Increasing anthropogenic atmospheric nitrogen deposition has the potential to result in nitrogen saturation in Northeastern forests. The response of forests to chronic N additions may be governed by the stand composition and may differ across spatial scales. This suite of experiments addresses three objectives: (1) To determine the robustness of species-specific patterns of soil N availability across various spatial scales, and (2-3) To determine the potential species-specific effects of litter and seedlings of different species on soil N availability variables using a common-garden greenhouse experiment.

There are detectable species-specific differences in soil N availability and related properties beneath dominant canopy trees growing in the mixed deciduous forests of central Appalachia and it appears that the species sampled form a gradient of soil N availability consistent with previous results at coarser spatial scales in the Appalachian region. When a common-garden greenhouse experiment was used to better the understand causality of these relationships, it appears that certain variables are more easily influenced than others by litter from various species or by the seedlings themselves. In appears that both litter and seedlings have the potential to influence N leaching patterns and to some extent soil variables associated with N availability, but in different ways. This may indicate that a combination of effects of litter decay and seedling influences, or life stage differences in seedling growth and maturation are responsible for these differences.

Due to the robustness of the associations between canopy trees and the soil properties found beneath them (Objective 1) and the apparent species-specific differences in N loss from pots containing different seedlings (Objective 3) and litter inputs (Objective 2), the abundance of certain species may be an indicator of soil N availability and the susceptibility of an area to N saturation. This implies that past, present, and future changes in the abundance of the species I examined could potentially result in significant alterations of the N cycle in the forests in which they grow.