Unique Hydrologic, Chemical, and Physical Properties of Relict Charcoal Hearths
Open Access
- Author:
- Bayuzick, Samuel
- Graduate Program:
- Soil Science
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- September 15, 2021
- Committee Members:
- Bradley Cardinale, Program Head/Chair
Patrick Joseph Drohan, Thesis Advisor/Co-Advisor
Marc Eric Mc Dill, Committee Member
Duane R Diefenbach, Committee Member
John Thomas Spargo, Committee Member
Thomas Raab, Special Signatory - Keywords:
- Relict charcoal hearths
charcoal
hearth
soil
forest - Abstract:
- Abrupt changes in a forest ecosystem 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 change may alter forest 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. Throughout the northeastern United States and Europe, relic charcoal hearths (RCHs) are more regularly being discovered in proximity to furnaces used for iron or quick-lime production; charcoal was used as a primary fuel source in furnaces. A landscape classification process was used to identify 6,758 RCHs in the vicinity of Greenwood Furnace (Greenwood Furnace State Park and greater Rothrock State Forest) and Pine Grove Furnace (Pine Grove Furnace State Park and greater Michaux State Forest). Topographic wetness index (TWI), and SAGA wetness index (SWI) were created using ~1m LiDAR data for two study areas to quantify surface hydrology effects and were compared to field soil volumetric water content (VWC) measurements. Modeled TWI and SWI values were different for RCH areas when compared to surrounding non-hearth areas indicating that RCHs were acting as a moisture sink. We also found that RCH platforms have different TWI and SWI values than rim areas. Using field measured volumetric water content, we found that as distance from the center of the RCH increases, the drier the soil becomes. Geomorphic position did not affect wetness. Surface soil samples were collected at 51 RCHs in the Greenwood Furnace study area. By analyzing soil samples collected perpendicularly to slope across RCHs and outside the RCH, we found that RCH soils have higher C content than surrounding native soils. Furthermore, while the pH of RCH soils is similar to native soils, the acidity is different due to the increase in extractable Al and Fe which may be toxic to some vegetation communities. RCH soils at Greenwood Furnace were found to have lower Mehlich 3 P concentrations and lower K potentially effecting plant growth. RCH soils were found to have higher Ca concentration when compared to native soils. To examine within RCH differences in soil chemistry and morphology more closely, 8 of the 51 RCHs were sampled intensely along a topographic gradient. Control pits were excavated directly upslope from the RCHs. The RCHs were sampled, by small excavation or bucket auger, in 5 positions across the hearth from the upslope to down slope position. Position A represents the upslope rim of the RCH; Position B represents the halfway point between Position A and C; Position C represents the center of the RCH; Position D represents halfway between Position C and E, and Position E represent the downslope rim of the RCH. Soil profiles were described and sampled at each position. The soil samples were analyzed for trace and rare earth element content (Aqua Regia digestion). Soil pH (water) and fertility (Mehlich 3 extraction) were also determined. Results indicated that there is a surface and subsurface enrichment of the downslope sampling positions with Ca, and Mg. Subsurface C increased while proceeding along the gradient whereas surface concentrations remained similar. Extractable Al was enriched in the surface and across the RCH; however, the subsurface concentrations of extractable Al decreased when compared to control soils. Soil macronutrients N, P, K concentrations decreased in surface samples while total N was slightly more abundant in the first 10 cm compared to control samples. Surface Mn concentrations from Aqua Regia digestion showed a trend downslope that indicates the enrichment of subsurface Mn concentrations. Accumulation of soil nutrients generally occurs across stabilized landscape positions and less stabilized landscape conditions cause more soil chemical variability. RCHs are potentially a unique location of refugia for forest flora and perhaps fauna due to the unique geochemistry with higher bases and C and some concentrated metals and a higher soil water content hypothesized to be due to an observed restrictive morphology. Future research should more closely investigate whether RCHs support unique species assemblages and how they may play a role in enhancing today’s forest biodiversity.