Wildfire regimes have markedly intensified over the past few decades, not only in the Mediterranean but also in other climate regions, and are not expected to slacken in the foreseeable future. Wildfires affect forests, woodlands, abandoned and agricultural lands worldwide representing the main natural hazard or disturbance for these environments. Depending on burn severity, fire changes vegetation, fauna and soils in a variety of ways. The changes affect a complex array of processes determining catchment hydro-geomorphic response and, thus, water quality. The intensity and duration of the burn can modify soil physical and chemical properties that in combination with changes to runoff generation and soil erodibility may lead to soil degradation and the delivery of a variety of constituents to streams and rivers. The transfer of ash from hillslopes also contributes to water quality impacts. The magnitude and persistence of alterations to stream water quality vary in response to soil and vegetation recovery rates as well as post-burn hydroclimatic conditions. In the end, fire impacts on water quality can have important implications for the provision of potable water supplies and may present a serious challenge to water treatment for urban, industrial and agricultural activity.

These processes interact in time and space in recently burnt areas. As argued by recent review studies, knowledge and methodological gaps continue to hamper a comprehensive assessment of the importance of wildfire, as compared to other agents of landscape disturbance and soil degradation. Among others, further research is needed following different but related goals: integration of different time and spatial scales of study; sources of sediment and associated chemical constituents within catchments for parameterising and testing models of fire effects on water quality in order to better assess the risk to water supplies; and prediction of soil degradation processes in recently burnt areas and the effectiveness of measures designed prevent or counterbalance these processes.

The aims of this interdisciplinary session are:

i) To present improvements with regard to the variety of techniques and methodologies applied for the study of wildfire effects on vegetation, soils and hydro-geomorphic processes from worldwide ecosystems.
ii) To discuss recent advances with respect to the importance of wildfire , compared to other agents of landscape disturbance and soil degradation, for instance, on erosion rates beyond the plot scale and/or beyond the initial stages of the window-of-disturbance, and post-fire exports of key soil fertility parameters.
iii) To explore the effect of fire on water quality, particularly in relation to the magnitude and duration of changes in concentrations of water quality constituents in streams, lakes and reservoirs.
iv) To advance in the integration and modelling of data collected at different spatial and temporal scales in burnt areas.