Effects of small mammals and vertebrate predators on vegetation in the Chilean semiarid zone |
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Authors: | J R Gutiérrez P L Meserve S Herrera L C Contreras F M Jaksic |
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Institution: | (1) Departamento de Biología Universidad de La Serena, Casilla 599, La Serena, Chile, CL;(2) Department of Biological Sciences, Northern Illinois University, Dekalb, IL 60115, USA, US;(3) CONAMA, Casilla 520-V, Santiago, Chile, CL;(4) Departamento de Ecología, Pontificia Universidad Católica de Chile, Casilla 114-D, Santiago, Chile, CL |
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Abstract: | We monitored the cover and seed bank response of shrubs, perennial herbs, and ephemeral plants to experimental exclusion
of both the principal rodent herbivore, Octodon degus, and its vertebrate predators from 1989 to 1994 in a semiarid Chilean mediterranean site. Although both richness and species
composition of the plant community at the study site were largely determined by abiotic factors (mainly rainfall and soil
nutrients), predator and herbivore exclusion had significant effects on the relative abundance of several plant species. Experimental
exclusion of herbivores was associated with increased cover of some shrubs and a perennial grass, and decreased cover and
seed densities of several ephemerals, especially those exotic or restricted to areas underneath shrubs. Herbivores apparently
reduced shrubs through browsing and indirectly affected herb cover and seed densities by opening up areas under shrubs and/or
modifying physical and chemical conditions of the soil. Plant responses to predator exclusion were less clear. Nevertheless,
higher cover of some shrubs and ephemerals in the presence of predators suggests tritrophic effects through changes in small
mammal densities and/or foraging behavior.
Received: 22 April 1996 / Accepted: 14 August 1996 |
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Keywords: | Herbivory Predation Tritrophic effects Ephemeral plants Chilean semiarid zone |
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