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Wildfires and climate change increasingly are transforming vegetation composition and structure, and postfire management may have long-lasting effects on ecosystem reorganization. Postfire aerial seeding treatments are commonly used to reduce runoff and soil erosion, but little is known about how seeding treatments affect native vegetation recovery over long periods of time, particularly in type-converted forests that have been dramatically transformed by the effects of repeated, high-severity fire. In this study, we analyze and report on a rare long-term (23-year) dataset that documents vegetation dynamics following a 1996 post-fire aerial seeding treatment and a subsequent 2011 high-severity reburn in a dry conifer landscape of northern New Mexico, USA. Repeated surveys between 1997 and 2019 of 49 permanent transects were analyzed for differences in vegetation cover, richness, and diversity between seeded and unseeded areas, and to characterize the development of seeded and unseeded vegetation communities through time and across gradients of burn severity, elevation, and soil-available water capacity. Seeded plots showed no significant difference in bare ground cover during the initial years postfire relative to unseeded plots. Postfire seeding led to a clear and sustained divergence in herbaceous community composition. Seeded plots had a much higher cover of non-native graminoids, primarily Bromus inermis, a likely contaminant in the seed mix. High-severity reburning of all plots in 2011 reduced native graminoid cover by half at seeded plots compared with both prefire levels and with plots that were unseeded following the initial 1996 fire. In addition, higher fire severity was associated with increased non-native graminoid cover and reduced native graminoid cover. This study documents fire-driven ecosystem transformation from conifer forest into a shrub-and-grass-dominated system, reinforced by aerial seeding of grasses and high-severity reburning. This unique long-term dataset illustrates that post-fire seeding carries significant risks of unwanted non-native species invasions that persist through subsequent fires-thus alternative postfire management actions merit consideration to better support native ecosystem resilience given emergent climate change and increasing disturbance. This study also highlights the importance of long-term monitoring of postfire vegetation dynamics, as short-term assessments miss key elements of complex ecosystem responses to fire and postfire management actions.

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Global burned area has declined by nearly one quarter between 1998 and 2015. Drylands contain a large proportion of these global fires but there are important differences within the drylands, for example, savannas and tropical dry forests (TDF). Savannas, a biome fire-prone and fire-adapted, have reduced the burned area, while the fire in the TDF is one of the most critical factors impacting biodiversity and carbon emissions. Moreover, under climate change scenarios TDF is expected to increase its current extent and raise the risk of fires. Despite regional and global scale effects, and the influence of this ecosystem on the global carbon cycle, little effort has been dedicated to studying the influence of climate (seasonality and extreme events) and socioeconomic conditions of fire regimen in TDF. Here we use the Global Fire Emissions Database and, climate and socioeconomic metrics to better understand long-term factors explaining the variation in burned area and biomass in TDF at Pantropical scale. On average, fires affected 1.4% of the total TDF' area (60,208 km2 ) and burned 24.4% (259.6 Tg) of the global burned biomass annually at Pantropical scales. Climate modulators largely influence local and regional fire regimes. Inter-annual variation in fire regime is shaped by El Niño and La Niña. During the El Niño and the forthcoming year of La Niña, there is an increment in extension (35.2% and 10.3%) and carbon emissions (42.9% and 10.6%). Socioeconomic indicators such as land-management and population were modulators of the size of both, burned area and carbon emissions. Moreover, fires may reduce the capability to reach the target of "half protected species" in the globe, that is, high-severity fires are recorded in ecoregions classified as nature could reach half protected. These observations may contribute to improving fire-management.

El área global quemada se redujo en casi una cuarta parte entre 1998 y 2015. Los bosques secos contienen una gran proporción de esos incendios globales, pero existen diferencias importantes dentro de ellos, por ejemplo, las sabanas y los bosques secos tropicales (SBC). Las sabanas, son un bioma propenso y adaptado al fuego, y que en los últimos años han reducido su área quemada. Mientras que el fuego en la SBC es uno de los factores más críticos que impactan la biodiversidad y las emisiones de carbono. Además, bajo escenarios de cambio climático, se espera que la SBC aumente su extensión actual y aumente el riesgo de incendios. A pesar de los efectos a escala regional y global, y la influencia de este ecosistema en el ciclo global del carbono, se le ha dedicado poco esfuerzo a estudiar la influencia del clima (estacionalidad y eventos extremos) y las condiciones socioeconómicas del régimen de incendios. Aquí usamos la base de datos global de emisiones de incendios y métricas climáticas y socioeconómicas para comprender mejor los factores a largo plazo que explican la variación en el área quemada y la biomasa a escala Pantropical. En promedio, los incendios afectaron el 1,4% del área total de la SBC (60 208 km2 ) y quemaron el 24,4% (259,6 Tg) de la biomasa global quemada anualmente a escala Pantropical. Los moduladores climáticos influyen en gran medida en los regímenes de incendios locales y regionales. La variación interanual del régimen de incendios está determinada por El Niño y La Niña. Durante El Niño y el año subsecuente de La Niña, se produce un incremento en la extensión (35,2% y 10,3%) y en las emisiones de carbono (42,9% y 10,6%). Los indicadores socioeconómicos como la gestión de la tierra y la población fueron moduladores del tamaño tanto del área quemada como de las emisiones de carbono. Además, los incendios pueden reducir la capacidad de alcanzar el objetivo de "protección de la mitad de las especies" en el mundo, es decir, los incendios de alta gravedad se registran en ecorregiones clasificadas como naturaleza que podría alcanzar la protección de la mitad de su biodiversidad. Estas observaciones pueden contribuir a mejorar la gestión de incendios.

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The identification of fire causes and characteristics is of fundamental importance to better understand fire regimes and drivers. Particularly for Brazil, there is a gap in the quantification of lightning-caused fires. Accordingly, this work is a novel probabilistic assessment of the spatial-temporal patterns of lightning-ignited wildfires in the Pantanal wetland. Here, remote sensing information such as VIIRS active fires, MODIS burned area (BA) and STARNET lightning observations from 2012 to 2017, were combined to estimate the location, number of scars and amount of BA associated with atmospheric discharges on a seasonal basis. The highest lightning activity occurs during summer (December-February), and the lowest during winter (June-August). Conversely, the highest fire activity occurred during spring (September-November) and the lowest during autumn (March-May). Our analysis revealed low evidence of an association between fires and lightning, suggesting that human-related activities are the main source of ignitions. Weak evidence of natural-caused fire occurrence is conveyed by the low spatial-temporal match of lightning and fire throughout the studied period. Natural-caused fires accounted for only 5% of the annual total scars and 83.8% of the BA was human-caused. Most of the fires with extension larger than 1000 ha were not related to lighting. Lightning-fires seem an important element of the summer fire regime given that around half of the total BA during this season may be originated by lightning. By contrast, in the rest of the year the lightning-fires represent a minor percentage of the fire activity in the region. The density of lightning-ignited fires varies considerably, being higher in the north part of the Pantanal. This work provides a basis for a better understanding of lightning-related fire outbreaks in tropical ecosystems, particularly wetlands, which is fundamental to improve region-based strategies for land management actions, ecological studies and modeling climatic and anthropogenic drivers of wildfires.

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The Brazilian savanna (Cerrado) is considered the most floristically diverse savanna in the world, home to more than seven thousand species. The region is a mosaic of savannas, grasslands and forests whose unique biophysical and landscape attributes are on the basis of a recent ecoregional map, paving the way to improved region-based strategies for land management actions. However, as a fire-prone ecosystem, Cerrado owes much of its distribution and ecological properties to the fire regime and contributes to an important parcel of South America burned area. Accordingly, any attempt to use ecoregion geography as a guide for management strategies should take fire into account, as an essential variable. The main aim of this study is to complement the ecoregional map of the Cerrado with information related to the fire component. Using remotely sensed information, we identify patterns and trends of fire frequency, intensity, seasonality, extent and scar size, and combine this information for each ecoregion, relying on a simple classification that summarizes the main fire characteristics over the last two decades. Results show a marked north-south fire activity gradient, with increased contributions from MATOPIBA, the latest agricultural frontier. Five ecoregions alone account for two thirds of yearly burned area. More intense fires are found in the Arc of Deforestation and eastern ecoregions, while ecoregions in MATOPIBA display decreasing fire intensity. An innovative analysis of fire scars stratified by size class shows that infrequent large fires are responsible for the majority of burned area. These large fires display positive trends over many ecoregions, whereas smaller fires, albeit more frequent, have been decreasing in number. The final fire classification scheme shows well defined spatially-aggregated groups, where trends are found to be the key factor to evaluate fire within their regional contexts. Results presented here provide new insights to improve fire management strategies under a changing climate.

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Biomass burning is one of the most critical factors impacting vegetation and atmospheric trends, with important societal implications, particularly when extreme weather conditions occur. Trends and factors of burned area (BA) have been analysed at regional and global scales, but little effort has been dedicated to study the interannual variability. This paper aimed to better understand factors explaining this variation, under the assumption that the more human control of fires the more frequently they occur, as burnings will be less dependent of weather cycles. Interannual variability of BA was estimated from the coefficient of variation of the annual BA (BA_CV) estimated from satellite data at 250 m, covering the period from 2001 to 2018. These data and the explanatory variables were resampled at 0.25-degree resolution for global analysis. Relations between this variable and explanatory factors, including human and climate drivers, were estimated using Random Forest (RF) and generalized additive models (GAM). BA_CV was negatively related to BA_Mean, implying that areas with higher average BA have lower variability as well. Interannual BA variability decreased when maximum temperature (TMAX) and actual and potential evapotranspiration (AET, PET) increased, cropland and livestock density increased and the human development index (HDI) values decreased. GAM models indicated interesting links with AET, PET and precipitation, with negative relation with BA_CV for the lower ranges and positive for the higher ones, the former indicating fuel limitations of fire activity, and the latter climate constrains. For the global RF model, TMAX, AET and HDI were the main drivers of interannual variability. As originally hypothesised, BA_CV was more dependent on human factors (HDI) in those areas with medium to large BA occurrence, particularly in tropical Africa and Central Asia, while climatic factors were more important in boreal regions, but also in the tropical regions of Australia and South America.

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RESUMEN El cambio en el uso del suelo y el fuego como mecanismo utilizado para el mismo han creado perturbaciones ecológicas a grandes escalas, como lo son la fragmentación y aislamiento de ecosistemas importantes en paisajes tropicales. En el presente estudio, analizamos los cambios de uso del suelo entre los años 2012-2016 y los eventos de fuego entre los años 2016-2018, para identificar la dinámica de cambio espaciotemporal en la Serranía de la Lindosa, Guaviare, a partir de información oficial y sensores remotos. Para 2016 la cobertura boscosa se redujo en un 17 % correspondiendo con el aumento de vegetación secundaria y pastizales en el área. Los focos de fuego detectados estuvieron concentrados en el noroeste y sureste de la serranía, puntos coincidentes en zonas de bosque primario y zonas de pastizal consolidadas. Estos resultados indican que existe un proceso activo de deforestación en la serranía, que fragmenta la matriz boscosa dejando parches de bosque aislados, lo cual tendría repercusiones sobre la biodiversidad allí presente. Asimismo, la sinergia entre dicho proceso y el uso de fuego se muestra como amenaza constante, a diferentes escalas, sobre los diferentes ecosistemas. Esta información se presenta como herramienta para elaborar estrategias puntuales para evitar mayores repercusiones negativas sobre la serranía, que actualmente se encuentra en estado vulnerable.

ABSTRACT The change in land use and fire as a mechanism used for this change, have created ecological disturbances at large scales, such as the fragmentation and isolation of essential ecosystems within tropical landscapes. In the present study, we analyze the land-use changes along 2012-2016 and fire events between 2016-2018, to identify the dynamics of spatial-temporal change in the Serranía La Lindosa, Guaviare using official information and remote sensors. Forest cover was reduced by 17 %, during 2012-2016, corresponding to an increase in secondary vegetation and pastures in the area. The fire-hotspots detected were concentrated on the northwest and southeast of the mountain range, coinciding with areas of primary forest and consolidated pasture areas. These results show that there is an active process of deforestation in La Lindosa, leaving a fragmented matrix and isolated forest patches, which would have repercussions on the local biodiversity. Besides, the synergy between this process and the use of fire, represent a constant threat, at different scales, on the different ecosystems. This information is presented as a resource to elaborate punctual strategies in order to avoid greater negative repercussions on the mountain range area, which is currently in a vulnerable state.

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Humans can alter fire dynamics in grassland systems by changing fire frequency, fire seasonality and fuel conditions. These changes have effects on vegetation structure and recovery, species composition, and ecosystem function. Understanding how human management can affect fire regimes is vital to detect potential changes in the resilience of plant communities, and to predict vegetation responses to human interventions. We evaluated the fire regimes of two recently protected areas in Madagascar (Ibity and Itremo NPA) and one in Brazil (Serra do Cipó NP) before and after livestock exclusion and fire suppression policies. We compare the pre- and post-management fire history in these areas and analyze differences in terms of total annual burned area, density of ignitions, burn scar size distribution, fire return period and seasonal fire distribution. More than 90% of total park areas were burned at least once during the studied period, for all parks. We observed a significant reduction in the number of ignitions for Ibity NPA and Serra do Cipó NP after livestock exclusion and active fire suppression, but no significant change in total burned area for each protected area. We also observed a seasonal shift in burning, with fires happening later in the fire season (October-November) after management intervention. However, the protected areas in Madagascar had shorter fire return intervals (3.23 and 1.82 years) than those in Brazil (7.91 years). Our results demonstrate that fire exclusion is unattainable, and probably unwarranted in tropical grassland conservation areas, but show how human intervention in fire and vegetation patterns can alter various aspects of the fire regimes. This information can help with formulating realistic and effective fire management policies in these valuable conservation areas.

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ABSTRACT An automated procedure is here presented that allows identifying and dating burned areas in Portugal using values of daily reflectance from near-infrared and middle-infrared bands, as obtained from the MODIS instrument. The algorithm detects persistent changes in monthly composites of the so-called (V,W) Burn-Sensitive Index and the day of maximum change in daily time series of W is in turn identified as the day of the burning event. The procedure is tested for 2005, the second worst fire season ever recorded in Portugal. Comparison between the obtained burned area map and the reference derived from Landsat imagery resulted in a Proportion Correct of 95.6%. Despite being applied only to the months of August and September, the algorithm is able to identify almost two-thirds of all scars that have occurred during the entire year of 2005. An assessment of the temporal accuracy of the dating procedure was also conducted, showing that 75% of estimated dates presented deviations between -5 and 5 days from dates of hotspots derived from the MODIS instrument. Information about location and date of burning events as provided by the proposed procedure may be viewed as complementary to the currently available official maps based on end-of-season Landsat imagery.