ESTIMATING EROSION RATES USING EXPOSED ROOTS AT A RECREATION SITE, GRASSE RIVER, CANTON, NY

A cut-bank exposure along the Grasse River in Canton, NY, near St. Lawrence University, has been a favorite warm-weather play spot; including two rope swings and a small beach. Concentrated use has caused erosion and root exposure in an approximately 0.25ha area. Soil erosion beneath trees on beaches, hillsides and slopes can lead to exacerbated, large-scale sheet erosion. As the top layer of soil is removed, the lower layers of soil are easier to erode by rain, snowmelt and foot traffic. When erosion uncovers a tree root it makes the root more susceptible to temperature fluctuations, which affects the wood anatomy. Gartner (2006) and Corona et al. (2011) were used as methodological guides to quantify erosion rates, and to determine whether roots exposed themselves due to growth, and/or were exposed due to soil erosion. Samples needed to be exposed and in contact with the ground, with bark on the exposed side. Approximately 2cm-wide root cookies were taken at least 1.0m from the bole of select Eastern white pines (Pinus strobus) using a wire saw. The samples were dried overnight in the oven at 55 degrees centigrade, and then prepared for microscopic analysis. Roots were dot counted for age, and six cell-width measurements were taken per year. Measurements were made using Leica V3.7 imaging software, to track growth changes associated with exposure. When choosing a year of exposure, we used the year of greatest, consistent change between cell-widths, and corroborated with the transition to narrower rings. The average exposure year for these root samples (n=8) was 2013 (±1.3yr). By measuring the amount of exposed root, we estimate that the active area lost approximately 16.7m³/year of alluvial sands; extrapolated to over 100m³(e.g., 10 dump truck loads) of sediment eroded from human activity since 2013. Despite abundant signage to prevent usage, this area remains very popular. The overall economic loss of sands from this area is only about $360/year, so the University could fill high erosion areas with sediment, to protect roots that have become exposed. Many of the St. Lawrence University trail ways, however, are covered in mulch, which is a great protectant for trees roots preserving consistent soil temperatures. The same amount of care that is taken by the University on those trails, could apply to the beach area as well.