Self-Organized Criticality of Wildfires Ecologically Revisited.

Wildfire cumulative frequency¿area distributions of Mediterranean landscapes are examined for agreement with self-similar (fractal) behavior. Our results support landscape-specific restricted scaling regions of 1.5¿3.5 orders of magnitude in size, which are delimited by breakpoints or `cut-offs¿. By identifying the extent of such regions in the fractal frequency¿area distribution of wildfires, fractal statistics may give a deeper insight into the scale-invariant dynamics of fire spread, whereas the observed cut-offs may be related to changes in the process¿pattern interactions that control wildfire propagation at the landscape scale.Peer Reviewe

Reappraisal of Vipera aspis Venom Neurotoxicity

BACKGROUND: The variation of venom composition with geography is an important aspect of intraspecific variability in the Vipera genus, although causes of this variability remain unclear. The diversity of snake venom is important both for our understanding of venomous snake evolution and for the preparation of relevant antivenoms to treat envenomations. A geographic intraspecific variation in snake venom composition was recently reported for Vipera aspis aspis venom in France. Since 1992, cases of human envenomation after Vipera aspis aspis bites in south-east France involving unexpected neurological signs were regularly reported. The presence of genes encoding PLA(2) neurotoxins in the Vaa snake genome led us to investigate any neurological symptom associated with snake bites in other regions of France and in neighboring countries. In parallel, we used several approaches to characterize the venom PLA(2) composition of the snakes captured in the same areas. [br/] METHODOLOGY/PRINCIPAL FINDINGS: We conducted an epidemiological survey of snake bites in various regions of France. In parallel, we carried out the analysis of the genes and the transcripts encoding venom PLA(2)s. We used SELDI technology to study the diversity of PLA(2) in various venom samples. Neurological signs (mainly cranial nerve disturbances) were reported after snake bites in three regions of France: Languedoc-Roussillon, Midi-Pyrénées and Provence-Alpes-Côte d'Azur. Genomes of Vipera aspis snakes from south-east France were shown to contain ammodytoxin isoforms never described in the genome of Vipera aspis from other French regions. Surprisingly, transcripts encoding venom neurotoxic PLA(2)s were found in snakes of Massif Central region. Accordingly, SELDI analysis of PLA(2) venom composition confirmed the existence of population of neurotoxic Vipera aspis snakes in the west part of the Massif Central mountains. [br/] CONCLUSIONS/SIGNIFICANCE: The association of epidemiological studies to genetic, biochemical and immunochemical analyses of snake venoms allowed a good evaluation of the potential neurotoxicity of snake bites. A correlation was found between the expression of neurological symptoms in humans and the intensity of the cross-reaction of venoms with anti-ammodytoxin antibodies, which is correlated with the level of neurotoxin (vaspin and/or ammodytoxin) expression in the venom. The origin of the two recently identified neurotoxic snake populations is discussed according to venom PLA(2) genome and transcriptome data

C sequestration issues in the Mediterranean soils

The Mediterranean region has distinct characteristics resulting from its climate, land use history and landforms that may largely affect soil C balances. In this paper we present data on C storage in Mediterranean soils and how it can be affected by changes in land use and fire. We also discuss the sensitivity of organic matter levels in Mediterranean soils to land use and management in order to set the basis for increasing C sequestration in the Mediterranean

Land use and land cover change modelling

Forest fires result from a number of interacting factors like ignitions, conditions amenable for fire initiation and spread, and landscapes with vegetation (i.e., fuels) that can support the combustion process. In Europe, most fires occur in the southern countries with a Mediterranean climate. But fires dominate also in other parts of the world. Factors driving fire have not been stable during the last decades, mainly due to modifications in the territory caused by socioeconomic changes. Climate has equally not been stable. In looking at the future, changes in climate and socioeconomics are projected to continue. Understanding how such modifications in the fire controlling factors affect fire activity is utmost important for anticipating future fire risks. In FUME we have come together 33 groups of scientists from 17 countries and 5 continents to investigate the relationships between the various drivers of forest fires. The main focus was the southern countries of Europe, although Northern Europe, Northern and South Africa, Anatolia, California and Chile were also investigated. The project addressed the relationships between socioeconomic, landscape and climate factors and fires across various scales and countries during the last decades. Additionally, future projections of these drivers were used to anticipate future risks. Modeling and experiments assessed impacts of future changes, including extreme episodes like droughts, on the vegetation and fuels. The effects of changes in fire regime on the vegetation were also investigated. Restoration needs under changing conditions and for reducing fire hazard were also explored. Policy needs and procedures used in a number of countries were evaluated in regards coping with fire. Following are some of the main results: \u25b8 Fire activity has been changing in the Euro Mediterranean countries (EUMed). Assessing fire regimes and changes through time require longterm databases that include more complete information about fire characteristics and harmonized data to permit comparisons among countries. Further efforts are still needed to have harmonized definitions, formats and methodologies in fire data acquisition and assemblage across countries. \u25b8 Mediterranean landscapes were dynamic in the last decades, and fires responded to the changes that occurred in them, independently of whether they were planned (e.g., afforestation) or unplanned (land abandonment). Fires often burned where hazardous changes occurred. Changes driven by socioeconomics are likely to continue in the future. Because they operate on large time scales, anticipating future risks should be possible. \u25b8 Assessing impacts and future risks requires spatially explicit information on burned areas, at least for the fires above a certain size (a few hectares). Reconstructing the near past and setting procedures to gather this information for the future is a requisite for a sound management of fire-prone areas. \u25b8 Fires do not burn equally all areas in a landscape, and preferentially burn certain surfaces over others. Furthermore, positive feedbacks driven by fire have been documented across Southern Europe. This is, fires favour burning again in a short time. Understanding these positive feedbacks to prevent certain areas entering into fire-driven degradation loops is a necessity. \u25b8 The rural-urban interface (RUI) is a particular area of risk. Methods have been developed to map the RUI and model fire risk in relation to RUI characteristics. Furthermore, RUI development can be modeled and taken into consideration in urban development to reduce risk. \u25b8 Socioeconomic factors were important for explaining fire occurrence in EUMed countries, and their knowledge should have an increasing role in operational fire risk systems that focus on prevention activities. \u25b8 Fires are driven by weather, and dry spells and other weather anomalies (heat waves, strong winds) play a major role in determining fires. Extreme episodes, like long dry spells, can be most relevant in determining fire season severity. Improvements in weather forecasting (seasonal, yearly) may allow developments in fire danger and risk prediction.\u25b8 Attributing fires to climate change requires differentiating the role of climate from other confounding factors. Using the appropriate mathematical procedures to relate climate and fires, while controlling for the possible interference of other factors in this relationship, a significant and positive relationship was revealed between climate and fires during the last three decades for the various EUMed regions. This occurred despite the fact that, in recent years, fires (numbers, area burned) were decreasing while fire weather danger was increasing. \u25b8 Anticipating future fire hazard and risk requires that concurrent changes in climate and socioeconomy are jointly analyzed to assess future allocations to land use and land cover types, including RUI development. Modelling at EUMed showed that land use and land cover (LULC) will continue changing, but changes can be affected by a priori decisions. \u25b8 Wildfire simulators can be used with different planning strategies, from tactical and strategic planning of wildfire management, to firefighter training, to even real-time firefighting. In a perspective of climate and global changes, these tools can assist policy makers and management agencies to evaluate risks and needs to mitigate them. \u25b8 With global warming, great increases are projected in mean fire-weather indices, length of the fire season and extreme values over large extensions of Europe, including areas in which fires were not prevalent until now. Procedures are now available to make projections in the near future, in the time when adaptation to changes in climate will be needed. \u25b8 Climate projections when used in fire models under the assumptions of persisting current fire-climate relationships and disregarding other limiting factors project an important (up to 3 times) increase in burned area in case-study areas like the Iberian Peninsula. \u25b8 Plant species differ in their seasonal variability in live fuel moisture content and in their capacity to produce necromass during drought periods. Live fuel moisture content can be modeled using drought indices, but improvements are possible using adjustments based on actual vegetation and soil. \u25b8 Despite increased meteorological fire danger with climate change, vegetation-fire models show that under scenarios of high climate change low productivity in parts of Southern Europe could limit burned area. \u25b8 Vegetation-fire models applied for contrasting climate change scenarios indicate that fire would enormously increase in Eastern Europe. This region is identified as the main potential new fire-prone area. Therefore, if climate change goes un-abated, this region would require specific new developments in fire research, management and protection. \u25b8 Regeneration by germination of Mediterranean species will suffer from changes in climate. However, species and populations showed idiosyncratic germination responses, which indicates that generalization of impacts will be difficult to make. \u25b8 Post-fire regeneration in field experiments simulating future drought can lead to altered vegetation due to the differential sensitivity of seeders (more sensitive) than resprouters (less sensitive). Alterations in ecosystem functioning are likely due to downstream effects on the plant community and nutrient cycling. \u25b8 Changes in fire regime due to increased fire frequency caused by climate change or other factors can compromise vegetation stability to fire in low fire-frequency areas but also in high-frequency areas with resilient vegetation. \u25b8 Pine woodlands burn frequently nowadays. The post-fire vegetation in these systems is affected by the interplay of previous management and geophysical variables. Changes in vegetation can occur due to fires, yet anticipating post-fire vegetation characteristics is difficult. Site-specific, local information is needed to identify possible vulnerable areas subject to change due to fire. \u25b8 Mediterranean pine forests require active management to increase resilience. Pine thinning and introduction of hardwood resprouting species are recommended. Management actions have to be adapted to each stage of the pine-stand dynamics and site conditions, especially considering soil moisture availability vs. light availability for selecting drought-tolerant vs. shade-tolerant resprouter species. \u25b8 Post-fire restoration should consider fire-resilient, drought-tolerant species in the perspective of climate change. A structured approach has been produced for post-fire impact assessment and restoration under climate change, including technical options for improving restoration success: seedling acclimation to drought, soil preparation to increase water supply, and microhabitat conditioners to reduce water losses. \u25b8 Increased fire load and costs are anticipated under future scenarios of climate and other global changes. This requires increased efficiency in investments in wildfire management operations, and resolving the disconnect problem between science, policy and management

Self-organized criticality of wildfires ecologically revisited

Wildfire cumulative frequency-area distributions of Mediterranean landscapes are examined for agreement with self-similar (fractal) behavior. Our results support landscape-specific restricted scaling regions of 1.5-3.5 orders of magnitude in size, which are delimited by breakpoints or 'cut-offs'. By identifying the extent of such regions in the fractal frequency-area distribution of wildfires, fractal statistics may give a deeper insight into the scale-invariant dynamics of fire spread, whereas the observed cut-offs may be related to changes in the process-pattern interactions that control wildfire propagation at the landscape scale. © 2001 Elsevier Science B.V. All rights reserved