DOI: 10.5061/dryad.d7wm37q13
title: Long-term shifts in the functional diversity of abandoned wet meadows – Impacts of historical disturbance and successional pathways

description: Investigating the direction of changes in functional diversity involving
 successional pathways and historical disturbances may be a promising tool
 for predictions of the effectiveness of the semi-natural meadows
 conservation, with great emphasis on formulation of more cost-effective
 restoration strategies. The goal of this research was to assess the
 differences in long-term shifts in the functional diversity of plant
 species in semi-natural wet meadows unmanaged for the last 40 years, under
 the influence of different successional pathways and historical
 disturbances. Using ordination techniques, linear mixed-effect models, a
 set of plant functional traits and parameters of functional diversity, we
 assessed the importance of habitat filtering, competition and niche
 partitioning in shaping community assembly changes over time. The most
 dramatic shifts in functional diversity were found in the Carex
 acutiformis successional pathway after topsoil removal, where colonization
 by successional inhibitors was the main driver causing decreases in
 functional dispersion and divergence. This was expressed as a decrease in
 the importance of habitat filtering and replacement of specialized species
 by competitors with heavier seeds and higher specific leaf area. Regarding
 the C. cespitosa and Salix cinerea pathways, the magnitudes of shifts in
 functional diversity were milder and differed less between the historical
 topsoil removal and mowing treatments, thereby maintaining a large role
 for niche partitioning in shaping the vegetation structure. The results of
 our study highlight the importance of tussock sedges and shrubs as
 effective buffers against the biotic homogenization of meadows driven by
 the simplification of functional composition, even from a long-term
 perspective.
description: The
 study was conducted on unmown meadows in the Reski Range, with an area of
 approximately 15 ha. The Reski Range is located in the northwestern part
 of the Białowieża Glade in Białowieża National Park (N
 52<sup>0</sup>42’32’’; E 23<sup>0</sup>50’06’’) in
 the Narewka River valley (NE Poland). Meadows of the Reski Range occupy
 the habitats of old ash-alder riparian forests. More than 200 years ago,
 in the part of the Narewka River valley, forests were cut down, and
 extensively mowed meadows were formed (Falińska 2003). Due to relatively
 low utility values and early spring flooding, the meadows in the Reski
 Range were gradually abandoned by farmers. The process of scything
 cessation began in the 1960s and ended in 1978. After stopping the use of
 these meadows, spontaneous secondary succession began. This created an
 opportunity to establish the first long-term permanent plot experiments,
 aiming to assess the population dynamics of single plant species over
 time, as well as the mechanisms of the replacement of populations of
 individual species by other plants during secondary succession (Falińska
 1991). This research was initiated by K. Falińska in 1972 (Falińska 1991).
 After approximately 20 years of these detailed investigations, she
 identified three main pathways, which were the most commonly occurring
 pathways in the study area, of secondary succession, based on life-history
 traits (e.g., clonal architecture, seed bank characteristics and
 reproductive strategies) of the dominant and co-occurring species
 (Falińska 2003). The pathway of succession, with the participation of
 <i>Salix cinerea</i> (hereafter ‘<i>S. cinerea
 </i>pathway’), involves the exchange of species composition
 according to the following scheme: meadow – tall herb communities –
 thicket – forest. In turn, the <i>Carex cespitosa</i>
 (hereafter ‘<i>C. cespitosa </i>pathway’) and <i>Carex
 acutiformis </i>(hereafter ‘<i>C. acutiformis
 </i>pathway’) pathways involve the simultaneous coexistence of
 species composition characteristics of rush, tall herb and thicket
 communities (Falińska 2003). An experiment
 was conducted in 1995-2015, approximately 20 years after the initial
 long-term research of plant demography during secondary succession
 (Falińska 1991, 2003). To study each of the three successional pathways
 identified by K. Falińska as the most common in the study area, one
 transect consisting of 30 permanent plots (1x1 m) was established and
 divided into three sub-transects, each one being 10 m in length and 1 m in
 width. Therefore, the total number of permanent plots for the three
 successional pathways and three treatments was 90. At the beginning of the
 experiment, different types of disturbances were applied once in each
 sub-transect for each successional pathway. The first sub-transect was
 subjected to strong disturbance (n=10): the plants, including roots and
 topsoil surface, were removed. In the second sub-transect (n=10), weak
 disturbance was applied: the aerial parts of the plants were cut down with
 a knife/scythe. The third sub-transect (n=10) was left intact as a control
 area, without the application of any disturbance. Thus, as each
 successional pathway was identified prior to our long-term experiment and
 application of different disturbance types, we did not take into account
 interactions between the successional pathway and disturbance, assuming
 that observations within each transect were independent. Permanent plots
 were established in 1994, and the first field survey took place in 1995.
 Then, within five-year intervals (to 2015), analyses of species
 composition were carried out on each plot (1 x 1 m) within each
 sub-transect and each successional pathway, and species abundance (the
 total number of ramets per species recorded) was noted. Plant species
 names were adopted after Mirek et al. (2002). Using the LEDA
 database, we compiled information on seven functional traits related to
 plant size and leaf morphology (i.e., canopy height, shoot growth form,
 leaf distribution along stem, and specific leaf area; SLA) and dispersal
 abilities (dispersal mode, seed mass and seed bank longevity).