INVESTIGATING GEOLOGIC CONTROLS ON ECOPHYSIOLOGY AND NUTRIENT CYCLING IN THE FORESTS OF NEW ENGLAND

Soil physicochemical properties are known to govern plant growth rates and their ecological niches. However, the influence of soils on tree growth rates and nutrient acquisition in New England are not well known, particularly across strikingly different surficial deposits. Our research investigates how different glacial deposits have affected the growth of New England forests. We hypothesized that forest tree species and their physical attributes (dbh, height, etc) are different across two common geologic deposits in New England: ablation glacial till deposits and glaciofluvial. We investigated forests and their underlying soils at 8 pairs of ablation till and glaciofluvial deposits (< 400 m of each other) located on the perimeter of glacial lake Hitchcock in Massachusetts. Deciduous hardwoods (Quercus spp., Betula papyrifera., Betula nigra, Fagus grandifolia, Acer rubrum, Fraxinus spp) and eastern hemlocks (Tsuga canadensis) were sampled using tree cores with an increment borer (poles were ignored) in a radius of 10 meters from a 1 x 1 m soil pit. Trees were randomly selected and sampled using a throw ball or pole lopper. A soil pit was dug and diagnostic soil horizons were identified and described according to U.S. Soil Taxonomy. A steel core (7.5cm diameter, 10.5cm length) was taken from each horizon and an O horizon (if present) was collected using a 15-cm square cut out. The tree cores were then prepared by sanding down from 60 grit to 400 grit to ensure all annual growth rings were visible. The vegetation and soil samples were prepared for nutrient testing using a strong acid digestion for analysis by ICP-OES/ICP-MS. Soil samples were analyzed for pH, texture and loss of ignition. Our physical soil data has not shown any significant difference in the pH, texture or loss on ignition between glaciofluvial and ablation till deposits. Our 190 tree cores show varying growth rates across the deposits which could be influenced by a difference in the physicochemical properties of the soils. Our soil and foliar nutrient extracts will indicate if nutrient availability and uptake by trees across geologic deposits and suggest if the soil parent material exerts edaphic controls on the trees. This information will help forests determine how geologic history influences long-term nutrient availability.