Early vegetation recovery after the 2008-2009 explosive eruption of the Chaiten Volcano

Abstract

In May 2008, Chaiten volcano entered in eruptive process, one of the world largest eruptions in the last decades. The catastrophic event left different type of disturbance and caused diverse environmental damage distributed heterogeneously in the surrounding areas of the volcano. We went to the field to assess the early vegetation responses a year after the eruption, in September 2009. Particularly, we evaluated the lateral-blast disturbance zone. We distributed a set of plots in three disturbed sites, and one in an undisturbed site. In each of these sites, in a plot of 1000m2 we marked all stand tree, recording whether they were alive, resprouting or dead. Additionally, in each site 80 small-plots (~4m2) we tallied the plants regeneration, its coverage, and the log-volume. We described whether the plant regeneration was growing on mineral or organic substrate. In the blast-zone the eruption created a gradient of disturbance. Close to the crater we found high devastation marked by no surviving species, scarce standing-dead trees and logs, as well as no tree regeneration. On the other extreme of the disturbance gradient, the trees with damaged crown were resprouting, small-plants were regrowing and seedlings were more dispersed. The main regeneration strategy was the resprouting of trunks or buried roots, while few seedlings were observed in the small plots and elsewhere in disturbed areas. However, the assessment was too soon after the eruption and updated monitoring is required to confirm observed patterns. The main findings of this study are: i) a mosaic of pioneering-wind dispersed species, scattered survivors regrowing and spreading from biological legacies, and plant species dispersed by frugivorous birds, likely favored by the biological legacies; (ii) the early succession is influenced by the interaction of the species-specific life history, altitudinal gradient and the different intensity of disturbance.