Joan Llovet

Effects of land use and eventual fire on soil erodibility in dry Mediterranean conditions

The Mediterranean countries of Europe have suffered deep land-use transformations during this century and the expansion of wildfires after generalized land abandonment in the marginal uplands. Differences in soil properties due to land use may lead to different responses of the ecosystem in case of fire. We analyze how soil erodibility in a cropland and oldfields of different age after abandonment (bushland, shrubland and pine forest) would be affected by wildfire. Soil samples taken in each land use were analyzed to characterize soil erodibility. From fuel load measures, the range of temperatures to be attained in case of a fire were estimated for the topsoil. From these temperatures and from the information available in the literature, we predicted the changes in soil properties produced by the fire and estimated soil erodibility for the burned lands. Changes in soil erodibility were slight in the field crop with low fuel load, and increased according to biomass and forest floor accumulation. As the initial soil erodibility was inversely related to fuel load, the fire would increase the values of soil erodibility of the different land uses up to close to those of the field crop. In addition, the fire would produce very similar soil erodibility values for the different land uses, and therefore a homogenizing post-fire soil response in the landscape.

Soil responses to fire in Mediterranean forest landscapes in relation to the previous stage of land abandonment

The current paper presents a study on the interaction between land abandonment and soil responses to fire in old agricultural terraced landscapes. The study area, located near the Guadalest reservoir (E Spain), was partially affected by a forest fire in August 1998. We monitored burned and unburned areas as well as two pre-fire stand ages since agricultural abandonment: 8-15 years (dry grassland with young Pinus halepensis) and >35 years (mature pine forest). We analysed soil surface structure, water repellency and infiltrability, and we monitored plant response, runoff and sediment production for a period of 7 years after the fire. Aggregate stability increased with both time-since-abandonment and fire. Water repellency increased with land abandonment but was not affected by fire. Unburned erosion plots produced almost no runoff, even during heavy rainstorms. Fire scarcely modified runoff and erosion rates in recently abandoned terraces. A dry period following fire restricted plant recovery in burned pine forest. Burned forest plots registered runoff and sediment yields one to four orders of magnitude higher than unburned forest plots. In burned pine forest, the maximum sediment production was registered 3 years after the fire, when rainstorms took place and plant cover was still low. Old agricultural terraces colonised by pines were found to be both vulnerable to degradation as a consequence of fire and highly dependent on post-fire rain for their recovery.

Integrating knowledge exchange and the assessment of dryland management alternatives – A learning-centered participatory approach

The adoption of sustainable land management strategies and practices that respond to current climate and human pressures requires both assessment tools that can lead to better informed decision-making and effective knowledge-exchange mechanisms that facilitate new learning and behavior change. We propose a learning-centered participatory approach that links land management assessment and knowledge exchange and integrates science-based data and stakeholder perspectives on both biophysical and socio-economic attributes. We outline a structured procedure for a transparent assessment of land management alternatives, tailored to dryland management, that is based on (1) principles of constructivism and social learning, (2) the participation of stakeholders throughout the whole assessment process, from design to implementation, and (3) the combination of site-specific indicators, identified by local stakeholders as relevant to their particular objectives and context conditions, and science-based indicators that represent ecosystem services of drylands worldwide. The proposed procedure follows a pattern of eliciting, challenging, and self-reviewing stakeholder perspectives that aims to facilitate learning. The difference between the initial baseline perspectives and the final self-reviewed stakeholder perspectives is used as a proxy of learning. We illustrate the potential of this methodology by its application to the assessment of land uses in a Mediterranean fire-prone area in East Spain. The approach may be applied to a variety of socio-ecological systems and decision-making and governance scales.