Effects of herbivory and patch size on tree seedling survivorship in a fog-dependent coastal rainforest in semiarid Chile |
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Authors: | Ek del-Val Juan J Armesto Olga Barbosa Pablo A Marquet |
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Institution: | (1) Center for Advanced Studies in Ecology and Biodiversity (CASEB), Departamento de Ecología, Facultad Ciencias Biológicas, Pontificia Universidad Católica de Chile, Casilla 114-D, Santiago, Chile;(2) Instituto de Ecología y Biodiversidad (IEB), Facultad de Ciencias Universidad de Chile, Casilla 653, Santiago, Chile;(3) National Center for Ecological Analysis and Synthesis, 735 State Street, Suite 300, Santa Barbara, CA 93101, USA;(4) Present address: Centro de Investigaciones en Ecosistemas, Universidad Nacional Autónoma de México, Apartado Postal 27-3 (Xangari), Santa Maria Guido, Morelia, Michoacán, 58089, Mexico;(5) Present address: BIOME, University of Sheffield, Sheffield, UK |
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Abstract: | The landscape (matrix) surrounding habitat fragments critically affects the biodiversity of those fragments due to biotic
interchange and physical effects. However, to date, there have been only a limited number of studies on plant–animal interactions
in fragmented landscapes, particularly on how tree seedling herbivory is affected by fragmentation. We have examined this
question in a fog-dependent mosaic of rainforest fragments located on coastal mountaintops of semiarid Chile (30°S), where
the effects of the surrounding semiarid matrix and forest patch size (0.1–22 ha) on tree seedling survival were simultaneously
addressed. The rainforest is strongly dominated by the endemic evergreen tree species Aextoxicon punctatum (Olivillo, approx. 80% of basal area). To assess the magnitudes and causes of Olivillo seedling mortality, we set up a field
experiment where 512 tree seedlings of known age were transplanted into four forest fragments of different sizes in four 1.5 × 3-m
plots per patch; one-half of each plot was fenced off with chicken wire to exclude small mammals. The plots were monitored
for 22 months. Overall, 50% of the plants died during the experiment. The exclusion of small mammals from the plots increased
seedling survival by 25%, with the effect being greater in smaller patches where matrix-dwelling herbivores are more abundant.
This experiment highlights the important role of the surrounding matrix in affecting the persistence of trees in forest fragments.
Because herbivores from the matrix cause greater tree seedling mortality in small patches, their effects must be taken into
account in forest conservation–restoration plans. |
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Keywords: | Habitat fragmentation Plant– animal interactions Tree regeneration Water limitation |
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