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Fire is a frequent disturbance in most grasslands around the world, being key for the structure and dynamics of the biodiversity in such ecosystems. While grassland species may be resilient, little is known on how plant-pollinator networks reassemble after fire. Here, we investigate the structure and dynamics of plant-pollinator networks and the variation in species roles over a 2-year post-fire chronosequence on grassland communities in Southern Brazil. We found that both network specialization and modularity were similar over the chronosequence of time-since-fire, but in freshly burnt areas, there were more species acting as network hubs. Species roles exhibited high variation, with plant and pollinator species shifting roles along the post-disturbance chronosequence. Interaction dissimilarity was remarkably high in networks irrespective of times-since-fire. Interaction dissimilarity was associated more with rewiring than with species turnover, indicating that grassland plant and pollinator species are highly capable of switching partners. Time-since-fire had little influence on network structure but influenced the identity and diversity of pollinators playing key roles in the networks. These findings suggest that pollination networks in naturally fire-prone ecosystems are highly dynamic and resilient to fire with both plants and pollinators being highly capable of adjusting their interactions and network structure after disturbance.

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Cement and water within the concrete mass create a hydrated phase which acts as the glue for holding the sand and coarse aggregates in place to develop a strong construction material. The most important phase within the cement matrix is that of calcium silicate hydrate (CSH), which is largely responsible for the concrete strength. Decomposition of the CSH phase due to high temperatures will affect compressive strength of the concrete. Raman bands at 1083, 709 and 276 cm-1, which are representative of the CaCO3 and CSH presence in the concrete matrix phases can be used to assess changes in compressive strength as a result of thermal decomposition. The ratio between 1083/709 cm-1 bands was calculated and correlated to the compression strength of the concrete. The results show there is a rapid decline in strength around a critical peak ratio of 8.78 and a residual compressive strength of 0.62, closely following a polynomial curve. The tool developed here allows an indirect evaluation of the temperature the concrete has been exposed to by studying the band. A case study from a fire scene taken from a warehouse in Kingston (Jamaica) is also presented with the conclusion and results compared. The study showed that Raman spectroscopy has the potential to provide in-situ non-destructive testing of fire damaged concrete rapidly and accurately.

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PREMISE: Although fire cues (high temperatures and smoke) influence seed germination in numerous species from fire-prone environments, their effects on seed germination of species from neotropical savannas are poorly understood. METHODS: We exposed seeds of eight grass species from the Cerrado, the Brazilian savanna to heat-shock (80°C or 110°C for 5 min) and/or smoke water, and then set them to germinate in light or dark, at either summer (28°C/18°C) or winter (27°C/14°C) temperature regimes in an incubator. In addition, we evaluated the effects of smoke water on seedling root and shoot growth for four of the species. RESULTS: Smoke interacted with the dark treatment to increase germination from 28% to 93% in Aristida recurvata and 77% to 95% in Aristida riparia. Smoke had no effect on germination of either of these species in the light. Heat-shock alone also promoted seed germination in A. recurvata. For Digitaria lehmanniana, smoke interacted with heat-shock to improve germination from 5% to 16%. In contrast, the fire treatments did not have any effect on the seed germination of the remaining five species. Smoke water stimulated root growth for A. riparia, A. recurvata, and Ctenium cirrosum but had no effect on their shoot growth. CONCLUSIONS: The strong promotive effect of smoke on Aristida germination suggests that these species are fire-adapted. Aristida species have an active awn system, which facilitates seed burial, and the smoke and dark interaction would ensure buried seeds germinated post-fire. The species that showed no response to fire cues may either have adapted via alternative strategies or require different concentrations of smoke or levels of heat. This study is one of very few examples showing a positive germination and seedling growth response to smoke for species from neotropical savannas.

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Drought-induced wildfires have increased in frequency and extent over the tropics. Yet, the long-term (greater than 10 years) responses of Amazonian lowland forests to fire disturbance are poorly known. To understand post-fire forest biomass dynamics, and to assess the time required for fire-affected forests to recover to pre-disturbance levels, we combined 16 single with 182 multiple forest census into a unique large-scale and long-term dataset across the Brazilian Amazonia. We quantified biomass, mortality and wood productivity of burned plots along a chronosequence of up to 31 years post-fire and compared to surrounding unburned plots measured simultaneously. Stem mortality and growth were assessed among functional groups. At the plot level, we found that fire-affected forests have biomass levels 24.8 ± 6.9% below the biomass value of unburned control plots after 31 years. This lower biomass state results from the elevated levels of biomass loss through mortality, which is not sufficiently compensated for by wood productivity (incremental growth + recruitment). At the stem level, we found major changes in mortality and growth rates up to 11 years post-fire. The post-fire stem mortality rates exceeded unburned control plots by 680% (i.e. greater than 40 cm diameter at breast height (DBH); 5-8 years since last fire) and 315% (i.e. greater than 0.7 g cm-3 wood density; 0.75-4 years since last fire). Our findings indicate that wildfires in humid tropical forests can significantly reduce forest biomass for decades by enhancing mortality rates of all trees, including large and high wood density trees, which store the largest amount of biomass in old-growth forests. This assessment of stem dynamics, therefore, demonstrates that wildfires slow down or stall the post-fire recovery of Amazonian forests.This article is part of a discussion meeting issue 'The impact of the 2015/2016 El Niño on the terrestrial tropical carbon cycle: patterns, mechanisms and implications'.

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ABSTRACT Seasonally dry tropical forest is one of the highly threatened biome. However, studies on the effect of fire on these tree communities are still scarce. In this context, a floristic and structural survey in three forest areas in the southeast of Brazil that were affected by fire between 14 and 25 years ago was performed with the objective of evaluating post-fire regeneration. In each site, five systematically placed plots (25 m x 25 m each) were established. The more recently burnt site had significantly lower values of richness and diversity than the other two sites. However, the sites did not differ in density and basal area. Annona dolabripetala, Astronium concinnum, Joannesia princeps and Polyandrococos caudescens were within the 10 most important species for the three sites. Comparing these data with adjacent mature forests, the results indicated differences both in structural and floristic aspects, suggesting that the time after fire was not sufficient for recuperation of these areas. The recovery process indicate at least 190 years for areas return to basal area values close to those observed in mature forests nearby.

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Fire represents a frequent disturbance in many ecosystems, which can affect plant-pollinator assemblages and hence the services they provide. Furthermore, fire events could affect the architecture of plant-pollinator interaction networks, modifying the structure and function of communities. Some pollinators, such as wood-nesting bees, may be particularly affected by fire events due to damage to the nesting material and its long regeneration time. However, it remains unclear whether fire influences the structure of bee-plant interactions. Here, we used quantitative plant-wood-nesting bee interaction networks sampled across four different post-fire age categories (from freshly-burnt to unburnt sites) in an arid ecosystem to test whether the abundance of wood-nesting bees, the breadth of resource use and the plant-bee community structure change along a post-fire age gradient. We demonstrate that freshly-burnt sites present higher abundances of generalist than specialist wood-nesting bees and that this translates into lower network modularity than that of sites with greater post-fire ages. Bees do not seem to change their feeding behaviour across the post-fire age gradient despite changes in floral resource availability. Despite the effects of fire on plant-bee interaction network structure, these mutualistic networks seem to be able to recover a few years after the fire event. This result suggests that these interactions might be highly resilient to this type of disturbance.

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Cordilleran cypress (Austrocedrus chilensis [D.Don] Pic. Serm. et Bizarri) forests occupy 140,000 ha along a sharp environmental gradient of central Andean-Patagonia in Argentina. Every summer, about 3200 ha of these forests are affected by wildfires, taking thereafter long time to recover. To accelerate forest recovery, we determined in xeric and mesic cypress stands burned 5 and 2 year before whether survival and growth of two planted cypress seedling stocktypes are affected by plant cover and contrasting precipitation conditions. Two experiments were conducted on each site, involving 100 replicates of two seedling stocktypes, having each significantly different morphological attributes. The experiments comprised a dry and humid growing season on each site. Both stocktypes performed similarly within stands, but differently between stands. In the xeric stand, plant cover had neutral effects on seedling survival, favored seedling height growth in the dry season, and was negative on collar diameter and stem growth. In the mesic site, high plant cover favored survival and height growth, but was inconsequential for collar diameter and stem growth. In this short-term post-fire period, and independent of precipitation received during both seasons (dry or humid), plant cover appears as playing a facilitative role, having neutral or even positive effects on survival and growth of planted seedlings. During the early post-fire successional stages, and besides seedling stocktype, there was a synergistic balance between light and soil moisture that seems to benefit planted seedling performance in burned cypress forests, and especially in mesic sites.

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AbstractFire occurrences are a common perturbation in Cerrado ecosystems, and may differently impact the local biodiversity. Arthropods are one of the taxa affected by fires, and among them, ants are known as good bioindicators. We aimed to evaluate the effect of anthropic fires on epigaeic and hypogaeic ant communities (species richness and composition) in Cerrado areas with different post-fire event recovery periods. We conducted the study in four Cerrado areas during two weeks of 2012 dry season: one unburned and three at different post-fire times (one month, one and two years). We sampled ants with pitfall traps in epigaeic and hypogaeic microhabitats. We collected 71 ant morpho-species from 25 genera. In the epigaeic microhabitat we sampled 56 morpho-species and 42 in the hypogaeic microhabitat. The area with the shortest recovery time presented lower epigaeic ant species richness (4.3 ± 2.00) in comparison to the other areas (8.1 ± 2.68 species on one year area; 10.3 ± 2.66 species on two years area; 10.4 ± 2.31 species on control area), but recovery time did not affect hypogaeic ant species richness. Regarding ant species composition, fire did not directly affect hypogaeic ant species, which remained the same even one month after fire event. However, two years were not enough to reestablish ant species composition in both microhabitats in relation to our control group samples. Our study is the first to assess anthropic fire effects upon epigaeic and hypogaeic ants communities; highlighting the importance of evaluating different microhabitats, to more accurately detect the effects of anthropic disturbances in biological communities. We concluded that ant communities are just partially affected by fire occurrences, and epigaeic assemblages are the most affected ones in comparison to hypogaeic ants. Furthermore the study provides knowledge to aid in the creation of vegetation management programs that allow Cerrado conservation.Rev. Biol. Trop. 64 (1): 95-104. Epub 2016 March 01.

ResumenLos incendios son una alteración común en los ecosistemas del Cerrado brasileño y pueden causar diferentes efectos sobre la biodiversidad. Los artrópodos son uno de los taxones comúnmente afectados por el fuego, y entre ellos, se conoce que las hormigas son buenos bioindicadores. El objetivo de este trabajo fue evaluar el efecto de los incendios antrópicos sobre las comunidades de hormigas epígeas e hipógeas (riqueza de especies y composición) en áreas del Cerrado en diferentes tiempos de recuperación. Para ello, el estudio se realizó en cuatro áreas del Cerrado durante la temporada seca del 2012: una área no quemada y otras tres áreas en diferentes momentos post-incendio (un mes, uno y dos años). Las hormigas fueron muestreadas utilizando trampas de caída en los microhábitats epígeo e hipógeo. Fueron recolectadas 71 morfo-especies de hormigas pertenecientes a 25 géneros. En el microhábitat epígeo recolectamos 56 morfo-especies y en el microhábitat hipógeo 42. El área con el menor tiempo de recuperación presentó una menor riqueza de especies de hormigas epígeas (4.3 ± 2.00) en comparación con las otras áreas (8.1 ± 2.68 especies en el área de un año; 10.3 ± 2.66 especies en el área de dos años; 10.4 ± 2.31 especies en el área de control), pero el tiempo de recuperación no afectó riqueza de especies de hormigas hipógeas. En cuanto a la composición de especies, el fuego no afectó directamente a las especies de hormigas hipógeas, la cual se mantuvo igual, incluso un mes después del incendio. Sin embargo, dos años no fueron suficientes para restablecer la composición de especies de hormigas en ambos microhábitats en relación con las muestras del área control. Nuestro estudio es el primero en evaluar los efectos del fuego antrópico sobre las comunidades de hormigas epígeas y hipógeas; se destaca la importancia de la evaluación de diferentes microhábitats para detectar con mayor precisión los efectos de las alteraciones antrópicas en las comunidades biológicas. Las comunidades de hormigas son solo parcialmente afectadas por incendios y las epígeas son las más perjudicadas. Además, este estudio proporciona conocimientos que pueden ayudar a la creación de programas de manejo de la vegetación del Cerrado, lo que permite conservar este importante bioma brasileño.

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Secondary succession in degraded areas is little studied, especially where long-term observation of evolutionary processes is concerned. The aim of this work was to follow the qualitative and quantitative changes in vegetation throughout the regeneration process after fire in a cerrado with forest physionomy. The area under study is a reserve on CPPSE-EMBRAPA's farm, São Carlos region of São Paulo State, Brazil. In 1981, an especially destructive fire eliminated the aerial part of the vegetation and litter. From that time, the vegetation in three permanent quadrats of 2 x 20 m was recorded for twenty years. The results demonstrated the rapid growth of herbs, shrubs, climbers and trees successively, with a great species richness and, after a certain time, a decline in density at a rate similar to the initial recovery. Both the soil seed bank and sprouting subterranean organs played important parts in the recovery of the vegetation. Three phases were observed in the plant succession: plant growth, followed by intraspecific competition with a reduction in the number of individuals and finally interspecific competition with the disappearance of some species from the quadrats. The different populations behaved similarly and the rise and fall in density of each species over time reflected their ecological role.

A sucessão secundária em áreas degradadas é pouco estudada, principalmente em relação ao acompanhamento dos processos evolutivos por longo período. O objetivo deste trabalho foi de verificar as mudanças qualitativas e quantitativas da vegetação durante o processo de regeneração após fogo em um cerrado com fisionomia de cerradão. A área estudada pertence a uma reserva institucional da CPPSE EMBRAPA, São Carlos, SP, Brasil. No ano de 1981 ocorreu um incêndio de proporções elevadas eliminando todo o folhedo e o dossel. O acompanhamento foi realizado em três parcelas fixas de 2 x 20 m ao longo de vinte anos. Os resultados demonstraram um rápido estabelecimento de indivíduos sucessivamente com plantas herbáceas, arbustivas, lianas e arbóreas, uma grande riqueza em espécies e, depois de determinado tempo, uma regressão em densidade na mesma ordem de estabelecimento. O banco de sementes do solo e o rebrotamento subterrâneo tiveram papel importante na recuperação da vegetação. No processo sucessional ocorreram três fases sucessivas: estabelecimento de plantas; competição intra-específica devido ao reajuste no número de indivíduos por espécies e competição interespecífica com a eliminação de algumas espécies das parcelas. As populações analisadas apresentaram padrões semelhantes de comportamento e a maior ou menor densidade ao longo do tempo refletiu o comportamento ecológico das espécies.

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Secondary succession in degraded areas is little studied, especially where long-term observation of evolutionary processes is concerned. The aim of this work was to follow the qualitative and quantitative changes in vegetation throughout the regeneration process after fire in a cerrado with forest physionomy. The area under study is a reserve on CPPSE-EMBRAPA's farm, São Carlos region of São Paulo State, Brazil. In 1981, an especially destructive fire eliminated the aerial part of the vegetation and litter. From that time, the vegetation in three permanent quadrats of 2 x 20 m was recorded for twenty years. The results demonstrated the rapid growth of herbs, shrubs, climbers and trees successively, with a great species richness and, after a certain time, a decline in density at a rate similar to the initial recovery. Both the soil seed bank and sprouting subterranean organs played important parts in the recovery of the vegetation. Three phases were observed in the plant succession: plant growth, followed by intraspecific competition with a reduction in the number of individuals and finally interspecific competition with the disappearance of some species from the quadrats. The different populations behaved similarly and the rise and fall in density of each species over time reflected their ecological role.

A sucessão secundária em áreas degradadas é pouco estudada, principalmente em relação ao acompanhamento dos processos evolutivos por longo período. O objetivo deste trabalho foi de verificar as mudanças qualitativas e quantitativas da vegetação durante o processo de regeneração após fogo em um cerrado com fisionomia de cerradão. A área estudada pertence a uma reserva institucional da CPPSE EMBRAPA, São Carlos, SP, Brasil. No ano de 1981 ocorreu um incêndio de proporções elevadas eliminando todo o folhedo e o dossel. O acompanhamento foi realizado em três parcelas fixas de 2 x 20 m ao longo de vinte anos. Os resultados demonstraram um rápido estabelecimento de indivíduos sucessivamente com plantas herbáceas, arbustivas, lianas e arbóreas, uma grande riqueza em espécies e, depois de determinado tempo, uma regressão em densidade na mesma ordem de estabelecimento. O banco de sementes do solo e o rebrotamento subterrâneo tiveram papel importante na recuperação da vegetação. No processo sucessional ocorreram três fases sucessivas: estabelecimento de plantas; competição intra-específica devido ao reajuste no número de indivíduos por espécies e competição interespecífica com a eliminação de algumas espécies das parcelas. As populações analisadas apresentaram padrões semelhantes de comportamento e a maior ou menor densidade ao longo do tempo refletiu o comportamento ecológico das espécies.