Comparative growth trends of five northern hardwood and montane tree species reveal divergent trajectories and response to climate

Abstract

In the northeastern United States, tree declines associated with acid deposition induced calcium depletion have been documented, notably for red spruce (Picea rubens Sarg.) and sugar maple (Acer saccharum Marsh.). There is conflicting evidence concerning whether co-occurring tree species capitalized on these declines or suffered similar growth reductions and on how growth has fluctuated relative to environmental variables. We examined five species along three elevational transects on Mt. Mansfield, Vermont: sugar maple, red spruce, red maple (Acer rubrum L.), yellow birch (Betula alleghaniensis Britton), and balsam fir (Abies balsamea (L.) Mill.). We found baseline differences in growth. Red maple and yellow birch had the highest growth, sugar maple and red spruce had intermediate growth, and balsam fir had the lowest growth. While some year-to-year declines were associated with specific stress events, protracted patterns such as recent increases in red spruce and red maple growth were correlated with increased temperature and cooling degree days (heat index). For most species and elevations, there was a positive association between temperature and growth but a negative association with growth in the following year. Based on our comparisons, for some species, growth at Mt. Mansfield aligns with regional trends and suggests that patterns assessed here may be indicative of the broader region.