DOI: 10.5061/dryad.rm068
title: Data from: Species pools and environmental sorting control different aspects of plant diversity and functional trait composition in recovering grasslands

description: Succession theory argues that the taxonomic and functional structure of
 assembling communities is regulated by the interplay of local
 environmental conditions and regional factors such as available species
 pools or landscape configurations that moderate dispersal. Yet, the
 relative importance of these factors and whether they control different
 aspects of community structure, for example species diversity or the
 composition of plant traits, is not well understood. This limits
 predictions of spatial variation in successional outcomes. We explored
 patterns of species diversity and traits in recovering calcareous
 grasslands that varied in environmental conditions, age, past and present
 spatial landscape configuration, as well as in the propagule pressure they
 receive from historical grasslands that have large and functionally
 distinct species pools. Mixed-effects modelling and multimodel inference
 were used to dissect the leading drivers of species diversity and
 functional composition. Propagule pressure from the regional species pools
 of old grasslands during early stages of grassland re-assembly was an
 important determinant of community structure, with significant effects not
 only on species diversity but also on the composition of traits related to
 resource economics. Such species pool effects exceeded positive influences
 of environmental heterogeneity on species richness and confounded
 well-known diversity–environment and trait–environment relationships. As
 an orthogonal axis of community assembly, environmental sorting occurred
 along a gradient of soil texture that discriminated species according to
 their canopy height and – to a smaller extent – phenology. Additionally,
 high grassland perimeter–area ratios favoured specialist species richness
 and increased the proportion of species with predicted poor epizoochorous
 and wind dispersal. Synthesis. We provide empirical evidence that both
 species pool effects and local environmental sorting operate during
 community assembly of recovering calcareous grasslands, but that they
 influence different aspects of plant community structure. Further, we show
 that geographic variation in propagule pressure from large and
 functionally distinct source species pools can confound
 diversity–environment and trait–environment relationships. Therefore,
 besides accounting for environmental factors, considering the location of
 source species pools, as well as their compositional and functional
 characteristics, is a prerequisite for robust predictions of contingencies
 in taxonomic and functional community structure of successional habitats.
description: Species Composition
 DataThis file contains
 presence/absence data of 233 plant species in 23 recovering calcareous
 grasslands (‘Sites’) in southern Germany. Species are in columns, rows
 indicate presence [1] or absence [0] of a species in a
 grassland.grass_species.txtPlot Environmental DataThis file contains soil variables measured in 161 vegetation sampling plots located in 23 recovering calcareous grasslands (‘Sites’) in southern Germany. Each row represents a grassland. See associated ReadME file for variable description and measurement units.grass_env.txtGrassland Spatial DescriptorsThis file contains 9 variables describing the age and spatial landscape context of 23 recovering calcareous grasslands (‘Sites’) in southern Germany. See associated ReadME file for variable description and measurement units.grass_site.txtHabitat Specialist ClassificationThis file contains information on the habitat specialism of all species in the associated file ‘grass_species.txt’. Column ‘Specialist’ is a binary variable where 1 = habitat specialist, and 0 = non-specialist.grass_specialists.txt