Wind and Water Dispersal of Wetland Plants Across Fragmented Landscapes

Hester Soomers,Martin J. Wassen,Pita A. Verweij,Derek Karssenberg,Jos T. A. Verhoeven,Merel B. Soons

doi:10.1007/s10021-012-9619-y

Abstract

Biodiversity in wetlands is threatened by habitat loss and fragmentation, of which agricultural activities often are a cause. Dispersal of plant seeds via wind and ditches (water) may contribute to connecting remnant wetland plant populations in modern agricultural landscapes, and help to maintain and restore biodiversity. We developed a spatially explicit model to assess the relative importance of dispersal by wind and dispersal by water through drainage ditches for two wetland plant species in agricultural landscapes: a typical wind disperser and a typical water-disperser. Simulation results show that the typical wind disperser had a much higher capability to disperse by wind (90th percentile <30 m) than the typical water-disperser (90th percentile <2 m). Surprisingly, the capability to disperse via water was similar for the two species: 90th percentile dispersal distances following a combination of wind and water dispersal were between approximately 100 and 1000 m. Dispersal by water transported more seeds over long distances for both species. The main determinants for dispersal distance by water were roughness of the ditch (determined by, for example, bank vegetation) and the presence of obstructions (for example, culverts). Density or direction of the ditch network did not seem to affect water dispersal distances substantially. From a biodiversity conservation perspective, it would be most useful if areas with suitable riparian wetland habitat were intersected with a network of shallow ditches with a high roughness promoting seed deposition. These areas should then be connected to other suitable areas by a few regularly cleaned ditches with no obstructions and low seed trapping probability.

Highlights

Habitat destruction and habitat fragmentation have reduced large, continuous natural areas to smaller and less connected habitat patches globally
Using the anemochory–hydrochory model, we address the following research questions: (i) what is the relative contribution of wind dispersal and water dispersal to seed dispersal distances in landscapes with different configurations of drainage ditches and (ii) to what extent do system characteristics of the landscape determine the dispersal distances of seeds? Our results provide new insights into the relative importance of wind and water dispersal in agricultural landscapes and how different landscape characteristics and features determine deposition patterns of seeds across these landscapes
Our results show that typical wind dispersers can be transported over long distances by water, and may disperse by water over similar distances as typical water-dispersers

Summary

Introduction

Habitat destruction and habitat fragmentation have reduced large, continuous natural areas to smaller and less connected habitat patches globally. These patches contain smaller and more isolated populations of plants and animals, which often experience an increased risk of extinction In fragmented, isolated habitats, seed dispersal can become limiting for the regional survival of species (Soons and others 2005; Ozinga and others 2009). Populations of wild species can persist in fragmented habitat patches surrounded by an agricultural matrix (Donald and Evans 2006). Exchange between fragmented habitats takes place by seed dispersal via wind, water, animals, and human activity. Few studies have tried to combine seed dispersal by wind and water

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