Foliar Nitrogen Responses to the Environmental Gradient Matrix of the Adirondack Park, New York

Abstract

Maps derived from remote sensing of canopy nitrogen (N) provide a potential avenue to make spatially explicit, regional-scale predictions of the vital forest ecosystem services that are coupled to the cycling of N and carbon. Yet, to fully use canopy N maps in this capacity, it is necessary to understand how canopy species with differing resource strategies will adjust foliar N in response to environmental variability. In this study, we relate a regional survey of foliar N data from a diverse set of forest tree species in the Adirondack Park, New York, to a holistic matrix of environmental gradients thought to control spatial variability of foliar N. Stepwise multiple regression models developed for each species indicate that neighboring species and abiotic gradients of resource availability play a lesser role, and anthropogenic influences (caused by historic disturbances and atmospheric N deposition) are the strongest drivers of spatial variability in foliar N. Moreover, we find that the plasticity of the total foliar N response to measured environmental variability is strongly related to two indexes of a species’ resource strategy—leaf mass per area and shade tolerance. Collectively, these results (1) further demonstrate the utility of an environmental gradient matrix approach to studying complex ecosystems; (2) emphasize the potentially dominant role of humans in controlling future nutrient cycling, even within this “forever wild” forest ecosystem; and (3) suggest that spatially explicit measurements of foliar N, environmental gradients, and plant resource strategies might provide a pathway to map and forecast ecosystem services at regional scales.