Succession patterns and the role of fire in long-term dynamics of a mixed deciduous stand in Białowieża Forest, Poland

In temperate Europe, the ecological importance of fire is poorly understood, especially in the dynamics of forests with high share of broadleaved tree species. The aim of this thesis was to explore the role of fire in a 43-ha mixed-deciduous forest stand in Białowieża Forest, NE Poland. The changes in the tree species composition were investigated using dendrochronological data obtained from three circular 5000 m2 sample plots and one 25m-long transect. In addition, to reconstruct the local fire history, all fire-scarred trees from the whole stand were cored and cross-sections from pine and oak stumps were collected. From 288 cores and one pine stump, tree establishment back to the end of the 1500s and 19 fire events between 1720 and 1908 were reconstructed. The stand’s age structure revealed a shift from light-demanding fire-adapted species (oak and pine) to shade-tolerant fire-sensitive species (hornbeam and lime) undergoing a transitional phase with codominance of a plastic species (spruce). Up to the end of the 18th century, oak and pine regenerated sporadically under frequent fires. The change gradually began with relaxation in the fire regime in the first half of the 19th century. This permitted more seedlings to survive and initiated cohorts of both oak and pine, followed by spruce encroachment. The canopy became denser, likely leading to more humid and less flammable fuel conditions after mid-1800s. Thus, the fires propagated less, permitting recruitment of more shade-tolerant species up to date. The data suggests that fire exclusion played an important role in the cessation of oak and pine regeneration in the studied stand. To my knowledge, this study is one of the first in temperate Europe highlighting the role of fire in shaping the long-term vegetation dyamics of mixed-deciduous forest ecosystems

Pioneer tree species accelerate restoration of tree-related microhabitats in 50-year-old reserves of Bialowieza Forest, Poland

Retention of structural elements such as deadwood and habitat trees at the level of forest stands has been promoted to integrate biodiversity conservation into multiple-use forest management. The conservation value of habitat trees is largely determined by the presence, richness, and abundance of tree-related microhabitats (TreMs). Since TreMs are often lacking in intensively managed forests, an important question of forest conservation is how the abundance and richness of TreMs may be effectively restored. Here, we investigated whether the strict protection of forest through cessation of timber harvesting influenced TreM occurrence at tree and stand levels. For that purpose, we compared four managed and four set-aside stands (0.25 ha each) in the Bialowieza Forest, with identical origin following clear-cuts approximately 100 years ago. We found that the abundance and richness of TreMs on living trees were not significantly different between stands that were either conventionally managed or where active forest management ceased 52 years ago. Yet, our analysis of TreMs on tree species with contrasting life-history traits revealed that short-lived, fast-growing species (pioneers) developed TreMs quicker than longer-lived, slower-growing species. Hence, tree species such as Populus or Betula, which supply abundant and diverse TreMs, can play an important role in accelerating habitat restoration

Where are we now with European forest multi-taxon biodiversity and where can we head to?

International audienceForestry implementation significantly impacts forest biodiversity. Despite the promotion of Sustainable Forest Management (SFM) in Europe, sustainability assessments hardly account for direct biodiversity indicators. We aim to i) gather and map the existing information on forest multitaxon biodiversity associated with stand structure and management in Europe; ii) identify knowledge gaps for forest biodiversity research; and iii) discuss the research potential associated with multitaxon biodiversity data. We established a research network focused on multi-taxon biodiversity, stand structure and management data of European forests; and fitted species records, standing trees, lying deadwood, and sampling unit metadata from 34 local datasets. Suitable information was available for 3,591 sampling units, each surveyed for on average 4.6 taxonomic groups. Standing tree diameters, tree height deadwood and tree-related microhabitats were sampled in respectively 2,889; 2,356; 2,309 and 1,388 sampling units. Sampling unit metadata includes spatial coordinates, and compositional and management descriptors. Available data cover all the 14 European forest compositional categories but are unevenly distributed among them, with European beech forests being over-represented as compared to thermophilous and boreal forests. Overall, the available information has the potential to inform the development of conservation and SFM strategies for European forests by supporting: (i) methodological harmonization and coordinated monitoring; (ii) the definition and testing of SFM indicators and thresholds; (iii) datadriven assessment of the effects of environmental and management drivers on multi-taxon forest biological and functional diversity, (iv) multi-scale forest monitoring integrating in-situ and remotely sensed information