Holocene peatland vegetation, climate, and fire reconstruction in the Appalachian Mountains of West Virginia

Abstract

Pollen records in conjunction with charcoal records are useful in interpreting and reconstructing past vegetation and fires, but records of peatland fires and vegetation in the Eastern United States are sparse. Here we investigate how local fire regimes have interacted with peatland development and vegetation change in response to both climate and human impacts during the Holocene. We collected cores from two small peatlands: Big Run Bog (BRB) and a bog in the Dolly Sods Wilderness Area (DS), 25 km apart, and located in the Allegheny Mountain section of the Appalachian Plateaus physiographic province, in West Virginia (WV). Both cores were analyzed for radiocarbon dates, loss-on-ignition, pollen, plant macrofossils, charcoal counts, and charcoal morphotypes; we also reconstructed past climates from the pollen data using the modern analogue technique. The BRB spans the period from 18,000 cal yr BP to present, with a period of low accumulation or hiatus between 12,000 and 3500 cal yr BP. The DS record is younger, spanning at least the last 5,000 cal yr BP, but we did not attempt an age-depth model due to several age reversals in stratigraphic order. Pollen records show that the surrounding upland area began as a conifer dominated site, and our analyses of charcoal morphotypes corroborate this. The vegetation shifted from a conifer dominated area to a mixed hardwood forest around 10.7 ka. Climate reconstructions from the pollen data, based on the modern analogue technique, suggest that this shift corresponds to a sharp increase in mean annual temperature. Macrofossils identified from Big Run Bog show that the bog was first a rich fen, which later transitioned to a bog around 200 cal yr BP. A sharp increase in charcoal concentration in the uppermost samples (> 65 cm) of BRB corresponds to the increase in Ambrosia in our pollen records, which indicates the onset of forest clearance by European colonists. After the logging period, there was an increase in Sphagnum moss at 60 cm from our macrofossil record, suggesting that European deforestation may have led to the formation of a bog through decreases in forest transpiration. The paludification is also recorded by increases in organic matter. The paleoecological records from Big Run Bog and Dolly Sods Bog therefore show strong influence of both climate and human impacts on fire and vegetation in the West Virginian region of the Appalachian Mountains during the late Quaternary.