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Herbivory and plant growth rate determine the success of El Niño Southern Oscillation-driven tree establishment in semiarid South America

Authors

  • MILENA HOLMGREN,

    1. Resource Ecology Group, Wageningen University, Bornsesteeg 69, Building 119, 6708 PD Wageningen, The Netherlands,
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  • BERNAT C. LÓPEZ,

    1. CREAF (Center for Ecological Research and Forestry Applications) and Unit of Ecology, Department of Animal and Plant Biology and Ecology, Autonomous University of Barcelona (UAB), E-08193 Bellaterra, Catalonia, Spain,
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  • JULIO R. GUTIÉRREZ,

    1. Departamento de Biología, Facultad de Ciencias, Universidad de La Serena, Centro de Estudios Avanzados en Zonas Aridas (CEAZA) and Instituto de Ecología y Biodiversidad (IEB), Casilla 599, La Serena, Chile
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  • FRANCISCO A. SQUEO

    1. Departamento de Biología, Facultad de Ciencias, Universidad de La Serena, Centro de Estudios Avanzados en Zonas Aridas (CEAZA) and Instituto de Ecología y Biodiversidad (IEB), Casilla 599, La Serena, Chile
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Milena Holmgren, tel. +31 317 484320, fax +31 317 484845, e-mail: Milena.Holmgren@wur.nl

Abstract

While climatic extremes are predicted to increase with global warming, we know little about the effect of climatic variability on biome distribution. Here, we show that rainy El Niño Southern Oscillation (ENSO) events can enhance tree recruitment in the arid and semiarid ecosystems of north-central Chile and northwest Peru. Tree-ring studies in natural populations revealed that rainy El Niño episodes have triggered forest regeneration in Peru. Field experiments indicate that tree seedling recruitment in Chile is much less successful than in Peru due mostly to larger mortality caused by herbivores. The dramatic impact of herbivores in Chile was derived from the combined result of slower plant growth and the presence of exotic herbivores (European rabbits and hares). The interplay of herbivory and climatic effects we demonstrated implies that rainy ENSO events may represent ‘windows of opportunity’ for forest recovery if herbivore pressure is minimized at the right moment.

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