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The presence of belowground organs with buds and carbohydrate storage is typical of perennial plants in fire-prone ecosystems. The bud-bearing storage organs allow regeneration after fire, and they may lose their regeneration capacity if the disturbance is excluded, because of the depletion in the bud bank. We assessed the morphology, anatomy, and storage of carbohydrates in the belowground organs of eight perennial species from open savannas and analyzed their bud banks at different fire frequencies (annual, biennial, and exclusion). Xylopodium was found in all the study species as bud-bearing organ, associated with proliferated storage parenchyma tissue, often in the tuberous roots. We found that bud bank size varied according to different fire frequencies for only half of the studied species (most forbs), and a tendency for lower bud bank sizes in fire-excluded areas was found for all shrub species. Our study highlights the significance of bud-bearing storage organs, particularly xylopodium, and that the species-specific responses of bud bank size to different fire frequencies underscore the need to consider individual plant strategies when analysing fire effects, emphasizing the critical role of belowground organs in sustaining these ecosystems. [ABSTRACT FROM AUTHOR]

Aim: Changes in fire regimes and biological invasions are major threats to tropical savannas. Fire is a key driver of community composition in these ecosystems and can be used as a management tool to control some invasive alien species, while being advantageous to native ones. However, we still do not fully comprehend the interactive effects of these threats on native plant communities. Here, we conducted an experiment in southeastern Brazil to investigate how variation in the composition of native communities invaded either by Melinis minutiflora or Urochloa brizantha is affected by fire in different seasons: early‐dry season, mid‐dry season and late‐dry season in comparison to fire suppression. Location: Itirapina, state of São Paulo, southeastern Brazil (22°14′07″S 47°53′07″W). Results: The effects of fire seasons and invasive species were independent for species richness but interactive for species gains and losses. In general, the identity of the invasive species was a key factor driving community dynamics, with fire seasons playing a weaker role. Invaded communities changed gradually over time and the major changes happened over longer time lags. Communities invaded by M. minutiflora gained more species than those invaded by U. brizantha. Thus, communities invaded by M. minutiflora also had more variation in their species richness through time than those invaded by U. brizantha. Conclusions: Although biological invasions and fire seasons interacted as drivers of change in native savanna communities, the identity of the invasive species played a stronger role. Communities invaded by M. minutiflora gained more species and were more variable than those invaded by U. brizantha. [ABSTRACT FROM AUTHOR]

Background and Aims Bark allows species to survive fire, protecting their inner tissues and allowing new branches to resprout from aerial buds. Thus, bark production is likely to be selected with aerial bud protection in fire-prone ecosystems. By considering the coexistence of fire-prone and fire-free ecosystems, in addition to the different impacts of flames on different growth forms, in this study we tested whether: (1) species from areas with higher fire frequencies have a faster bark production; (2) bark growth rate differs between trees and shrubs; (3) generalists adjust their bark production according to their environment (fire-prone or fire-free ecosystems); and (4) fast bark production results in better aerial bud protection. Methods We sampled two different types of forests and savannas in the Cerrado and registered every woody individual with height between 1.5 and 3 m tall (directly exposed to the flames). For the 123 species registered, we sampled three different individuals in each vegetation type where the species occurred to assess their bark production and aerial bud protection. We then checked, for each species, their preferred habitat (savanna and forest specialists or generalists) and their predominant growth form. Key Results A minimal threshold of 0.13 mm per growth unit of bark production differentiated woody communities from savannas and forests. Shrubs and trees did not differ in terms of bark growth rate, despite being exposed to the flames in a different manner. Generalist species in savannas were able to produce bark above the threshold. However, when these species were in forests they produced bark below the threshold. Finally, a higher bark growth rate accounted for a better aerial bud protection. Conclusions Generalist species are likely to be capable of displaying plasticity in their bark production, which could be important for their success in contrasting ecosystems. The relationship between aerial bud protection and bark growth rate suggests that bark production plays an important role in protecting the dormant buds, in addition to being selected in fire-prone ecosystems. [ABSTRACT FROM AUTHOR]

Aims: Tropical savanna evolved in the presence of fire, depending on it to maintain its physiognomies and biodiversity. Open ecosystems of tropical savanna burn frequently, and thus changes in fire frequency can affect their plant communities. In this study we aimed to analyze the effects of different fire frequencies on the composition, structure and post‐fire regeneration of open savanna plant communities of the Cerrado. Location: Open savannas, Central Brazil (13°35–38′S and 47°45–51′W). Methods: We conducted surveys in areas with different fire frequencies (fire exclusion, burned annually and burned biennially for 6 years, from 2013). Vegetation sampling was carried out before application of fire treatments in 2017, and then 1 and 2 years after. Species cover was estimated visually and later grouped into graminoids, shrubs and forbs. Results: Evaluation of the plant communities after 6 years of fire treatment indicated that fire frequency did not affect species richness. Fire frequency did, however, promote alteration in species occurrence and abundance, resulting in three dissimilar plant communities. Regarding post‐fire regeneration, annually burned plots showed consistency in species richness and growth form cover over 6 years of annually applied fire. Biennially burned plots tended to be more variable than the other treatments, with a large increase in species richness and growth form cover in the first year after fire, succeeded by a decrease in the second year. Not all species that were recruited just after fire were able to persist in the above‐ground community in the second year after fire. Conclusions: Open savannas of the Cerrado are highly resilient to fire, even to annual fires, with 6 years of annual fire treatments not affecting post‐fire species diversity or growth form cover. However, communities differed in species composition, which can influence their functional diversity and lead to alterations in ecosystem services. Our findings encourage long‐term studies to evaluate the resilience of areas frequently burned, as well as longer fire exclusion periods. [ABSTRACT FROM AUTHOR]

Question: How does seasonality affect the below‐ground bud bank dynamics in open savannas from the Cerrado and the density of below‐ground bud‐bearing organs? As the Cerrado is subject to marked seasonality, many herbaceous plants may lose their above‐ground biomass during the dry season, and regenerate it later in the rainy period through resprouting from below‐ground buds. Herein, we tested the hypothesis that seasonality may directly affect bud bank dynamics and below‐ground bud‐bearing organs, with a larger bud bank size and higher densities of below‐ground organs in the rainy season. Location: Open savannas of the Cerrado, southeastern Brazil. Methods: The bud bank was sampled in three open areas of the Cerrado. In each area, 10 plots were established, and, within each plot, the biomass was sampled to 10 cm below‐ground level. In the lab, buds and below‐ground organs were counted. We fitted generalized linear mixed models (GLMM) to test the differences in the bud bank and the below‐ground organ densities between the dry and rainy seasons. Results: The bud bank size was smaller in the dry season. Buds found in the dry season suggest they were developed in the rainy season and remained dormant, not forming new shoots. Non‐woody rhizomes of caespitose grasses were more abundant during the rainy season. Xylopodia and woody rhizome densities were not significantly affected by seasonality. Conclusions: Bud bank dynamics in the Cerrado is affected by seasonality. There is a decrease in bud bank density in the dry season, suggesting that buds were developed into new branches in the rainy season, but not all of them develop into new shoots in the same season. Thus, the bud bank evaluated in the dry season probably is formed by an accumulation of dormant preformed buds, highlighting the occurrence of a resprouting dynamic of native species of the Cerrado in the rainy season. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Applied Ecology is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The herbaceous layer is the dominant fuel for fire in tropical savannas, the world's most fire‐prone biome. However, little is known about variation in flammability among different growth forms, as well as how flammability varies seasonally. Here, we describe such variation in Brazilian Cerrado, the world's most phytodiverse tropical savanna. We measured three components of flammability (maximum burning temperature, burning rate, and burnt biomass) and morphophysiological traits (dead biomass percentage, moisture content, and specific leaf area) of five species of each of grasses, forbs, and shrubs throughout the wet and dry season. We found that grasses were the most flammable growth form and that their flammability was highest in the middle of the dry season when the percentage of dead biomass was highest (60%), and moisture content was low (25%). Flammability did not vary across seasons for either forbs or shrubs. Dead biomass, moisture content, and specific leaf area were all strongly correlated with flammability. These findings explain the dominant role played by grasses as drivers of flammability in tropical savannas, and they improve our understanding of how savanna flammability varies across space and time depending on the composition of the grass layer and its level of seasonal curing. This enables a better prediction of fire spread and behavior in different savanna types based on grass‐layer composition. [ABSTRACT FROM AUTHOR]

Belowground bud bank regeneration is a successful strategy for plants in fire-prone communities. It depends on the number and location of dormant and viable buds stored on belowground organs. A highly diverse belowground bud-bearing organ system maintained by a frequent interval of fire events guarantees the supply of a bud bank that enables plants to persist and resprout after disturbance. We investigated how different fire exclusion and fire frequencies, affected the herbaceous layer in tropical savannas, by assessing belowground persistence and regeneration traits. Contrary to our hypothesis, we found that under a shorter fire exclusion period, the total bud bank increased at a lower fire frequency. But sites at longer fire exclusion and infrequent fire, the bud bank was smaller the longer the period since the last fire. However, the major shift was concerning organ diversity since fire exclusion was more related to loss of belowground diversity rather than decreasing of the belowground bud bank size. Furthermore, fire-associated bud-bearing structures like xylopodia disappeared in the fire suppressed areas, whereas clonal organs, such as rhizomes, developed in the bud bank. By quantifying belowground bud bank traits under different fire histories, we highlight the importance of the local fire regime on the composition of the belowground plant components, which can affect the tropical savanna aboveground plant community. Given that, loss of the belowground bud-bearing component of the plant community will have a direct effect on vegetation regeneration in post-fire environments, and consequently, on plant community resilience. [ABSTRACT FROM AUTHOR]

Questions: 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. Locations: Open savannas (campo sujo) of the Cerrado in central Brazil (Reserva Natural Serra do Tombador [RNST], 13°35–13°38′ S, 47°45′–47°51′ W). Methods: We sampled flowering individuals in 10 Poaceae species and counted flowering/vegetative tillers of grass species in 1 m × 1 m plots after wet‐ and dry‐season fires and under different fire histories (3, 18 and 72 months post fire). Results: 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. Conclusions: We describe a unique event for tropical savannas: beside 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. [ABSTRACT FROM AUTHOR]

Questions: Bush encroachment, (i.e. disproportionate woody vegetation increase at the cost of grassland) has negative impacts for biodiversity conservation and tourism by homogenising habitat structure and decreasing grazing and game‐viewing. While herbivory, rainfall, and CO2 all influence changes in woody vegetation cover, fire has the best potential for vegetation management. Changes in fire management can either encourage or suppress bush encroachment and a better understanding of how changes in fire regime affect vegetation structure is needed. Therefore, this study addressed three questions: (a) how has woody cover changed over two decades (1999–2019); (b) what is the role of land use, rainfall, and fire in influencing woody cover change; and (c) what are the management implications? Location: Bwabwata National Park (BNP), Namibia. Methods: The study used a novel combination of repeat ground photography and satellite‐based remote‐sensing products to explore the change in woody vegetation in relation to rainfall, land use, and fire seasonality. Results: Woody vegetation has increased by 13% since 1999 in BNP. Change in vegetation structure differed in the east and west of the park. Early‐season burns in the east of the park were associated with an increase in trees over 3 m tall consisting primarily of Dialium englerianum, Terminalia sericea and Burkea africana. Repetitive late dry‐season fires in the west of the park were associated with an increase in shrubs under 3 m dominated by Baphia massaiensis and Terminalia sericea. Conclusions: Both early‐ and late‐season fires are of value in management of bush encroachment. Early dry‐season fires appear to reduce the rate of bush encroachment and contribute to maintaining a heterogeneous vegetation structure. This fire management strategy reduces wildfire risk, conserves biodiversity, and promotes tourism and is, therefore, recommended for the park. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Ecology is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Question: Suppression of Aboriginal burning and wildfire from forests in which fires were historically frequent may trigger environmental changes that further suppress fire frequency and intensity. In high‐rainfall regions of eastern Australia, long‐unburnt open forests are frequently invaded by rain forest pioneer trees, which in turn modify open‐forest understorey structure and composition. We examine altered understorey fuel properties as potential fire suppression feedback mechanisms reinforcing switches from fire‐dependent eucalypt open forest to fire‐resistant closed forest. Location: Northeastern New South Wales, Australia. Methods: We characterized forest understorey leaf traits, plant crown architecture and vegetation structure to test for differences in flammability across a mosaic of contrasting times since fire (recently burnt — 4 years; long unburnt — 16 years) and midstorey composition (open, sclerophyll, rain forest) in subtropical shrubby dry sclerophyll eucalypt forest. Results: Drivers of flammability were lower in long‐unburnt open forest with a rain forest pioneer midstorey at multiple scales (leaf, foliage clump, crown and stratum) than either long‐unburnt open forests with a sclerophyll midstorey or recently burnt open forest with an open midstorey. Grassy (graminoid) and sclerophyllous shrub fuels declined sharply beneath a rain forest pioneer midstorey, consistent with the fire suppression feedbacks regulating tropical savanna to closed forest transitions. Rain forest pioneers also reduced understorey flammability drivers through floristic compositional changes that increased leaf and foliage clump separation in shrub and midstorey fuel strata, and increased leaf moisture in the shrub stratum. Conclusion: Our results suggest that rain forest pioneers are ecosystem engineers that modify open‐forest fuel properties, initiating a positive fire suppression feedback that facilitates their persistence and continued transition to a fire‐resistant closed forest. The fire suppression feedbacks we identify may help explain paleoecological and modern observations of rain forest expansion under high CO2 atmospheres, despite increased temperatures and seasonal drought severity. [ABSTRACT FROM AUTHOR]

Questions: Species defined as ecosystem engineers (e.g. elephant) are able to strongly shape their habitat. In African savannas, elephants have often been shown to reduce woody‐plant abundance and diversity. However, recent studies highlight more complex elephant‐induced effects on vegetation. Here, we assessed if long‐term high elephant densities (>2 km−2) in a large open landscape resulted in the depletion of savanna woodland woody communities or if it led to a new alternative equilibrium. Location: Woodland savanna of Hwange National Park, Zimbabwe. Elephant densities at the study site have remained high for the past two decades (>2 km−²). Methods: We measured long‐term (>15 years) elephant utilisation of woody‐plant communities and their effects on vegetation structure, species composition and functional traits (e.g. N leaf concentration, specific leaf area) in 12 vegetation plots. Results: We observed opportunistic foraging behaviour by elephants with only a slight temporal shift in species composition, mainly explained by changes in rare species. Further, we did not observe any modification in mean functional trait values, overall height, and stem diameters of the woody‐plant communities. However, we found differential changes in woody‐plant abundance according to the height layer (decrease in the number of tall plants [>200 cm] and increase in the number of short plants [<50 cm]) and a strong reduction in crown diameter for plants in the 50–200 cm height class. Conclusion: Our study strongly suggests that long‐term high elephant densities have led to a stable state in savanna woodland vegetation in terms of plant community composition and their functional traits. However, high elephant densities did affect vegetation structure, which would have several important indirect effects on this ecosystem (e.g. predator–prey interactions). We hope that this study stimulates more work on the long‐term effects of ecosystem engineers in large and open ecosystems. [ABSTRACT FROM AUTHOR]

Species growing in fire‐prone savannas usually persist by resprouting from their buds. In this study, we evaluated how various persistence traits allow bud protection for improved survival in fire‐prone ecosystems.Using an integrative morphological and macroanatomical approach, we analysed how woody plants protect their buds. We tested bud protection at the community level and evaluated: (a) how bud protection changes along a fire frequency gradient, (b) if it differs between shrubs and trees and (c) whether the level of bud protection is related to post‐fire responses of 28 woody savanna species.A mix of traits involving bud protection may enable woody species persistence in fire‐prone ecosystems. Savanna species better protected their buds than forest species by developing bark and trichomes that allowed resprouting after fire. Regarding growth forms, shrub species capable of resprouting above‐ground had their buds better protected than trees.Bud protection is not only linked with their position to the bark, but also with the presence of trichomes. Profuse trichomes covering buds were related to savanna species. Some species with no bud protection by bark but with trichomes covering their buds were able to resprout after fire. The presence of accessory buds is also a trait more related to savannas, possibly influencing the resprouting after fire as they are better protected and increase the bud bank. Finally, different persistence traits interact with one another to better protect the buds, requiring a detailed screening of the traits to assess species responses to fire.Synthesis. During fire, species have their aerial biomass consumed by the flames. To be able to resprout new branches and persist in the environment, they must have well‐protected buds. In this study, we evaluated different ways that woody species protect their buds and related them with their resprouting strategy after fire. We investigated the protection by the bark, the presence of trichomes and accessory buds. By studying the woody community in a gradient of savannas and forests we found that buds can be protected by bark, trichomes or soil. Species can present a mix of these traits and strategies, which enhances their resprouting after fire. A free Plain Language Summary can be found within the Supporting Information of this article. [ABSTRACT FROM AUTHOR]

Despite growing recognition of the conservation value of grassy biomes, our understanding of how to restore biodiverse tropical and subtropical grassy biomes (grasslands and savannas; TGB) remains limited. Several tools have recently been identified for TGB restoration, including prescribed fires, appropriate management of livestock and wild herbivores, tree cutting and shrub removal, invasive species control, and the reintroduction of native grasses and forbs via seeding or transplants. However, additional research for improved TGB restoration is needed. This article aims to identify ecological research priorities for TGB restoration. The following points are crucial to scale up TGB restoration and meet the challenges of the UN Restoration Decade. Research should focus on: disentangling the reasons why TGB are often undervalued and misunderstood; mapping TGB restoration opportunities; identifying regions where TGB and other biomes naturally exist as alternative stable states; recognizing areas with natural regeneration potential to avoid unnecessary intervention; restoring soil conditions; disentangling factors driving low seed quality, determining germination requirements and developing vegetative propagation techniques for TGB species; disentangling the limiting factors and key ecological processes underlying seedling establishment and community assembly; improving and validating long‐term management to mimic natural disturbance regimes; setting the minimum attributes of desirable TGB in terms of structure, composition, functioning, and resilience; and improving monitoring of restoration outcomes. Such research has the potential to advance theory, policy, and practice in TGB restoration, ultimately resulting in long‐term benefits for people and nature in some of the more neglected ecosystems of our planet. [ABSTRACT FROM AUTHOR]

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 shortinterval 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. [ABSTRACT FROM AUTHOR]

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.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.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. [ABSTRACT FROM AUTHOR]

Fire is a frequent disturbance in the Cerrado and is one of the major factors affecting vegetation structure and diversity. Fire events open gaps within the herbaceous layer and increase temperature fluctuation in the soil surface. In addition to being an important environmental filter for germination, fire is a germination cue for species with physiological dormancy. This study aimed to evaluate the germination of native grasses, using daily temperature fluctuations and heat shock to overcome physiological dormancy in native grasses. We also evaluated seed longevity after dispersal for some species. We conducted the daily temperature fluctuation experiments on seeds of ten native grass species, which were collected and then placed in germination chambers simulating thermal fluctuation throughout the day (19–55°C). We also subjected seeds to different heat-shock treatments: 100°C for 1 min, 100°C for 3 min and 200°C for 1 min. To determine seed longevity, we stored seeds for 6 and 12 months after collection and then set them to germinate (27°C, 12/12 h light). Non-germinated seeds from all experiments were tested for viability. Most species had low longevity and germination percentages. Those that had physiological dormancy were stimulated to germinate when exposed to temperature fluctuations. One species resisted temperatures up to 200°C. For all other species, neither treatment affected germination percentages. Our results indicate the importance of these environmental filters for seedling recruitment of these species, considering the low longevity and the presence of physiological dormancy. [ABSTRACT FROM AUTHOR]

Background and Aims In many flammable ecosystems, physically dormant seeds show dormancy-break patterns tied to fire, but the link between heat shock and germination in the tropical savannas of Africa and South America remains controversial. Seed heat tolerance is important, preventing seed mortality during fire passage, and is usually predicted by seed traits. This study investigated the role of fire frequency (ecological effects) and seed traits through phylogenetic comparison (historical effects), in determining post-fire germination and seed mortality in legume species of the Cerrado, a tropical savanna–forest mosaic. Methods Seeds of 46 legume species were collected from three vegetation types (grassy savannas, woody savannas and forests) with different fire frequencies. Heat shock experiments (100 °C for 1 min; 100 °C for 3 min; 200 °C for 1 min) were then performed, followed by germination and seed viability tests. Principal component analysis, generalized linear mixed models and phylogenetic comparisons were used in data analyses. Key Results Heat shocks had little effect on germination, but seed mortality was variable across treatments and species. Seed mortality was lowest under the 100 °C 1 min treatment, and significantly higher under 100 °C 3 min and 200 °C 1 min; larger seed mass decreased seed mortality, especially at 200 °C. Tree species in Detarioideae had the largest seeds and were unaffected by heat. Small-seeded species (mostly shrubs from grassy savannas) were relatively sensitive to the hottest treatment. Nevertheless, the presence of physical dormancy helped to avoid seed mortality in small-seeded species under the hottest treatment. Conclusions Physical dormancy-break is not tied to fire in the Cerrado mosaic. Heat tolerance appears in both forest and savanna species and is predicted by seed traits (seed mass and physical dormancy), which might have helped forest lineages to colonize the savannas. The results show seed fire responses are better explained by historical than ecological factors in the Cerrado, contrasting with different fire-prone ecosystems throughout the world. [ABSTRACT FROM AUTHOR]

Despite growing recognition of the conservation values of grassy biomes, our understanding of how to maintain and restore biodiverse tropical grasslands (including savannas and open‐canopy grassy woodlands) remains limited. To incorporate grasslands into large‐scale restoration efforts, we synthesised existing ecological knowledge of tropical grassland resilience and approaches to plant community restoration. Tropical grassland plant communities are resilient to, and often dependent on, the endogenous disturbances with which they evolved – frequent fires and native megafaunal herbivory. In stark contrast, tropical grasslands are extremely vulnerable to human‐caused exogenous disturbances, particularly those that alter soils and destroy belowground biomass (e.g. tillage agriculture, surface mining); tropical grassland restoration after severe soil disturbances is expensive and rarely achieves management targets. Where grasslands have been degraded by altered disturbance regimes (e.g. fire exclusion), exotic plant invasions, or afforestation, restoration efforts can recreate vegetation structure (i.e. historical tree density and herbaceous ground cover), but species‐diverse plant communities, including endemic species, are slow to recover. Complicating plant‐community restoration efforts, many tropical grassland species, particularly those that invest in underground storage organs, are difficult to propagate and re‐establish. To guide restoration decisions, we draw on the old‐growth grassland concept, the novel ecosystem concept, and theory regarding tree cover along resource gradients in savannas to propose a conceptual framework that classifies tropical grasslands into three broad ecosystem states. These states are: (1) old‐growth grasslands (i.e. ancient, biodiverse grassy ecosystems), where management should focus on the maintenance of disturbance regimes; (2) hybrid grasslands, where restoration should emphasise a return towards the old‐growth state; and (3) novel ecosystems, where the magnitude of environmental change (i.e. a shift to an alternative ecosystem state) or the socioecological context preclude a return to historical conditions. [ABSTRACT FROM AUTHOR]

Copyright of Biotropica is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Questions Grasslands are usually neglected as potential carbon stocks, partially due to the lack of studies on biomass and carbon dynamics in tropical grasslands. What is the importance of Brazilian tropical wet grasslands as carbon sinks? Does fire frequency and season affect biomass and carbon allocation in Brazilian wet grasslands? Location Wet grasslands, tropical savanna, Jalapão, Tocantins, northern Brazil. Methods We determined biomass above- and below-ground, estimated carbon stocks in biennially burned plots ( B2) and plots excluded from fire for 4 yr ( B4). Moreover, we determined biomass in both rainy and dry seasons. Samples were 0.25 m × 0.25 m × 0.2 m (eight samples per treatment, applying a nested design, total of 48 samples). The biomass was classified in above-ground graminoids, forbs and dead matter, and below-ground roots and other below-ground organs. We used ANOVA to compare variables between treatments and seasons. Results More than 40% of the total biomass and carbon stocks were located below-ground, mostly in roots. A high proportion of dead biomass ( B4) was found in the above-ground material, probably due to low decomposition rates and consequent accumulation over the years. Although these grasslands do not experience water stress, we found significant evidence of resource re-allocation from below-ground organs to the above-ground biomass in the rainy season. Conclusions We found more dead biomass in the rainy season, probably due to low decomposition rates, which can increase fire risk in these grasslands during the following dry season. These tropical wet grasslands stored high amounts of carbon (621 to 716 g C.m−2), mostly in the roots. Thus, policymakers should consider tropical grasslands as potential carbon stocks, since they are one of the most threatened and unprotected ecosystems in Brazil. [ABSTRACT FROM AUTHOR]

• Post-fire flowering is an underused fire-adaptive trait in flammable ecosystems • We present a database with >400 species from the Cerrado showing post-fire flowering • Most species showed to be fire-stimulated, mostly eudicots • Fire-stimulated flowering was found mostly in forb and shrub species. 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. [ABSTRACT FROM AUTHOR]

• Fire frequency affects the fuel load and distribution in Cerrado's open savannas. • The dead fuel and fuel moisture are the major factors influencing fire intensity. • Annual fires are of lower intensity, temperatures, and residence time than biennial. • Bare soil percentage and dead fuel cover have a major effect on fire parameters. Fire is an environmental factor that helps in shaping plant communities by influencing their structure and function. Frequency is an important component of the fire regime. In tropical savannas, fire frequency is high, mostly owing to the high production and accumulation of fuel, which mainly comprising grasses, the dominant growth form in the Cerrado (Brazilian savanna) open physiognomies. We evaluated how the quantity, quality, and horizontal and vertical distribution of fuel influence fire behavior. We performed fire experiments with different fire frequencies (annual and biennial, from 2013 to 2017) in open savannas of the Cerrado (Central Brazil). Before each experimental fire, the quantity and distribution of the fuel as well as the moisture content and estimated the percentages of bare soil, dead biomass, and grass cover in the community were evaluated. During the experiments, we measured wind speed, air temperature, and fire behavior parameters, such as flame height, fire propagation rate, flame temperature, and residence time of the fire. Finally, we calculated fire intensity. Annually burned plots showed a lower fuel load and higher percentages of bare soil than biennially burned plots. Regarding the fire parameters, the intensity, flame height, maximum temperatures, and residence time were lower in the annually burned plots than in biennially burned plots. After four years of fire treatment, the annual fire frequency changed the vegetation structure, and the fire parameters responded to these changes. Thus, we conclude that the fuel load distribution influences fire behavior alongside the quantity of fuel in open savannas. The percentage of soil covered by each of the community structural components influences fire temperatures and residence time, which in turn affects fire severity. These findings allow for a more precise evaluation of the fire effects on plant communities facing fire behavior and help in developing better management plans. [ABSTRACT FROM AUTHOR]

One of the major threats to tropical savannas globally is the invasion by alien grasses. In systems frequently disturbed, individuals can be recruited from the seed bank, and areas under natural regeneration can be more easily invaded when exotic newcomers are in the system, including the presence of invasive propagules in the soil seed bank. This study analyzed the dynamics of the soil seed bank in invaded and non-invaded areas of open savannas elucidating the potential of grass regeneration from the seed bank. Soil samples were collected in areas with different invasive grasses: Urochloa brizantha (Hochst. ex A. Rich.) R.D.Webster – synonym Brachiaria brizantha (Hochst. ex A. Rich.) Stapf, Melinis minutiflora Beauv. and areas with native vegetation. Soil seed bank was assessed using two techniques: seed counting and seedling emergence. Dominant species in each area influenced the seed bank composition, showing the highest densities from April to September. In invaded areas, the seed bank was composed mainly of invasive grasses that contributed to 98% (670 ± 382 seeds.m−2) of total seeds. In non-invaded areas, the soil seed bank presented the highest density (65%, 135 ± 38 seeds.m−2) of native species. However, the presence of invasive grasses was significant, with 35% of the total seeds belonging to U. brizantha. Although non-invaded areas have a higher potential for regeneration by native grasses, the presence of invasive grasses in the seed bank is an indication that the invasive species is already in the system and changes in the aboveground cover could accelerate the invasion process. Early management efforts towards establishing and/or established invasive species before seed dispersal could help reduce the soil seed bank load and should be carried out to control and avoid the establishment of African grasses, since they can dominate the seed bank in non-invaded areas if they are present in neighboring areas, affecting the dynamics of plant communities. • The soil seed bank in invaded areas is dominated mainly by invasive species. • Invasive species impeded on the establishment of native species. • Seed density of native species was higher than 50% only in non-invaded areas. • Invasive species' propagules were present in areas with native vegetation. • Management of seed bank should be targeted to avoid invasive species from re-seeding. [ABSTRACT FROM AUTHOR]

Invasive grasses are a threat to some tropical savannas, but despite being fire-prone ecosystems, little is known about the relationships between fire season, climatic conditions and invasive species on these systems. We evaluated the response of the perennial invasive grasses Melinis minutiflora and Urochloa brizantha to three fire seasons in an open tropical savanna in South America: Early-Dry (May), Mid-Dry (July) and Late-Dry (October) in relation to unburned Controls. Moreover, we investigated how these responses were influenced by precipitation and extreme air temperatures. We hypothesized that biomass of both species would be reduced by fires during their reproductive period and that climatic conditions would affect them equally. We conducted prescribed burns on 15 × 15 m plots (4 plots x 4 treatment x 2 invasive species = 32 plots) in 2014. We sampled the biomass before the burn experiments and for the next two years (five 0.25 m2 samples/plot). Our experiments revealed that the fire season did not influence the abundance of either species. However, the two species responded differently to fire occurrence: M. minutiflora decreased whereas U. brizantha was not affected by fires. Early-Dry and Late-Dry fire treatments enhanced the replacement of M. minutiflora by U. brizantha. We found that the influence of precipitation depended on the species: it reduced M. minutiflora but increased U. brizantha abundance. Lower monthly minimum temperatures decreased the abundance of both species. It directly reduced live M. minutiflora and increased dead U. brizantha biomass. Monthly maximum temperatures affected the invasive grasses by reducing live M. minutiflora. Since tropical savannas are predicted to face climatic instability and that climate influences the differential response of invasive species, the management of invaders should consider both the identity of the target species and the possible interactions with other invasive species. Moreover, it is essential to keep an adaptive management approach to face the uncertainties that climate change may pose to biodiversity conservation. • Disturbance regime must focus into the target invasive grass species. • Managers should be aware of the turnover in dominant invasive species. • Climate distinctly affect management's results due to its influence on invasive species. • Climate change should be considered in future management plans for control of invasive species. [ABSTRACT FROM AUTHOR]

• Fire is usually linked to negative impacts and thus, it is considered to be the "bad guy". • Wildfires are usually viewed as destructive, reinforcing the negative view of fire from the general public. • Fire is an important ecological and evolutionary factor in several ecosystems in the world. • Fire affects differently fire-sensitive ecosystems from fire-prone ecosystems.•When, where and how fire occurs should be considered for understanding its effects on ecosystem diversity and services. Much distortion about the real role of fire in different ecosystems exists, mostly because fire events attract media attention, usually focusing on the negative aspects of fire. In the perception of the general public, fire events are usually linked to disasters that affect humans in several ways, from losses of lives to negative effects on human well-being. However, while some ecosystems are fire-sensitive and fire will thus bring more negative than positive effects (e.g. in tropical rain forests), other systems are fire-prone and depend on fire in their existence and ecological characteristics (e.g. in savannas). In this paper, I show the different sides of fire, trying to elucidate its evolutionary and ecological role in fire-prone ecosystems and the consequences of wildfires in fire-sensitive ecosystems. Finally, I make a case for the need to debate how the misinterpretation of the role of fire as being always the "bad guy" can threaten fire-prone, but protect fire-sensitive vegetation. [ABSTRACT FROM AUTHOR]

• Developing a specialized organ belowground is not traded by aboveground bark production. • Plants spreading laterally produce more bark aboveground than those persisting on spot. • Species persisting fire on spot are often smaller and multi-stemmed. Two key strategies enable woody species persistence and survival in fire-prone ecosystems after fire: the aboveground protection of stems and buds by thick bark and the allocation of biomass belowground to specialized bud bearing storage organs – both strategies allowing plants to resprout new branches after the aboveground parts are damaged by fire. Here we investigate whether those two strategies can be combined with each other. We compared 24 woody species from the Cerrado (tropical savannas from Brazil) and analyzed their underground storage organs (USOs) in relation to their aboveground bark production and aerial bud protection – two key traits allowing species to first survive and then persist after fire – together with plant potential height. We then compared if bark growth rate, aerial bud protection and plant potential height are linked to the ecological function of the underground storage organs (on spot persistence vs clonal growth through lateral spreading). Species with woody rhizomes (capable of spreading laterally) better protected their aboveground stems with thicker bark when compared to species with xylopodium and root-crown organs (adapted for on spot basal resprouting). A clear division was found concerning how well species are protecting their aerial buds and the type of underground storage organ, with species spreading laterally displaying a greater aerial bud protection. The results suggest that the presence of a specialized organ belowground does not appear to be mutually exclusive with producing thick bark on aboveground stems. It does exist, however, a different expression of bark production and aerial bud protection between species displaying lateral spread and those persisting on spot, suggesting the existence of a trade-off between above- and belowground strategies in species displaying on spot persistence. This highlights that Cerrado species can combine different fire-survival strategies, further questioning which fire conditions promote each strategy and their combination and in which cases trade-offs occur. [ABSTRACT FROM AUTHOR]

In Brazil, the country with the highest plant species richness in the world, biodiverse savannas and grasslands – i.e., grassy ecosystems, which occupy 27% of the country – have historically been neglected in conservation and scientific treatments. Reasons for this neglect include misconceptions about the characteristics and dynamics of these ecosystems, as well as inconsistent or regionally restricted terminology that impeded a more adequate communication about Brazil's savannas and grasslands, both within the country and internationally. Toward improved communication and recognition of Brazil's diversity of ecosystems, we present the key drivers that control the main types of grassy ecosystems across Brazil (including in regions of the country where forests dominate). In doing so, we synthesize the main features of each grassy ecosystem in terms of physiognomy and ecological dynamics (e.g., relationships with herbivores and fire). We propose a terminology both for major grassland regions and for regionally relevant vegetation physiognomies. We also discuss terms associated with human land management and restoration of grassy ecosystems. Finally, we suggest key research needs to advance our understanding of the ecology and conservation values of Brazil's grassy ecosystems. We expect that a common and shared terminology and understanding, as proposed here, will stimulate more integrative research that will be fundamental to developing improved conservation and restoration strategies. [Display omitted] • 27% of Brazil's natural vegetation are grasslands and savannas. • Brazil's grassy ecosystems remain undervalued in conservation: 46% have been converted to other uses. • Eleven major regions of grassy ecosystems can be identified across Brazil. • Disturbances (e.g., fire, grazing) are key determinants of Brazil's grassy ecosystems. • Efforts are needed to map grassy ecosystems and develop conservation strategies. [ABSTRACT FROM AUTHOR]

The article discusses the highlights of a workshop about bud banks and below-ground plant organs held in Sao Paulo, Brazil in May 2019. Topics discussed include the significant role of below-ground structures in regeneration strategies of plant communities following disturbances, the resilience of South African grasslands and savannas to disturbances, and the management and conservation of ecosystems.