Factors regulating nitrogen mineralization along an elevation gradient in the southern appalachian mountains, USA

Reaction rates typically decrease with decreasing temperature. Temperature decreases with increasing elevation. Thus, nitrogen (N) mineralization rates are predicted to decrease with increasing elevation. However, N mineralization rates are more than an order of magnitude greater at a high elevation northern hardwood (NH) stand than at a lower elevation Oak Pine stand (OP) at the Coweeta Hydrologic Laboratory in the southern Appalachian mountains, NC. A preliminary experiment tested whether a promoter substance existed in the leachate of the herbs, leaf litter or soils of the NH site, by treating soils with cold water extracts of these components. The extracts did not have significant effects on N mineralization rates. Nitrogen budgets were then constructed for both sites to compare the sizes of N pools and fluxes. Values from the N budgets were used to develop a STELLA model. Sensitivity analysis was performed for 200-yr simulations. The large N soil pool, finer textured soil, and higher soil moisture content at the NH seems to be the most important variables in explaining the N mineralization rate differences between these two sites.