Assessing woody vegetation recovery in the Rayas River following the eruption of the Chaitén Volcano in 2008

Abstract

We studied the recovery of the woody vegetation in a segment of the Rayas River, that drains the Chaitén Volcano, in southern Chile. Data collection in the river corridor was performed to assess the regeneration rates of the colonizing vegetation within the river corridor, to investigate the site-specific regeneration modes (i.e., with respect to the different morphological units), to determine the species composition and to observe potential similarities with the regeneration process on hillslopes (i.e., outside the river corridor). We first performed a sampling of the shrub and tree vegetation regenerating in the Forest adjacent to the study segment. Further samplings were executed on Islands, High bars, the Floodplain, and in association to Wood jams. Results show that nine years after the volcano's last eruption, pre-eruption remnant Islands and the Floodplain exhibited an abundant regeneration, with the highest density of recruits and species richness. In addition, a clear difference was observed between the river corridor and the Forest, both in the characteristics of the plants that were regenerating as well as in the species composition. Finally, the vegetation that has re-established after the eruption have not yet acquired the capacity to play a stabilizing role in the fluvial corridor. New insights are provided on reforestation patterns at sites impacted by Large Infrequent Disturbances.