CHARCOAL REMAINS IN LITCHFIELD COUNTY CONNECTICUT RECORD WIDESPREAD HILLSLOPE DISTURBANCE IN THE IRON CORRIDOR FROM MID-18TH TO EARLY 20TH CENTURIES AND PRESENT DAY CARBON STORAGE

Landscape evolution in post-industrial southern New England reflects an industrial past revealed on LiDAR imagery and by field studies in the now-wooded landscape. Construction of >20,000 earthen platforms for charcoal production (mounds) in an area of 2450 km2 affected hillslope processes and altered soil development in Litchfield County (northwestern Connecticut) from mid-18th to early 20th century. Charcoal mounds varied from 7 to 13 m in diameter and were similar to earthen charcoaling mounds built elsewhere in the northeastern USA and Europe at the time. However, colliers supporting northwestern Connecticut’s iron industry built their mounds on platforms carved from the region’s steep to moderate slopes. We estimate that mound construction moved approximately 10,000 m3 of sediment downslope and charcoal production operations likely disturbed large hillslope areas. Field measurements show that the steep sides of the platforms have eroded in the past ~120 years, suggesting that platforms enhance movement of adjacent slopes.

The forests of southern New England convert a significant amount of atmospheric CO2 to organic matter, a portion of which is stored in soils. Understanding changes to this regional C sink is therefore important for understanding CO2 cycling at a global level. Mound construction mixed the upper meter of local sediment such that texture and moisture retention of the mounds differs from those of background sediments. The upper 10 to 40 cm of relict mounds are rich in charcoal and have high C/N ratios compared to soils on adjacent hillslopes. The concentration of charcoal in the upper meter of the mounds is about 5%, or about 2.5% C. By weight, this suggests that up to 31,800 kg of C is stored in forest soils over the entire study area due to historic charcoal production. C concentration in soils outside the mounds likely contain an average concentration of C in the upper meter that is <2%, and this C would be concentrated in the uppermost layers of the soil profile (<15-20 cm).