Reintroduction of Nassella pulchra to California coastal grasslands: Effects of topsoil removal,plant neighbour removal and grazing |
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Authors: | Elise Buisson Sean Anderson Karen D Holl Emmanuel Corcket Grey F Hayes Alain Peeters Thierry Dutoit |
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Institution: | 1. Université d'Avignon et des Pays du Vaucluse, Institut Méditerranéen d'Ecologie et de Paléoécologie (UMR CNRS IIRD), IUT, Site Agroparc, BP1207, 84911 Avignon cedex 9, France;2. Environmental Science and Resource Management Department, One University Drive, California State University, Channel Islands, Camarillo, CA 93012–8599, USA;3. Environmental Studies Department, University of California Santa Cruz, CA 35064, USA;4. UMR 1202 INRA BIOdiversité, Gènes, ECOsystèmes, Université Bordeaux 1, Avenue des Facultés, 33405 Talence Cedex France;5. Elkhorn Slough National Estuarine Research Reserve, 1700 Elkhorn Rd, Watsonville, CA 95076, USA;6. Laboratoire d'Ecologie des Prairies, Université Catholique de Louvain, Place Croix du Sud, 2 bld 11,1348 Louvain‐La‐Neuve, Belgium |
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Abstract: | Question: What is the most appropriate combination of treatments to reintroduce Nassella pulchra, a perennial bunchgrass, into degraded mediterranean coastal grasslands? Location: Central coast of California, USA. Methods: N. pulchra was sown from seeds and transplanted into a degraded grassland in a multi‐factorial experiment testing the effects of (1) two grazing intensities (lightly grazed by native mammal species or ungrazed); (2) topsoil removal and (3) reduction of plant neighbours. The experiment was carried out on two types of surrounding vegetation (exotic annual grasses and exotic forbs). Results: Topsoil removal greatly enhanced establishment from seeds and transplant survival, mainly because it reduced the exotic vegetation and thus reduced competition. While removing neighbours was essential when topsoil was left intact, it had a negative effect on N. pulchra when surrounding species included exotic forbs (Brassica spec, and Asteraceae) at low density (after topsoil removal). Moderate grazing by native mammals (deer, rabbits and gophers) did not affect N. pulchra. Conclusion: Our results suggest that seeding after topsoil has been removed is a promising method to reintroduce N. pulchra to highly degraded sites where there is little to no native seed bank. |
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Keywords: | Competition Exotic annual species Native perennial bunchgrass Nitrogen reduction Weeding |
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