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Title The role of animal-mediated seed removal/ dispersal for shrub encroachment during a drought in a Namibian highland savannah.

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Short title Animal-mediated seed dispersal and shrub encroachment

Author(s) Osterried, K.; Wasiolka, B.; Rossmanith, E.; Jeltsch, F.; Blaum, N.

Presenting author Blaum, N.

Institution(s) Plant Ecology and Nature Conservation, University of Potsdam

Keywords seed removal; savannah highland; drought; shrub encroachment

Abstract Many plant species that are dispersed by zoochorous seed dispersal drop their seeds at maturity to facilitate seed harvest by ground-foraging animals. Also Acacia mellifera shrubs, the main shrub encroacher in Namibian highland savannas drop their seeds at maturity. However, in savannas, zoochorous seed dispersal and their impact for shrub encroachment are poorly investigated. In a first step, this study experimentally assessed animal-mediated (rodents, insects, birds) seed removal during a drought period where seed predation is expected to by highest. We used seed trays including seeds of three woody species (Acacia mellifera, Prosopis spec. and Catophractes alexandrii) and one grass species (Cenchrus ciliaris). Seed removal rates were compared between shrub encroached and grass dominated savannah habitats. Multi-factorial ANOVA showed that animal taxa and seed species affected removal rates. Removal rates of Prosopis spec. were highest but also Acacia mellifera and Catophractes alexandrii were removed.

Congress Topic Land use, impact and value

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