Macroscale Variation in Red Maple (Acer rubrum) Foliar Carbon, Nitrogen, and Nitrogen Resorption.

Many tree species grow across large climatic and geographical gradients, but there is a lack of information related to intraspecific variation in leaf traits for some of the most abundant trees in temperate forests as related to these gradients. In particular, understanding intraspecific variation in carbon (C)- and nitrogen (N)-based traits of both plant foliage and senesced leaves is important as they provide insight into leaf physiology, tree nutrient status, and forest biogeochemical processes. We report on a community science project that focused on variation in Acer rubrum (red maple) foliar C and N concentrations, C:N of green and fallen leaves, and N resorption across broad mean annual temperature (MAT), precipitation (MAP), and latitudinal gradients. MAT was negatively correlated with green leaf %N and both fallen leaf C:N and N resorption, but was positively correlated with green leaf C:N and fallen leaf %N. MAP was positively related to fallen leaf %N and negatively with fallen leaf C:N and N resorption. Green leaf %C and %N was significantly higher in open than closed grown sites, but green leaf C:N was significantly higher in closed grown sites. Our results suggest red maple's leaf physiology and role in biogeochemical processes systematically vary throughout its broad geographic range. Further, our results suggest red maple's N resorption and recycling through litterfall impacts ecosystem C and N cycles differently throughout its geographic range, such that trees in warmer climates may have a greater reliance on litter-derived N on an annual basis relative to trees in cooler climates, which may be more adept at reusing N via resorption. [ABSTRACT FROM AUTHOR]