Purpose The impact of wildfire on (a) slope hydrological processes, (b) soil erodibility, and (c) post-fire hillslope sediment and phosphorus (P; dissolved and particulate) yields are quantified for natural forest areas of the burned Evrotas River basin, Peloponnese, Greece. Further, the geochemical partitioning of P in burned and unburned sediment is evaluated by sequential extraction to assess potential bioavailability of particulate P (PP) in downstream aquatic ecosystems. Materials and methods A series of field-based rainfall simulation and infiltration experiments were undertaken in burned and unburned terrain of contrasting vegetation and soil type, after severe wildfires in summer 2007. Resulting water and sediment samples were analyzed for P concentration to permit calculation of hillslope yields for 20, 40, and 60 mm h -1 rainfall events. Samples of soil were collected from each site type for physical and geochemical analyses.Results and discussion Plot-scale rainfall simulation experiments and measurements demonstrate enhanced runoff and erosion rates in burned terrain. While dissolved P concentrations in runoff from burned terrain are elevated (0.21± 0.09 mg l -1 ) against background levels (0.01±0.01 mg l -1 ) and exceed European water quality guidelines, PP represents 99% of the severely burned hillslope P yield (2.32± 1.63 kg ha -1 for a 15-min rainfall event). Sequential extraction data demonstrate that up to 20% of total PP in burned sediment is potentially bioavailable and that bioavaliable PP yields are two orders of magnitude greater than dissolved P yields. Conclusions Release of P from eroded sediment stored in downslope/downstream sink zones may protract the postfire risk to downstream resources. Quantification of PP partitioning in eroded sediment is a key requirement when assessing the downstream impacts of wildfire.

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