Semicentennial dynamics of old silver birch (Betula pendula Roth) forests in the Belavezhskaya Pushcha National Park

In this study, we present the results of an investigation of the long-term dynamics of natural silver birch (Betula pendula Roth) forests within the Belavezhskaya Pushcha National Park, Belarus. Six sample plots represent two primary forest associations: Tilio-Carpinetum and Querco roboris-Pinetum sylvestris. All stands originated from clear-cuttings in the early 20th century, and their age varies from 84 to 111 years as of 2023. The study spans from 1972 to 2023, encompassing the observation of various forest parameters, including diameter at breast height (DBH), tree height, canopy positioning, living ground cover, and the shrub layer, conducted multiple times (from 2 to 4). Successional patterns were observed to develop in three main directions, contingent upon the initial composition of the forest stand. In most cases, Betula pendula forests transition directly to spruce (Picea abies) forests or through the short (around 20 years) European aspen Populus tremula phase. The emergence of broadleaved forests in their place typically occurs no earlier than 200 years after logging, coinciding with the period of decline of Picea abies due to droughts and bark beetle attacks. Exceptions are observed in forest phytocenoses thriving on more fertile soils, where Quercus robur and/or Acer platanoides can swiftly replace mixed Populus tremula-Betula pendula stands after a century of development. Consequently, a considerable reduction in Betula pendula forests within Belavezhskaya Pushcha is anticipated in the forthcoming decades, gradually replaced by Picea abies and mixed broadleaved forests. These findings are significant for predicting the stand structure, biodiversity, and carbon sequestration potential of unmanaged forests. Keywords: long-term study; permanent plots; Betula pendula; DBH structure; regeneration; succession