DOI: 10.5061/dryad.44j0zpcck
title: Temporal biodiversity change following disturbance varies along an environmental gradient

description: Aim The diversity and composition of natural communities are rapidly
 changing due to anthropogenic disturbances. Magnitude of this
 compositional reorganization varies across the globe, but reasons behind
 the variation remain largely unknown. Disturbances induce temporal
 turnover by stimulating species colonizations, causing local extinctions,
 altering dominance structure, or all of these. We test which of these
 processes drive temporal community changes, and whether they are
 constrained by natural environmental gradients. Moreover, we assess to
 what degree identity shifts translate to changes in dominance structure.
 Location Finland Time period Observations 1985-2006, disturbance history
 &gt;140 years. Major taxa studied Vascular plants. Methods We
 investigated temporal turnover of boreal forest understory in response to
 disturbance, here forest management, along a soil fertility gradient. We
 disentangle the roles of species gains, losses and abundance changes in
 driving temporal turnover in response to and after disturbance by
 comparing turnover rates in different forest age categories along
 fertility gradient. We quantify temporal turnover richness-based
 complement of Jaccard’s similarity index and proportional-abundance based
 dissimilarity index. We also test whether disturbance history or fertility
 influence the relationship between identity shifts and dominance
 structure. Results We found that the impact of disturbance on temporal
 turnover depends on soil fertility. The greatest turnover occurred in most
 fertile forests immediately after disturbance. There, species gains and
 losses strongly altered dominance structure leading to high turnover,
 whereas undisturbed old forests and nutrient-poor habitats were
 characterized by stable dominant species even when the majority of species
 shifted their identity. Main conclusions Our results suggest that human
 impacts on temporal biodiversity change vary along environmental
 gradients. In boreal forests, the fertile habitats have higher probability
 than nutrient-poor sites to change their composition in response to
 anthropogenic disturbances. Resource availability and disturbance history
 may thus influence consequences of temporal turnover for ecosystem
 functioning.
description: Vascular
 plants in forest understory were surveyed on a systematic network of 1700
 sites established on mineral-soil in forested land in 1985–86. These sites
 are a part of a systematic sampling network of the
 8<sup>th</sup> Finnish National Forest Inventory (Reinikainen
 <i>et al.</i>, 2000). This network consists of clusters, which
 were located 16 km from each other in Southern Finland, and 24 and 32 km
 apart in Norther Finland along east-west and north-south axes,
 respectively. Each cluster consists of four linearly located sampling
 sites 400 m apart from each other in Southern Finland and three sampling
 sites 600 m apart from each other in Northern Finland. All 1700 sites were
 resurveyed in 1995, and a subset of 443 of them (max 1 site per cluster)
 were resurveyed in 2006 (Fig. 1). The spatial extent of this subset was
 comparable to previous surveys covering whole country. The survey
 performed on 443 sites in 2006 was part of the BioSoil project carried out
 under the Forest Focus scheme, which is a subset of the pan-European
 UN-ECE ICP Forests extensive monitoring site network (Level I, Lorenz
 & Fischer, 2013). The following files contain a
 two subsets of these understory surveys: 'SubsetA.csv' includes
 sites, with NO forest management between two surveys, while
 'SubsetB.csv' includes sites, which encountered some type of
 forest management between 1985 and 1995. Species
 abundances are given as an average percent cover across four
 2m<sup>2</sup> study quadrats within a
 'Site'.
description: Data files SubsetA and SubsetB contain the necessary data to
 perform the analyses in the linked manuscript. Both files comprise
 of species abundance data, environmental covariates (explained in the
 methods of the article) and timing of the latest forest management
 action. 'Site_year_pair' is an unique identifier for each 10
 years sampling period, while 'Site' identifies the location.
 Missing values are indicated with 'NA'.
 Please see the attached Metadata_Subsets_A_B.doc for a detailed
 description of the variables.
 <strong>SubsetA.csv</strong> contains sampling
 periods WITHOUT forest management between the 'Start_year' and
 the 'End_year' and known 'Time_since_disturbance'
 before the 'Start_year'. In SubsetA, some 'Sites' were
 re-surveyed twice (both in 1995 and 2006) and have thus two
 'Site_year_pairs'.
 <strong>SubsetB.csv </strong>contains sampling
 periods WITH known timing and type of forest management during the period,
 i.e. between the 'Start_year' and the
 'End_year'.