DOI: 10.5061/dryad.h8p4n
title: Data from: Dispersal versus environmental filtering in a dynamic system: drivers of vegetation patterns and diversity along stream riparian gradients

description: 1. Both environmental filtering and dispersal filtering are known to
 influence plant species distribution patterns and biodiversity.
 Particularly in dynamic habitats, however, it remains unclear whether
 environmental filtering (stimulated by stressful conditions) or dispersal
 filtering (during re-colonization events) dominates in community assembly,
 or how they interact. Such a fundamental understanding of community
 assembly is critical to the design of biodiversity conservation and
 restoration strategies. 2. Stream riparian zones are species-rich dynamic
 habitats. They are characterized by steep hydrological gradients likely to
 promote environmental filtering, and by spatiotemporal variation in the
 arrival of propagules likely to promote dispersal filtering. We quantified
 the contributions of both filters by monitoring natural seed arrival
 (dispersal filter) and experimentally assessing germination, seedling
 survival and growth of 17 riparian plant species (environmental filter)
 along riparian gradients of three lowland streams that were excavated to
 bare substrate for restoration. Subsequently, we related spatial patterns
 in each process to species distribution and diversity patterns after 1 and
 2 years of succession. 3. Patterns in initial seed arrival were very
 clearly reflected in species distribution patterns in the developing
 vegetation and were more significant than environmental filtering.
 However, environmental filtering intensified towards the wet end of the
 riparian gradient, particularly through effects of flooding on survival
 and growth, which strongly affected community diversity and generated a
 gradient in the vegetation. Strikingly, patterns in seed arrival
 foreshadowed the gradient that developed in the vegetation; seeds of
 species with adult optima at wetter conditions dominated seed arrival at
 low elevations along the riparian gradient while seeds of species with
 drier optima arrived higher up. Despite previous assertions suggesting a
 dominance of environmental filtering, our results demonstrate that
 nonrandom dispersal may be an important driver of early successional
 riparian vegetation zonation and biodiversity patterns as well. 4.
 Synthesis: Our results demonstrate (and quantify) the strong roles of both
 environmental and dispersal filtering in determining plant community
 assemblies in early successional dynamic habitats. Furthermore, we
 demonstrate that dispersal filtering can already initiate vegetation
 gradients, a mechanism that may have been overlooked along many
 environmental gradients where interspecific interactions are (temporarily)
 reduced.
description: Seed arrival,
 recruitment and presence in vegetation along riparian
 gradients11 worksheets with data
 on seed arrival, experimentally studied recruitment processes
 (germination, seedling survival and seedling growth), and natural
 developing vegetation (worksheets 3-7), model predictions of seed arrival
 and recruitment processes (worksheets 8-11), abiotic variables (worksheet
 2) and description of column headers (worksheet 1).Fraaije et al 2015
 JEcol.xlsx