Dendrochronological reconstruction reveals a mixed-intensity fire regime in Pinus sylvestris-dominated stands of Biaowiea Forest, Belarus and Poland

QuestionsWhat were the features of the historical forest fire regime, fire intensity in particular, in Pinus sylvestris-dominated stands of Biaowiea Forest? Did tree recruitment patterns relate to the fire history? LocationBiaowiea Forest, western Belarus and northeast Poland. MethodsWe used dendrochronological methods to reconstruct the fire regime in a 8.5-ha mixed coniferous (Pinus sylvestris-Picea abies) forest stand located in the Belarusian part of Biaowiea Forest. We analysed fire frequency at stand and point scale, seasonal distribution of fires and fire intensity. We compared the results to a previous study done in a 13.0-ha site of similar habitat and stand structure, located in the Polish part of Biaowiea Forest. ResultsWe reconstructed fires back to 1655, the most recent fire dating to 1918. Mean fire interval at stand scale during 1645-2010 was 97.8yrs (+/- SD). Fire frequency gradually declined after 1811, with mean fire interval at stand scale increasing from 5 +/- 2.5yrs prior to 1811 to 18 +/- 9.3yrs thereafter. Most fires were likely of low intensity, as suggested by (1) small average tree diameter (5.1 +/- 2.9cm) at the first scar, (2) absence of strong negative growth reactions after fire, and (3) high fire frequency likely limiting fuel build-up. However, a fire in 1718 was intense and resulted in a wave of P.sylvestris regeneration. The reconstructed fire history in the Belarusian part of Biaowiea Forest showed many similarities with that done in the Polish section of this forest. Similarities included dominance of low-intensity dormant and early-season fires, sporadic occurrence of high-intensity fires, high fire frequencies between the 1650s and the early 1800s, and cessation of fires since the early 20th century. Six out of 50 fire dates reconstructed in both sites were common and represented a level of synchrony that was significantly higher than expected under a random pattern of fire occurrence. ConclusionsLow-intensity surface fires dominated the historical fire regime of Biaowiea Forest. However, occasional high-intensity stand-replacing fires led to successional changes at the stand scale.