in N or C pool sizes in the Oi+Oe or Oa horizons of the forest floor or any mineral-soil depth stratum. Estimates of variability for pool sizes in the forest floor were much higher after harvest. Concentrations of N and C decreased significantly in the Oi+Oe and Oa horizons of the forest floor but increases in Oa mass offset these reductions, resulting in no significant changes in pool sizes. Logging operations resulted in an immediate disturbance which displaced or buried the original forest floor on 24% of the watershed. This mechanical disturbance contributed to an increase in variability of soil N and C pool-size estimates, and made it more difficult to distinguish the forest-floor/mineral-soil boundary in the field. © 1990.