Both trait-neutrality and filtering effects are validated by the vegetation patterns detected in the functional recovery of sand grasslands

P Török,J Sonkoly,B Tóthmérész,G Matus,E Tóth,M Papp,A Kelemen

doi:10.1038/s41598-018-32078-x

Abstract

Neutral theory of species assembly means that species assembly is governed by stochastic dispersal processes and fluctuations in established populations. An alternative theory suggests that assembly is strongly determined by functional trait filtering governed by abiotic and biotic filtering selecting species from the local species pool. To test these assumptions, in the current paper we analysed vegetation changes in the first 12 years of succession after heavy goose grazing on acidic sand. With trait-based analyses using permanent plots we addressed the following hypotheses: (i) High fluctuations in the trait values are typical in the first years; later a temporally divergent change in the trait patterns of sites with different vertical position became characteristic. (ii) In the functional diversity of regenerative and vegetative traits we expected different temporal patterns. We confirmed the first hypothesis, as in the first few years most traits displayed high fluctuations with no clear patterns. Our findings weakly supported the second hypothesis; while there were distinct patterns detected in the functional richness of traits, functional divergence and evenness displayed no clear distinctive patterns. We can conclude that both trait neutrality and filtering effects operate in the vegetation changes of the first period of secondary succession.

Highlights

Grassland ecosystems are suffering worldwide from area loss and changing levels of human pressure mostly in form of altered management ranging from intensification to underuse and abandonment[1]
We found a marked increase in community-weighted means (CWMs) of clonal spreading (Fig. 2A), life span (Fig. 2B), and leaf dry matter content (LDMC) (Fig. 2F)
We found a trend of decrease in the CWMs of plant height (Fig. 2C) and specific leaf area (SLA) (Fig. 2G)

Summary

Introduction

Grassland ecosystems are suffering worldwide from area loss and changing levels of human pressure mostly in form of altered management ranging from intensification to underuse and abandonment[1]. This view is deeply rooted in the view of Gleason[5] and in the initial floristic composition theory of Egler[6] (revisited by Wilson et al.[7]) Another approach suggests that community assembly is strongly determined by functional trait filtering governed by more or less definite interaction of abiotic and biotic filtering processes selecting species from the available local species pool. We used a permanent plot setup and trait-based analyses to address the following hypotheses: (i) Former research suggests that early vegetation development is characterised by stochastic processes and the interaction of abiotic and biotic filtering become increasingly important driver of vegetation changes in the later period[12,22]. We expected different temporal patterns in the functional diversity of regenerative and vegetative traits

Methods

Results

Conclusion