Abstract

RUGGIERO, Adriana  and  WERENKRAUT, Victoria. Legacy patterns in the abundance of epigaeic mountain beetles after the eruption of the Puyehue-Cordón Caulle volcanic complex (NW Patagonia, Argentina). Ecol. austral [online]. 2014, vol.24, n.1, pp.31-41. ISSN 1667-782X.

Organisms that survive a volcanic eruption are part of the biological legacies that are fundamental to subsequent succession and ecosystem development. In January 2012, the summer immediately after the eruption of the Puyehue-Cordón Caulle volcanic complex, we evaluated the short-term response of epigaeic beetle abundance to ash deposition. We focused on three mountains (La Mona, Bayo, Challhuaco) in northwestern Patagonia (Argentina) that were differentially affected by ash deposition. We re-established 32, 100 m² sampling plots of nine pitfall traps, every 100 m of altitude from the base to the summit of each peak, which we had previously sampled in January 2005 and 2006. We compared the shape of pre- and post- eruptive abundance-elevation relationship (AER), and assessed whether the relative importance of environmental predictors of AER (ambient energy, vegetation cover, plant species richness and soil attributes) changed after the eruption. La Mona and Bayo were most affected by ash deposition; Challhuaco was considerable less affected. Yearly fluctuations in abundance levels were significant in Bayo; here, the shape of AER changed significantly after the eruption. In La Mona, abundance was similar among sampled years, and the shape of AER departed weakly from the overall trend after the eruption. In Challhuaco, abundance tended to increase weakly with time, and the shape of AER did not change after the eruption. Gravel percentage and tree canopy cover were the two most important predictors of pre-eruptive AER, but only tree canopy cover remained as important after the eruption. We conclude that short-term effects of ash deposition on epigaeic mountain beetles were subtle and suggest that the presence of a gradient of ash deposition may lead to associated patterns in biological legacies. Long-term monitoring is essential to fully understand the structural and functional recovery of these mountain ecosystems.

Keywords : Ash deposit; Coleoptera; Elevation gradient; Generalized additive models; Multi-model inference approach.

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