THE EFFECT OF HILLSLOPE GRADIENT ON THE LEGACY OF RELICT CHARCOAL HEARTHS IN CONNECTICUT, USA

Relict charcoal hearths (RCHs) are round elliptical landforms that served as the site where charcoal was produced in the 18th and 19th centuries to support local industries. They can be identified across much of the northeastern United States in slope maps derived from LiDAR DEMs. The effect of hillslope gradient on the legacy of RCHs is not well studied, specifically the degree to which increased hillslope gradients leads to the downhill movement of charcoal enriched soil material. This study examines the effect of hillslope gradient on the legacy of relict charcoal hearths in the towns of Simsbury and Oxford, Connecticut, USA. At each site, three to five hearths with varying hillslope gradients (ranging from <4 degrees to 10-15 degrees) were sampled along a transect running through the RCH center, extending 20 m in the up- and downslope orientations. Soil layers were described in the field and LOI was performed in the lab to characterize charcoal material in the transects. To supplement field and lab work, topographic analysis was completed in ArcGIS using LiDAR DEMs, including measurements such as background slope, diameter and lower lip height. Preliminary results suggest that charcoal migrates in both upslope and downslope directions, especially within ~5-10 m of the RCH edges. Hearths in both high and low hillslope gradient regions showed variations of ~4-6 cm of charcoal enriched soil, though effects were more prominent in higher gradient regions. Current GIS analysis indicates that higher hillslope gradients correspond with larger lower lip heights and smaller diameters. Many charcoal hearths in lower hillslope gradients are circular, while ones in high-intermediate gradient regions tend to be elliptical or teardrop shaped. These findings provide implications for the impact of historic charcoal production on geomorphic processes operating in these forests today.