PARENT SESSION
Poster Session 34: Herbivory
Thursday, August 11, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal

The effects of shrubs, herbivory and rainfall on the structure and dynamics of ephemeral plants in a coastal semiarid ecosystem of north-central Chile.

Gutiérrez, Julio^{*,1, 1}, Squeo, Francisco^{2, 2}, Aguilera, Lorgio, Meserve, Peter, Kelt, Douglas, ¹ Departamento de Biología, La Serena, Chile² Centro de Estudios Avanzados en Zonas Áridas, La Serena, Chile

ABSTRACT- We analyzed the individual and combined effects of shrubs, herbivory and rainfall on the structure and dynamics of ephemeral plants (i.e., annuals and geophytes) in Fray Jorge National Park, north-central Chile for two years (2003 and 2004). This park contains semiarid thorn scrub vegetation and remnant fog forests which has been protected from grazing and disturbance since 1941. Total shrub cover at the study site is ca. 60%. The dominant shrub species are Porlieria chilensis, Adesmia bedwellii, and Proustia pungens; they differ greatly in shape, leaf density, woodiness, deciduoudness, and root systems. This park has also a diverse assemblage of small mammals which are mostly herbivores. We show that the individual and/or combined effects of shrubs, herbivory by small mammals and temporal variation in rainfall accounts for the high diversity of ephemeral plant species in this system. We assessed the relative importance of these three factors using a factorial design and experimental approach. Different shrub species generate patches of different environmental quality (e.g., microclimate, soil nutrients, soil moisture), providing sites suitable for different ephemeral plant assemblages. Annual rainfall accounts for temporal variation of ephemeral plant assemblages, but spatial variation of these plant assemblages is determined by the presence of different shrub species. Responses of ephemeral plants to rainfall depend on the abundance of herbivores. This study is being financed by FONDECYT 1030225.

Key words: aridlands, ephemeral plants, herbivory, north-central Chile