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.

The paper examines the relationships between soil aggregate stability, selected soil properties and land use in central Spain.Aggregate stability indices derived from three procedures were found to be significantly (p > 0.01) correlated with each other as well as with clay content, organic carbon and a range of water-soluble salts. Soils with a higher clay content have a lower aggregate stability. It appears that the presence of expandable clays has a major negative influence, although this impact is strongly modified by recent land-use history and contemporary land-management practices. Agricultural land, abandoned in the 1940s, was subsequently invaded by Cistus matorral or planted with Pinus. The most stable aggregates occur under matorral and may represent a lag of more resistant aggregates surviving past land-use-related erosional processes. Comparisons with aggregates under Pinus however suggest that hydrophobic substances from the Cistus may have increased aggregate stability. Aggregates from areas remaining in cultivation are the least resistant although the stability envelope overlaps with areas under Pinus. These differences may be related to cultivation practices whereby clay-rich subsurface horizons characterized by higher proportions of expandable clays are drawn to the surface, and to enhancement of aggregate stability under forest by fungal hyphae.

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contemporary sediment fingerprinting methods to question hypotheses of aeolian geomorphology suggests that such methods have great potential for addressing other terrestrial geomorphological questions where identifying sediment pathways can provide vital insight.

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