Towards the understanding the impact of fire on the lower montane forest in the Polish Western Carpathians during the Holocene

Abstract

In this article, we aim to decipher the effect of fire on the changes in the forest composition during the past ca. 10,700 years in the lower montane zone of the Polish Western Carpathians (Beskid Makowski Mountains, Central Europe). The results revealed that during the Early Holocene, the Ulmus population (a fire-intolerant taxon) was well-established under high fire activity, induced by the prominent presence of Pinus sylvestris. Ulmus probably was only slightly affected by fire because it occurred in wetter habitats, whereas P. sylvestris occupied drier ones. The final disruption of Pinus sylvestris–Betula woodlands were linked to a declining trend in fire activity but stable fire frequency, combined with the rapid expansion of Corylus avellana at ca. 9680 cal. BP. A low magnitude of fire disturbance with an increasing fire frequency supported the expansion of Tilia cordata (a fire-sensitive species) and C. avellana (a fire-adapted species) against Picea abies during ca. 7650–7270 cal. BP. Cooler and wetter conditions during the 4.2 and 2.8 ka. BP climatic events probably forced humans to migrate to higher altitudes, which contributed to fire-induced deforestation of a small area, which in turn, together with climatic changes, stimulated the expansion of Abies alba and Fagus sylvatica (both are fire-intolerant taxa). The discontinuities in the deposits of mire might be related to the global climatic changes of the 8.2 and 4.2 ka. BP events and extended deforestations linked to the Wallachian colonisation during the Middle Ages. Such depositional gaps, when remaining undetected during palaeoecological studies, may distort the reconstruction process of fire–vegetation relationships. In this study, we unequivocally show that small disturbances in fire may be an advantageous factor for the expansion of tree taxa devoid of morphological–physiological fire traits.