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Do plant-community-based grazing regimes lead to epizoochorous dispersal of high proportions of target species?

Wessels, Saskia and Eichberg, Carsten and Storm, Christian and Schwabe, Angelika :
Do plant-community-based grazing regimes lead to epizoochorous dispersal of high proportions of target species?
[Online-Edition: http://www.sciencedirect.com/science/article/pii/S0367253008...]
In: Flora, 203 (4) pp. 304-326.
[Article], (2008)

Official URL: http://www.sciencedirect.com/science/article/pii/S0367253008...

Abstract

The contribution of large-herbivore epizoochory to the transfer of seeds within and between areas is thought to be significant. But often seeds of ubiquitous species are dispersed, which may enhance ruderalization processes. In order to study the dispersal of target species by sheep, we employed a community-based grazing approach followed by intra- and inter-area sheep transfers (maximum transfer distance 3 km). In case of inter-area transfers, well-developed target communities of an open inland sand ecosystem are used as "source", linked to less-developed sand habitats ("sink") via sheep. Also other factors determining which species become dispersed under field conditions were tested: seed surface structure, seed mass, plant seed-releasing height and animal behaviour. Finally the influence of animal movement on seed detachment and the actual arrival of seeds within a "sink" were studied. Sheep transfers resulted in the dispersal of 56 seed species, dominated by Red List (seven species) and other target species. Quantitatively, most transported seeds belonged to target species, whereas graminoid competitors were highly under-represented. Morphological traits enhance the attachment probability regardless of seed mass. But for seeds without these epizoochory-facilitating traits, mass seems to affect attachment negatively. Plant height affected the number of species present in sheep coats but not the seed quantities. Probably certain species in the vegetation produced large numbers of seeds, e.g. low-growing Medicago minima with seed surface structures and high-growing species Verbascum phlomoides without seed surface structures. Also, although transfer half-times were three times lower than grazing half-times, naturally attached Stipa capillata and Agrimonia procera seeds showed no significant detachment rates during transfer, whereas considerable losses were found during grazing. Other 3-km sheep transfers did not result in significant losses of either epizoochorously transported seed or species quantities. Our study shows that community-based grazing can lead to the dispersal of especially target species. Besides that, different habitat fragments can be connected to each other via sheep without significant seed losses along the way. (c) 2008 Elsevier GmbH. All rights reserved.

Item Type: Article
Erschienen: 2008
Creators: Wessels, Saskia and Eichberg, Carsten and Storm, Christian and Schwabe, Angelika
Title: Do plant-community-based grazing regimes lead to epizoochorous dispersal of high proportions of target species?
Language: English
Abstract:

The contribution of large-herbivore epizoochory to the transfer of seeds within and between areas is thought to be significant. But often seeds of ubiquitous species are dispersed, which may enhance ruderalization processes. In order to study the dispersal of target species by sheep, we employed a community-based grazing approach followed by intra- and inter-area sheep transfers (maximum transfer distance 3 km). In case of inter-area transfers, well-developed target communities of an open inland sand ecosystem are used as "source", linked to less-developed sand habitats ("sink") via sheep. Also other factors determining which species become dispersed under field conditions were tested: seed surface structure, seed mass, plant seed-releasing height and animal behaviour. Finally the influence of animal movement on seed detachment and the actual arrival of seeds within a "sink" were studied. Sheep transfers resulted in the dispersal of 56 seed species, dominated by Red List (seven species) and other target species. Quantitatively, most transported seeds belonged to target species, whereas graminoid competitors were highly under-represented. Morphological traits enhance the attachment probability regardless of seed mass. But for seeds without these epizoochory-facilitating traits, mass seems to affect attachment negatively. Plant height affected the number of species present in sheep coats but not the seed quantities. Probably certain species in the vegetation produced large numbers of seeds, e.g. low-growing Medicago minima with seed surface structures and high-growing species Verbascum phlomoides without seed surface structures. Also, although transfer half-times were three times lower than grazing half-times, naturally attached Stipa capillata and Agrimonia procera seeds showed no significant detachment rates during transfer, whereas considerable losses were found during grazing. Other 3-km sheep transfers did not result in significant losses of either epizoochorously transported seed or species quantities. Our study shows that community-based grazing can lead to the dispersal of especially target species. Besides that, different habitat fragments can be connected to each other via sheep without significant seed losses along the way. (c) 2008 Elsevier GmbH. All rights reserved.

Journal or Publication Title: Flora
Volume: 203
Number: 4
Divisions: Fachbereich Biologie, Biology > Vegetationsökologie und Restitution, Vegetation ecology - Restoration
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Fachbereich Biologie, Biology
Date Deposited: 19 Oct 2011 11:55
Official URL: http://www.sciencedirect.com/science/article/pii/S0367253008...
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