Spatial and temporal patterns of initial plant establishment in salt marsh communities

Kertu Lõhmus,Michael Kleyer,Thorsten Balke,Péter Török

doi:10.1111/jvs.12915

Kertu Lõhmus, Michael Kleyer + Show 2 more

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https://doi.org/10.1111/jvs.12915

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Abstract

AbstractQuestionsHow are dispersal processes, abiotic and biotic interactions determining the initial salt marsh plant community establishment and development when connectivity is different? We aim to answer this question by analysing the spatial and temporal patterns of plant establishment along an environmental gradient at two connectivity settings.LocationBack‐barrier salt marsh and tidal flats of Spiekeroog, northwest Germany.MethodsWe established an experiment along a saltmarsh elevation gradient with bare sediment open for spontaneous colonisation on the natural salt marsh and on the experimental salt marsh islands built on the tidal flats approximately 500 m from the natural salt marsh for low connectivity. Plant establishment was identified from georeferenced photos at least monthly.ResultsExperimental islands as low‐connectivity plots had limited colonisation by annual halophytes that produced large number of small seeds. Number of individuals increased with higher connectivity at patches enclosed by salt marsh. Number of individuals was highest at the mid elevations whereas peak species richness was at the upper salt marsh. Temporal patterns of seedling emergence showed increasing plant numbers until the end of April followed by a gradual decline over the season at the pioneer and lower salt marsh zones. Upper elevations on the other hand had a stable number of low individual counts over time. Spatial clustering of plant individuals indicating possible facilitation was important at the initial stages of salt marsh development at pioneer and lower salt marsh elevation, but only early in the season.ConclusionsStochastic patterns of early salt marsh colonisation indicated that success of species colonisation was determined by seed properties, seed availability and environmental conditions mediated by elevation. We found indications that at the initial stages, further colonisation was supported by already colonised plants but shifted to avoidance later in the season.

Highlights

The long-term stability and resilience of ecosystems depends partially on the species' ability to recover and regenerate after disturbances, which is realised by colonisation and establishment (Loreau et al, 2003; Leibold et al, 2004)
The combination of environmental conditions and competitive abilities of species leads to a distinct zonation of vegetation along elevational gradients in European salt marshes (Petersen et al, 2014)
We aim to understand plant establishment during initial salt marsh vegetation development. This was done by quantifying the effects of seed availability, environmental conditions and biotic interactions on salt marsh vegetation assembly

Summary

| INTRODUCTION

The long-term stability and resilience of ecosystems depends partially on the species' ability to recover and regenerate after disturbances, which is realised by colonisation and establishment (Loreau et al, 2003; Leibold et al, 2004). The combination of environmental conditions and competitive abilities of species leads to a distinct zonation of vegetation along elevational gradients in European salt marshes (Petersen et al, 2014). We aim to understand plant establishment during initial salt marsh vegetation development This was done by quantifying the effects of seed availability, environmental conditions and biotic interactions on salt marsh vegetation assembly. We address the following questions: (a) is plant colonisation determined by connectivity and plant dispersal traits; (b) how does the elevational gradient affect initial colonisation; (c) how are the temporal changes in plant numbers affected by the environmental conditions (i.e. elevation as a proxy for flooding and biotic interactions); and (d) does initial colonisation indicate clustering or avoidance of individuals?

| METHODS

Findings

| DISCUSSION