Northern Appalachian, USA relic charcoal hearths and their unique Ecological Fingerprint

Abrupt changes in a forest ecosystem, whether natural or anthropogenic, are changes that occur over short time periods; such disturbance has the potential to drive state changes and alter forest resilience. Understanding how present-day abrupt forest change may alter ecosystem services is becoming more important due to ever-growing anthropogenic stresses. Forest managers trying the adapt to anthropogenic stress can benefit from the study and quantification of past abrupt changes in forests, especially when the legacy of past disturbance is still evident. Across the United Kingdom, Europe, and recently the northeastern United States, the examination of historic forest change due to charcoal manufacturing for the firing of iron or lime furnaces is yielding new insights relative to landscape stability, anthropogenic vs natural soil genesis, and forest evolution. We present results of a study that strives to evaluate how historic land clearing for the charcoal industry (supporting iron furnaces) affected local soils and may drive surrounding present day forest composition. We incorporate field sampling of hearth soils and modeled hydrologic parameters (in hearth and non-hearth areas), to quantify the uniqueness of relict charcoal hearth (RCH) systems. We identified 1,239 hearths using a LiDAR terrain analysis; approximately 10% of these were visited to quantify hearth morphology and soil moisture differences on and off hearth. Nine hearths from this 10% were intensively sampled and were associated with a northern Appalachian, USA furnace that was in operation from 1867 to 1904. Three profiles were excavated across each hearth and compared to an adjacent soil profile on the same contour. Soil descriptions were made of hearths and soil samples analyzed for total, trace and rare earth element content (Aqua Regia digestion). Soil pH (water) and fertility (Mehlich III extraction) were also determined. Results indicate that hearths have a unique geochemistry with higher bases and some concentrated metals and higher organic carbon. Coupled with a higher hearth soil water content, hypothesized to be due to an observed restrictive subsurface morphology and higher organic carbon, hearths are potentially unique locations of refugia for forest flora and fauna. Future research should more closely investigate whether hearths support unique species assemblages and how they may play a role in enhancing today’s forest biodiversity.