Paloma Ibarra

Integrating geospatial information into fire risk assessment

Fire risk assessment should take into account the most relevant components associated to fire occurrence. To estimate when and where the fire will produce undesired effects, we need to model both (a) fire ignition and propagation potential and (b) fire vulnerability. Following these ideas, a comprehensive fire risk assessment system is proposed in this paper,whichmakesextensiveuseofgeographicinformationtechnologiestoofferaspatiallyexplicitevaluationoffirerisk conditions. The paper first describes the conceptual model, then the methods to generate the different input variables, the approachestomergethosevariablesintosyntheticriskindicesandfinallythevalidationoftheoutputs.Themodelhasbeen applied at a national level for the whole Spanish Iberian territory at 1-km 2 spatial resolution. Fire danger included human factors, lightning probability, fuel moisture content of both dead and live fuels and propagation potential. Fire vulnerability was assessed by analysing values-at-risk and landscape resilience. Each input variable included a particular accuracy assessment, whereas the synthetic indices were validated using the most recent fire statistics available. Significant relations (P,0.001) with fire occurrence were found for the main synthetic danger indices, particularly for those associated to fuel moisture content conditions.

Modelling the Ecological Vulnerability to Forest Fires in Mediterranean Ecosystems Using Geographic Information Technologies

Forest fires represent a major driver of change at the ecosystem and landscape levels in the Mediterranean region. Environmental features and vegetation are key factors to estimate the ecological vulnerability to fire; defined as the degree to which an ecosystem is susceptible to, and unable to cope with, adverse effects of fire (provided a fire occurs). Given the predicted climatic changes for the region, it is urgent to validate spatially explicit tools for assessing this vulnerability in order to support the design of new fire prevention and restoration strategies. This work presents an innovative GIS-based modelling approach to evaluate the ecological vulnerability to fire of an ecosystem, considering its main components (soil and vegetation) and different time scales. The evaluation was structured in three stages: short-term (focussed on soil degradation risk), medium-term (focussed on changes in vegetation), and coupling of the short- and medium-term vulnerabilities. The model was implemented in two regions: Aragón (inland North-eastern Spain) and Valencia (eastern Spain). Maps of the ecological vulnerability to fire were produced at a regional scale. We partially validated the model in a study site combining two complementary approaches that focused on testing the adequacy of model’s predictions in three ecosystems, all very common in fire-prone landscapes of eastern Spain: two shrublands and a pine forest. Both approaches were based on the comparison of model’s predictions with values of NDVI (Normalized Difference Vegetation Index), which is considered a good proxy for green biomass. Both methods showed that the model’s performance is satisfactory when applied to the three selected vegetation types.

Erodibility and Hydrology of Arid Burned Soils: Soil Type and Revegetation Effects

A set of experiments with a rainfall simulator was performed in the field to evaluate the efficiency of parallel contour seeding as a post-fire restoration strategy in the arid central Ebro Valley (NE Spain). Rainfall simulations were conducted in spring, after seeded plant development, on calcareous and gypsiferous soils, with the same experimental design (two-soil treatments—seeded and nonseeded—per two soil types and per nine replicates). The parallel contour seeding treatment increases soil cover and soil surface roughness, which significantly ameliorates the hydrological and erosional response of both calcareous and gypsiferous burned soils. Seeding decreased soil loss, both in calcareous (23-fold) and gypsiferous soils (4-fold). In addition, it decreased the sediment concentration of runoff for calcareous (6-fold) and gypsiferous soils (2-fold) and the runoff coefficient for calcareous (3.5-fold) and gypsiferous soils (1.5-fold). On the other hand, seeding increased the steady state infiltration rate (3-fold), as well as surface soil moisture (1.2-fold) and wetting front depth (2-fold), with a similar order of magnitude for both soils. Time to runoff and runoff quality (electrical conductivity [EC] and pH) were not affected by seeding. Gypsiferous soils had a higher soil loss, runoff coefficient, and EC flow and a lower time to runoff, steady state infiltration rate, and wetting front depth than calcareous soils. Some of these differences were directly related to differences in soil gypsum and carbonate content (i.e., EC and pH of water runoff) and others are related to the proportion of surface soil protection, an indirect effect of soil characteristics. The results suggest that parallel contour seeding is an effective restoration measure with a short-term response that allows conservation of water and soil on recently burned arid lands, especially in situations of high erosion risk as occurs with soils with low plant cover.

Effects of Fire on Vegetation, Soil and Hydrogeomorphological Behavior in Mediterranean Ecosystems

In the Mediterranean context, wildfire has ceased to be a natural ecological factor and has become an anthropic factor of frequent and intense occurrence. Fires cause environmental alterations based the disappearance or modification of the vegetation cover, soil changes and soil hydrogeomorphological behavior. These transformations are mainly concentrated in the immediate aftermath of the fire and are closely linked with fire frequency, fire severity and the period of the year in which the fires occur. A systematic outline of the effects of fire and the factors implicated in the post-fire environmental dynamic is offered. The role of remote sensing methods on fire effects is well known; this chapter also refers to experiences and works on monitoring temporal patterns of vegetation recovery and mapping erosion-sensitive areas

The influence of elevation on soil properties and forest litter in the Siliceous Moncayo Massif, SW Europe

Understanding the effects of elevation and related factors (climate, vegetation) on the physical and chemical soil properties can help to predict changes in response to future climate or afforestation forcings. This work aims to contribute to the knowledge of soil evolution and the classification of forest soils in relation to elevation in the montane stage, with special attention to podzolization and humus forms. The northern flank of the Moncayo Massif (Iberian Range, SW Europe) provides a unique opportunity to study a forest soils catena within a consistent quartzitic parent material over a relatively steep elevation gradient. With increasing elevation, pH, base saturation, exchangeable potassium, and fine silt-sized particles decrease significantly, while organic matter, the C/N ratio, soil aggregate stability, water repellency and coarse sand-sized particles increase significantly. The soil profiles shared a set of properties in all horizons: loamy-skeletal particle-size, extreme acidity (pH-H2O<5.6) and low base saturation (<50%). The most prevalent soil forming processes in the catena include topsoil organic matter accumulation and even podzolization, which increases with elevation. From the upper to lower landscape positions of wooded montane stage of the Moncayo Massif, mull-moder-mor humus and an Umbrisol-Cambisol-Podzol soil unit sequences were found.

A method for regional-scale assessment of vegetation recovery time after high-severity wildfires Case study of Spain

This study aims to develop a method to estimate the recovery time of plant communities after high-severity wildfires. The designed methodology is based on map algebra and a geographical information system, which enabled calculation of the approximate time required to restore vegetation to conditions similar to pre-fire regarding plant height and canopy cover. The methodology considered, first, the vegetation in the territory, characterized by the structure of the dominant plant community (tree, shrub, or grassland) and its regeneration strategy (resprouter or seeder); and, second, two of the main factors determining recovery time – water availability and soil loss. We also considered the influence of observed rainfall trends over the past 50 years on these latter two factors. The methodology was applied to Spain to test its performance. The results suggest a period of 2 and approximately 100 years for grassland communities and tree communities with low germination, respectively. There are significant differences in plant communities between the two biogeographic regions (Euro-Siberian and Mediterranean) as well as within each community, directly linked to variability in terrain and climatic conditions.

Impact of forest fires in Sub-Mediterranean plant communities : multi-temporary evaluation of the landscape diversity using Landsat TM images

Se analiza el impacto y la evolucion de la estructura del paisaje en un incendio del Prepirineo aragones utilizando 6 imagenes Landsat 5 TM, identificando relaciones entre valores de heterogeneidad espacial y comunidades vegetales. Se extraen los NDVI (Normalized Difference Vegetation Index), se calcula el indice de Shannon y se cartografia para cada ano. Se definen tres componentes representativos de los valores de diversidad (preincendio, a corto plazo y a medio plazo). Se concluye que a nivel de comunidad vegetal el incendio ha supuesto un incremento de la diversidad interna en algunas comunidades. No obstante, a medio plazo y a escala global el fuego provoca la homogeneizacion del paisaje, tal y como describen otros autores utilizando fuentes de informacion similar.