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The authors propose that the spatial structure of woody vegetation on former arable lands can be used as a diagnostic feature that indicates the occurrence or absence of grass fires after land abandonment. Based on the analysis of a series of Landsat satellite images from 1985 to 2016 for an area of 256.5 km2 located in Central European Russia, the authors have reconstructed the history of spring fire events. They found correlations between the frequency of fire events and the density and spatial structure of woody vegetation on abandoned arable lands. Without fires, areas with homogeneous woody vegetation are formed: individuals of pioneer tree species (Betula pendula, B. pubescens and Salix caprea) are evenly distributed and exist in high densities over the entire area. Affected by fires, trees become unevenly distributed over the area: pioneer trees grow in groups or as separate individuals depending on the intensity and frequency of grass fires. With frequent fires, the vegetation remains in a weedy stage for decades. [ABSTRACT FROM AUTHOR]

Abstract The impacts of wildfires on the hydrological and erosive response of forest ecosystems have been extensively studied worldwide. Nevertheless, few studies have measured post-fire runoff and erosion over large time scales in Mediterranean-climate type environments and even fewer studies considered the effects of pre-fire land management practices on post-fire hydrological and erosive processes. In a previous study in the Colmeal study area, Vieira et al. (2016) revealed that post-fire runoff and erosion may not follow the classic window of disturbance model, since the peak of post-fire response occurred in the second and third years after fire. This previous study also showed that pre-fire land management can substantially influence the post-fire response, since annual runoff and erosion were lower in pre-fire unplowed than plowed sites. In this follow-up work, a multiple regression model (MRM) analysis was performed to understand how several key factors influence the hydrological and erosive response of a burned Mediterranean forest, taking into account the wildfire; pre-fire land management practices (unplowed, downslope plowed, and contour plowed) and soil moisture conditions. Based on the results of the present study, post-fire runoff was largely explained by rainfall amounts and soil water repellency (SWR)-related variables, whereas erosion processes were better explained by rainfall intensity and ground cover variables. Fewer factors were found to control the hydrological response of plowed sites when compared to the unplowed site. Aside from rainfall intensity, which was the major factor controlling sediment losses, bare soil cover also seems to have been important for erosion processes at the unplowed site, whereas at the plowed sites stone cover was the second most relevant factor. Rainfall-related variables (rainfall and maximum 30-min rainfall intensity) were more important for explaining runoff and erosion under dry conditions than under wet conditions. The results of the MRM analysis are an important contribution to understand the dynamics of burned forest areas and should be considered when adapting hydrological and erosion models to post-fire environments. Highlights • Post-fire runoff is better explained by rainfall and soil water repellency. • Post-fire erosion is better explained by rainfall intensity and cover variables. • Pre-fire land management seems to affect post-fire runoff and erosion processes. • Statistical models indicate runoff and erosion processes change in wet and dry soil moisture conditions. [ABSTRACT FROM AUTHOR]

Erosion is one of the primary land management concerns following wildfire. This study examines controls on post-fire hillslope-scale erosion for the 2012 High Park Fire in northern Colorado, develops simple empirical models for predicting post-fire sediment yields, and evaluates model performance on several nearby fires. From 2013 to 2015 we collected ground cover, rainfall, topographic, and sediment yield measurements from 29 convergent hillslopes; eight of these hillslopes had varying amounts of mulch applied to reduce erosion. From these data we examined correlations between annual sediment yield and three categories of predictor variables (ground cover, precipitation, and topography). Percent bare soil was the single largest control on sediment yield, followed by rainfall variables. Sediment yield generally decreased with flow path length, but the correlation was weak. The empirical models each predicted sediment yield with three variables: percent bare soil, one precipitation variable, and one topographic variable. The models had similar accuracy for the High Park Fire using varying combinations of precipitation and topographic variables (Nash-Sutcliffe coefficients 0.70–0.84). An empirical model predicting annual sediment yields as a function of percent bare soil, June–October precipitation, and the maximum flow path length had variable performance when applied to other fires in the same region, with predictions ranging from poor to good for individual fires and Nash-Sutcliffe coefficients of 0.26–0.32 for all fires combined. These tests show some promise for applying the empirical model to fires in the study region, but further model testing is needed to determine the range of conditions under which the model can be applied. [ABSTRACT FROM AUTHOR]

The Santa Ana winds occur in Southern California during the September-May time frame, bringing low humidities across the area and strong winds at favored locations, which include some mountain gaps and on particular slopes. The exceptionally strong event of late October 2007, which sparked and/or spread numerous fires across the region, is compared to more recent events using a numerical model verified against a very dense, limited-area network (mesonet) that has been recently deployed in San Diego County. The focus is placed on the spatial and temporal structure of the winds within the lowest two kilometers above the ground within the mesonet, along with an attempt to gauge winds and gusts occurring during and after the onset of October 2007's Witch fire, which became one of the largest wildfires in California history. [ABSTRACT FROM AUTHOR]

Periodical ground fires of high frequency in permafrost forest ecosystems of Siberia (Russian Federation) are essential factors determining quantitative and qualitative parameters of permafrost soil organic matter. Specific changes in physical and chemical parameters and microbial activity of permafrost soil mineral horizons of northern taiga larch stands were revealed after heating at high temperatures (150–500 °C) used for imitation of different burn intensities. Burning at 150–200 °C resulted in decreasing of soil pH, whilst heating at 300–500 °C caused increase of pH compare to unheated soils. Water-soluble organic carbon concentration in permafrost soils heated at 150–200 °C was much higher than that of unheated soils. All these changes determined soil microbial activity in heated soils. In particular, in soils heated at 300–500 °C there was momentary stimulating effect on substrate-induced respiration registered and on basal respiration values in soils burned at 150 °C and 300–400 °C. Four-month laboratory incubation of permafrost soils heated at different temperatures showed stimulation of microbial activity in first several days after inoculation due to high substrate availability after heating. Then soon after that soil microbial community started to be depleted on substrate because of decreasing water-soluble organic carbon, C and N content and it continued to the end of incubation. [ABSTRACT FROM AUTHOR]

Altered fire regimes in the face of climatic and land-use change could potentially transform large areas from forest to shorter-statured or open-canopy vegetation. There is growing concern that once initiated, these nonforested landscapes could be perpetuated almost indefinitely through a suite of positive feedbacks with fire. The rapid deforestation of much of New Zealand following human settlement (ca. 750 years ago) provides a rare opportunity to evaluate the feedback mechanisms that facilitated such extensive transformation and thereby help us to identify factors that confer vulnerability or resilience to similar changes in other regions. Here we evaluate the structure of living and dead vegetation (fuel loading) and microclimate (fuel moisture) in beech ( Nothofagaceae) forests and adjacent stands that burned within the last 60-140 years and are dominated by mānuka ( Leptospermum scoparium) or kānuka ( Kunzea spp.). We show that the burning of beech forests initiates a positive feedback cycle whereby the loss of microclimatic amelioration under the dense forest canopy and the abundant fine fuels that dry readily beneath the sparse mānuka/kānuka canopy enables perpetuation of these stands by facilitating repeated burning. Beech regeneration was limited to a narrow zone along the margin of unburned stands. The high flammability of vegetation that develops after fire and the long time to forest recovery were the primary factors that facilitated extensive deforestation with the introduction of human-ignited fire. Evaluating these two characteristics may be key to determining which regions may be near a tipping point where relatively small land-use- or climatically driven changes to fire regimes could bring about extensive deforestation. [ABSTRACT FROM AUTHOR]

Fire regimes are strongly dependent on human activities. Understanding the relative influence of human factors on wildfire is an important ongoing task especially in human-dominated landscapes such as the Mediterranean, where anthropogenic ignitions greatly surpass natural ignitions and human activities are modifying historical fire regimes. Most human drivers of wildfires have a temporal dimension, far beyond the appearance of change, and it is for this reason that we require an historical/temporal analytical perspective coupled to the spatial dimension. In this paper, we investigate and analyze spatial-temporal changes in the contribution of major human factors influencing forest fire occurrence, using Spanish historical statistical fire data from 1988 to 2012. We hypothesize that the influence of socioeconomic drivers on wildfires has changed over this period. Our method is based on fitting yearly explanatory regression models-testing several scenarios of wildfire data aggregation-using logit and Poisson generalized linear models to determine the significance thresholds of the covariates. We then conduct a trend analysis using the Mann-Kendall test to calculate and analyze possible trends in the explanatory power of human driving factors of wildfires. Finally, Geographically Weighted Regression Models are explored to examine potential spatial-temporal patterns. Our results suggest that some of the explanatory factors of logistic models do vary over time and that new explanatory factors might be considered (such as arson-related variables or climate factors), since some of the traditional ones seem to be losing significance in the presence-absence models, opposite to fire frequency models. In particular, the wildland-agricultural interface and wildland-urban interface appear to be losing explanatory power regarding ignition probability, and protected areas are becoming less significant in fire frequency models. GWR models revealed that this temporal behavior is not stationary neither over space nor time. [ABSTRACT FROM AUTHOR]

A large body of research focuses on identifying patterns of human populations most at risk from hazards and the factors that help explain performance of mitigations that can help reduce that risk. One common concept in such studies is social vulnerability-human populations' potential exposure to, sensitivity from and ability to reduce negative impacts from a hazard. While there is growing interest in social vulnerability for wildfire, few studies have critically evaluated the characteristics that scholars often indicate influence social vulnerability to that hazard. This research utilizes surveys, wildfire simulations, and GIS data to test the relationships between select demographic, perceptual and parcel characteristics of property owners against empirically simulated metrics for wildfire exposure or wildfire-related damages and their performance of mitigation actions. Our results from Flathead County, MT, USA, suggest that parcel characteristics such as property value, building value, and the year structures were built explaining a significant amount of the variance in elements of social vulnerability. Demographic characteristics commonly used in social vulnerability analysis did not have significant relationships with measures of wildfire exposure or vulnerability. Part-time or full-time residency, age, perceived property risk, and year of development were among the few significant determinants of residents' performance of fuel reduction mitigations, although the significance of these factors varied across the levels of fuel reduction performed by homeowners. We use these and other results to argue for a renewed focus on the finer-scale characteristics that expose some populations to wildfire risk more than others. [ABSTRACT FROM AUTHOR]

Wildfires are expected to increase in Mediterranean landscapes as a result of climate change and changes in land-use practices. In order to advance our understanding of human and physical factors shaping spatial patterns of wildfires in the region, we compared two independently generated datasets of wildfires for Israel that cover approximately the same study period. We generated a site-based dataset containing the location of 10,879 wildfires (1991-2011), and compared it to a dataset of burnt areas derived from MODIS imagery (2000-2011). We hypothesized that the physical and human factors explaining the spatial distribution of burnt areas derived from remote sensing (mostly large fires, >100 ha) will differ from those explaining site-based wildfires recorded by national agencies (mostly small fires, <10 ha). Small wildfires recorded by forestry agencies were concentrated within planted forests and near built-up areas, whereas the largest wildfires were located in more remote regions, often associated with military training areas and herbaceous vegetation. We conclude that to better understand wildfire dynamics, consolidation of wildfire databases should be achieved, combining field reports and remote sensing. As nearly all wildfires in Mediterranean landscapes are caused by human activities, improving the management of forest areas and raising public awareness to fire risk are key considerations in reducing fire danger. [ABSTRACT FROM AUTHOR]

No records exist in the scientific literature about lightning fires in the eastern Mediterranean (EM). Although thunderstorms are frequent in winter, if spontaneous fire is ignited, it will immediately be extinguished by rain. No thunderstorms occur in summer, and therefore no favourable weather conditions for natural ignitions exist. In October 2014, the synoptic conditions over theEMcomprised a Red Sea Trough (RST) with an easterly axis (a less frequent version of this system). A convective storm, accompanied by thunderstorms with intense local rains developed rapidly. Simultaneously, six wildfires were reported from different locations in northern Israel (in the EM). Lightning activity documented by the Israel Electric Co. was at the same time and locations as the reported wildfires. To the best of our knowledge, this is the first case recorded in recent history of wildfires in the EM as a result of lightning. Moreover, in the literature, the RST is associated with fires only when its axis is in a western position, thus driving very hot and dry air masses. A different way of thinking is needed on the potential of lightning in autumn as a possible cause of fires under different situations of the RST. [ABSTRACT FROM AUTHOR]

In Lithuania, fire is frequently used by farmers as a tool to remove dry grass, improve soil nutrient status and help soil tilling. However, little is known about the ecological impacts of these fires, including vegetation recovery. The objective of this work is to study the impacts of a spring grassland fire on vegetation recuperation on an east-facing (A) and a west-facing slope (B), considering fire severity and slope position, 10, 17, 31 and 46 days after the fire. Because of their effects on fire behaviour, aspect, steepness and heterogeneity of topography favoured higher fire severity on slope B than on slope A. Three different slope positions were identified on slope A - flat top, middle slope and flat bottom - and five on slope B - flat top, middle slope, flat middle slope, slope bottom slope and flat bottom. Fire severity was high in top slope positions. The recovery of vegetation was very fast. By the end of the study, vegetation covered nearly 100% of the study area, although fire severity, aspect and slope characteristics had implications on vegetation recovery. Plant cover recovered quickly on slope A. Ten and 17 days after the fire, plant cover was high in the bottom positions, where fire severity was relatively low. The major vegetation recuperation was observed between 17 and 31 days after the fire, in response to high rainfall. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Peatlands are found around the world and cover ~3.4% of the Earth's surface. In the UK, peatlands cover 17.2% or ~1.58 Mha of the land surface and occur mainly in upland areas covering the headwaters of most major British rivers. However, large areas are now subject to prescribed vegetation burning despite policy guidance that recommends a strong presumption against burning on deep blanket peat. Wildfires occur sporadically but are forecast to increase in frequency in the future. This paper provides a synthesis of current knowledge about how UK peatland-dominated river catchments respond to fires caused by prescribed vegetation burning and uncontrolled wildfire. We provide insight into the effects of fire on the hydrology, biogeochemistry, and biota of peatland river ecosystems, and the peatland-soil-driven controls on these effects at the catchment scale. Burning increases the depth to water table and water-table variability, although some small-scale studies indicate shallower water table in some places. More work is needed on fire effects on peatland river flow, but recent results suggest a complex response with smaller flow peaks for burned systems associated with most rainfall events, but enhanced peaks compared to unburned systems for the top quintile of rainfall events with the largest total rain. Evidence from biogeochemical studies suggests that fire leads to increased dissolved organic C concentrations in rivers. River biota responses primarily include significant reductions in the density of grazing mayflies but increases among detritivores including Chironomidae and Baetis mayflies. We provide a conceptual synthesis that links the main responses of terrestrial and aquatic systems to fire, and we summarize some major research gaps that should be prioritized to inform future policy around peatland management. [ABSTRACT FROM AUTHOR]

Smoldering fires in organic soils have negative effects on air quality and motorist safety as well as global implications from their release of large quantities of refractory C. However, the ecological implications of their occurrence are relatively unexplored despite their potential importance to the management of wetland ecosystems. We developed a conceptual model of the ecohydrologic implications of peat-consuming fires that explores the interactive effects of fire, hydrology, and C dynamics on hydrology. We modify an existing wetland hydrology model parameterized with climate, soil, and spatial data from a low-relief region in southern Florida (USA) to explore hypothesized pyrogeomorphic changes to upland water table elevation, wetland inundation (depth and hydroperiod), and groundwater exchange as a function of fire severity (area and depth of burn). Smoldering fires increase hydroperiod and storage in organic soils in burned wetlands by changing soil elevation. After fire, negative feedbacks to fire occurrence are likely because of increased hydroperiods in burned areas. However, adjacent, unburned wetland areas and uplands may experience drier conditions that increase fire frequency in distal locations. Simulation results indicate that increasing the area of soil combustion or depth of burn increases wetland hydroperiod, flooding depths, and groundwater exchange between wetlands and surrounding uplands. Additional field data characterizing fire effects on organic soil elevations and wetland bathymetry are needed, but the model supports our hypothesis about the effects of soil-consuming fires on hydrology and habitat, and these results will inform future work on the ecological role of peat-consuming fires. [ABSTRACT FROM AUTHOR]

The infrequent occurrence of large wildfires in the southern Appalachian Mountains over the last several decades has offered few opportunities to study their impacts. From 2000 to 2008, five wildfires burned a large portion of the area in and surrounding the Linville Gorge Wilderness in North Carolina. Areas were burned either once or twice. The response of acid cove and thermic oak plant communities (structure, cover, richness, diversity) was measured in 78 vegetation monitoring plots, established in 1992 and remeasured in 2010-11. Fire altered forest structure in both communities, resulting in the mortality of larger trees and increases in the abundance of smaller (<5 cm diameter at breast height (DBH)) stems. Burning twice decreased stem counts for mountain laurel (Kalmia latifolia) in both communities, whereas oaks (Quercus spp.) responded positively to burning twice in the thermic oak community. Table Mountain pine stem counts increased in acid cove and thermic oak communities burned once. Fire appears to promote princesstree (Paulownia tomentosa) invasion. Herbaceous species cover responded positively to fire (once or twice; both communities), with concurrent increases in woody species richness and diversity. Tree species composition in acid cove plots was not affected by burning, although some slight changes occurred in thermic oak plots burned twice. Five severe wildfires between 2000 and 2008 provided a unique opportunity to study how burning influences plant communities across Appalachian landscapes. This study assessed how plant community structure, composition, cover, richness and diversity in unburned areas differed from areas burned once or twice. [ABSTRACT FROM AUTHOR]

Mechanical fuel treatments are a common pre-fire strategy for reducing wildfire hazard that alters fuel structure by converting live canopy fuels to a compacted layer of dead surface fuels. Current knowledge concerning their effectiveness, however, comes primarily from forest-dominated ecosystems. Our objectives were to quantify and compare changes in shrub-dominated chaparral following crushing, mastication, re-mastication and mastication-plus-burning treatments, and to assess treatment longevity. Results from analysis of variance (ANOVA) identified significant differences in all fuel components by treatment type, vegetation type and time since treatment. Live woody fuel components of height, cover and mass were positively correlated with time since treatment, whereas downed woody fuel components were negatively correlated. Herbaceous fuels, conversely, were not correlated, and exhibited a 5-fold increase in cover across treatment types in comparison to controls. Average live woody fuel recovery was 50% across all treatment and vegetation types. Differences in recovery between time-since-treatment years 1-8 ranged from 32-65% and exhibited significant positive correlations with time since treatment. These results suggest that treatment effectiveness is short term due to the rapid regrowth of shrubs in these systems and is compromised by the substantial increase in herbaceous fuels. Consequences of not having a full understanding of these treatments are serious and leave concern for their widespread use on chaparral-dominated landscapes. Mechanical fuel treatments differ significantly between treatment types, yet all types alter fuel structure in shrub-dominated chaparral by transforming live-canopy fuels to a compacted layer of dead surface fuels. The effectiveness of these treatments, however, is short term due to the rapid regrowth of shrubs, and is compromised by the increase in herbaceous fuels. [ABSTRACT FROM AUTHOR]

Wildfire-potential information products are designed to support decisions for prefire staging of movable wildfire suppression resources across geographic locations. We quantify the economic value of these information products by defining their value as the difference between two cases of expected fire-suppression expenditures: one in which daily information about spatial variation in wildfire-potential is used to move fire suppression resources throughout the season, and the other case in which daily information is not used and fire-suppression resources are staged in their home locations all season. We demonstrate the method by constructing a hypothetical wildland management unit calibrated to represent a region typical in the US West. The method uses estimated suppression costs and probabilities of significant fire, as provided by an information service, to estimate expected suppression costs. We analyse differences in expected suppression costs for a range of risk scenarios. Economic savings occur for the majority of risk scenarios. This approach can be used to evaluate investments in wildfire-potential information services, and for assessing the value of investing in new resources. We develop a method to value wildfire-potential information as a fire suppression decision-support tool. We demonstrate the method by calculating expected suppression expenditures for 'with' and 'without' information cases for a hypothetical management unit. The value of this information is defined as the difference in expected wildfire suppression expenditures. [ABSTRACT FROM AUTHOR]

Estimation of the amount of dead grass fuel is essential for the assessment of risk of grassland fires. This paper develops a method to estimate the amount of dead grass fuel based on spectral reflectance. Samples of soil and dead grass were collected in the Songliao Plain, China. The spectral reflectance of these samples at different densities and at various wavelengths (350-2500 nm) was measured in the laboratory. A new spectral index for dead grass was designed based on the equivalent bands of a Moderate Resolution Imaging Spectroradiometer (MODIS) satellite image. In the short-wave infrared region of the electromagnetic spectrum, an absorption feature associated with cellulose and lignin was observed at ~2100 nm in the spectra of dead grass. This absorption feature was not present in the spectra of soil. This observation provides a basis for discriminating between dead grass and soil. The dead grass fuel index created using bands 6 and 7 of MODIS correlated significantly with the field measurements of the mass of dead grass fuel (R² = 0.84). Hence, the dead grass fuel index can be used to produce an estimate of the amount of dead grass fuel, via the regression function identified above. Such methods of estimating the amount of dead grass fuel can contribute to studies of grassland fire hazard. This study uses spectral measurements to examine the reflectance characteristics associated with cellulose and lignin near 2100 nm and develops an index for dead grass fuel. We found that the regression functions based on the dead grass fuel index can be applied to estimate the amount of dead grass fuels. [ABSTRACT FROM AUTHOR]

The article focuses on a study exploring the critical role of ground and peat fires as contributors to carbon dioxide emissions into the atmosphere. It provides an overview about natural fires, which play a vital role in the dynamics of terrestrial ecosystems and emissions of different substances from these ecosystems. Information about carbon cycle scheme is presented.

Most grassfires that occur in southern Australia are contained to small areas by local suppression resources. Those that are not require extra resources from neighbouring districts. Identifying these fires at the start of initial attack can prompt early resource requests so that resources arrive earlier when they can more effectively assist with containment. This study uses operational data collected from Australian grassfires that used ground tankers and aircraft for suppression. Variables were limited to those available when the first situation report is provided to incident controllers and included weather parameters, resource response times, slope, curing state, pasture condition and estimated fire area at initial attack. Logistic regression and classification trees were used to identify grassfires likely to escape initial attack by (a) becoming large(final area $100 ha),(b) being of long duration (containment time ≥4h) or (c) either or both of these. These fires would benefit from having more resources deployed to them than are normally available. The best models used initial fire area and Grassland Fire Danger Index as predictor variables. Preliminary operational decision guides developed from classification trees could be used by fire managers to make quick assessments of the need for extra resources at early stages of a fire. [ABSTRACT FROM AUTHOR]

Abstract: The aim of this work is to study the spatio-temporal effects of a grassland fire in Lithuania. Immediately after the fire, a experimental plot was designed in a east-faced slope. Vegetation cover and height were measured 10, 17, 31 and 46 days after the fire (vegetation cover was only measured until 31 days after the fire because in the last measurement campaign the plot was completely covered). The results showed that vegetation recovered very fast. Ten days after the fire vegetation cover and height distribution were heterogeneous, decreasing with the time due to vegetation spread. Vegetation recovered was specially observed between 17 and 31 days after the fire due vegetation recuperation. This increase might reduce the soil vulnerability to erosion However, the spatial structure of this recuperation was different in both variables, and spatial autocorrelation was higher in vegetation cover than vegetation in height in all measurements. Despite these differences, vegetation cover and height values were higher in the bottom part of the plot that was attributed to lower fire severity and ash and nutrient transport. [Copyright &y& Elsevier]

In this paper, the threshold of the early warning of grassland fire disaster risk is determined by the optimal segmentation, and it can give a quantitative and objective classification and make a scientific result. GIS grid has both the display form of raster data and vector data's attribute information, it is the details of traditional vector data. Grid GIS technology combined was used in the spatial distribution of indicators of the constituency which will make space rating scale more accurate. With the optimal partitioning of the fire cases from 1994 to 2004, early warning threshold was identified and was divided into the blue, yellow, orange and red alarm. [ABSTRACT FROM AUTHOR]

Local observations, repeat photos, and broad-scale remote sensing suggest that tall shrubs are becoming an increasingly dominant component of Low Arctic ecosystems. This shift has the potential to alter the surface energy balance through changes to the surface albedo, snow accumulation and melt, and ground thermal regimes. However, to date there have been few quantitative estimates of the rate of tall shrub expansion. We used soft copy stereo visualization of air photos to map fine-scale changes in tall shrub tundra and green alder density in the upland tundra north of Inuvik, NT between 1972 and 2004. We also used 2004 photos to map tall shrub tundra in areas affected by fires that occurred between 1960 and 1968. To assess the potential impact of vegetation change on microclimate, we used pyranometers to measure albedo and net solar radiation, thermistors attached to data loggers to record ground temperatures, and field surveys to record winter snow conditions in three common vegetation types. Fine-scale mapping shows that green alder stem density has increased by 68% (±24.1) since 1972. Average tall shrub tundra cover has also increased by 15% (±3.6) since 1972. Historical tundra fires had the highest proportion of tall shrub cover of all areas mapped using 2004 photos, ranging from 92 to 99%. Based on these results, we suggest that predicted increases in the size and frequency of tundra fire are likely to drive rapid shrub proliferation in the Low Arctic. Shrub-dominated sites have decreased albedo, increased net solar radiation, deeper snow pack, and elevated near-surface ground temperatures, indicating that continued increases in shrub cover will affect regional climate, hydrology, permafrost temperatures, and terrain stability. [ABSTRACT FROM AUTHOR]

Fires modify the structure of vegetation communities, the carbon and water cycles, the soil's chemistry, and affect the climate system. Within this context, this work aimed to understand the distribution patterns of burned areas in Brazil, during the period of 2002 to 2010, taking into consideration each one of the six Brazilian biomes (Amazon, Caatinga, Cerrado, Atlantic Forest, Pampa and Pantanal) and the respective major land cover classes. Data from the MODIS MCD45A1 product (burned area), as well as thermal anomalies (MOD14 and MYD14) and precipitation (TRMM), were analyzed according to the 2002 Brazilian official land cover and land use map (PROBIO). The Brazilian savanna biome, known as Cerrado, presented the largest concentration of burned areas detected by MODIS (73%), followed by the Amazon (14%), Pantanal (6%), Atlantic Forest (4%), Caatinga (3%), and Pampa (0,06%) biomes. Indeed, in the years of 2007 and 2010, 90% and 92% of Brazil's burned areas were concentrated in the Cerrado and Amazon biomes, respectively. TRMM data indicated that during these two years there was a significant influence of La Niña, causing low rainfall in the Amazon, Cerrado, Caatinga, and Atlantic Forest biomes. Regarding the land cover classes, approximately 81% of the burned areas occurred over remnant vegetation areas. Although no unequivocal correlation can be established between burned areas and new land conversions, the conspicuous concentration of fire scars, particularly in Amazon-Cerrado transition (i.e., the Arc of Deforestation) is certainly not a simple coincidence. Such patterns and trends corroborate the need of improved territorial governance, in addition to the implementation of systematic fire warning and preventive systems. [ABSTRACT FROM AUTHOR]

The article presents information on the research paper "Assessing Discontinuous Fire Behaviour and Uncertainty Associated With the Onset of Crowning," by M.G. Alexander and M.G. Cruz.

The devastating series of fire events that occurred during the summers of 2007 and 2009 in Greece made evident the need for an operational mechanism to map burned areas in an accurate and timely fashion to be developed. In this work, Système pour l'Observation de la Terre (SPOT)-4 HRVIR images are introduced in an object-based classification environment in order to develop a classification procedure for burned area mapping. The development of the procedure was based on two images and then tested for its transferability to other burned areas. Results from the SPOT-4 HRVIR burned area mapping showed very high classification accuracies (∼0.86 kappa coefficient), while the object-based classification procedure that was developed proved to be transferable when applied to other study areas. [ABSTRACT FROM AUTHOR]

A new model for Mediterranean forest fire regime assessment is presented and discussed. The model is based on the experimental evidence that fire is due to both hydrological and ecological processes and the relative role of fuel load versus fuel moisture is an important driver in fire ecology. Diverse scenarios are analyzed where either the hydrological forcing or the feedback between fire and hydrological characterization of the site is changed. The model outcome demonstrates that the two-way interaction between hydrological processes, biology, and fire regime drives the ecosystem toward a typical fire regime that may be altered either by an evolution of the biological characterization of the site or by a change of the hydrological forcing. This tenet implies that not every fire regime is compatible with the ecohydrological characterization of the site under study. This means that natural (nonantropogenic) fire cannot be modeled as an arbitrary external forcing because the coupled hydrological and biological processes determines its statistical characterization, and conversely, the fire regime affects the soil moisture availability and the outcome of different species competition under possible water stress. The new modeling approach presented here, when provided by a proper model parameterization, can advance the capability in predicting and managing fires in ecosystems influenced by climate and land use changes. [ABSTRACT FROM AUTHOR]

The article presents a study which characterizes the temporal variability of forest fires in eastern Amazonia. The study utilizes satellite data to derive a 23-year time series of annual landscape-level burn scars in a fragmented forest of the region. It reveals that fire return interval is 5 to 11 times more frequent than the estimated natural fire regime. It provides quantification of the substantial influence of climate and droughts on the likelihood of returning forest fires in landscapes.

The article presents a study regarding the role of variations in fire severity in driving the potential shifts in dominant forest cover in interior Alaska. The study utilizes ensemble techniques using regression trees as base learner to determine fire severity using spectral data in concert with other relevant geospatial data. It also reveals how disturbance-driven modification can affect the carbon cycle and climate system at regional to global scales.

The article explores the history of bushfires, fire control, and fire-stick farming among Aboriginal peoples in Australia. The author reflects on land management practices that involve the setting of controlled fires to kill insects, to hunt and lure game animals, and to develop grasslands and open forests. Emphasis is given to Aboriginal efforts to locate systematically plants and animals within the native landscape. Other topics include fire management, the spiritual aspects of fire control, and contact with European settlers.

1. Fire is an important process in Mediterranean-ecosystem shrublands, and prescribed burning is often used to manage these ecosystems. Analyses of past fire regimes are required to interpret biotic responses to fire, as well as to assess the degree to which management interventions have been able to influence the fire regime. 2. We used a spatial data base of fires within 10 protected areas covering >720 000 ha to examine the frequency, seasonality, size and cause of fires over four decades. Our study covered five fire climate zones and a range of mountain fynbos shrubland types. We examined whether regular prescribed burning would be necessary to rejuvenate the vegetation, and also to reduce the incidence and extent of wildfires. 3. Cumulative fire frequency distributions indicated that the probability of fire was not strongly affected by post-fire age, with 50% of the area experiencing a successive fire within 10–13 years after the previous fire in most areas. This suggests that the accumulation of fuel did not limit the occurrence of wildfires, and that regular prescribed burning would not necessarily reduce the risk of wildfires. 4. Inland zones experienced more severe fire weather than coastal zones (∼35% vs. 11–19% of days with high to very high fire danger, respectively). Despite these differences, fire return periods were similar (10–13 years), suggesting that the availability of ignitions, and not fuel or weather, limited the occurrence of wildfires. 5. Despite a policy that promoted prescribed burning, a relatively small area (between 4·6% and 32·4% of the area of all fires) burned in prescribed burns. Seasonal restrictions for safety and ecological reasons, the imperative to integrate planned fires with invasive alien plant treatments and unplanned wildfires have all contributed to the relatively small area that burnt in prescribed burns. 6. Synthesis and applications. Recurrent wildfires,... [ABSTRACT FROM AUTHOR]

The article presents a study which determines the importance of charred litter and the ash-bed on water repellency, runoff generation and soil loss in the post-fire period at the Mediterranean heathland in southern Spain. The study conducts a prescribed fire a year after the fire in the heathland and compares the pre- and post-changes which took place in the ground surface. The result reveals that the ash and charred litter layers reduces water repellency and minimizes soil loss.

Fire is widely used in conservation management of native grasslands. Burning is often carried out under conditions that are marginal for sustained fire spread, and therefore it would be useful to be able to predict fire sustainability. There is currently no model allowing such prediction in temperate grasslands. This study aims to identify the environmental variables that determine whether fires will sustain in native grasslands in Tasmania, Australia, and develop a model for predicting fire sustainability in this vegetation. Fuel characteristics and weather conditions were recorded for 111 test fires. Logistic regression modeling identified dead fuel moisture content, fuel load, and percentage dead fuel as predictors of fire sustainability. Classification tree modeling identified dead fuel moisture and fuel load threshold values for sustaining fires. There was also evidence indicating a percentage dead fuel threshold. The logistic regression model and a model combining the results of the classification tree and the percentage dead fuel threshold accurately predicted the outcomes of a small set of experimental fires. These models are likely to have utility in predicting fire sustainability in Tasmanian grasslands and are also likely to be applicable to similar grasslands elsewhere. [ABSTRACT FROM AUTHOR]

As woody plants encroach into grasslands, grass biomass, density and cover decline as wood plant biomass, density and cover increase. There is also a shift in location of the biomass from mostly below-ground in the grasslands to aboveground in the woodlands. In addition, species richness and diversity change as herbaceous species are replaced by woody species. This is not a new phenomenon, but has been going on continually as the climate of the Planet has changed. However, in the past 160 years the changes have been unparalleled. The process is encroachment not invasion because woody species that have been increasing in density are native species and have been present in these communities for thousands of years. These indigenous or native woody species have increased in density, cover and biomass because of changes in one or more abiotic or biotic factors or conditions. Woody species that have increased in density and cover are not the cause of the encroachment, but the result of changes of other factors. Globally, the orbit of the Earth is becoming more circular and less elliptical, causing moderation of the climate. Additional global climate changing factors including elevated levels of CO2 and parallel increases in temperature are background factors and probably not the principal causes directing the current wave of encroachment. There is probably not a single reason for encroachment, but a combination of factors that are difficult to disentangle. The prime cause of the current and recent encroachment appears to be high and constant levels of grass herbivory by domestic animals. This herbivory reduces fine fuel with a concomitant reduction in fire frequency or in some cases a complete elimination of fire from these communities. Conditions would now favor the woody plants over the grasses. Reduced grass competition, woody plant seed dispersal and changes in animal populations seem to modify the rate of encroachment rather than being the cause. High concentrations of atmospheric CO2 are not required to explain current woody plant encroachment. Changes in these grassland communities will continue into the future but the specifics are difficult to predict. Density, cover and species composition will fluctuate and will probably continue to change. Increased levels of anthropogenic soil nitrogen suggest replacement of many legumes by other woody species. Modification and perhaps reversal of the changes in these former grassland communities will be an arduous, continuing and perhaps impossible management task. [Copyright &y& Elsevier]

Understory plant composition and diversity levels in oak-hickory (Quercus-Carya) forests have historically been maintained by periodic low-intensity ground fires, but fire suppression has altered the structure and function of these communities. We examined burned and unburned oak-hickory stands to determine the influence of repeated burning on understory communities. We compared understory herbaceous, shrub, and tree species diversity and composition among four burn categories: unburned stands, and stands that had burned once, twice, and three times over a 20-year period (late 1960s to late 1980s). We hypothesized that stands that have received repeated burns will have greater understory diversity and reduced importance of shade-tolerant mesophytic species. We found that burned stands had greater species richness than unburned stands, regardless of burn frequency. Species composition was not drastically different among the four burn categories; however, individual species were indicative of particular burn categories. More forest herbs were associated with the single burn category, while more disturbance-dependent species (Desmodium spp. and Solidago spp.) were associated with the repeated burn categories. Burned stands contained greater densities of white oak (Quercus alba L.) and hickory species seedlings. Our results suggest that restoring and maintaining the historic fire return interval (10-15 years) will promote herbaceous species diversity and favor the regeneration of oak and hickory species. However, it has been 15-22 years since the stands we sampled last burned, and the similarity among burn categories suggests that additional burning is needed to prevent these stands from reverting to a suppressed condition. [ABSTRACT FROM AUTHOR]

Fires are common in grassland regions of the world, and the frequency and severity of fire is linked to climate-driven changes in fuel loads. Western Mongolia is dominated by grasslands but the fire history of this region is largely unknown. We reconstructed modern fire (48 lakes) and historical fires (9 lakes) using sediment charcoal. Modern fuel loads were estimated using a combination of clipped plots, satellite-based estimates of annual aboveground net primary productivity (NPP) and NPP modeled from annual temperature and precipitation. Loss-on-ignition and environmental magnetics of lake sediments were analyzed as proxies for climate. We found little evidence for modern or historical fire in the landscape, as charcoal was absent from the surface sediments of 34 of 48 lakes. Charcoal influxes were uniformly low, averaging from 0.002 to 0.028 mm²/cm² per yr, over the past 1200 years at nine lakes, and the past 6000—5000 years at two of the lakes with longer sediment records. In the modern landscape, livestock grazing has eliminated most of the fuels necessary to carry a fire, as measured fuel loads (27.3±4.9 g/m²) were only ∼20% of aboveground annual NPP estimated using MODIS Imagery or modeled from climate data. The historical absence of fire may indicate a longer history of intensive grazing than sometimes assumed, and cultural prohibitions against burning may also play a role. Regional summary indicated a >50% decrease in charcoal influxes since AD 1600 at most sites which may be related to lower temperatures or greater aridity during the 'Little Ice Age'. Alternatively this decrease in charcoal influxes may reflect increases in livestock numbers or increased local concentrations because of restrictions on the movement of animals coincident with the establishment of Manchu rule in the late seventeenth century. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Central Chile differs from other areas with Mediterranean-type climate by the scarcity of natural wildfires. The Chilean matorral is highly invaded by alien plant species from other Mediterranean zones of the world, where natural, recurrent wildfires have been one of their ecological features at least since the Pliocene. This suggests that anthropogenic fires in Chile might favour alien plant recruitment, increasing the invasive process. We assessed the effect of litter burning on the emergence of alien and native species from the soil seedbank of a matorral of central Chile. Soil samples were taken from three types of microhabitats: (i) closed matorral; (ii) beneath the canopy of shrubs and trees from an open matorral; (iii) grassland. Each sample was split in two subsamples. One subsample was exposed to fire by burning the litter taken from its corresponding microhabitat, and the other subsample was left unburned and used as a control. Fire intensity, determined by the fuel type, affected more markedly the native seedbank survival than the alien one. The low-intensity fire produced by grassland litter did not significantly affect the emergence of native herbs but increased alien species richness. The high-intensity and the very high-intensity fires produced by litter burning from beneath the canopy of the closed and the open matorral, respectively, negatively affected the seedling emergence of both native and alien species, but did so in a more pronounced manner to native species. Therefore, anthropogenic fires in central Chile may promote the invasion of alien plants with favourable traits (i.e. heat-shock resistance of seeds) that are not present in the native flora. [ABSTRACT FROM AUTHOR]

Effective fire suppression and land use practices over the last century have altered forest structure and increased fuel loads in many forests in the United States, increasing the occurrence of catastrophic wildland fires. The most effective methods to change potential fire behavior are to reduce surface fuels, increase the canopy base height and reduce canopy bulk density. This multi-tiered approach breaks up the continuity of surface, ladder and crown fuels. Effectiveness of fuel treatments is often shown indirectly through fire behavior modeling or directly through monitoring wildland fire effects such as tree mortality. The present study investigates how prescribed fire affected fuel loads, forest structure, potential fire behavior, and modeled tree mortality at 90th and 97.5th percentile fire weather conditions on eight National Forests in California. Prescription burning did not significantly change forest structure at most sites. Total fuel loads (litter, duff, 1, 10, 100, and 1000-h) were reduced by 23 to 78% across the sites. The reduction in fuel loads altered potential fire behavior by reducing fireline intensity and increasing torching index and crowning index at most sites. Predicted tree mortality decreased after treatment as an effect of reduced potential fire behavior and fuel loads. To use limited fuel hazard reduction resources efficiently, more effort could be placed on the evaluation of existing fire hazards because several stands in the present study had little potential for adverse fire effects before prescribed fire was applied. [ABSTRACT FROM AUTHOR]

The behaviour of five landscape fire models (CAFÉ, FIRESCAPE, LAMOS(HS), LANDSUM and SEMLAND) was compared in a standardised modelling experiment. The importance of fuel management approach, fuel management effort, ignition management effort and weather in determining variation in area burned and number of edge pixels burned (a measure of potential impact on assets adjacent to fire-prone landscapes) was quantified for a standardised modelling landscape. Importance was measured as the proportion of variation in area or edge pixels burned explained by each factor and all interactions among them. Weather and ignition management were consistently more important for explaining variation in area burned than fuel management approach and effort, which were found to be statistically unimportant. For the number of edge pixels burned, weather and ignition management were generally more important than fuel management approach and effort. Increased ignition management effort resulted in decreased area burned in all models and decreased number of edge pixels burned in three models. The findings demonstrate that year-to-year variation in weather and the success of ignition management consistently prevail over the effects of fuel management on area burned in a range of modelled ecosystems. [ABSTRACT FROM AUTHOR]

Relative to the western United States, where fire and fuel management programs have received greater emphasis, few community-based studies have focused on the Great Lakes region. The present paper describes public opinion research from counties surrounding National Forests in Wisconsin, Minnesota and Michigan. Survey data address citizen perspectives on (1) fuel reduction practices and related risks, (2) confidence in the US Forest Service to effectively implement treatments, and (3) interactions between the agency and forest communities. Substantial support for prescribed fire and thinning treatments is evident, with few participants believing these practices should not be considered or are unnecessary. However, ratings of agency actions were weak at all three study sites; in particular, there is some skepticism that managers can safely implement prescribed fire programs. Overall, Minnesota residents had fewer concerns whereas Michigan respondents were more cautious. These results are discussed and compared with findings from the western US. [ABSTRACT FROM AUTHOR]

Although the prevalence of asthma and allergic rhinitis has been increasing in tropical regions, little is known about the allergenicity of pollens from tropical plant families or the importance of ongoing environmental changes. We investigated associations between daily average pollen counts of several tropical plant families and sales of medications for the treatment of allergic rhinitis in Darwin, Australia—a tropical setting in which grass abundance has increased due to increased fire frequencies and the introduction of African pasture grasses. Daily pollen counts with detailed identification of plant species were undertaken in conjunction with a weekly survey of flowering plant species from April 2004 to November 2005. Five pharmacies provided daily sales data of selected medications commonly used to treat allergic rhinitis. We used generalized linear modeling to examine outcomes. All analyses accounted for the potential confounding effects of time trends, holidays, respiratory viral illnesses, meteorological conditions, and air pollution. The peak total pollen count was 94 grains/m3. Despite the low levels of Poaceae (grass) pollen (maximum daily count, 24 grains/m3), there was a clear association with daily sales of anti-allergic medications greatest at a lag of 1 day. Sales increased by 5% with an interquartile range rise (3 grain/m3) in Poaceae pollen (5.07%, 95%CI 1.04%, 9.25%). No associations were observed with pollen from other plant families. Although further testing is required, we suggest that an overlooked aspect of the “grass-fire cycle” that is degrading many tropical landscapes, could be an increase in the prevalence of allergic rhinitis. [ABSTRACT FROM AUTHOR]

We present an automated method for mapping burned areas using 500-m Moderate Resolution Imaging Spectroradiometer (MODIS) imagery coupled with 1-km MODIS active fire observations. The algorithm applies dynamic thresholds to composite imagery generated from a burn-sensitive vegetation index and a measure of temporal texture. Cumulative active fire maps are used to guide the selection of burned and unburned training samples. An accuracy assessment for three geographically diverse regions (central Siberia, the western United States, and southern Africa) was performed using high resolution burned area maps derived from Landsat imagery. Mapped burned areas were accurate to within approximately 10% in all regions except the high-tree-cover sub-region of southern Africa, where the MODIS burn maps underestimated the area burned by 41%. We estimate the minimum detectable burn size for reliable detection by our algorithm to be on the order of 120 ha. [Copyright &y& Elsevier]

The major source of uncertainty in wildfire behavior prediction is the transient behavior of wildfire due to changes in flow in the fire's environment. The changes in flow are dominated by two factors. The first is the interaction or 'coupling' between the fire and the fire-induced flow. The second is the interaction or 'coupling' between the fire and the ambient flow driven by turbulence due to wind gustiness and eddies in the atmospheric boundary layer (ABL). In the present study, coupled wildfire-atmosphere large-eddy simulations of grassland fires are used to examine the differences in the rate of spread and area burnt by grass fires in two types of ABL, a buoyancy-dominated ABL and a roll-dominated ABL. The simulations show how a buoyancy-dominated ABL affects fire spread, how a roll-dominated ABL affects fire spread, and how fire lines interact with these two different ABL flow types. The simulations also show how important are fire-atmosphere couplings or fire-induced circulations to fire line spread compared with the direct impact of the turbulence in the two different ABLs. The results have implications for operational wildfire behavior prediction. Ultimately, it will be important to use techniques that include an estimate of uncertainty in wildfire behavior forecasts. [ABSTRACT FROM AUTHOR]

Abstract: The propagation of grassland fires is simulated using a fully physical based model, partially developed during the FIRESTAR European Union programme. This approach, based on a multiphase formulation, includes the calculation of the degradation of the vegetation (by dehydration and pyrolysis) and the turbulent/reactive flow resulting from the mixing between the ambient gas (wind flow) and the pyrolizate. The solid fuel is simulated as homogeneous distribution of solid particles forming a porous media, interacting with the gas flow using a continuous distribution of drag forces. Other source terms representing the interactions between the vegetation and the gas flow are also taken into account, such as the production of water vapour and gaseous fuel, the radiation of soot particles and ashes, and the convective exchange in the energy balance. The model was validated from preliminary calculations carried out at small scale, for a homogeneous fuel bed (pine needles, excelsior, sticks) and compared with experimental results obtained in a wind tunnel. Calculations are then extended to study the propagation of fires through a flat grassland, for various wind speed conditions. The numerical results are compared to empirical and semi-empirical predictions obtained in similar conditions. [Copyright &y& Elsevier]

We develop empirical models for the rate of spread and intensity of fires in grass fuels. The models are based on a well-known physical analogy for the rate of spread of a fire through a continuous fuelbed. Unlike other models based on this analogy, we do not attempt to directly estimate the model parameters. Rather, we use data on the rate of spread to indirectly estimate parameters that describe aggregate properties of the fire behaviour. The resulting models require information on the moisture content of the fuel and wind speed to predict the rate of spread of fires. To predict fire intensity, the models additionally use information on the heat yield of the fuel and the amount of fuel consumed. We evaluate the models by using them to predict the intensity of independent fires and by comparing them with linear and additive regression models. The additive model provides the best description of the training data but predicts independent data poorly and with high bias. Overall, the empirical models describe the data better than the linear model, and predict independent data with lower bias. Hence our physically motivated empirical models perform better than statistical models and are easier to parameterise than parameter-rich physical models. We conclude that our physically motivated empirical models provide an alternative to statistical models and parameter-rich physical models of fire behaviour. [ABSTRACT FROM AUTHOR]

The groundcover levels after corn ( Zea mays L.) silage harvest are rarely adequate to prevent soil erosion, but most corn-growers do not plant cover crops due to time and cost limitations. Herbicide-resistant corn hybrids provide opportunities to control weeds and to utilize cover crops in previously unexplored combinations. Field studies were conducted in 1999 and 2000 at Dryden and Valatie, New York, USA, to determine the potential for managing existing quackgrass ( Elytrigia repens[L.] Nevski) as a cover crop in herbicide-resistant silage corn. Three isolines of the corn hybrid, DKC493, were treated with glyphosate, glufosinate, primisulfuron, nicosulfuron or sethoxydim. Averaged over all site–years, the corn silage yields with glufosinate were similar to those with glyphosate. Glufosinate also resulted in a quackgrass ground cover greater than the 30% threshold for preventing soil erosion. Quackgrass could be managed as a perennial cover crop in silage corn–perennial forage dairy rotations in north-eastern USA. [ABSTRACT FROM AUTHOR]

In our previous article (Odion and Hanson, Ecosystems 9:1177–89, 2006), we reported that fire severity in the conifer forests of the Sierra Nevada mountains of California, contrary to prevailing assumptions, did not burn with predominately stand-replacing, high severity fire. The reply by Safford and others ( Ecosystems, this issue) using a new mapping approach also found this pattern. Their methods identify more high severity fire; however, as we illustrate here, this may be attributed to the different mapping approaches used. We previously also found that condition class based upon fire return interval departure (FRID) was not an effective predictor of fire severity. Safford and others (this issue) concluded that there was a strong correlation between FRID-based condition class and fire severity based upon data from the McNally fire of 2002. The difference between these findings about McNally fire reflects the fact that they combined FRID categories whereas we kept the categories separate. Here, using their fire severity data to evaluate all three fires, we found that severity was not predicted by FRID. Developing a consensus definition of fire severity within the scientific community might help alleviate future contradictions regarding fire effects. [ABSTRACT FROM AUTHOR]

We comment on a recent Ecosystem paper by Odion and Hanson (Ecosystems 9:1177–1189, ), in which the authors claim that high severity fire is rare in the Sierra Nevada under current conditions. Odion and Hanson’s results are predicated on BAER soil burn severity maps, which are based primarily on fire effects to soil, not vegetation. Odion and Hanson, and we fear others as well, are misinformed as to the nature of the BAER severity mapping process, and proper applications of BAER soil burn severity maps. By comparing the BAER soil burn severity maps to a true vegetation burn severity measure (RdNBR) calibrated by field data, we show that the area in the high soil burn severity class for the three fires analyzed by Odion and Hanson is substantially less than the area of stand-replacing fire, and that BAER maps—especially hand-derived maps such as those from two of the three fires—also greatly underestimate the heterogeneity in vegetation burn severity on burned landscapes. We also show that, contrary to Odion and Hanson’s claims, Fire Return Interval Departure (FRID) is strongly correlated with fire severity in conifer stands within the perimeter of the McNally Fire. [ABSTRACT FROM AUTHOR]