Fire history and tree population dynamics in Białowieża Forest, Poland and Belarus

Fire history and fire regime parameters in relation to the long-term tree population dynamics were studied with dendroecological methods across coniferous habitats of Białowieża Forest (E Poland and W Belarus), a semi-natural European temperate woodland ecosystem. In four different studies various aspects of fire dynamics were explored by using nearly 1500 tree ring samples of Pinus sylvestris and Picea abies. By applying tree diameter at the first fire scar and post-fire growth response as proxies for fire intensity, the fire regime of Białowieża Forest was proven to have been dominated by low-intensity surface fires. However, occasional occurrence of high-intensity stand-replacing fires that were causing substantial successional changes at the stand scale was also recorded (I). Using a multiple-site fire history reconstruction combined with historical maps, eye-witness accounts and information on the abundance of light-demanding flora the omnipresence of fire throughout the coniferous sections of Białowieża and its role in shaping landscape-scale Scots pine dominance was revealed (II), as well as massive spruce encroachment following the fire cessation across those habitats (III). By reconstructing the extent of historical fires in a 9 km2 part of the study area, exploring the spatial dimension of fire disturbance in Białowieża Forest was proven to be possible and documented the occurrence of large-scale fires exceeding 500 ha (IV). The conclusion from these studies is that fire was the main driver of tree population dynamics across the coniferous portions of the Białowieża landscape until relatively recently, i.e. 100–150 yrs ago, with substantial influence on the tree species composition, habitat openness and the following biological diversity, especially of the light-demanding taxa. In that respect, the common opinion that fire is less important in shaping forest dynamics of both, Białowieża Forest, and temperate Europe, was challenged