Plant species over-occupancy indicates river valleys are natural corridors for migration

Anežka Holeštová,Jan Douda

doi:10.1007/s11258-021-01191-9

Abstract

River valleys are considered natural corridors for migration of plant species; however, there is a lack of studies confirming higher colonisation rates of plant species in these areas. We compare plant species richness between ancient and recent forests (developed during and after the nineteenth century) and those located in a river valley with those located outside the river valley. We hypothesise that, close to a river, higher plant species richness will be associated with recent forests, thus indicating a higher colonisation rate. The study area includes parts of the Elbe River Valley and a landscape outside the river valley in the Czech Republic. We sampled an equal number of recent and ancient forests (20/20), but lying at different distances from the river. We used generalised linear models to test the effect of distance from the river in dependence upon forest continuity (recent/ancient forest) on two plant species richness categories, i.e. richness of forest species and overall species richness. Outside the river valley, higher richness of forest species was associated with ancient forests, whereas overall species richness was comparable. In the river valley, richness of forest species as well as overall species richness was higher in the recent forests. Recent forests in the river valley were more saturated by plant species than those outside the river valley, indicating that in the river valley, the colonisation rate of plant species is higher. These results confirm the importance of river valleys as natural corridors for migration of plant species.

Highlights

It is well known that the plant species diversity is markedly different in a river valley compared to in the surrounding flat landscape (Blažková 1964; Naiman et al 1993; Renöfält et al 2005; Zelený and Chytrý 2007; Nobis et al 2016)
Higher richness of forest species was associated with recent forests in the river valley, whereas outside of the river valley higher richness of forest species was associated with ancient forests
Our results show a higher saturation of plant species in recent forests and this finding is consistent with our predictions that recent forests in river valleys are exposed to higher migration

Summary

Introduction

It is well known that the plant species diversity is markedly different in a river valley compared to in the surrounding flat landscape (Blažková 1964; Naiman et al 1993; Renöfält et al 2005; Zelený and Chytrý 2007; Nobis et al 2016). We lack studies which estimate whether the colonisation rate of plant species is higher in a river valley, than in the surrounding landscape. The decrease in habitat connectivity outside of a river valley has a negative effect on colonisation rate (Yao et al 1999; Renöfält et al 2005; Vellend 2016; Nobis et al 2016; Nobis et al 2017). Outside of a river valley, compared to colonisation, both the distance from the riverbank and habitat fragmentation increase the importance of local community processes including competition and ecological drift. The balance between the rate of colonisation and that of extinction determines the composition and species richness of a local plant community (Vellend 2016)

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Conclusion