A continuous record of fire covering the last 10,500 calendar years from southern Sweden - The role of climate and human activities
Résumé
A high-resolution, continuous 10,500 cal. yrs-long macroscopic charcoal record from a peat and lake sediment deposit at Storasjö, in the hemiboreal vegetation zone of southern Sweden, is presented. This record was compared with the microscopic charcoal record from the same core, and tentatively correlated with the macroscopic and microscopic charcoal records from another site (Stavsåkra), situated 30 km West of Storasjö. The charcoal records are also compared with regional climate proxy records with the aim to separate climate ƒ from human-induced fire activity. The results suggest that the major signal of both microscopic and macroscopic charcoal records represents local fire history. The best record of local fire history was obtained from the continuous macroscopic charcoal analysis. A tentative correlation of the charcoal records between the sites indicates that most fire episodes of the early and middle Holocene are probably of regional character. Both sites exhibit three major phases of high fire activity 1) 87008300 BC, 2) 7250 BC to ca. 4000 BC, and 3) 750 BC to the 19th century. These three phases are separated by periods with lower or very low fire activity. This general trend is in good agreement with the pattern emerging for Europe from the analysis of the recently developed global charcoal database. Fire appears to have been controlled by climate during the early and middle Holocene and by humans during the late Holocene. Warmer and drier climate during the early and middle Holocene caused frequent and intensive fires, which suggests that natural fire activity might increase under predicted future climate scenarios. The results also suggest that fire was an important disturbance factor in the hemiboreal vegetation zone of Sweden and played an important role in the forest dynamics and characteristics of the flora and fauna of the region.