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Burnt Areas (burnt + area)
Selected AbstractsCharacterizing interannual variations in global fire calendar using data from Earth observing satellitesGLOBAL CHANGE BIOLOGY, Issue 9 2005César Carmona-Moreno Abstract Daily global observations from the Advanced Very High-Resolution Radiometers on the series of meteorological satellites operated by the National Oceanic and Atmospheric Administration between 1982 and 1999 were used to generate a new weekly global burnt surface product at a resolution of 8 km. Comparison with independently available information on fire locations and timing suggest that while the time-series cannot yet be used to make accurate and quantitative estimates of global burnt area it does provide a reliable estimate of changes in location and season of burning on the global scale. This time-series was used to characterize fire activity in both northern and southern hemispheres on the basis of average seasonal cycle and interannual variability. Fire seasonality and fire distribution data sets have been combined to provide gridded maps at 0.5° resolution documenting the probability of fire occurring in any given season for any location. A multiannual variogram constructed from 17 years of observations shows good agreement between the spatial,temporal behavior in fire activity and the ,El Niño' Southern Oscillation events, showing highly likely connections between both phenomena. [source] Regional-scale spatial patterns of fire in relation to rainfall gradients in sub-tropical mountains, NW ArgentinaGLOBAL ECOLOGY, Issue 2 2001Héctor Ricardo Grau Abstract 1Spatial patterns of burns are described using Landsat TM images from the sub-tropical mountains of north-west Argentina, over a span of 6 degrees of latitude, and a precipitation range from 250 to 1300 mm/yr. Burns were discriminated easily from unburnt vegetation, mainly by using infrared spectral bands from images taken at the end of the fire season of 1986. 2Nineteen sampling units were defined on the basis of geographical proximity and relatively homogeneous rainfall as inferred from topography, and they were characterized in terms of percentage of burnt area and burn size distribution during one fire season. Regression and Correspondence Analysis were used to assess the relationship between rainfall and spatial descriptors of fire regime. 3Burnt size area was log-normally distributed with most fires in the small-size classes. Of a total of 643 burns, the five largest (more than 2000 hectares each) represented about 30% of the total burnt area. 4Percentage of burnt area, density of burns per unit area, and skewness of the burn-size frequency distribution showed a unimodal pattern along the rainfall gradient, peaking between 700 and 900 mm/yr. Mean and maximum burn size showed a negative but weak correlation with rainfall. The first axis of a Correspondence Analysis ordination of sampling units, on the basis of different descriptors of spatial patterns of fire, was significantly correlated with the rainfall of the sampling unit. 5The results suggest that climate is an important factor controlling fuel conditions and therefore fire regime at the spatial scale of this study, which includes different mountain ranges spanning , 700 km. [source] Atmospheric conditions associated with the exceptional fire season of 2003 in PortugalINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 13 2006Ricardo M. Trigo Abstract The summer of 2003 was characterised by exceptional warm weather in Europe, particularly during the first two weeks of August, when a devastating sequence of large fires was observed, reaching an amount of circa 450 000 ha, the largest figure ever recorded in Portugal in modern times. They were concentrated in two relatively confined regions of Portugal and a considerable proportion of burnt area was due to fires started on the 2nd and 3rd of August. It is shown that the 850 hPa temperature values observed over Portugal for the 1st and 2nd of August 2003 were the highest recorded since 1958. Using data from synoptic stations covering the entire Portuguese territory, the event was characterised in fine detail, including the evolution of both maximum and minimum temperatures, surface relative humidity, and wind anomaly fields. The different spatial extent of maximum and minimum temperatures is analysed leading to the new all-time Portuguese records of 47.3 °C for maximum and 30.6 °C for minimum temperatures that were recorded on the 1st of August near the main area of occurrence of the largest fire. Finally, it is shown that the summer of 2003 was preceded by a wet winter followed by a very dry month of May, a precipitation anomalous regime that contributed to a climatic background that favoured the role played by the early August heatwave and the associated meteorological surface conditions. Copyright © 2006 Royal Meteorological Society [source] The role of environmental gradients in non-native plant invasion into burnt areas of Yosemite National Park, CaliforniaDIVERSITY AND DISTRIBUTIONS, Issue 2 2006Rob Klinger ABSTRACT Fire is known to facilitate the invasion of many non-native plant species, but how invasion into burnt areas varies along environmental gradients is not well-understood. We used two pre-existing data sets to analyse patterns of invasion by non-native plant species into burnt areas along gradients of topography, soil and vegetation structure in Yosemite National Park, California, USA. A total of 46 non-native species (all herbaceous) were recorded in the two data sets. They occurred in all seven of the major plant formations in the park, but were least common in subalpine and upper montane conifer forests. There was no significant difference in species richness or cover of non-natives between burnt and unburnt areas for either data set, and environmental gradients had a stronger effect on patterns of non-native species distribution, abundance and species composition than burning. Cover and species richness of non-natives had significant positive correlations with slope (steepness) and herbaceous cover, while species richness had significant negative correlations with elevation, the number of years post-burn, and cover of woody vegetation. Non-native species comprised a relatively minor component of the vegetation in both burnt and unburnt areas in Yosemite (percentage species = 4%, mean cover < 6.0%), and those species that did occur in burnt areas tended not to persist over time. The results indicate that in many western montane ecosystems, fire alone will not necessarily result in increased rates of invasion into burnt areas. However, it would be premature to conclude that non-native species could not affect post-fire succession patterns in these systems. Short fire-return intervals and high fire severity coupled with increased propagule pressure from areas used heavily by humans could still lead to high rates of invasion, establishment and spread even in highly protected areas such as Yosemite. [source] Wildfires and the expansion of threatened farmland birds: the ortolan bunting Emberiza hortulana in Mediterranean landscapesJOURNAL OF APPLIED ECOLOGY, Issue 4 2008Lluís Brotons Summary 1It has been argued that wildfires are one of the major agents involved in landscape transformation in many European regions and their impact is expected to increase in the near future. Despite the recognized impact of fire on wildlife at a local scale, we lack information on the species responses to fire at larger spatial scales. 2In this study, we used the ortolan bunting Emberiza hortulana to evaluate the potential effects of wildfires on open-habitat species distribution. In contrast to most European countries, this farmland species has experienced a consistent range expansion during the last decades in Catalonia (northeast Iberian peninsula). Distribution data of the species collected at different time periods allowed us to test the role of fires in determining range expansions at a regional scale, and to evaluate the importance of dispersal constraints on distribution changes. 3Analyses of distribution data from 1975,1983 and 1999,2002 showed a consistent expansion of the ortolan bunting in Catalonia. After correcting for differences in sampling effort, changes in distribution showed a strong spatial pattern with colonization and stability, but not local extinction, being clumped in space. Patterns of change were also strongly and significantly associated with the amount of shrubland burnt between the two time periods, since areas that experienced a larger impact of fires in terms of burnt area showed a much higher probability of maintaining species presence or of being colonized. Colonization events appeared to be more likely in areas affected by fire especially when surrounding areas had already been colonized by the species. 4Synthesis and applications. Overall, our results support the hypothesis that wildfires, especially those affecting open woodlands or shrubby areas, play a critical role in the ecology of the ortolan bunting and have contributed to the recent expansion of the species in Catalonia. Furthermore, we have shown that colonization appears to be limited, not only by the availability of new burnt habitat but also by specific dispersal constraints. We suggest that, for several European threatened species associated with open habitats, burnt areas may partially compensate for the widespread loss and deterioration of farmland habitat, opening new management opportunities for their conservation. [source] Variability in survival and mortality of Acacia drepanolobium Sjøstedt following prescribed burning at Olpejeta Conservancy, KenyaAFRICAN JOURNAL OF ECOLOGY, Issue 3 2010Geoffrey M. Wahungu Abstract Mortalities to Acacia drepanolobium, a main item in the diet of the eastern black rhino (Diceros bicornis Michaeli) in Olpejeta conservancy, Kenya, are caused by three main factors: drought, browsers and fire. The effect of controlled fires on A. drepanolobium was examined by monitoring survival and growth in experimental plots before and after fire episodes between 2003 and 2007. Density, survival and growth in A. drepanolobium trees were compared eighteen months before and after burning. Tall trees were more likely to die from fire compared to short trees (R2 = 0.575; df = 6; P = 0.048), while seedling densities increased after fire (,2 = 36.57; df = 1; P = 0.001). Even with increased seedling densities, burned areas attracted large numbers of seedling predators, lowering the possibility of seedling recruitment into adult, as mean seedling heights reduced significantly (ANOVA, F = 204.42; df = 1; P = 0.036). Fires also significantly lowered flowering (F = 346; df = 1; P < 0.05) in A. drepanolobium, thereby affecting fruit production. Although fires caused mortalities to adult A. drepanolobium, the most significant effect was tree reversals into seedling height class as trees resprouted. Although fire may increase browse biomass of A. drepanolobium available for black rhino, it is not an appropriate black rhino habitat management tool because burnt areas attract many seedling predators that lower seedling recruitment into adult trees. Résumé La mortalité d'Acacia drepanolobium dans l'aire de conservation d'Olpejeta, au Kenya, est causée par trois facteurs principaux, la sécheresse, les herbivores et les feux. On a examiné l'effet des feux contrôlés sur A. drepanolobium en suivant la survie et la croissance dans des parcelles expérimentales 18 mois avant et après les feux, entre 2003 et 2007. On a comparé la densité, la survie et la croissance d'A. drepanolobium 18 mois avant et après les feux. Les grands arbres étaient plus susceptibles de mourir à cause des feux que les petits (R² = 0,575; ddl = 6; P = 0,048) alors que la densité des jeunes plants augmentait après les feux (,² = 36,57; ddl = 1; P = 0,001). Même si la densité de jeunes plants était accrue, les zones brûlées attiraient de grands nombres de prédateurs de ces plants, diminuant ainsi la possibilité de recrutement vers l'âge adulte, parce que la hauteur moyenne des jeunes plants était significativement réduite (Anova, F = 204,42; ddl = 1; P =0,036). Les feux réduisaient aussi significativement la floraison (F = 346; ddl = 1; P < 0,05) chez A. drepanolobium, affectant dès lors la production de fruits. Même si les feux causaient une certaine mortalité chez les A. drepanolobium adultes, l'effet le plus significatif était le retour des arbres dans des classes de hauteur des jeunes plants lorsque les arbres rejetaient. Même si les feux peuvent augmenter la biomasse de brout d'A. drepanolobium disponible pour les rhinos noirs, ils ne sont pas un outil de gestion approprié pour l'habitat des rhinos parce que les zones brûlées peuvent attirer des nombreux prédateurs des jeunes plants qui réduisent le recrutement de ceux-ci vers l'âge adulte. [source] Resprouting of saplings following a tropical rainforest fire in north-east Queensland, AustraliaAUSTRAL ECOLOGY, Issue 8 2005MATTHEW J. MARRINAN Abstract In 2002, fire burnt areas of Mesophyll- and Notophyll Vine Forest in the Smithfield Conservation Park near Cairns, Australia. We assessed the ability of rainforest plant species to persist through fire via resprouting. Natural rates of mortality and resprouting in unburnt areas were assessed for all saplings (stems < 2 m) via 13, 2 × 50 m belt transects, and compared to estimates of mortality and resprouting in 26 transects in burnt areas. We also tested the resprouting ability per-individual stem of each species against all other stems with which it co-occurred. Totals of 1242 stems (138 species) were sampled in burnt transects and 503 stems (95 species) in unburnt transects (total number of unique species = 169). There was no difference in the number of stems existing prior to the fire in burnt and unburnt areas when expressed on a per-sample area basis. Resprouting from basal shoots and root suckers was significantly greater in burnt than in unburnt areas, but rates of stem sprouting were not different. In burnt areas 72 species were tested for resprouting ability and most (65/72) resprouted at similar rates. All species analysed contained individuals that resprouted. The resprouting response of five species was significantly lower, and in two species was significantly higher. For these species especially, fire may act as a mechanism altering relative abundances. The fire coincided with an extreme El Niño event. Current predictions indicate El Niño conditions may become increasingly common, suggesting fire events within rainforest could become more frequent. Resprouting as a general phenomenon of rainforest species, and differential resprouting ability between species should therefore be an important consideration in assessing the potential path of vegetation change in rainforests after fire. [source] | |||||||||||||||||||