Plant Traits and Community Metrics across a Snowmelt Gradient at Alpine Snowbank Sites on Mt. Washington, New Hampshire

ABSTRACT. In northeastern North America, alpine snowbank communities are rare plant assemblages that form in sheltered sites above treeline where late-lying snow provides insulation from late-season frosts and a longer-lasting source of water. We measured snowpack and studied community composition and plant traits at the species and community scales across the snowmelt gradient at snowbank sites on Mt. Washington, New Hampshire. We used nonmetric multidimensional scaling ordination and analysis of similarity to examine community composition across the snowmelt gradient and measured plant traits (height, leaf dry matter content, leaf area, and specific leaf area) of four focal species (Carex bigelowii, Chamaepericlymenum canadense, Clintonia borealis, and Maianthemum canadense). We assessed trait variability of the four focal species across the snowmelt gradient and evaluated community-weighted mean trait values and phenotypic plasticity between snowbank core and edge habitats. Analysis of similarity indicated that vascular plant diversity increased (p < 0.001), lichen and bryophyte cover decreased (p < 0.001; p < 0.025), and community-weighted mean leaf area increased (p < 0.001) in the core of snowbank communities where melting dates were later. Analysis of similarity indicated that vascular plant communities varied significantly across the snowmelt gradient. The transition in community composition and trait values across the snowmelt gradient are indicative of changing environmental conditions and ecosystem functions, though more research is needed to determine the extent to which phenotypic plasticity and ecotypic uniqueness influence trait expression of snowbank species. Genetic analysis may be necessary to evaluate population dynamics among isolated alpine communities, which may be vulnerable to climate change or displacement by exotic or lowland species.