ABSTRACT Sedimentation after wildfire is a profound disturbance to the biogeomorphic character of fluvial systems. Despite this significant alteration, field data focusing on the geomorphic processes and bed morphology that form the physical structure of habitat are limited, especially over a longer-term perspective. We report results of detailed field studies following two wildfires in the same steep fluvial system in the southern California Transverse Ranges three decades apart. Substantial channel sedimentation during storms following both fires altered physical elements of habitat, which included bed elevation, step height and spacing, pool depth and spacing, grain-size distribution ( D 84 ), and transport capacity (τ o /τ c ). The postfire sediment deposits buried bedforms, decreased D 84 , and increased τ o /τ c by an order of magnitude. Incision during subsequent storms initiated recovery that depended on the attributes of post-wildfire climate variability that characterize the semiarid Mediterranean-type environment. Step-pool bedforms reappeared or reformed during the decades between wildfires as the relatively fine gravel-sized post-wildfire sediment was transported downstream, thus reestablishing the physical elements of habitat characterizing the dynamic system.

Abstract Volcaniclastic sedimentological studies in Japan have addressed Miocene–Holocene volcaniclastic fluvial and lacustrine successions. These research approaches can be categorized into: (1) the ‘from volcanic source to sink’ concept focusing on hydrological volcaniclastic sedimentation (including lahars), environmental impacts and cascading processes by explosive volcanism; and (2) the ‘from sink to volcanic source’ view, with a focus on elucidating volcanic and eruptive information such as the location of the eruption centre, eruption style and eruption age from analyses of distally deposited volcaniclastic sediments other than tephra fall deposits, despite the occasional absence of correlative eruption records in proximal areas and/or on the volcanic edifice itself. Geological records, which have a longer time span, can reveal decadal- to millennial-scale hydrological and cascading volcaniclastic sedimentation that cannot be assessed currently by direct observation. In addition, distal volcaniclastic successions in sinks have a continuous depositional record that can provide precise ages and the recurrence intervals of past eruptions and eruption-associated hydrological events. Both perspectives, beyond the borders of sedimentology and volcanology, are necessary to capture the geological record fully and to understand past volcanisms and their impacts, which will eventually lead to better prediction and preparation for future volcanic events.

Abstract We studied the recovery of the woody vegetation in a segment of the Rayas River, which 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 sampling efforts were executed on Islands, High bars, the Floodplain, and in association with Wood jams. Results show that 9 years after the volcano's last eruption, pre-eruption remnant Islands and the Floodplain exhibited 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 has 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.