Rain Forest Islands in the Chilean Semiarid Region

Authors: Ek delVal Juan J Armesto Olga Barbosa Duncan A Christie Alvaro G Gutiérrez Clive G Jones Pablo A Marquet Kathleen C Weathers

Publish Date: 2006/05/31

Volume: 9, Issue: 4, Pages: 598-

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Abstract

Tree presence in semiarid ecosystems is generally constrained by insufficient annual rainfall However in semiarid Chile rainforest patches dominated by Aextoxicon punctatum are unexpectedly found on coastal mountaintops 450–600 m at 30°S surrounded by a xerophytic vegetation matrix that receives only 147 mm of annual precipitation It has been proposed that these forests persist as a result of fogwater inputs If so then because fogwater deposition is spatially heterogeneous and shows strong edge effects the potential environmental gradient created by the direction of fog input should determine forest structure and tree regeneration patterns To investigate this hypothesis we measured fog inputs forest structural attributes age and size distribution basal area and coarse woody debris and tree regeneration in three different habitats the windward edges WE leeward edges LE and the interior center of rainforest patches varying in area from 02 to 22 ha Mean fogwater input was estimated from passive collectors over 1 year in WE and LE of patches Tree regeneration was greater in the WE and forest interior FI and decreased toward the LE of patches following a marked pattern of decline in fog inputs Older trees and coarse woody debris were concentrated in the FI and LE of patches Tree regeneration and patch structure appear to be largely controlled by foginput direction and edge effects We propose that forest patches may be slowly growing toward the incoming fog edge while dying at the opposite edgeThis work was supported by Fondo de investigación Avanzada en Areas Prioritarias FONDAP – FONDECYT 15010001 Centro de Estudios Avanzados en Ecologia Biodiversidad CASEB the Biocores Project funded by the European Community EC under the INCO IV program contract ICA 4CT2001–10095 Centro Milenio para Estudios Avanzados en Ecología e Investigación en Biodiversidad CMEB PO2051F ICM the National Science Foundation International Americas Program INT0313927 and the Institute of Ecosystem Studies The Corporación Nacional Forestal CONAF IV Región Chile kindly gave permission to work at Fray Jorge National Park We thank J Monardes A Abarzúa M Nuñez D Fernández J P François J Valdez J M Valenzuela T Catalán N Davis and D Gho for their help with field data collection and N Carrasco and A Rivera for laboratory assistance Pablo Necochea kindly drew the Fray Jorge map Other than the first author order of authorship is alphabetical This is a contribution to the program of the Institute of Ecosystem Studies

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