Heckford, T.R.✉, Leroux, S.J., Vander Wal, E., Rizzuto, M., Balluffi-Fry, J., Richmond, I.C., Wiersma, Y.F. [in revision] Foliar elemental niche responses of balsam fir (Abies balsamea) and white birch (Betula papyrifera) to differing community types across geographic scales. 