Human-induced changes in fire regime and subsequent alteration of the sandstone landscape of Northern Bohemia (Czech Republic)

Abstract

Multiproxy palaeoecological evidence from a sandstone region in northern Czech Republic was collected to explore the impact of fire disturbances on the decline of the broadleaved forests during the Late Bronze Age (3250–3050 cal. BP). It has been hypothesized that human-accelerated soil leaching affected the nutrient availability in the sandstone area, thus promoting the expansion of oligotrophic-adapted plant communities in the late-Holocene. Little is known about the mechanisms which induced such large-scale vegetation transformation. We sought to determine which driving forces were involved using independent proxy records – soil and sedimentary charcoal, pollen and fungal spores. Local fire history was derived from the variation in charcoal accumulation rates (CHAR) preserved in Eustach peatbog. The fire frequency (FF) estimation over the past ~7500 years revealed distinct phases of increased burning between 3100 and 2120 cal. BP (3.0 fires 1000 yr⁻¹) and 1400–600 cal. BP (4.3 fires 1000 yr⁻¹). Rapid compositional changes in the pollen assemblage were documented during the Late Bronze Age period, suggesting vegetation responded to increased fire disturbances. The human influence on the fire regime is implied by the short-term increase in cereal pollen concurrent with a major fire event, indicating possible use of slash-and-burn cultivation by Late Bronze societies. This type of human subsistence strategy practised in the sandstone landscape further evolved to pastoralism as suggested by continuous presence of coprophilous fungi Sporormiella and Sordaria, which occurred since the Hallstatt/La Tène period (2750–1950 cal. BP). Our study documents, for the first time, the intentional, human-caused biomass burning from densely forested areas of Northern Bohemian sandstone region. Our results imply that increased rate of fire disturbances contributed to the Late Bronze Age transformation of broadleaved forests to oligotrophic forest communities of late-Holocene.