DOI: 10.5061/dryad.2fqz612ks
title: Over 80 years without major disturbance, late successional Białowieża woodlands exhibit complex dynamism, with coherent compositional shifts towards true old‐growth conditions

description: 1. Controversies about successional dynamics of woodland communities have
 a long history, dating back to the classical debates between Clements and
 Gleason and continuing into the present. These debates have largely
 concerned the predictability or convergence of forest developmental trends
 as well as the relative importance of different mechanisms and forces
 driving forest succession. However, opportunities for rigorous testing of
 competing hypotheses are limited, mainly because plot-based studies of
 forest vegetation spanning more than a decade are scarce and even fewer
 concern late-successional stands. 2. We exploit a unique long-term data
 set from mesic temperate forests of eastern Poland, spanning ca. 80 years
 (1936-2012) in strictly protected, late-successional woodlands assigned to
 seven different ‘structural types’. We use non-metric multidimensional
 scaling to assess stability of species composition over the study period.
 We examine predictability of composition and change trajectories over time
 using Mantel statistics, and we examine changes in distributions of
 dissimilarity indices to assess convergence or divergence at the examined
 time and spatial scales. 3. Tree communities in Białowieża Forest have
 changed substantially over the last eight decades. Several species (aspen,
 birch, pine, oak, ash, maple and spruce) exhibited large decreases in
 density, while few other species (especially hornbeam and lime) have
 increased in importance across a wide range of initial compositional
 types. Forest types recognized in earlier periods have become much less
 distinguishable. Metrics do not yet show clear successional convergence,
 mainly due to a) declines in the previously broadly distributed spruce and
 b) persistence of large individuals of intermediate, long-lived species
 (even though these species lack significant regeneration). 4. Synthesis.
 Late-successional woodland communities of Białowieża Forest are clearly
 dynamic and do not show quasi-equilibrial properties often assumed of
 old-growth forests. Forest types previously recognized as distinct have
 become progressively less differentiated. Plausible explanations invoke
 alteration in competitive relationships due to complex changes in
 environment, including climate, N deposition, natural and human
 disturbance, and ungulate herbivory over 70 years. Hornbeam and lime have
 been favored over spruce, pine, oak and birch, although the resulting
 successional convergence is far from complete at this time. In the absence
 of major disturbance, we expect future decades to show continued and
 successional homogenization.
description: Paper Over 80 years without major
 disturbance, late-successional Białowieża woodlands exhibit complex
 dynamism, with coherent compositional shifts towards true old-growth
 conditions.  Brzeziecki B., Woods K., Bolibok L., Zajączkowski<sup>
 </sup>J., Drozdowski<sup> </sup>S., Bielak<sup>
 </sup>K., Żybura<sup> </sup>H. <b>Data
 scope</b> This data file contains numbers
 for tree species basal area (m<sup>2</sup>), calculated for
 all live trees with DBH ≥5cm, occurring on quadrats 20 m x 20 m. Quadrats
 were selected in a chess-board pattern within the permanent research plots
 located in Białowieża National Park (cf. the paper). Calculations were
 performed separately for 11 tree species, 5 research plots, and 7 census
 dates. <b>Research
 plots</b> The permanent research plots are
 transects of different width (40-60m) and length (200-1380m) (total area =
 15.44 ha), located in the core section of the Białowieża National Park,
 the so called „Strict Reserve” (see Appendix 1 in the paper).
 <b>Census dates and
 scope of measurements</b> Transects have been sampled on a
 total of 7 major occasions: in 1936, 1955-1959 (1957), 1968-1972 (1970),
 1981-1983 (1982), 1991-1993 (1991), 2001-2003 (2002) and 2011-2013 (2012).
 During the first survey, all trees with a DBH (diameter at breast height)
 of at least 5 cm were identified and their spatial locations were mapped.
 During subsequent censuses, similar measurements were made. Additionally,
 recruits, i.e. trees which had increased in diameter by up to 5 cm in the
 period between consecutive censuses, were identified, as well as trees
 which had died since the time of the last record (losses). Scientific
 species names and numbers of live trees measured during the first and last
 census are given in Appendix 2 in the paper.