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Abstract

Background: Fire has been reported to trigger the production of flowers and fruits in many fire-prone ecosystems around the world. However, for tropical savannas, little is known about the effects of fire on flower production at community and species scale, especially for the ground-layer. Aims: We assessed the role of fire as a trigger to short-term flowering in a preserved cerrado grassland, compared with unburnt vegetation. Methods: We recorded the presence of flowers or fruits in 2441 individuals from 47 plant species (grasses, forbs and subshrubs), during six months after fire, in burnt and unburnt areas of cerrado grasslands, in southeastern Brazil. Results: In the burnt areas, 63% of individuals sampled flowered, in contrast to 19% in unburnt areas, demonstrating a strong and positive effect of fire on plant communities of cerrado grasslands. Fire significantly induced flowering in 79% of the studied species, of which 20 species flowered only after fire (nine grasses, seven subshrubs and four forbs). Conclusions: These results highlight the role of fire triggering important ecological processes in the cerrado grasslands, potentially benefiting seed production and genetic diversity of many species. Fire is a crucial factor to be maintained for conservation of these ecosystems and their biodiversity.

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... There are, however, a few studies that analyzed the effects of fire on plant communities, mostly describing an increase in flowering for a short period after fire (e.g. Massi et al., 2017;Pilon et al., 2018;Zirondi et al., 2021). ...
... However, Zirondi et al. (2021) also found that some grasses are affected negatively by fire during the dry season, such as Mesosetum loliiforme, which only flowers in unburned sites, and other species flower independently of fire, such as Axonopus aureus (S1, Zirondi et al., 2021). Pilon et al. (2018) found all of the grass species at their study site to respond to fire with flowering and 81% of all individuals in burned sites flowered after fire, compared to 2% in unburned areas, showing the strong fire response of grasses in the Cerrado. Flowering responses to fire can be observed within the first two years after a fire (Lamont & Downes, 2011), or within the first few weeks or months (Zirondi et al. 2021). ...
... Trees were the growth-form most negatively affected by fire, with 50% of the species being fire-sensitive (S1). Grasses, however, had 25.5% of species classified as FD and 61.8% as FS, showing to be a growth-form with a strong positive response to fire, as already mentioned by Pilon et al. (2018) and Zirondi et al. (2021). Although shrubs have to resprout first, and may take longer to respond to fire, they also showed a strong response to fire, with ca. ...
Article
Post-fire flowering is a fire-adaptive trait that is underused in fire ecology literature to describe plant responses to fire. Most of the species described so far as having this strategy occur in mediterranean vegetation, while less is known about this event in tropical savannas. European naturalists described this fire-related response in the Cerrado when visiting Brazil and the first experiments to show the stimulation of flowering by fire were carried out by L. Coutinho, a pioneer in fire and savanna ecology in Brazil. The present study reviewed the literature on the Cerrado and compiled a database with 402 species that had any flowering response related to fire. As a result, we classified species based on flowering responses to fire (fire-dependent, fire-stimulated, fire-independent and fire-sensitive). About 85% of all the species included in the database are known to flower after fire, most of which are eudicots of the families the Asteraceae and Fabaceae, and ca. 45% are forbs. According to the classification, 267 of the species are fire-stimulated, 73 are fire-dependent, while only 11 of all the species are fire-sensitive. We encourage the use of post-fire flowering response in the future to analyze plant community responses to fire and help address knowledge gaps about how fire affects plant community assembly in tropical savannas.
... Species displaying either obligate or facultative PFF occur under a range of ecosystems with varying fire regimes (Lamont & Downes, 2011). Despite this, there are surprisingly few published studies how prevalent PFF is at the community level in savannas, or indeed little comparative analysis of PFF between different savanna types (Coutinho, 1976;Lamont & Downes, 2011;Massi et al., 2017;Pausas, 2017;Pilon et al., 2018;Fidelis and Zirondi, submitted). ...
... However, although some observations of this phenomenon were made, studies quantifying the PFF responses in the Cerrado are lacking. Mass PFF events have been documented (Coutinho, 1976;Massi et al. 2017;Pilon et al., 2018); however, in general, most studies have focused on the responses of single species rather than at the community level (e.g., Franceschinelli & Bawa, 2005;Conceição & Orr, 2012;Dodonov et al., 2018;Shearman et al., 2019;Sousa and Cunha, 2019). ...
... In the Cerrado, some studies have shown an increase in flowering (Neves & Damasceno-Junior, 2011;Massi et al.,2017;Pilon et al., 2018) in the first few post-fire months. One extraordinary case was reported for a Cerrado sedge species, Bulbostylis paradoxa, which is able to start flowering just 24 hr after fire . ...
Article
Questions In fire‐prone ecosystems, fire can enhance the flowering and fruiting of many species, a strategy assumed to be well represented in savanna. Despite this, there are surprisingly few studies assessing how prevalent fire‐stimulated flowering is. Thus, we asked: (a) are there differences in the reproductive phenology of Cerrado plants between recently burned and unburned areas; (b) how does fire affect the speed of flowering and how does this differ between growth forms; and (c) what are the post‐fire flowering (PFF) strategies of Cerrado species and is there evidence for high proportions of obligate PFF? Location Open savannas (campo sujo in the Cerrado) in Central Brazil (Reserva Natural Serra do Tombador — RNST, 13°35–13°38' S and 47°45'–47°51' W). Methods We established six plots, three recently and frequently burned (FB) and three excluded from fire for six years (E). In all treatments, the number of species flowering and fruiting was counted every 15 days for three months, and then at six, nine and 12 months after fire. We also counted the number of reproductive and vegetative shoots in 10 subplots (1 m × 1 m) per plot. Results Approximately 66% of species studied were fire‐stimulated, with half of these only flowering after fire (obligate PFF). Fire‐enhanced flowering was rapid, with the clearest differences between burned and unburned plots seen in the first 30 days, and up to three months after fire, where there were up to two times more species flowering in the FB than E areas. Conclusions The extremely high proportion of PFF species, at least five times that reported for heathlands and other shrub communities, highlights the role that short‐interval fire regimes have in savanna ecosystems, selecting for resprouting life forms and PFF dominance, particularly in herbaceous species. Rapid post‐fire reproduction may be a strategy to disperse large quantities of seed into an environment with a small recruitment window.
... This resprouting strategy is species-dependent and related to plant size (Massi and Franco, 2016). Fire exposure can also promote rapid and intense flowering in species from the herbaceous-subshrub layer and some species only bloom after fire events (Coutinho, 1976;Pilon et al., 2018). Fire events are known to stimulate the dehiscence of anemochore fruits, thus favoring seed dispersion in herbaceous species (Coutinho, 1977). ...
... From September 2013 (30 days after the fires) to August 2014 (360 days after the fires), we monitored all individuals within each plot monthly and counted the number of angiosperm species that were sprouting, flowering and fruiting (Table A.1 in the Supplementary Material). Although monthly observations are not ideal for collecting phenological data in burned areas, this frequency still allowed us to distinguish the effects of fire on the phenological responses of plants (see Pilon et al., 2018). We evaluated the presence and absence of vegetative and reproductive structures in all individuals. ...
... In burned areas, species of the herbaceous-subshrub layer anticipate the beginning of the flowering period and more species bloom throughout the year compared to unburned areas; these are considered fire responses (Coutinho, 1976;Lamont and Downes, 2011;Pilon et al., 2018). Fire promotes flowering by removing the foliage and stimulating the development of vegetative and reproductive buds (Coutinho, 1976;Lamont and Downes, 2011). ...
Article
In fire-prone ecosystems, such as savannas, fire has been a common event for thousands of years. In these biomes, phenology is a functional trait characterizing the responses of plant communities to fire. In this study, we aimed to evaluate the effects of fire on the period of occurrence, seasonality, and number of species expressing vegetative and reproductive phenophases (sprouting, flowering, and fruiting) in a South American savanna community. We burned experimental plots in 2013, and during the subsequent year, we performed monthly evaluations of the presence and absence of vegetative and reproductive structures in 44 species of angiosperms in the control and burned plots. We described plant phenology at two levels: (i) considering all sampled plant species together (community); and (ii) separately considering the species found in the herbaceous-subshrub and shrub-tree layers (vegetation strata). We analyzed the data using circular statistics and generalized linear mixed models. At the community level, fire did not alter the mean period of occurrence of vegetative and reproductive phenophases; however, we observed changes in fruiting seasonality, which were mainly caused by the changes occurring in the shrub-tree layer. Except for those found in the shrub-tree layer, more species expressed the analyzed phenophases after fire compared to the “control” treatment. This study provides information regarding the responses of plants to burning at the end of the dry season, when most anthropogenic fires occur. Additionally, according to climate change predictions, the Southern Hemisphere is expected to experience longer dry seasons, which may contribute to an increased frequency of anthropogenic fires. Therefore, this phenological information can motivate subsidies that are important for the conservation of this biome and management plans related to the prescription of fires.
... Accordingly, fire suppression may lead to the loss of the shade-intolerant herbaceous species due to canopy closure (Abreu et al. 2017). Notably, the herbaceous layer recovers its total biomass within 2 years after fire (Coutinho 1990;Neto et al. 1998), and is favoured by frequent fires (Abreu et al. 2017;Buisson et al. 2019), showing intense positive reproductive feedbacks (Sarmiento 1992;Munhoz and Felfili 2005;Massi et al. 2017;Pilon et al. 2018). Although vegetative reproduction is considered the prevalent reproductive strategy of the herbaceous layer (Coutinho 1990;Miranda and Klink 1996), reproduction via seeds is stimulated by fires, and herbaceous species show synchronous profuse flowering in post-fire communities (Munhoz and Felfili 2005;Massi et al. 2017;Pilon et al. 2018). ...
... Notably, the herbaceous layer recovers its total biomass within 2 years after fire (Coutinho 1990;Neto et al. 1998), and is favoured by frequent fires (Abreu et al. 2017;Buisson et al. 2019), showing intense positive reproductive feedbacks (Sarmiento 1992;Munhoz and Felfili 2005;Massi et al. 2017;Pilon et al. 2018). Although vegetative reproduction is considered the prevalent reproductive strategy of the herbaceous layer (Coutinho 1990;Miranda and Klink 1996), reproduction via seeds is stimulated by fires, and herbaceous species show synchronous profuse flowering in post-fire communities (Munhoz and Felfili 2005;Massi et al. 2017;Pilon et al. 2018). ...
... In the Brazilian cerrado, fire suppression is the prevailing fire policy (Abreu et al. 2017) even though fire may be a major factor for maintenance of the herbaceous layer (Veldman et al. 2015;Pilon et al. 2018;Buisson et al. 2019). For grasses, many species may rely on fire for seed production (Canales and Silva 1987;Sarmiento 1992;Le Stradic et al. 2015;Massi et al. 2017;Pilon et al. 2018), suggesting that fire is essential to the conservation of the cerrado biodiversity (Buisson et al. 2019). ...
Article
Full-text available
Fire is a key factor triggering ecological processes in old-growth grasslands and savannas and could have strong implications for reproduction via seeds for the herbaceous layer. In the Neotropical savannas, grasses show strong synchronous post-fire flowering, and their reproduction is often considered fire-dependent, with their massive post-fire seed production being suggested as a source of population maintenance. However, literature lacks studies to provide evidence of fire-dependent flowering and no study has assessed the quality of the post-fire seed production. Therefore, we aimed to describe a phenological pattern across early-flowering Neotropical savanna grasses in both recently burnt and unburnt cerrado communities addressing three questions: (1) Do the early-flowering species rely on fire for reproduction via seeds? (2) If no, what are the effects of fire on their reproductive phenology? (3) Does the massive seed production in post-fire cerrado communities lead to high-quality seeds? We recorded the reproductive phenology of nine early-flowering grasses for 17 weeks in unburnt and recently burnt cerrado communities. We collected the seeds, estimated the production of fertile seeds, and tested germination. No species showed a pattern of fire-dependent reproduction. Fire stimulated earlier flowering while reproduction in the unburnt community was related to continuous rainfall. Seed production following fire was of low quality, and no species produced > 7% fertile seeds. Seed germination remained below 50% for most species. Post-fire seed production of early-flowering species led to poor seed quality, suggesting a constraint to the recruitment of new individuals of early-flowering Neotropical savanna grasses in recently burnt cerrados.
... Evidence that competition drives local extinction in prairies where fire is suppressed comes from observational community-level studies (Bowles & Jones, 2013;. Other studies have recognized the importance of fire for stimulating flowering in many prairie species (Ehrenreich & Aikman, 1963;Pemble et al., 1981;Hartnett, 1990;Peter, 2002a,b) and in other fire-prone systems such as the cerrado (Pilon et al., 2018;Zirondi et al., 2021). Building on these observations, Wagenius et al. (2020) proposed a mechanism by which fire affects reproductive outcomes. ...
... Many perennials produce more flowers after a burn (i.e. fire increases reproductive allocation) (Ehrenreich & Aikman, 1963;Pemble et al., 1981;Hartnett, 1990;Peter, 2002a,b;Pilon et al., 2018;Zirondi et al., 2021), but reproductive outcomes such as seed production are usually unknown. Annual reproductive fitness depends on both allocation of resources to reproduction and on pollination. ...
... We suspect that fire affects S. speciosa differently than L. aspera in part because S. speciosa is more likely to flower each year and produces stems every year regardless of flowering status, whereas L. aspera flowers infrequently with drastic differences in aboveground structure and biomass between vegetative and flowering years. Fire appears to stimulate flowering in many plant species in fire-prone habitats (Ehrenreich & Aikman, 1963;Pemble et al., 1981;Hartnett, 1990;Peter, 2002a,b;Pilon et al., 2018;Zirondi et al., 2021), as we found in L. aspera (Table 1). Synchronized flowering, which we conceptualize as a continuous trait, at least in perennial prairie species, may be an adaptive trait, as posited for masting species (Janzen, 1971;Bogdziewicz et al., 2020Bogdziewicz et al., , 2021Kelly, 2021). ...
Article
A recent study posited that fire in grasslands promotes persistence of plant species by improving mating opportunities and reproductive outcomes. We devised an investigation to test these predicted mechanisms in two widespread, long-lived perennials. We expect fire to synchronize flowering, increase mating and boost seed set. We quantified individual flowering phenology and seed set of Liatris aspera and Solidago speciosa for 3 yr on a preserve in Minnesota, USA. The preserve comprises two management units burned on alternating years, allowing for comparisons between plants in burned and unburned areas within the same year, and plants in the same area across years with and without burns. Fire increased flowering synchrony and increased time between start date and peak flowering. Individuals of both species that initiated flowering later in the season had higher seed set. Fire was associated with substantially higher flowering rates and seed set in L. aspera but not S. speciosa. In L. aspera, greater synchrony was associated with increased mean seed set. Although fire affected flowering phenology in both species, reproductive success improved only in the species in which fire also synchronized among-year flowering. Our results support the hypothesis that reproduction in some grassland species benefits from fire.
... Fire maintains savanna herbaceous plant diversity by limiting tree and shrub densities (Bond & Keeley, 2005;Veldman et al., 2014) and influencing herbaceous community dynamics, including fire-stimulated reproduction and post-fire resprouting (Andrade & Miranda, 2014;Lamont & Downes, 2011;Moraes, Carvalho, Franco, Pollock, & Figueiredo-Ribeiro, 2016;Pilon, Hoffmann, Abreu, & Durigan, 2018). ...
... The soils at Assis State Forest are deep and welldrained oxisols, with low nutrient availability (Juhász, Cursi, Cooper, Oliveira, & Rodríguez-Echeverría, 2006 Both reference sites (Santa Bárbara and Assis) have a gradient of native vegetation from old-growth savanna to dense woodlands (i.e., encroached savanna) which has resulted from fire exclusion. These sites have served as reference communities for several savanna restoration studies in São Paulo (Abreu et al., 2017;Cava, Pilon, Ribeiro, & Durigan, 2018b;Dalle Laste et al., 2019;Pilon, Hoffmann, et al., 2018). Although the three sites are distant from one another ( Figure S1), all experience the same rainy season, receive similar mean annual precipitation and temperature, occur on deep, welldrained and low-fertility oxisols, and were all historically part of the same, and historically extensive, savanna ecosystem (cerrados of São Paulo). ...
... In Brazilian Cerrado, savannas have higher rates of flowering (Pilon, Hoffmann, et al., 2018) and increase in native herbaceous biomass after fire (Oliveras et al., 2013). Although the mechanisms by which fire directly stimulates resprouting, flowering, and seed germination are still not clear (Buisson et al., 2019;Fidelis, Rosalem, Zanzarini, & Camargos, 2019), fire does indirectly stimulate herbaceous plants by increasing light availability and soil nutrients (Araújo, Amaral, Bruna, & Vasconcelos, 2013) and increases native species richness by reducing exotic grass cover (Martins, Hay, Scaléa, & Malaquias, 2017). ...
Article
Afforestation and fire exclusion are pervasive threats to tropical savannas. In Brazil, laws limiting prescribed burning hinder the study of fire in the restoration of Cerrado plant communities. We took advantage of a 2017 wildfire to evaluate the potential for tree cutting and fire to promote the passive restoration of savanna herbaceous plant communities after destruction by exotic tree plantations. We sampled a burned pine plantation (Burned Plantation); a former plantation that was harvested and burned (Harvested & Burned); an unburned former plantation that was harvested, planted with native trees, and treated with herbicide to control invasive grasses (Native Tree Planting); and two old-growth savannas which served as reference communities. Our results confirm that herbaceous plant communities on post-afforestation sites are very different from old-growth savannas. Among post-afforestation sites, Harvested & Burned herbaceous communities were modestly more similar in composition to old-growth savannas, had slightly higher richness of savanna plants (3.8 species per 50-m²), and supported the greatest cover of native herbaceous plants (56%). These positive trends in herbaceous community recovery would be missed in assessments of tree cover: whereas canopy cover in the Harvested & Burned site was 6% (less than typical of savannas of the Cerrado), the Burned Plantation and Native Tree Planting supported 34% and 19% cover, respectively. By focusing on savanna herbaceous plants, these results highlight that tree cutting and fire, not simply tree planting and fire exclusion, should receive greater attention in efforts to restore savannas of the Cerrado.
... Most species produced flowers and fruits the year after the fire; however, there were reductions in the following years. Similar patterns of higher flowering peaks after fire and a reduction in subsequent years has been demonstrated in other studies from the Cerrado (Pilon, Hoffmann, Abreu, & Durigan, 2018), Australia (Burrows, Wardell-Johnson, & Ward, 2008;Lamont & Downes, 2011) and South Africa (Lamont & Downes, 2011). The flowering peaks observed by us after fire may be a result of the increased availability of light and nutrients, mainly nitrogen and cations (Kauffman, Sapsi, & Till, 1997). ...
... In other cases, the reduction of flowering may be explained by the higher energy input of plants to replace the vegetative part lost during burning (Fontenele, Cruz-Lima, Pacheco-Filho, & Miranda, 2020;Gawryszewski, Sato, & Miranda, 2020;Palermo & Miranda, 2012). However, the responses of woody species reproduction to fire events in fire-prone-ecosystems are still controversial, providing an open field for research (Pilon et al., 2018;Sato et al., 2010). ...
Article
Although fires have occurred in the Brazilian savannas (Cerrado) without human influence, current human activities are changing the fire regimes and negatively affects the vegetation resilience and recovery rates. Contrasting effects of fire on biodiversity and structure of vegetation in the Cerrado are dependent on fire frequency. Some anthropogenic fire regimes have increased fire frequency with shorter intervals between fires. However, the dynamics post-fire and the time needed for vegetation recovery are still poorly understood for the woody plants of Cerrado. We aimed to respond to two questions: Do the structure, floristic, and functional composition of woody species recover eight years post-fire? Do two consecutive fire events with seven years interval affect the floristic and structure of woody plants over time? We evaluated the woody dynamics in Cerrado savannas under three different fire regimes in central Brazil. We measured all trees and shrubs in 10 plots (totaling 1 ha) from 1997 to 2019 (22 years) and in 10 additional plots from 2008 to 2019 (11 years) in three areas: unburned area (fire exclusion for 30 years – fire regime 0), burned area 1 (one fire event in 2011 – fire regime 1), and burned area 2 (burned in 1998 and 2005 – fire regime 2). We analyzed the vegetation structure, floristic, and functional composition through multiple inventories to evaluate the vegetation recovery status. Density, basal area, and biomass increased similarly over time in the burned area 1 and the unburned area, showing that the woody vegetation parameters has recovered eight years after one fire event. Our results also showed that vegetation structure (i.e., density, basal area, and aboveground biomass) remained relatively constant between 2006 and 2013 (8 years after the occurrence of two fires). The data indicate growth only in the inventory after 14 years without fire.
... The lack of a consistent general response pattern in forbs could be explained by the high heterogeneity of functional groups included within this growth form (e.g., annual, perennial, climber, fern) that can have different responses to fire (Keeley et al. 1981;Bates et al. 2014;Heydari et al. 2016;Arcamone and Jaureguiberry 2018;Vidaller et al. 2019). In the case of grasses, the tendency of increasing reproductive fitness early post fire (Fig. 6C) could be related to the positive fire-colonization feedback generally described for this growth form (Bond et al. 2003;Bond and Keeley 2005;Pausas and Keeley 2009;Pilon et al. 2018). Previous studies had observed an increase in reproductive fitness of grasses after fire (Baruch and Bilbao 1999;Araújo et al. 2013;Pilon et al. 2018;Vidaller et al. 2019). ...
... In the case of grasses, the tendency of increasing reproductive fitness early post fire (Fig. 6C) could be related to the positive fire-colonization feedback generally described for this growth form (Bond et al. 2003;Bond and Keeley 2005;Pausas and Keeley 2009;Pilon et al. 2018). Previous studies had observed an increase in reproductive fitness of grasses after fire (Baruch and Bilbao 1999;Araújo et al. 2013;Pilon et al. 2018;Vidaller et al. 2019). On the contrary, vegetative fitness showed a negative impact early post fire. ...
Article
Full-text available
Background Fire is an important driver of ecosystem dynamics worldwide. However, knowledge on broad-scale patterns of ecosystem and organism responses to fires is still scarce. Through a systematic quantitative review of available studies across South America, we assessed fire effects on biodiversity and abundance of different organisms ( i.e., plants, fungi, invertebrates, and vertebrates), plant fitness, and soil properties under four climate types, and time since the last fire ( i.e., early and late post fire). We addressed: (1) What fire effects have been studied across South America? (2) What are the overall responses of biodiversity, abundance, fitness, and soil properties to fires? (3) How do climate and time since fire modulate those responses? Results We analyzed 160 articles reporting 1465 fire responses on paired burned and unburned conditions. We found no effect of fire on biodiversity or on invertebrate abundance, a negative effect on woody plant species and vertebrate abundance, and an increase in shrub fitness. Soil in burned areas had higher bulk density and pH, and lower organic matter and nitrogen. Fire effect was significantly more positive at early than at late post fire for plant fitness and for soil phosphorus and available nitrogen. Stronger negative effects in semiarid climate compared to humid warm climate suggest that higher temperatures and water availability allow a faster ecosystem recovery after fire. Conclusions Our review highlights the complexity of the climate–fire–vegetation feedback when assessing the response of soil properties and different organisms at various levels. The resilience observed in biodiversity may be expected considering the large number of fire-prone ecosystems in South America. The recovery of invertebrate abundance, the reduction of the vertebrate abundance, and the loss of nitrogen and organic matter coincide with the responses found in global reviews at early post-fire times. The strength of these responses was further influenced by climate type and post-fire time. Our synthesis provides the first broad-scale diagnosis of fire effects in South America, helping to visualize strengths, weaknesses, and gaps in fire research. It also brings much needed information for developing adequate land management in a continent where fire plays a prominent socio-ecological role.
... Using resources stored in extremely specialized underground organs, these species are able to resprout repeatedly under frequent burning (Klimešová et al., 2018;Ottaviani et al., 2017). Besides on-spot persistence, bloomers contrast with resprouters by displaying a massive bloom few months after fire (Coutinho, 1977;Fidelis, Rosalem, Zanzarini, Camargos & Martins, 2019;Pilon et al., 2018). These species use the narrow window of post-fire resources as an opportunity to produce flowers and fruits, ...
... This architecture ensures the protection of the meristems, allowing grasses to quickly resprout after fire and thus re-establishing their photosynthetic capacity (Ripley et al., 2015;Zimmermann et al., 2010). After fire, graminoids rapidly recolonize the burned landscape, most of them producing and dispersing seeds in the first 3 months after fire (Bond & van Wilgen, 1996;Fidelis et al., 2019;Pilon et al., 2018). ...
Article
1. Disentangling species strategies that confer resilience to natural disturbances is key to conserving and restoring savanna ecosystems. Fire is a recurrent disturbance in savannas, and savanna vegetation is highly adapted to and often dependent on fire. However, although the woody component of tropical savannas is well studied, we still do not understand how ground‐layer plant communities respond to fire, limiting conservation and management actions. 2. We investigated the effects of prescribed fire on community structure and composition, and evaluated which traits are involved in plant community regeneration after fire in the cerrado ground layer. We assessed traits related to species persistence and colonization capacity after fire, including resprouter type, underground structure, fire‐induced flowering, regeneration strategy and growth form. We searched for functional groups related to response to fire, to shed light on the main strategies of post‐fire recovery among species in the ground layer. 3. Fire changed ground‐layer community structure and composition in the short term, leading to greater plant species richness, population densities, and increasing bare soil, compared with unburned communities. Eight months after fire, species abundance did not differ from pre‐disturbance values for 86% of the species, demonstrating the resilience of this layer to fire. Only one ruderal species was disadvantaged by fire and 13% of the species benefited. Rapid recovery of soil cover by native vegetation in burned areas was driven by species with high capacity to resprout and spread vegetatively. Recovery of the savanna ground‐layer community, as a whole, resulted from a combination of different species traits. We summarized these traits into five large groups, encompassing key strategies involved in ground layer regeneration after fire. Synthesis: Fire dramatically changes the ground layer of savanna vegetation in the short term, but the system is highly resilient, quickly recovering the pre‐fire state. Recovery involves different strategies, which we categorized into five functional groups of plant species: grasses, seeders, bloomers, undergrounders, and resprouters. Knowledge of these diverse strategies should be used as a tool to assess conservation and restoration status of fire‐resilient ecosystems in the cerrado.
... Fire in the Australian savanna increases ant seed removal and removal distances, probably because microhabitat simplification increases ant foraging activity (Parr et al., 2007). Fire can also affect the populations of animals that interact with seeds (van Eeden et al., 2020;Pausas & Parr, 2018;Vasconcelos et al., 2016;Vieira & Briani, 2013) and resource availability (Pilon et al., 2018). As a consequence, seed removal can sometimes decrease in burned sites, and gradually increase with recovery of rodent populations and resources to them (Puig-Gironès et al., 2018). ...
... We are aware of no study combining all these factors, but fire probably has contrasting effects on demography according to plant traits. Since fire triggers plant sexual reproduction in Cerrado (Coutinho, 1976;Pilon et al., 2018) and enhance seeds production (Fidelis et al., 2019), animals (specially ants) may benefit from the F I G U R E 3 Mean number of sunflower and M. rubiginosa seeds removed from fire and control treatments in Cerrado. (I) Seed removal from treatments C1 (one month after fire control; n = 80), F1 (one month after fire; n = 80), C2 (one year after fire control; n = 128) and F2 (one year after fire; n = 128); (II) Seed removal from treatments of exclusion (accessible only to ants) and control (accessible to all animals) in unburned (n = 208) and burned (n = 208) treatments; (III) Seed removal from each seed species discriminated by fire and exclusion treatment. ...
Article
Seed dispersal and predation by animals often drive plant regeneration. In tropical savannas, such as the Cerrado of Brazil, fire is also a key process in ecosystem dynamics, consuming the lower vegetation strata and killing wildlife, but how fire affects seed-animal interactions is virtually unknown. We investigated the effects of prescribed fires on the removal of diaspores from Miconia rubiginosa and sunflower Helianthus annuus in Cerrado from southeast Brazil. Using plots burned one month or one year before sampling and unburned controls, we assessed the effect of prescribed fire on microhabitat structure and diaspore removal by vertebrates and ants. Covered microhabitats experienced higher seed removal by vertebrates than open microhabitats, but microhabitat features did not influence seed removal by ants. Prescribed fire did not change the total amount of seed removal, and ants were responsible for most removals in burned and control plots. However, fire increased the importance of ants as agents of removal compared to vertebrates. These changes were probably mediated by changes in microhabitat cover. It is likely that species, whose seeds are often preyed upon by vertebrates, benefit from fire to escape predation, while the opposite would be true for those removed by granivorous ants. By changing microhabitats composition and frequency of seed removal by different agents, fire may create pulses of opportunities for certain plant species to increase their populations and enlarge their spatial distribution, while constraining others. However, how different fire intensities and frequencies influence seed fate of different species is still to be investigated. Abstract in Portuguese is available with online material.
... 100% of all grass species flowered after fire in a savanna in Brazil, with more than 95% of the individuals having reproductive tillers (Pilon et al., 2018). Grasses also respond very fast to dry-season fires by resprouting and allocating reserves to flowering, with their flowering peak being just 30 days post fire, with ca. ...
... Therefore, changes in fire season may affect grass flowering responses differently: if fire occurs during their flowering period (wet season), it may have negative consequences, while if it occurs during the dry season, it may stimulate flowering outside of their flowering period. The most outstanding post-fire response in the Cerrado, even during the dry season, is the rapid resprouting and immediate flowering of most forbs and grasses (Pilon et al., 2018;, which can be considered a unique event among the other tropical savannas in the world. ...
Article
Post‐fire flowering is an underestimated plant trait of many fire‐prone ecosystems and is rarely considered for tropical savannas. Therefore, we analyzed the effects of fire season and history on post‐fire flowering of grass species in a tropical savanna (Cerrado), by evaluating the number of species, frequency of individuals and number of reproductive tillers after wet‐ and dry‐season fires, and under different fire histories. Open savannas (campo sujo) of the Cerrado in central Brazil (Reserva Natural Serra do Tombador – RNST, 13º35‐13º38’S, 47º45’‐47º51’W). We sampled flowering individuals in 10 Poaceae species and counted flowering/vegetative tillers of grass species in 1 x 1‐m plots after wet‐ and dry‐season fires and under different fire histories (three, 18 and 72 months post‐fire). Some of the studied species responded differently to fire according to season but most flowered after fire events. Moreover, the exclusion of fire led to a decrease in the number of flowering individuals and reproductive tillers of grass species. We describe a unique event for tropical savannas: besides rapid resprout after fire events, grasses can allocate resources for both vegetative and reproductive tiller production, even during the dry season. If fire is excluded from the system, fewer grass species and individuals will flower and there will be a lower percentage of reproductive tillers, showing the importance of fire for grass flowering in these tropical savannas, independently of fire season.
... Natural selection resulted in plant adaptations related to fire (Coutinho, 1976(Coutinho, , 1977Keeley et al., 2011;Simon and Pennington, 2012) as well as in animal strategies to escape or to survive fire (Pausas and Parr, 2018). Among plant adaptations are, for instance, C4-grasses (Keeley and Rundel, 2005), trees with corky and insulating bark (Fig. 2a) (Simon and Pennington, 2012;Lawes et al., 2011), small plants with robust root systems and a superb ability to re-sprout many times after fire (Coutinho, 1982;Pausas and Keeley, 2009), sexual reproduction vigorously stimulated by fire ( Fig. 2b) (Coutinho, 1977;Pilon et al., 2018b;Fidelis et al., 2019), and serotiny (Schwilk and Ackerly, 2001). Since many from these plant adaptations are also advantageous to survive drought, frost or herbivory, ecological studies are still needed to disentangle the relative influence of these different factors. ...
Article
Fire has been a natural force modulating the vegetation of the Brazilian Cerrado since long before the first humans arrived in this region about 12 thousand years BP. Cerrado plants are, therefore, adapted to fire and some of them depend on fire to maintain their reproduction and survival. However, after the use of fire as a tool to destroy vast extents of forests in the last centuries, Brazilians in general formed a very negative opinion about the use of fire and burning native vegetation was prohibited in the country. Although this decision was effective in protecting tropical forests, the zero-fire policy has been quite negative in the Cerrado. Fire suppression in Cerrado reserves has caused a dramatic loss of biodiversity at landscape level (homogenizing the vegetation structure), at species level (leading non-tree species to local extinction) and likely at population level (sexual reproduction impaired). Furthermore, fuel accumulation over several years without fire increases the risks of catastrophic firestorms that will inevitably occur. Such negative consequences of fire suppression in the Cerrado have not been noticed even among ecologists, including myself in early career and until recently. The biased tree-and-carbon perspective of environmental campaigns and ecological studies have reinforced the misunderstanding of fire effects in Cerrado vegetation. Both neglect that the absolute majority of Cerrado plant species, as well as associated fauna and ecosystem services, depend upon open vegetation-structures which are mostly maintained by fire.
... Flowering post-fire is a well-known adaptation of Cerrado plants, including species of Lantana and Lippia (Coutinho 1976(Coutinho , 1977. Fire acts as a trigger to flowering and ensures a successful reproduction in communities (Coutinho 1977, Keeley et al. 2011, Pilon et al. 2018. Besides this adaptation, we verified for the first time in Verbenaceae that L. horridula presents a pronounced heterophylly linked with the fire regime of the Cerrado. ...
Article
Lippia horridula is an endemic species from the Brazilian Cerrado with exclusively post-fire flowering records. It is often confused in herbaria collections with Lantana glaziovii and Lippia grandiflora, due to the subshrubby habit, the flowering branches raising from a well-developed xylopodium, and the pink colored corollas. Lippia horridula presents different morphotypes during its vegetative and flowering stages related to the fire regime in the Cerrado. The absence of observation and description of such variations has led to taxonomical confusion regarding its identity. Thus, in order to clarify this, we here present the morphological variation of this species during the vegetative and flowering stages, including modifications in the habit and remarkable heterophylly related to fire regime. An epitype is here designated to aid in the proper delimitation of this species. Moreover, a new record in the state of Maranhão (the northernmost known record for this species) is here presented, plus information about its conservation status, a geographical distribution map, in addition to a comparison with morphologically most similar species.
... However, Silvério et al. [199] reported that the negative effects of fire on the vegetative phenophases were normally followed by an increase in sprouting and the production of leaves, revealing an epigeous recovery mechanism from fire damage. In a reproductive approach, Pilon et al. [200] reported a similar pattern, with fire triggering the production of flowers and fruits in 79% of 47 plant species such as grasses, forbs, and subshrubs. Moreover, several studies have reported flowering in several plant species after the passage of fire [201,202] and, more recently, Fidelis et al. [203] reported massive flowering in Bulbostylis paradoxa (Cyperaceae) within just 24 h after the fire. ...
Chapter
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Plants under field conditions are subject to different types of abiotic stresses such as drought, salinity, and light excess that adversely affect their growth and survival. In addition, several studies have pointed out the effect of climate change such as an increase in the concentration of atmospheric CO2 , as well as an increase in global temperature on the distribution and wealth of plants. Adaptation to abiotic stress and survival occurs on different scales, at the cellular level for each individual , and requires a range of strategies, whether morphological, physiological, molecular or structural. Such strategies may be determinant in the distribution of plant species in natural habitats, depending on ecological adaptations shaped by the evolutionary history of species. In this chapter, we discuss recent information about mechanisms of plant adaptation to abiotic stress in the Neotropical savannah based on the cell and individual scales.
... We sought to focus on species able to maintain viable individuals under the study conditions, so we considered only flowering individuals native herbs. Since many herbaceous species in the Cerrado exhibit firestimulated flowering Massi et al., 2017;Pilon et al., 2018,) and fire is a common and inevitable disturbance in these ecosystems, we performed our surveys-over a 1-yr period after a wildfire. ...
Article
Exotic grasses and high-nutrient availability are common factors that may limit recovery of herbaceous diversity in derived savannas, while tree encroachment is a threat to diversity in old-growth savannas. To understand the impacts of these factors on herbaceous communities, we studied the effect of nutrient addition, and the resulting increase in the exotic grass, Melinis minutiflora, at a savanna-forest boundary in the Brazilian Cerrado. We inventoried richness of reproductive herbs, tree basal area and cover of the exotic grass, Melinis minutiflora, in each plot. Nutrient addition caused a large increase in Melinis and a large decrease in richness of flowering plants. Unexpectedly, structural equation model analysis suggests that the decline in herbaceous richness was a direct result of nutrient addition, rather than an indirect effect caused by the increase in Melinis. Tree density had a strong negative effect on both Melinis cover and herbaceous richness. Our results reveal that high-nutrient availability imposes a barrier to the restoration of a diverse, native herbaceous layer in anthropogenic savannas, while tree encroachment is a threat to diversity in old-growth savannas. Abstract in Portuguese is available with online material.
... We found change in species richness, but only for graminoids in grassland areas, with colonization by new species triggered by fire. The arrival of 10 new species of grasses was likely favored by two fire effects: (i) intensifying sexual reproduction (Eiten, 1972;Coutinho, 1977Coutinho, , 1990Le Stradic et al., 2015;Pilon et al., 2018) and (ii) clearing the ground and thus favoring seed dispersal and germination (Coutinho, 1990;Fidelis et al., 2012), since both processes are constrained by the vast amount of biomass accumulated after a long period without fire. Studies on grasses and forbs of tropical savannas have shown that the effect of fire reducing woody biomass and cover is remarkably beneficial for the ground layer plant communities (Sheuyange et al., 2005;Zimmermann et al., 2010). ...
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Although savannas are fire-adapted ecosystems, prescribing fire for biodiversity conservation remains controversial at least in some regions where savannas occur. Faced with uncertainty, many decision makers and even scientists are still reluctant to prescribe fire for conservation purposes in fire-prone ecosystems, invoking the precautionary principle. Knowledge gaps on the ideal fire regime, such as how and when to burn, and especially the fear of biodiversity losses, are among the main arguments against fire management applied to remnants of native savanna vegetation. To inform this debate, we assessed the impact of prescribed fires on diversity of plants (different growth forms), ants, frogs, lizards, birds, and small mammals, in savannas and grasslands of the Brazilian Cerrado. We assessed the existing species richness, composition, and abundance in areas subjected to long periods of fire suppression and compared to that observed over a short period after prescribed dry-season fires, within each group of plants and animals. Whenever possible, we carried out separate analyses for grassland and savanna. Burning did not significantly reduce species richness of any of the groups analyzed, but had a positive effect on richness of graminoids in grassland. When analyzed at the species level, abundance of most animal groups did not show consistent responses to fire, except for a decrease in some frog populations in grasslands. Forbs, graminoids, and subshrubs increased in abundance after fire in grassland areas, though in savanna areas, abundance of forbs, and subshrubs tended to decline after fire. Species composition changed little in response to fire as indicated by low levels of dissimilarity between burned and unburned areas. These results confirm the high resilience of Cerrado biota to fire, as expected for savanna ecosystems in general. Besides, we demonstrate here that the risk of biodiversity losses cannot justify the objections to the use of prescribed fire for conservation purposes in the Cerrado.
... Some research points to the ability of the Cerrado biome as a carbon sink (Morais et al., 2017;Pellegrini, Socolar, Elsen, & Giam, 2016). Interestingly, fires in the Cerrado biome may be beneficial to the biome, according to Pilon, Hoffmann, Abreu, and Durigan (2018) fire triggers important ecological processes in Cerrado grasslands, such as seed production and the genetic diversity of many species. However, it is noteworthy that this only applies to areas where the biome maintains its natural conditions, in degraded areas or where land use has changed in the Cerrado, the effect may be the opposite. ...
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The fires and biomass burning are responsible for affect ecosystem processes in a wide range of biomes at regional and global scales. In Brazil, the state of Mato Grosso is one of the most affected by the occurrence of forest fires. Thus, this study aims to quantify the long-term changes in the temporal and spatial patterns of fire occurrence and their effect on gross primary productivity (GPP) in the state of Mato Grosso, Brazil, considering the biomes that compose it. The images used in the study were acquired by satellite Terra and Aqua combined in the product MCD64A1.006, a monthly resolution of 500m by the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor, during the period from 01/10/2000 to 12/31/2018. The MOD17A2 product derived from the MODIS sensor provides the accumulated value of GPP. The points without the presence of burning presented higher values of GPP for all studied biomes. In some points with the presence of burning the GPP even decreased by 44.20%, 30.04% and 55.78% for Amazonia, Cerrado, and Pantanal, respectively. According to the results presented here, it is concluded that the burnings negatively impact gross primary production in the biomes of the state of Mato Grosso, Brazil and the dynamics of the burns do not keep up with the intensity of drought years. The use of cluster analysis techniques, such as principal component analysis (PCA), is an alternative to bigdata analysis when the objective is to evaluate the presence of forest burning in more than one biome. ARTICLE HISTORY
... On the one hand, many woody species have their sexual reproduction negatively affected by fire incidence (Miranda and Sato, 2005;Dodonov et al., 2017). On the other hand, many ground-layer species are generally associated with a massive bloom of reproduction three months after the fire passage, which stimulates seed production (Neves and Damasceno-Junior, 2011;Pilon et al., 2018). ...
Article
Changes in savanna's fire regimes, either through fire suppression or through an increase in fire frequency, can negatively affect their resilience. We evaluated the extent to which the aboveground biomass, diversity (taxonomic and functional) and resilience (functional redundancy and functional response indices) of savanna tree communities differ between burned and unburned plots. Burned plots experienced two fire events over the ten-years prior to sampling, while unburned plots experienced fire suppression over the same time period. We found that aboveground biomass was 40% smaller in burned plots, indicating that fire regimes must be included as a source of variation in models estimating the potential of savannas to store carbon. Burned plots had a higher functional diversity of vegetative traits but a smaller functional diversity of reproductive traits, indicating that generalizations about the effect of fire on tree functional diversity should be viewed with caution. Periodic fires can benefit savanna tree biodiversity by maintaining the balance between light-demanding and shade-tolerant species but can also increase the dominance of species with less specialized reproductive traits that do not rely on animal interactions. Burned plots had slightly lower functional redundancy but similar functional response diversity compared to unburned plots, suggesting that both communities harbor tree species that might respond positively or negatively to fire and, therefore, will be able to maintain the ecosystem functions considered under a future scenario of fire-suppression or increased fire frequency. Therefore, a longer-term fire suppression (>10 years) or a return fire interval of less than 4 years may be necessary to reduce the resilience of the savanna tree component, considering the ecosystem functions analyzed in this study.
... Fire is a natural source of disturbance in many ecosystems worldwide, including tropical savannas (Bowman et al. 2009). In such habitats, fire is an important evolutionary force for the biota (Beerling and Osborne 2006;Simon and Pennington 2012), resulting in numerous fire adaptations and dependence on fire in many cases (Pilon et al. 2018). Suppressing fires in fire-prone ecosystems can, therefore, cause the local loss of endemic species (Bond and Parr 2010), as was found to be the case in the Brazilian Cerrado, where long-term fire-suppression results in tree encroachment and the loss of plant and animal savanna-specialist species (Abreu et al. 2017). ...
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Fire-suppression is of concern in fire-prone ecosystems because it can result in the loss of endemic species. Suppressing fires also causes a build-up of flammable biomass, increasing the risk of severe fires. Using a Before-After, Control-Impacted design, we assessed the consequences of high-severity fires on Neotropical savanna arboreal ant communities. Over a 9-year period, we sampled the ant fauna of the same trees before and after two severe fires that hit a savanna reserve in Brazil and the trees from an unburned savanna site that served as a temporal control. The ant community associated with the unburned trees was relatively stable, with no significant temporal variation in species richness and only a few species changing in abundance over time. In contrast, we found a strong decline in species richness and marked changes in species composition in the burned trees, with some species becoming more prevalent and many becoming rare or locally extinct. The dissimilarity in species richness and composition was significantly smaller between the two pre-fire surveys than between the pre- and post-fire surveys. Fire-induced changes were much more marked among species with strictly arboreal nesting habits, and therefore more susceptible to the direct effects of fire. The decline of some of the ecologically dominant arboreal ant species may be particularly important, as it opens substantial ecological space for cascading community-wide changes. In particular, severe fires appear to disrupt the typical vertical stratification between the arboreal and ground-dwelling faunas, which might lead to homogenization of the overall ant community.
... Consequently, light incidence and thermal amplitude also increase in the soil surface (Coutinho 1990;Fidelis et al. 2012). In addition, while fire creates opportunities for seed dispersal, seed germination, blooming and seed production in open savannas and grasslands (Coutinho 1977(Coutinho , 1990Pilon et al. 2018;Zirondi et al. 2019), frost may hamper seed dispersal and germination, hindering the establishment of new individuals. Conversely, the accumulated litter can create safe sites for shade-tolerant and generalist woody species to germinate (Hoffmann 1996). ...
Article
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Frost effects on savanna plant communities have been considered as analogous to those from fire, both changing community structure and filtering species composition. However, while frost impacts have been well-studied for the woody component of savannas, it is still poorly explored for the ground-layer community. Here, we investigated effects of frost in the Cerrado along a gradient of tree cover, focusing on ground-layer plant species, near the southern limit of the Cerrado in Brazil. We aimed to elucidate if the pattern already described for the tree layer also extends to the ground layer in terms of mimicking the effects of fire on vegetation structure and composition. We assessed how damage severity differs across species and across the tree-cover gradient, and we examined the recovery process after frost in terms of richness and community structure along the canopy cover gradient. Frost caused immediate and widespread dieback of the perennial ground-layer, with greatest impact on community structure where tree cover was lowest. However, frost did not reduce the number of species, indicating community resilience to this natural disturbance. Although frost mimicked the effects of fire in some ways, in other ways it differed substantially from fire. Unlike fire, frost increases litter cover and decreases the proportion of bare soil, likely hindering crucial processes for recovery of plant populations, such as seed dispersal, seed germination and plant resprouting. This finding calls attention to the risk of misguided conclusions when the ground layer is neglected in ecological studies of tropical savannas and grasslands.
... Anthropogenic fires are less intense at the beginning of the dry season than wildfires at the end of the dry season (Sabiiti & Wein, 1987). Hence, considering plant phenology (Buisson, Alvarado, Le Stradic, & Morellato, 2017;Palermo & Miranda, 2012;Pilon, Hoffmann, Abreu, & Durigan, 2018;Schmidt, Sampaio & Borghetti, 2005), fire can be prescribed at the beginning of the dry season, when C. parviflora diaspores have already been dispersed, and to avoid more severe fires, which may achieve temperatures above 600 C in savanna areas of the Cerrado (Miranda et al., 1993). ...
Article
Optimal sexual reproduction in relation to fire effects varies in Fabaceae species. Calliandra species have a large investment in reproduction. We investigated the consequences of fire during the fruiting period of Calliandra parviflora Benth., by checking fruit exposure to fire, pre‐dispersal seed predator infestation, and the effect of fruit burning on germination. We conducted this study in a floodable savanna in central Brazil, where we collected burnt and unburnt fruits. We measured the fruit and seed mass, and counted the number of damaged and undamaged seeds and live larvae per fruit. We analyzed the seed germination percentage from burnt and unburnt fruits. The burnt fruits presented greater mass than the unburnt fruits, despite their seed mass being similar. The number of damaged seeds per fruit was only slightly higher in burnt compared to unburnt fruits (p = 0.047). The number of larvae on pre‐dispersal seeds per fruit varied from 0 to 4 and did not differ between burnt and unburnt fruits. The germination percentage of unburnt fruit seeds (mean = 22 ± 17%), was significantly higher than that of burnt fruit (mean = 3.0 ± 2.0%, p < 0.001). Fire during fruiting or pre‐dispersion decreases seed germination from 22 to 3%, but it does not hurt vegetative regeneration or resprout capacity of C. parviflora, which is a facultative seeder. Hence, we suggest that C. parviflora has potential for post‐fire restoration in floodable open grassy savannas, in the ecotone between Cerrado and Pantanal, because this species may sprout quickly after first post‐fire rains. Fire during fruiting or pre‐dispersion decreases seed germination from 22 to 3%, but it does not hurt vegetative regeneration or resprout capacity of Calliandra parviflora, which is a facultative seeder. In addition to fire, the sexual C. parviflora reproduction is under another ecological filter, infestation by seed predators larvae. These ecological filters helps to decrease dissemination of C. parviflora, considering its apparent degree of rusticity. These traits enable its potential for post‐fire restoration in floodable open grassy savannas, in the ecotone between Cerrado and Pantanal, where C. parviflora may sprout quickly after first post‐fire rains.
... In the Brazilian Cerrado, a Neotropical savanna, adaptations to fire date from 9.8 to 0.4 Mya (million years ago) (Simon et al., 2009). The vegetation in this biome presents numerous fire adaptations, such as high resprouting capacity, thermal insulation by a thick bark and synchronous flowering after burns (Neves and Damasceno-Junior, 2011;Dantas and Pausas, 2013;Pausas et al., 2018;Pilon et al., 2018). Despite the possible negative impacts of fire, burned areas represent new establishment opportunities for the surviving organisms and seedling recruitment due to the nutrient input and alleviated interplant competition (Miranda and Klink, 1996a,b;Lamont and Downes, 2011;Musso et al., 2015). ...
Article
The Brazilian Cerrado, a Neotropical savanna, is a fire-prone ecosystem where the ground layer biomass consists mainly of graminoids. However, as for other savannas, the effects of fire cues (such as smoke) on Cerrado grasses do not present a clear pattern, either for germination or seedling development. Smoke can stimulate different stages of the plant life cycle, which can alter the community and invasion processes. So far, most research on the subject focuses on germination, not addressing post-germinative phases, a sensitive stage of plant development. Here, we investigated the effect of smoke on a native ( Echinolaena inflexa ) and an invasive ( Urochloa decumbens ) grass species common in the Cerrado. We analysed germinative parameters and seedling mass and length after exposing the seeds to dry smoke for 5, 10, 15 or 20 min. Seedling development was assessed by measuring shoot and root systems after cultivating germinated seeds for 3, 7 or 15 d. Smoke did not affect germination percentages. However, fumigation reduced the mean germination time of both species and the germination onset of E. inflexa . U. decumbens had higher length values in all periods of cultivation, whereas mass values only surpassed that of E. inflexa at 15 d. Smoke exposure reduced the aboveground length of 7-d seedlings of U. decumbens , and mass of 15-d plants of both species. Also, smoke enhanced the root investment of the native and invasive species in different cultivation periods. Therefore, studying post-germinative parameters on seedling development may bring further insights into the smoke effects.
... Over the last 50 years, the fire regimes in the region have been particularly intensified: fires have become more frequent and concentrated at the end of the dry season (August to October) [4]. In addition, significant wildfires spread throughout the vegetation, both resistant and susceptible to fire, causing severe adverse ecological effects [5,80,81]. ...
Article
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The Brazilian savannah-like Cerrado is classified as a fire-dependent biome. Human activities have altered the fire regimes in the region, and as a result, not all fires have ecological benefits. The indigenous lands (ILs) of the Brazilian Cerrado have registered the recurrence of forest fires. Thus, the diagnosis of these events is fundamental to understanding the burning regimes and their consequences. The main objective of this paper is to evaluate the fire regimes in Cerrado’s indigenous lands from 2008 to 2017. We used the Landsat time series, at 30 m spatial resolution, available in the Google Earth Engine platform to delineate the burned areas. We used precipitation data from a meteorological station to define the rainy season (RS), early dry season (EDS), middle dry season (MDS), and late dry season (LDS) periods. During 2008–2017, our results show that the total burned area in the indigenous lands and surrounding area was 2,289,562 hectares, distributed in 14,653 scars. Most fires took place between June and November, and the annual burned area was quite different in the years studied. It was also possible to identify areas with high fire recurrence. The fire regime patterns described here are the first step towards understanding the fire regimes in the region and establishing directions to improve management strategies and guide public policies.
... Em biomas dependentes do fogo (por exemplo, Cerrado, Pantanal), as queimadas geralmente estimulam a regeneração, floração e frutificação de muitas espécies de plantas, que em pouco tempo após o fogo começam a oferecer uma grande quantidade de alimento (por exemplo, Jharlya e Raj, 2014; Tunes et al., 2017;Pilon et al., 2018;Pausas e Keeley, 2019;. Mas os efeitos do fogo nas populações animais dependerão muito do regime de queima (Quadro 1). ...
Article
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O Brasil tem vivenciado incêndios sem precedentes na última década. Imagens de imensas áreas queimadas ou animais mortos que não conseguiram escapar dos incêndios em 2020 chocaram o mundo. Para prevenir ou minimizar desastres similares no futuro nós devemos compreender os fatores que levaram a esses eventos catastróficos. As causas e consequências dos incêndios estão vinculadas a interações complexas entre as esferas biofísica e sociocultural, e decisões acertadas de gestão requerem uma sólida base científica. Apresentamos aqui o panorama recente do aumento dos focos de incêndio nos biomas brasileiros e discutimos as causas que têm contribuído para esses incêndios, seus impactos no meio ambiente e as consequências gerais para o bem-estar humano, com base numa extensa revisão da literatura sobre o assunto, no conhecimento especializado dos autores e informações fornecidas por gestores ambientais, pesquisadores e políticos durante uma oficina organizada para debater o tema dos incêndios no Brasil. Esta revisão atualizada é direcionada ao público acadêmico, gestores ambientais, tomadores de decisão e formuladores de políticas. Num primeiro momento, apresentamos evidências dos contrastantes efeitos do fogo nos diferentes ecossistemas. A seguir, traçamos, numa perspectiva histórica, a percepção e as principais políticas relacionadas ao uso e manejo do fogo no Brasil, desde a colonização até o presente. Depois, propomos meios de avançar na prevenção e desenvolvimento de estratégias de gestão do fogo. Finalmente, nós procuramos esclarecer e/ou desmistificar algumas questões nem sempre apropriadamente abordadas pela mídia
... Although shrubs can benefit from fire-suppression to the point of dominating communities (i. e., shrub encroachment), they can also benefit from fire events through fire-induced flowering, which can produce subsequent advantages such as increased population size and overall fitness (Coutinho, 1976;Pilon et al., 2018) and could allow the species to persist longer in the disturbance-suppressed community. It seems that this mechanism can be extended to other lignified life forms: we found the lignified forb Lantana montevidensis in all post-fire stages, although the species Table 3 Indicator species of three post-fire successional stages for plant communities collected in 12 grassland sites from Southern Brazil. ...
Article
Fire is among the major forces shaping patterns in nature. Although sometimes it is only acknowledged for its destructive power, it was one of the evolutionary drivers that produced present-day species and biome distributions, being inextricably linked to fire-prone ecosystems such as grasslands. Knowing how fire influences grassland biodiversity is therefore fundamental to conserve it. Here we analyzed the taxonomic and functional structure of grassland plant communities from Southern Brazil under different post-fire successional stages. We sampled 12 sites that were fire-suppressed for varying amounts of time (3 to 300 months), categorized in three post-fire stages: freshly-burnt (FB), intermediate-burnt (IB), and old-burnt (OB). We compared these stages regarding taxonomic composition, species richness, diversity (partitioned in different spatial components), and functional composition (based on plant life forms and metabolism). We sampled 307 plant species from 52 families. Species richness was lower in the OB stage, and did not differ between FB and IB stages. Species composition was markedly different between stages. Forty-five percent of the sampled species were exclusive to one post-fire stage, and only 23% were shared among them. Old-burnt sites share only up to 5% species with other stages and concentrated most of the trees and tussocks. Because long-term fire suppression allowed for the entry of different floristic elements in the community, taxonomic diversity (beta and gamma levels) was higher in old-burnt sites. Our results provide empirical evidence that fire suppression is likely to shift the fire-prone grasslands from Southern Brazil towards different ecosystem states, although whether this process is leading towards a closed forest system or to a different system with coexisting grassland and forest elements, remains an open question. The sharp floristic differences and exclusive species in the different post-fire stages reinforce the need to include fire in the conservation framework for fire-prone grasslands.
... These different growth forms can be considered different functional groups based on their leaf physiological traits: graminoids show higher photosynthetic capacity and low leaf nutrient content, while herbs show higher leaf nutrient content, but lower photosynthetic rates, and subshrubs show intermediate photosynthetic rates and leaf nutrient concentration (Rossatto and Franco 2017). Since these different growth forms may differ in carbon, water and nutrient use, response to fire may change among such distinct functional groups, with grasses being favoured under recent fire events, given the high growth rates of these plants after fire (Pilon et al., 2018, Zirondi et al. 2021. ...
Article
Fire is one of the most important factors driving community assembly and ecosystem functioning in tropical savannas. However, few studies have evaluated the physiological responses of ground layer plant communities to fire disturbance. Here we used different fire regimes to investigate possible changes in leaf maximum gas exchange (Amax and gs) and leaf nutritional content (N, P, K, Ca and Mg) among different plant growth forms in savanna ground layer communities. We compared responses of ground layer plant communities under two different fire regimes: (1) no recent fire occurrence; and (2) two recurrent fire events in the last 20 years. We estimated canopy cover, soil chemical properties and species abundance on burned and unburned plots in order to calculate abundance-weighted species average trait values for gas exchange and leaf nutrient content. We found that burned plots exhibited lower canopy cover and soil organic matter content, and an overall higher soil macronutrients availability compared to unburned plots. These environmental differences clearly influenced the ground layer plant communities, which depicted higher Amax and gs in burned areas regardless of growth form. We found no significant differences among leaf nutrient traits, except for a lower Mg concentration in the burned site species. Our results support the hypothesis that distinct fire regimes select for a different set of leaf functional traits, with fire occurrence acting as an important driver increasing the maximum photosynthetic rate on the ground layer. While nutrient use seems not to be affected by medium-term recurrent fires, physiological plasticity on carbon and water use processes in response to changes in resource availability can promote the persistence of savanna species under frequent fire.
... Fire is a determinant driver for savanna dynamics, which has a historical evolution modeled by fire and herbivory processes, along with other fire-prone ecosystems (Bond and Keeley, 2005;Parr et al., 2014;Fidelis, 2020). The Cerrado high biodiversity is a result of these processes, with a rich mosaic of habitats (from open grasslands to woodland savannas) and endemic species adapted and often dependent on frequent fire events to maintain their populations (Simon et al., 2009;Fidelis and Blanco, 2014;Pilon et al., 2018Pilon et al., , 2020. Brazilian Cerrado already lost about half of its natural vegetation due to extensive agriculture, especially soybean monoculture, and human occupation, leading to a high level of fragmentation (Motta et al., 2002;Sano et al., 2010;Alencar et al., 2020). ...
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Years of fire suppression, decreases in herbivores, and global climate change have led to shifts in savannas worldwide. Natural open vegetation such as grasslands and shrublands is increasing in wood density, but the effects for small mammals are not well understood. While most of the mammal studies from the Brazilian Cerrado are concentrated in the core area of this large Neotropical savanna, its southern portions are suffering from biome shifting through woody encroachment. Herein, we surveyed a small mammal community from the southeastern boundary of Cerrado (Santa Bárbara Ecological Station) and evaluated the micro and macro environmental variables shaping community structure in order to investigate how the woody encroachment in the last 15 years may have influenced this assemblage. We recorded 17 species of marsupials and rodents along five distinct habitats in a gradient from grasslands to woodlands. Although richness was not affected by microhabitat variables, total and relative abundance varied according to habitat type and in relation to herbaceous, shrub, and tree density. Rodents such as Calomys tener and Clyomys laticeps were positively affected by increasing herb cover, Cerradomys scotti and Oligoryzomys nigripes by shrub cover, while the marsupial Didelphis albiventris had higher association with increasing tree cover. We detected an increase of 27.4% in vegetation density (EVI) between 2003 and 2018 in our study site, and this woody encroachment negatively affected the abundance of some small mammals. The open-area specialists Cryptonanus chacoensis and C. scotti had a decrease in abundance, while D. albiventris and O. nigripes were favored by woody encroachment. Our data suggest that woody encroachment is shifting community composition: small mammals often associated with grasslands and open savannas are likely to be negatively affected by woody encroachment; while species that rely on tree-covered habitats are likely to benefit from an increasing woody landscape. Therefore, forest-dwellers are gradually replacing open-vegetation inhabitants. Active management of open formations (e.g., with prescribed burning) may be needed to maintain Cerrado biodiversity, especially considering the open-area endemics.
... Because of this, unburned refuge areas are important for sustaining plant-pollinator interactions in burned landscapes (Adedoja et al., 2019;Peralta et al., 2017). However, fire can also stimulate post-disturbance flowering in grassland plants (though responses are variable and species specific; Fidelis & Blanco, 2014;Pilon et al., 2018;Wagenius et al., 2020). Postfire flowering can be immediate, or delayed until the following season (Hinman & Brewer, 2007). ...
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Grasslands provide essential floral resources for both managed and wild pollinators. However, grassland flowers in remaining native landscapes are threatened due to nonnative plant invasions and alterations to historic disturbance regimes such as fire and grazing. The potential for managed disturbance to promote grassland floral resources remains unclear. Fire and grazing historically occurred interactively, but uniform application of each may be a detriment to floral resources and the pollinators depending on them. Though fire can increase resources available to plants and stimulate flowering, it initially destroys floral resources and may delay flower availability. Similarly, grazing removes competitors of flowering plants, but destroys flower heads. To address this knowledge gap, we investigated the impacts of rotational fire and cattle grazing (patch‐burn grazing with one and two seasons of fire per year) versus traditional season‐long grazing with no fire on floral resources in mixed‐grass prairie. In patch‐burn treatments, part of each pasture is burned each year, which focuses grazing activity due to the high quality regrowth. We aimed to use fire to remove litter around flowering plants while also sheltering established flower heads from grazing pressure by directing cattle away from regenerating forbs in unburned portions of the landscape. Over two summers, we performed weekly flower surveys in season‐long grazing and patch‐burn grazing pastures. We analyzed total seasonal floral resources, maximum floral abundance, and seasonal species richness between treatments. Over two years, we surveyed 1,238,241 ramets of 160 species, focusing on 36 common species for individual analysis. We found broad positive associations between patch‐burn grazing and total seasonal flower abundance, maximum flower abundance, and species richness compared to traditional management. In most cases, patch‐burn grazing with dormant and growing season fires produced higher floral abundance, total seasonal floral resources, and species richness than patch‐burning with dormant season fires alone, suggesting benefits of increased levels of pyrodiversity. Synthesis and applications: Under increasing pressure to manage for declining pollinators, rangeland managers must consider strategies to enhance floral resources within the context of livestock production goals. The spatiotemporal interaction of cattle grazing and fire shows promise for promoting floral resource abundance and diversity.
... However, humans have been modifying the natural fire regimes for over 4000 years: from before European colonization, when indigenous peoples of Cerrado used fire for several activities (but practiced refined fire management methods), to the current use of fire in the region, mainly for agricultural practices and cattle ranching (Pivello 2011). Thus, even though fires are key in determining species composition (Loiola et al. 2010;Silva et al. 2013;Pilon et al. 2021) and plant reproductive success (Ara ujo et al. 2013;Pilon et al. 2018;Zirondi et al. 2021), its indiscriminate use, primarily for pasture management, threatens the Cerrado and has ultimately altered Cerrado fire regimes (Durigan & Ratter 2016;Schmidt & Eloy 2020). On the one hand, human activities have caused fires to become more frequent and occur mainly during the dry season; on the other hand, such misuse of fire has led to a policy of fire suppression in many areas (Durigan 2020;Schmidt & Eloy 2020;Barradas & Ribeiro 2021). ...
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Resprouting is an efficient life history strategy by which woody savanna species can recover their aboveground biomass after fire. However, resprouting dynamics after fire and the time it takes to start producing flowers and fruits are still poorly understood, especially for the Brazilian savanna (Cerrado biome), where fire is an important driver of vegetation structure and ecosystem functioning. We investigated the resprouting dynamics and production of flowers and fruits of 26 woody species (20 tree and 6 shrub species for a total of 485 individuals) that were burned and the production of flowers and fruits for a subset of 12 species (139 individuals) in an unburned area in a Brazilian savanna. We classified the species’ resprouting strategies as hypogeal (at the soil level, with main stem death), epigeal (on the main stem or crown), and hypogeal + epigeal. We used generalized linear mixed-effect models to identify the post-fire recovery patterns for five years. Individuals with basal resprouts (hypogeal and hypogeal + epigeal resprouting) produced an average of 6 basal resprouts, but only 33% of resprouts survived after five years. Individuals in burned areas produced fewer flowers and fruits than individuals in unburned areas. At least a subset of individuals in all the resprouting strategies started to produce flowers and fruits in the first-year post-fire. About 68% of the species with hypogeal resprouts produced flowers and fruits in the first-year post-fire, but the intensity of flowering and fruiting was lower compared to individuals with other resprouting strategies over time. Although woody species have invested in post-fire growth and sexual reproduction in all resprouting strategies, the long time needed to recover these processes can make these species more vulnerable to frequent fires.
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South American savannas are an ancient, open, and species-rich ecosystem, currently threatened by numerous anthropogenic impacts, including human-driven climate change. In this chapter, we synthesize available evidence on how climate change likely will affect regeneration from seeds, focusing on the Brazilian Cerrado, a Neotropical mosaic of vegetation types. We conducted a literature survey to evaluate the main environmental drivers (fire, temperature, drought) affecting regeneration of plants from seeds in a changing climate. Unlike Mediterranean ecosystems, germination of most Cerrado species is not stimulated by fire-related cues, but heat-tolerant propagules would be selected under increasing fire frequency scenarios. Emergence from soil seed banks is closely related to the distinct rainy season, but seed drought tolerance and seed bank recruitment are not well studied. We propose a list of key research areas that need to be addressed to increase our predictive power on the effects of climate change on regeneration of plants from seeds in tropical savannas.
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Recent studies indicate that after protection from human pressures (fire, cattle grazing and agriculture), structural changes occur in the cerrado vegetation, changing open physiognomies into more closed savannas. We analyzed the dynamics of vegetation types along 44 years, at Assis Ecological Station, one of the rare conservation units protecting the cerrado biome in the southeastern São Paulo State, Brazil, with the aim of characterizing and quantifying those changes in space and time. Protected against human pressures since a long time, field observations have shown an upgrade of local cerrado physiognomies, through a successional process whose structural climax can be a forest physiognomy, with a continuous arboreal stratum. The dynamics of the vegetation types was analyzed by using aerial photographs (1962, 1984 and 1994), Quick Bird satellite images (2006) and field surveys. During this 44 years period, field physiognomies were reduced from 23% to less than 1% of the total area studied. In the other extreme, woodland savanna increased from 53% to 91% of the area. Changes did not happen at the same rhythm across the area, and that is apparently correlated to microclimate and edaphyc differences. We believe that field and savannic physiognomies initially existing were mostly maintained due to heavy human pressures, constraining the secondary succession towards an edapho-climatic climax of greater biomass. Confirming the observations of cerrado areas elsewhere, protection against fire, cattle grazing and agriculture allowed the evolution of open vegetation types into more closed ones, tending to be locally extinct the first if new disturbances do not occur. Consequences of these changes related to management strategies, biodiversity conservation and carbon sink are discussed.
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Among the many effects caused by fires on native species of the Cerrado, the change in fruit production has been highlighted, since it results directly in the maintenance of local populations. The objective of this study was to investigate the effect of a prescribed burning on fruit set of Qualea parviflora Mart. in a cerrado sensu stricto area in Brasília-DF. Two areas of cerrado were studied, one submitted to biennial prescribed burnings in August (burned) and one fire protected for 14 years (control). In each area, 10 reproductive individuals were selected and their production of flower buds, flowers and fruits was monitored for 22 months. Two months after the prescribed fire on August 26, 2008, the production of reproductive structures was higher in the burned than in the control area. However, the proportion of flower buds that develop flowers and fruits (fruit set) was the same in both areas. One year after the fire, there was no inflorescence production in the burned area. However, in the control area the yield was higher than in the previous period. The absence of flower production in individuals of the burned area one year after the fire suggest that Q. parviflora may need more than a year to return to a normal cycle of reproduction, indicating that medium and long term effects of fire should be considered when using fire as a management tool to reduce fuel in areas of Cerrado.
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Palm swamps (veredas) are unique and diverse plant communities associated with the headwaters of streams in central Brazil, and they are frequently subjected to fires. We evaluated the effect of fire and the role of different fire-related cues on inducing reproduction by palm swamp vegetation. We compared the responses of species in burned plots, in plots in which the aboveground vegetation was clipped and then removed, and in unburned and unclipped control plots. Both the number of reproductive species and the total number of flowers/fruits produced by all species monthly were significantly greater in the burned than in the clipped and control plots, and greater in the clipped than in the control plots. For 34 of the 48 individual species analyzed the number of flowers/fruits produced per m2/month was greater in the burned than in the control plots, whereas the clipping treatment significantly increased the reproductive rate of only six species. This indicates that increased light availability was not the only factor inducing plant reproduction. Most likely, plant reproduction was also stimulated by the availability of soil nutrients whose concentrations increased significantly after burning. Although our results indicate that most plant species that occur in palm swamps are fire-recruiters, care must be taken in using fire as management tool, especially as the frequency of human-induced fires in palm swamps have increased dramatically in recent years.
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O conhecimento da flora herbáceo-subarbustiva, juntamente com o da flora lenhosa, auxilia a determinação dos padrões florísticos e permite descrever o espectro biológico com conseqüentes inferências sobre a atuação de fatores ambientais e históricos na vegetação. Considerando que poucos trabalhos se aprofundaram no estudo da flora herbáceo-subarbustiva de Cerrado, embora esta seja mais rica que a lenhosa, objetivou-se estudar a composição e os padrões florísticos das floras herbáceo-subarbustiva e lenhosa da Estação Ecológica de Santa Bárbara (EESB) (22º 46' 30'' a 22º 50' 30''S e 49º 10' 30'' a 49º15'30'' W , 600 a 680 m de altitude), Município de Águas de Santa Bárbara, Estado de São Paulo. Visou-se, ainda, determinar o espectro biológico para efetuar análises comparativas das diferentes fitofisionomias de Cerrado dessa Unidade de Conservação. Foram encontradas 314 espécies na EESB, sendo 285 em Cerrado sensu lato. As famílias mais ricas em número de espécies foram Asteraceae, Leguminosae, Myrtaceae e Poaceae. Há uma constante ocorrência de Asteraceae, Leguminosae e Poaceae entre as famílias mais ricas, concordando com o observado nos estudos florísticos de Cerrado que incluíram os estratos lenhoso e herbáceo-subarbustivo. O espectro biológico corroborou os padrões anteriormente descritos para o Cerrado sensu lato, exceto pela maior expressão de caméfitas em relação às hemicriptófitas nas fisionomias campestres da EESB, o que pode ser efeito da proteção ao fogo nessa Unidade de Conservação.
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Underground trees are a rare clonal growth form. In this survey we describe the branching pattern and estimate the age of the underground tree Jacaranda decurrens Cham. (Bignoniaceae), an endangered species from the Brazilian Cerrado, with a crown diameter of 22 meters. The mean age calculated for the individual was 3,801 years, making it one of the oldest known living Neotropical plants.Árvores subterrâneas são uma forma rara de crescimento clonal. Neste estudo descrevemos o padrão de ramificação e estimamos a idade da árvore subterrânea Jacaranda decurrens Cham. (Bignoniaceae), uma espécie ameaçada do Cerrado Brasileiro, com um diâmetro de “copa” 22 metros. A idade média calculada para o indivíduo foi de 3.801 anos, o que o torna uma das mais longevas plantas Nepotropicais.
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CONTENTS: I. II. III. IV. V. VI. VII. VIII. References SUMMARY: Resprouting as a response to disturbance is now widely recognized as a key functional trait among woody plants and as the basis for the persistence niche. However, the underlying mechanisms that define resprouting responses to disturbance are poorly conceptualized. Resprouting ability is constrained by the interaction of the disturbance regime that depletes the buds and resources needed to fund resprouting, and the environment that drives growth and resource allocation. We develop a buds-protection-resources (BPR) framework for understanding resprouting in fire-prone ecosystems, based on bud bank location, bud protection, and how buds are resourced. Using this framework we go beyond earlier emphases on basal resprouting and highlight the importance of apical, epicormic and below-ground resprouting to the persistence niche. The BPR framework provides insights into: resprouting typologies that include both fire resisters (i.e. survive fire but do not resprout) and fire resprouters; the methods by which buds escape fire effects, such as thick bark; and the predictability of community assembly of resprouting types in relation to site productivity, disturbance regime and competition. Furthermore, predicting the consequences of global change is enhanced by the BPR framework because it potentially forecasts the retention or loss of above-ground biomass.
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The objective of this study was to analyse the phenological events in the herbaceous and sub-shrub layer of a campo sujo (15º55'478"S and 47º54'225"W) community in relation to rainfall. The climate is Aw by Köppen classification with a mean annual precipitation of 1,500 mm. Three to ten individuals belonging to 61 species were studied totaling 519 individuals. The individuals were observed quarterly, from October 1999 to February 2001. An accidental fire happened in the area two months before the beginning of this study. It stimulated flowering and fruiting of the species. Flowering occurred continuosly over the study period but, with a concentration in the rainy season. Fruiting presented a similar pattern with most species maturing their diaspores from the middle to the end of the rainy season. During the dry season there was a higher production of dry leaves. However, some species did not have all leaves completely dried in that period, 3.2% produced new leaves while 31% remained with mature green leaves. The vegetative and reproductive events of the plants in the herbaceous layer were dependent on the precipitation.
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Fire is important for the maintenance and conservation of African savanna ecosystems. Despite the importance of fire intensity as a key element of the fire regime, it is seldom measured or included in fire records. 2. We estimated fire intensity in the Kruger National Park, South Africa, by documenting fuel loads, fuel moisture contents, rates of fire spread and the heat yields of fuel in 956 experimental plot burns over 21 years. 3. Individual fires were conducted in five different months (February, April, August, October and December) and at five different return intervals (1, 2, 3, 4 and 6 years). Estimated fire intensities ranged from 28 to 17 905 kW m(-1). Fire season had a significant effect on fire intensity. Mean fire intensities were lowest in summer fires (1225 kW m (-1)), increased in autumn fires (1724 kW m (-1)) and highest in winter fires (2314 kW m (-1)); they were associated with a threefold difference between the mean moisture content of grass fuels in winter (28%) and summer (88%). 4. Mean fuel loads increased with post-fire age, from 2964 kg ha (-1) on annually burnt plots to 3972 kg ha (-1) on biennial, triennial and quadrennial burnt plots (which did not differ significantly), but decreased to 2881 kg ha (-1) on sexennial burnt plots. Fuel loads also increased with increasing rainfall over the previous 2 years. 5. Mean fire intensities showed no significant differences between annual burns and burns in the biennial, triennial and quadrennial categories, despite lower fuel loads in annual burns, suggesting that seasonal fuel moisture effects overrode those of fuel load. Mean fire intensity in sexennial burns was less than half that of other burns (638 vs. 1969 kW m (-1)). 6. We used relationships between season of fire, fuel loads and fire intensity in conjunction with the park's fire records to reconstruct broad fire intensity regimes. Changes in management from regular prescribed burning to 'natural' fires over the past four decades have resulted in a decrease in moderate-intensity fires and an increase in high-intensity fires. 7. The highest fire intensities measured in our study (11 000 - > 17 500 kW m (-1)) were significantly higher than those previously reported for African savannas, but were similar to those in South American cerrado vegetation. The mean fire intensity for late dry season (winter) fires in our study was less than half that reported for late dry season fires in savannas in northern Australia. 8. Synthesis and applications. Fire intensity has important effects on savanna vegetation, especially on the dynamics of the tree layer. Fire intensity varies with season (because of differences in fuel moisture) as well as with fuel load. Managers of African savannas can manipulate fire intensity by choosing the season of fire, and further by burning in years with higher or lower fuel loads. The basic relationships described here can also be used to enhance fire records, with a view to building a long-term data set for the ongoing assessment of the effectiveness of fire management.
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Globally, plant-pollinator communities are subject to a diverse array of perturbations and in many temperate and semi-arid systems fire is a dominant structuring force. We present a novel and highly integrated approach, which quantifies, in parallel, the response to fire of pollinator communities, floral communities and floral reward structure. Mt Carmel, Israel is a recognised bee-flower biodiversity hotspot, and using a chronosequence of habitats with differing post-fire ages, we follow the changes in plant-pollinator community organisation from immediately following a burn until full regeneration of vegetation. Initially, fire has a catastrophic effect on these communities, however, recovery is rapid with a peak in diversity of both flowers and bees in the first 2 years post-fire, followed by a steady decline over the next 50 years. The regeneration of floral communities is closely matched by that of their principal pollinators. At the community level we quantify, per unit area of habitat, key parameters of nectar and pollen forage known to be of importance in structuring pollinator communities. Nectar volume, nectar water content, nectar concentration and the diversity of nectar foraging niches are all greatest immediately following fire with a steady decrease as regeneration proceeds. Temporal changes in energy availability for nectar, pollen, total energy (nectar+pollen) and relative importance of pollen to nectar energy show a similar general decline with site age, however, the pattern is less clear owing to the highly patchy distribution of floral resources. Changes in floral reward structure reflect the general shift from annuals (generally low-reward open access flowers) to perennials (mostly high-reward and restricted access flowers) as post-fire regeneration ensues. The impact of fire on floral communities and their associated rewards have clear implications for pollinator community structure and we discuss this and the role of other disturbance factors on these systems.
Book
The pulse of life with the seasons is a classic theme of biology, equally cap­ turing every man's curiosity about early and late milestones of every year's cycle and the critical physiologist's inquiry into life's subtle signals and responses. Natural historians of ancient and renaissance time as well as today have charted the commonsense facts behind inspired traditions of poetry and practical rules for growing food and fiber. This volume brings together several ways of organizing the basic principles of phenology. These find order in the otherwise overwhelming mass of detail that captures our fleeting attention, like the daily newspaper, and then tends to fade into the overstuffed archives of history. Is this order so obvious and understandable that there is no longer any scien­ tific challenge to "phenology" as a tradition? Or does apparent simplicity mask a complex and ultimately baffling obstacle to the understanding of seasonality in even those few indicator plants and animals we know best, not to men­ tion the less known species or races making up the rest of each major land­ scape unit or ecosystem? Denying both these hasty opinions, we think that this volume well illustrates a range of questions and answers-from soundly established (but not trivial) doctrine to exciting inquiry about how ecosystems are organized.
Article
Fire has played an important role in the plant dynamics and diversity of the Cerrado for millions of years. We evaluated fire behaviour in different fire seasons in areas of an open savanna, providing information for fire management plans. It has been hypothesised that early fires (May – end of the rainy season) will be less intense than those conducted in the middle and end of the dry season (July and October) owing to the amount of dead biomass accumulated. Therefore, we compared fire behaviour in early, mid- and late dry season, evaluating the main fire and environmental variables. Fire intensity was mainly influenced by the combination of dead fuel percentage and fuel load. Even though this combination was the best model to explain fire intensity variability, fire parameters (including fire intensity) did not differ between seasons. Flame height was best explained by dead fuel percentage + fuel moisture content, dead fuel percentage + fuelload and also by dead fuel percentage. Our study showed that, in areas with fire exclusion for 2 years, fire season did not influence fire parameters and fire behaviour and the main factors influencing fire intensity were the proportion of dead biomass and total fuel load.
Article
Professor Coutinho (1934–2016; Sao Paulo, Brazil) studied fire adaptations in Brazilian savannas during the 1970s, when very few researchers recognised fire as an evolutionary force. His main contributions were on fire-stimulated flowering, serotiny and nutrient cycling. However, he is little known, partly because he was not Anglo-Saxon but also because he was ahead of his time, when fire and evolution were still distant concepts.
Article
Understanding the role of the environmental drivers that determine plant population dynamics is essential to promote the conservation of target species and their habitats. Vellozia aff. sincorana is an endemic key species from the rupestrian grasslands (campos rupestres) of the Chapada Diamantina region in the Brazilian savanna (Cerrado). The branches are important in the local culture and are harvested to light wood stoves. Synchronized flowering is triggered by fire, and no flowers have been recorded in the absence of a recent fire. We built matrix population models to project the demography of six V. aff. sincorana populations, three that had recently burned and three that had not burned for four years. Based on local harvesting practices and our population models, we assessed the long-term effects of two common harvesting techniques and different fire intervals on this species' demography. Fire is necessary for the long-term persistence of V. aff. sincorana populations; adult survival is the most important vital rate for population persistence and it is mostly unaffected by fire. Recent fires primarily caused increases in reproductive rates, and populations are projected to decrease in size (λ. <. 1) under fire intervals longer than 25 years. Harvest effects depend on its frequency and intensity; our models indicated that harvesting may be sustainable as long as it is low-intensity and fire also occurs periodically. As in many other fire-prone ecosystems, this species benefits from fire occurrence. These results indicate that the 'zero-fire' policy currently in place in the Brazilian savanna is inadequate for the conservation of this, and probably many other, Cerrado species.
Article
Fire as a major evolutionary force has been disputed because it is thought to lack supporting evidence. If a trait has evolved in response to selection by fire then the plant’s environment must have been fire-prone prior to the appearance of that trait. Using outcomes of trait assignments on molecular phylogenies for fire-stimulated flowering, seed-release and germination, in this Opinion article we show that fire-proneness precedes, or rarely coincides with, the evolution of these fire-adapted traits. In addition, fire remains central to understanding germination promoted by smoke among species occurring in non-fire-prone environments because of the historical association of their clade with fire. Fire-mimicking selection and associated exaptations have no place in understanding the evolution of fire-adapted traits as we find no support for any reversal in the fire-trait sequence through time.
Article
Concerns over deforestation have led to attempts to identify suitable areas for reforestation around the world ( 1 ). The most ambitious effort to date is the World Resources Institute (WRI) Atlas of Forest and Landscape Restoration Opportunities ( 1 ). This map is linked to a global plan to reforest degraded lands to offset anthropogenic CO2 emissions. The immediate target is the reforestation of 1.5 million km2 by 2020 ( 2 , 3 ). Vast areas of open grassy vegetation have been identified as suitable for reforestation. But are all these grasslands secondary products of deforestations? Recent research shows that grasslands are often ancient and highly biodiverse, but it remains difficult to distinguish between primary and secondary grasslands on a large scale. Reforestation efforts thus risk converting ancient tropical grasslands to plantations.
Article
The seed-bank dynamics of cerrado, a savanna-like vegetation type in central Brazil, was monitored for a year after a fire event in the mid-dry season. Fifty paired soil and litter samples were collected 1 day before and 1 day after the fire to record the immediate effects on the seed bank, and thereafter at monthly intervals to investigate the post-fire seed bank dynamics. The samples were hand-sorted and the intact seeds were classified as monocot or dicot and counted. All seeds underwent germination trials in a germination chamber for 1 month. Seeds that did not germinate were checked for the presence and viability of the embryo. The sorted soil samples were placed in a greenhouse for 6 months, and the count of emerging seedlings was added to the number of germinated and dormant seeds from the germination trials to estimate the total number of viable seeds per sample. The fire did not affect the total seed-bank density: 63 ± 8 seeds m−2 before the fire, and 83 ± 20 seeds m−2 (mean ± se) immediately after it. Although monocots represented 65 % of the pre-fire seed bank, 1 year after the fire, the monocot seed density did not reach the pre-fire value, whereas the density of dicot seeds increased threefold. After the fire, the viable seed density and species richness, decreased with the onset of the rainy season coinciding with germination in the field. Therefore, post-fire recruitment increases genetic variability and contributes to the persistence of plant populations in cerrado communities.
Article
The Cerrado is a fire-dependent savanna requiring a clear and urgent fire management policy. The extensive misuse of fire for deforestation or pasture management in Brazil has created an overall perception that its use is always deleterious. This view, reinforced by threats of global warming and climatic change, has lead to current policies of fire suppression. Cerrado ecosystems depend on the historical fire regime to maintain their structure, biodiversity and functioning. The suppression of fire has transformed savanna vegetation into forests, causing biodiversity losses and drastic changes in ecological processes. Policy implications. The National Fire Policy required by law must be urgently implemented in Brazil, including use of fire for Cerrado conservation in public and private lands on the basis of existing knowledge of indigenous people and scientists. Objective regulations on prescribed burning, land manager training, incentives for fire research and experimentation and a broad campaign to disseminate the benefits of fire for Cerrado conservation should be the cornerstones of the policy. If implemented, the policy can give the biodiversity of the Cerrado a future that has previously been severely threatened by fire suppression.
Article
Flowering of certain fynbos geophytes has long been noted to have an obligate dependence upon fire. One of these species, Cyrtanthus ventricosus (Jacq.) Willd., is shown here to be stimulated to flower by smoke. Ethylene, a gaseous component of smoke, did not stimulate flowering in this species.
Chapter
Focuses on the effects of fire on South African plants and animals and the means by which they avoid, minimise, recover from or exploit these effects. Fire may act directly on an individual, eg through death or damage, or indirectly by changing the environment. Responses of plants to fire include discussion of avoidance in space, escape in time, tolerance (resistance and recovery), regeneration from seed, and post-fire flowering. The mobility of animals is stressed as an advantage, but some animals require shelter.-P.J.Jarvis
Article
The origin of fire-adapted lineages is a long-standing question in ecology. Although phylogeny can provide a significant contribution to the ongoing debate, its use has been precluded by the lack of comprehensive DNA data. Here, we focus on the ‘underground trees’ (=geoxyles) of southern Africa, one of the most distinctive growth forms characteristic of fire-prone savannas. We placed geoxyles within the most comprehensive dated phylogeny for the regional flora comprising over 1400 woody species. Using this phylogeny, we tested whether African geoxyles evolved concomitantly with those of the South American cerrado and used their phylogenetic position to date the appearance of humid savannas.� We found multiple independent origins of the geoxyle life-form mostly from the Pliocene, a period consistent with the origin of cerrado, with the majority of divergences occurring within the last 2 million yr. When contrasted with their tree relatives, geoxyles occur in regions characterized by higher rainfall and greater fire frequency. Our results indicate that the geoxylic growth form may have evolved in response to the interactive effects of frequent fires and high precipitation. As such, geoxyles may be regarded as markers of fire-maintained savannas occurring in climates suitable for forests.
Article
Stryphnodendron adstringens, conhecida como barbatimão, é uma espécie de distribuição geográfica ampla no bioma cerrado, ocorrendo desde o Pará, pelo planalto central, até Minas Gerais e São Paulo. Sua casca e frutos contêm tanino e apresentam propriedades medicinais. É uma espécie de baixa exigência nutricional e não acumuladora de alumínio. É hermafrodita e polinizada por pequenos insetos, especialmente abelhas. Está entre as principais espécies lenhosas encontradas na área de estudo. O objetivo deste estudo foi avaliar os eventos fenológicos desta espécie, numa área de cerrado sensu stricto na Fazenda Água Limpa (15°56'S e 47°46'W), durante cinco anos (1987-1991). Dez árvores foram selecionadas e observadas de 18/01/1987 até 07/11/1991 a intervalos quinzenais. A estacionalidade pluvial do clima foi bem definida durante o período de observação. Os padrões fenológicos foram analisados graficamente, pelo teste de Kruskall-Wallis a 5% e pelo coeficiente de correlação de Spearman. Todos os indivíduos floriram anualmente exceto dois que não floriram em 1990, provavelmente como conseqüência da queimada em 1989. A floração ocorreu entre julho e novembro, sendo que os picos variaram entre os anos. Todos os indivíduos frutificaram até 1989 quando os frutos foram abortados pela queimada. Nenhuma frutificação foi observada no ano seguinte e em 1991 a produção de frutos atingiu apenas a metade daquela observada nos dois primeiros anos. A espécie apresenta modelo fenológico anual com floração, frutificação, dispersão de sementes e picos de senescência e de emissão de folhas novas, todos na estação seca. Seus frutos requerem um longo período de maturação, cerca de 12 meses, alcançando a maturidade na época seca do ano seguinte. Queimadas ocasionais afetaram, de maneira acentuada, as atividades reprodutivas, especialmente a frutificação.
Article
Tropical grassy biomes (TGBs) are globally extensive, provide critical ecosystem services, and influence the earth-atmosphere system. Yet, globally applied biome definitions ignore vegetation characteristics that are critical to their functioning and evolutionary history. Hence, TGB identification is inconsistent and misinterprets the ecological processes governing vegetation structure, with cascading negative consequences for biodiversity. Here, we discuss threats linked to the definition of TGB, the Clean Development Mechanism (CDM) and Reducing Emissions from Deforestation and Forest Degradation schemes (REDD+), and enhanced atmospheric CO2, which may facilitate future state shifts. TGB degradation is insidious and less visible than in forested biomes. With human reliance on TGBs and their propensity for woody change, ecology and evolutionary history are fundamental to not only the identification of TGBs, but also their management for future persistence.
Article
The Xavantina-Cachimbo Expedition worked during 1967-9 in a 20 km square around a base camp (12^circ 49' N, 51^circ 46' W), ca. 260 km north of Xavantina (NE Mato Grosso) and near Xavantina itself. The vegetation is of special interest because the base camp is situated near the junction of the savanna region of Central Brazil and the Amazonian forest. It is a pattern of savanna (cerrado), savanna woodland (cerradao), forest and treeless grassland (campo) with often remarkably abrupt boundaries between the different communities. Until 1967 the area had been very little affected by man. The climate is characterized by high temperature throughout the year, an annual rainfall of about 1200 to 1400 mm, and a more or less rainless dry season from June to September inclusive. During the dry season the cerrado, campo and some forms of cerradao vegetation are subject to fire, but are not burned every year. The forest, except the Deciduous Seasonal forest, is not normally burned. The rocks consist of sandstones overlying shale and mudstones. The sandstone weathers to form widespread dystrophic soils of low nutrient content, whilst the finer textured rocks, exposed in some deeper valleys, produce somewhat richer mesotrophic soils. The woody vegetation types of dystrophic soils are classified into three types of Evergreen Seasonal forest ('Swampy Gallery' forest, 'Valley' forest and 'Dry' forest), cerradao and cerrado. The Swampy Gallery forest is found along streams where the water table is close to the surface even in the dry season and is often bordered on one or both sides by strips of campo. In composition it resembles an impoverished Amazonian rain forest. The top-storey is dominated by Qualea ingens and Q. wittrockii, growing sometimes to 40 m, and the undergrowth includes numerous dicotyledons, Scitamineae, grasses and other monocotyledons. At a slightly higher level in stream valleys there is another type of tall forest, Valley forest, in which characteristic trees (all growing to about 40 m) are Apuleia molaris, Copaifera langsdorfii, Hymenaea stilbocarpa and Ormosia sp. (Tento). Much the most extensive type of Evergreen Seasonal forest is the Dry forest which represents the southern fringe of the Amazonian forest and covers a vast area stretching away northwards from the base camp area. This is a mixed community in which the trees seldom grow to more than 20 m. The most abundant species of the upper storey in the area studied are Chaetocarpus echinocarpus, Licania blackii, L. kunthiana, Sacoglottis guianensis and Xylopia amazonica. The transition from Dry forest to cerrado is sometimes abrupt, but elsewhere there is an ecotone in which Hirtella glandulosa cerradao forms a recognizable nodum, occupying a zone up to 4 km wide. Characteristic species in this are Emmotum nitens, Sclerolobium paniculatum and Vochysia haenkeana, as well as H. glandulosa. The boundary between cerrado and Dry forest appears to be dynamic and there are some indications that the forest has recently invaded the cerrado. The present boundary does not seem to be primarily dependent on climate or burning but shows some relation to soil conditions, though apart from a higher clay content in the latter the cerrado and forest soils are much alike. Cerrado has a lower degree of crown cover than cerradao; it is a type of open savanna with grassy undergrowth and is extremely variable in floristic composition and no clearly defined associations could be recognized. The boundary between cerrado and campo in valleys is sharp and appears to be determined by the height of the water table in the wet season. The mesotrophic soils are occupied by Deciduous Seasonal forest, the only woody c