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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.
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... Moreover, we assessed short-term structural changes after frost (3 months after frost) in richness, density, and ground cover (native grass cover, nongrass cover, litter cover and bare soil). In particular, we aimed at evaluating how frost impacts the ground layer of the Cerrado and whether its short-term effects are analogous to the effects of fire (described for the same area in Pilon et al. 2021), as already reported for the tree layer (Brando and Durigan 2004;Whitecross et al. 2012;Hoffmann et al. 2019). ...
... At each gradient there was one plot in grassland (campo cerrado), one plot in savanna (cerrado sensu stricto), and one plot in forest (cerradão) (Fig. S1). These are permanent control plots (unburned) belonging to a larger experiment monitoring long-term changes in vegetation due to fire suppression and to different fire management approaches (Abreu et al. 2017;Durigan et al. 2020;Pilon et al. 2021). We sampled the ground-layer plant community in 40 1 m 2 subplots (1 m × 1 m) systematically distributed within each of the nine 0.1 ha plot (20 m × 50 m), totaling 360 1 m 2 subplots. ...
... However, we found contrasting results for the ground layer vegetation, suggesting that frost effects are antagonistic to the effects of fire. Increases in litter deposition and reductions in bare soil and in plant density in open vegetation types sharply contrast with the structural changes reported for the ground-layer community in the first months after fire (Coutinho 1990;Fidelis et al. 2012;Pilon et al. 2021). Even though frost has been shown to be more intense in open than in closed vegetation types and leads to high mortality and topkill of individuals (Silberbauer-Gottsberger et al. 1977;Filgueiras and Pereira 1989;Hoffmann et al. 2019), similarities with the effects of fire end in these aspects. ...
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.
... In this regard, given that disturbance frequency and severity have a direct influence on the size of bud banks within a community (Bellingham and Sparrow 2000;Fidelis et al. 2014;Klimešová et al. 2018aKlimešová et al. , 2019, a highly diverse belowground bud bank system will ensure the maintenance of a viable bud bank and contribute to guaranteeing successful regeneration after a fire event (Buisson et al. 2019;Ott et al. 2019). As belowground resprouting is the principal process whereby savanna plants regenerate (Bond and Midgley 2001;Clarke et al. 2013;Pilon et al. 2021;Zupo et al. 2021), and given that these ecosystems are resilient to fire (Keeley and Pausas 2019), changes in fire frequency (both an increase in fire frequency and fire exclusion) can have marked detrimental effects, including diminished system resilience, losses in ecosystem services, and shifts to alternative ecosystem states (Parr et al. 2014;Keeley and Pausas 2019;Buisson et al. 2019). ...
... Similar to other tropical savannas, the Cerrado is dominated by C4 grasses characterized by a rapid accumulation of biomass during the warm rainy summers, which during the dry winter months is transformed to an abundant source of readily flammable material (Miranda et al. 2009). Thus, fire events in this system are frequent, although generally of low intensity, consuming most of the aboveground biomass (Miranda et al. 2009;Rissi et al. 2017;Rodrigues et al. 2021;Silva et al. 2021), and ensuring the renewal of the herbaceous layer that re-sprouts after these events (Pilon et al. 2021;Zupo et al. 2021). In contrast, the suppression of fire, which consequently will promote an increase of dead aboveground biomass, can lead to a heightened probability of uncontrollable wildfires that can have significant detrimental effects on plant community regeneration (Durigan and Ratter 2016;Fidelis et al. 2018). ...
... Since resprouting is the major regeneration strategy after fire in tropical savannas (Pilon et al. 2021;Zupo et al. 2021) and the belowground bud bank plays an important role in open areas, we aimed to investigate if different fire frequencies and fire exclusion periods will distinctively affect the belowground bud bank traits related to persistence and regeneration strategies in the herbaceous layer of tropical savannas. To elucidate the effects of fire on the belowground bud bank traits, we investigated two open savanna communities in the Cerrado, which differ concerning fire regime, considering time since last fire and fire frequency, to answer the following question: will fire exclusion affect the belowground bud bank density and belowground organ composition, affecting thus, post-fire regeneration? ...
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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.
... To categorize the species, we followed Abreu et al. (2017), Cava et al. (2020), and Durigan et al. (2018). We categorized the species by their regeneration strategy as seeders (regeneration mainly by seed germination) and resprouters (regeneration mainly by resprouting), according to Pilon et al. (2020b). ...
... Additionally, the inherent fire suppression of silviculture, thick pine litter, and damage to underground organs by soil tillage when planting pine also play a vital role in the loss of herbaceous species Brewer et al., 2018;Zaloumis and Bond, 2011). The natural propagation of species in the ground layer of Brazilian savannas is mainly via regrowth, with low potential for recovery by seed dispersal (Fidelis et al., 2014;Hoffmann, 1999;Moraes et al., 2016;Pausas et al., 2018;Pilon et al., 2020b). Thus, once eliminated by pine plantation, the native ground layer will hardly recover naturally, even after clearcutting Zanzarini et al., 2019). ...
... Cerrado remnants are threatened by land conversion (Strassburg et al., 2017) and will hardly act an effective source of propagules where their presence is rare (Zanzarini et al., 2020). Additionally, the contribution of nearby cerrado remnants to colonize the areas to be restored tends to be low Cava et al., 2020), because the recovery of savanna species in the ground layer is mainly achieved via resprouting (Pilon et al., 2020b). Thus, if no potential for natural regeneration is detected after pine clearcutting, further restoration techniques will be necessary to restore and maintain the typical Brazilian savanna and its expected ecosystem functioning (Ferreira et al., 2015;Pilon et al., 2017;Sampaio et al., 2019). ...
Article
Planting tree monocultures in Brazilian savannas is a common practice for wood production. However, afforestation and fire suppression have caused significant ecological changes and biodiversity loss in the Cerrado region. Restoring these modified systems to their pre-plantation states remains a considerable challenge. In this study, we compared the recovery of savanna vegetation after afforestation in areas managed with three restoration strategies: (i) old pine plantation stands that are not managed anymore (control), (ii) passive restoration (natural regeneration after pine clearcutting), and (iii) native tree planting (native tree seedlings planted at high density after pine clearcutting). To compare the outcome of each strategy to native ecosystems that were never plantations, we sampled a cerrado sensu stricto (the desired restoration target), and a cerradão (the local alternative state when savannas are fire-suppressed). Fifteen years after applying the restoration approaches, we assessed the structure, richness, and composition of the plant communities. For the analyses, we separated the upper layer (woody native species, diameter at breast height (DBH) ≥ 5 cm) and ground layer (woody species with height ≥ 50 cm and DBH < 5 cm, and subshrubs and herbs), and distinguished savanna species from forest and generalist species. The results showed that both passive restoration and native tree planting restored the structure, richness, and composition of the upper layer, reaching the values of the cerrado sensu stricto. In contrast, in all treatments, the ground layer lacked the subshrubs and herbs typical of undisturbed savannas, with communities appearing similar to cerradão. Generalist species dominated all layers, and tree canopy cover in the treatments (mean values from 64.7% to 83.0%) ranged from 2.4 to 3 times the cover value recorded in the cerrado sensu stricto (mean of 28%). Pine clearcutting, independent of whether it was followed by native tree planting, improved the recovery of savanna woody vegetation. Therefore, we suggest that pine clearcutting, but not tree planting, is necessary to restore the woody community. Despite these apparently positive restoration outcomes for the woody plant community, it is important to note that after 15 years of passive restoration, communities are turning into low-diversity forests composed of generalist species and lacking savanna species in the ground-layer community. We therefore suggest that restoration of cerrado sensu stricto after pine clearcutting will require controlling woody encroachment, via prescribed fire or mechanical tree thinning, and planting of savanna subshrubs and herbs, rather than trees.
... In fire-prone ecosystems plant species may have fire-related traits such as bud protection (Charles-Dominique et al., 2015;Pausas et al., 2018), germination stimulated by temperature and smoke (Moreira et al., 2010;Ramos et al., 2016;Zirondi et al., 2019) and post-fire flowering (Lamont and Downes, 2011;Pyke, 2017;Zirondi et al., 2021). These traits can influence competitive abilities and result in different patterns of recruitment and mortality in populations (Bond and Keeley, 2005;Gignoux et al., 1997;Pilon et al., 2021). However, the removal of biomass can also be caused by other types of disturbance, such as mowing. ...
... Fynbos is known to comprise a great number of obligate seeder species (more than 50%, Cowling et al., 2004), whilst in Tallgrass Prairie seedling recruitment is less than 1% (Benson and Hartnett, 2006). In the Cerrado, resprouting is the main regeneration strategy after fire and obligate seeder species are rare (Pilon et al., 2021, Zupo et al. 2021. ...
... Resprouters have several advantages in post-fire environments over seedlings: the presence of protected and/or belowground buds allows them to resprout rapidly after biomass removal (Charles-Dominique et al., 2015;Clarke et al., 2013); the presence of storage organs permit resource allocation for regrowth (Bellingham and Sparrow, 2000;Pausas et al., 2018;Pilon et al., 2021); faster growth (Bond and Midgley, 2001); competitive benefit (Vesk et al., 2004); rapid recovery of reproductive capacity Lamont and Downes, 2011;Pilon et al., 2021). Moreover, resprouters do not depend on seedling recruitment from a dormant seed bank or seed rain (Bond and Midgley, 2012;Ojeda et al., 2005), a better water status (Clemente et al., 2005;, guaranteed plant persistence in disturbed environments (Ojeda et al., 2005;Vesk et al., 2004) and finally the maintenance of current generation and niche (Bellingham and Sparrow, 2000;Bond and Midgley, 2001). ...
Article
Fire is an important ecological and evolutionary factor affecting plant communities worldwide. After fire, plants can resprout or germinate and systems may differ according to their post-fire regeneration strategies. Therefore, the main aim of this study was to analyze the most important regeneration strategies in Brazilian subtropical grasslands. Moreover, we point out differences in seedlings and resprouts between burned and mowed plots, in order to detect differences in community response to different types of disturbance. We analyzed seven pairs of plots (burned and mowed) in two sites with different fire histories: FB-frequently burned grasslands, and E-exclusion of fire for six years. After treatments, vegetation was described and seedlings and resprouts were sampled. Plants were later grouped in species groups for statistical analyses. Less than 20% of established plants came from seedlings and only three species were obligate seeders. Most species resprouted after treatments. Number of seedlings and resprouts did not show significant differences between treatments in each site. However , a higher number of species with seedlings was observed in site FB. More new species with seedlings established in burned than mowed plots in site FB. Seedlings of forbs recruited more in burned than in mowed plots. Resprouter was the most important strategy for all studied species groups, particularly for graminoids. Our results show the importance of vegetative regeneration in the studied subtropical grasslands, independently of disturbance, and the importance of fire for the establishment of new species, maintaining thus, plant diversity.
... The Cerrado, a phytogeographic domain, composed of tropical grasslands (campo limpo), savannas (campo sujo, campo cerrado, and cerrado sensu stricto), and seasonal forest (cerradão) (Batalha 2011), comprises disturbanceprone ecosystems, where it is possible to find several vegetative regeneration strategies Pilon et al. 2021;Zupo et al. 2021). It is considered a biodiversity hotspot, with more than 7000 botanical species with high levels of endemism (Franco et al. 2014). ...
... Myrtaceae is one of the most dominant botanical families in Cerrado vegetation, including 21 genera and more than 344 species (de Mendonça et al. 2008;Fiaschi and Pirani 2009). From a wide perspective, this family has one of the highest resprouting potential through belowground organs after environmental disturbances (Burrows et Although there is information about the vegetative regeneration strategies of Myrtaceae species from the Cerrado (da Silva et al. 2020;Pilon et al. 2021), little is known about the belowground bud-bearing organs which contribute to regeneration after long-term suppression due to pine cultivation (de Abreu and Durigan 2011). ...
... Strategies of species of herbs and shrubs that use underground structures for resprouting and enable to recolonise post-fire have received considerable attention regarding plant community restoration (Pilon et al. 2021). Further, some methods using belowground organs fragments (Ferreira et al. 2015;Pilon et al. 2018) have been useful in savanna restoration. ...
Article
This study was carried out in a Cerrado (the largest savanna in the Neotropics) area where pine plantations, introduced in the 1970s, were removed by clear cutting of the trees and burning of the remaining material. After the removal and burning, some native shrub species resprouted. Since resprouting is dependent on buds that can be in the belowground bud-bearing (BBB) organs containing reserves, we selected three resprouting Myrtaceae species for analysis of morphology and anatomy of their BBB organs, to determine which compounds could be accumulated and to investigate the bud protection features. Standard histological techniques were used to analyse the BBB organs. The belowground bud bank at a depth of 10cm was determined. Nonstructural carbohydrates, total phenolics, and flavonoids were quantified on the roots. The large size of BBB organs suggest that these species were present before plantation establishment and survived plantation management treatments. All species produced a large number of axillary buds. All BBB organs exhibited significant lignification and stored starch and phenolic compounds in the parenchyma cells. The protective features and the storage of reserves associated with the bud-bank allowed the survival and subsequent resprouting of these species, contributing to the regeneration of this disturbed area.
... Fire modifies C flux balance by affecting both taxonomic (Abreu et al., 2017;Finn et al., 2013) and functional diversity (De Deyn et al., 2008;Hoffmann et al., 2012;Keeley et al., 2011). Fire maintains species richness and fitness in tropical savanna ecosystems Pilon et al., 2021a). Thus, fire can influence ecosystem function (Petchey and Gaston, 2006) by filtering species with functional traits that are key to ensure higher plant fitness and are related to C cycling in such ecosystems (Bardgett et al., 2014;De Deyn et al., 2008). ...
... Our results also showed a higher NEE and total SOC with fire whereas soil respiration declined i.e., soil C efflux (C output), corroborating the higher C input in burned compared to unburned areas. While fire enhanced functional diversity, our results did not support positive fire effects on taxonomic diversity as found in other studies (Abreu et al., 2017;Gomes et al., 2020;Pilon et al., 2021a). Although our results support direct Fig. 2. Effect of fire on (A) system function to carbon balance considering total soil carbon content (SOC), rates of net ecosystem exchange (NEE), ecosystem evapotranspiration (ET), ecosystem water use efficiency (eWUE) and soil respiration, (B) system structure considering total aboveground biomass as well as live and dead biomass, and total belowground biomass in addition to fine root, coarse root and belowground organs biomass, total aboveground biomass:belowground biomass ratio and live aboveground biomass:fine root biomass, and litter biomass; and (C) system diversity considering plant community taxonomic diversity (i.e. ...
... Fast regeneration in open savanna is primarily ensured by the quick regeneration of grass species that produce newly photosynthetic leaves (Pilon et al., 2021a), since grasses are the most resilient growth form to fire in savannas (Bond, 2004). Graminoids morphological architecture that protects buds and meristems ensures fast recovery (Linder et al., 2018;Pilon et al., 2021a;Wigley et al., 2020), being also the most flammable element of the fuel load (Simpson et al., 2016). ...
Article
Fire is an evolutionary environmental filter in tropical savanna ecosystems altering functional diversity and associated C pools in the biosphere and fluxes between the atmosphere and biosphere. Therefore, alterations in fire regimes (e.g. fire exclusion) will strongly influence ecosystem processes and associated dynamics. In those ecosystems C dynamics and functions are underestimated by the fire-induced offset between C output and input. To determine how fire shapes ecosystem C pools and fluxes in an open savanna across recently burned and fire excluded areas, we measured the following metrics: (I) plant diversity including taxonomic (i.e. richness, evenness) and plant functional diversity (i.e. functional diversity, functional richness, functional dispersion and community weighted means); (II) structure (i.e. above- and below-ground biomass, litter accumulation); and (III) functions related to C balance (i.e. net ecosystem carbon dioxide (CO2) exchange (NEE), ecosystem transpiration (ET), soil respiration (soil CO2 efflux), ecosystem water use efficiency (eWUE) and total soil organic C (SOC)). We found that fire promoted aboveground live and belowground biomass, including belowground organs, coarse and fine root biomass and contributed to higher biomass allocation belowground. Fire also increased both functional diversity and dispersion. NEE and total SOC were higher in burned plots compared to fire-excluded plots whereas soil respiration recorded lower values in burned areas. Both ET and eWUE were not affected by fire. Fire strongly favored functional diversity, fine root and belowground organ biomass in piecewise SEM models but the role of both functional diversity and ecosystem structure to mediate the effect of fire on ecosystem functions remain unclear. Fire regime will impact C balance, and fire exclusion may lead to lower C input in open savanna ecosystems.
... These environmental shifts induced by woody plant encroachment seem to act as filters for the persistence of typical savanna species and may affect their survival since they may alter both resource availability (Carlos & Rossatto 2017;Rossatto et al. 2018) and aspects related to the regenerative ability (Hoffmann et al. 2004;Abreu et al. 2017). Savanna species persist and regenerate through seed germination and recruitment, vegetative spread, and/or resprouting after disturbance (Pilon et al. 2021a). Recruitment from seed is particularly dependent on environmental filtering; seed germination and postgermination development traits can influence community assembly and contribute to population growth and species persistence or even disappearance in changing environments (Keddy 1992;Donohue et al. 2010;Jim enez-Alfaro et al. 2016). ...
... Although there is less litter in a typical savanna than in an encroached savanna, much of the ground in a typical savanna is covered by plant litter and by an almost continuously layer of herbs and grasses (Ribeiro & Walter 2008;Costa et al. 2020). Fire serves to remove litter and consumes the ground layer plants, which favors the appearance of bare soil patches, often called vegetation gaps (Fidelis et al. 2012;Pilon et al. 2021a). There is evidence that these gaps can facilitate germination of some species by increasing temperature fluctuations and reducing competition with established plants (Daibes et al. 2017;Daibes et al. 2018;Dairel & Fidelis 2020). ...
... That is, all study species showed some degree of establishment limitation (sensu Grubb 1977;Muller-Landau et al. 2002). However, it is important to consider that many of the savanna species rely on asexual reproduction as the main mechanism for their regeneration strategy (Pilon et al. 2021a). Thus, we can only attest establishment limitation concerning those species in which regeneration from seeds takes a relevant place for their ecology. ...
Article
Woody plants have been encroaching into savannas on a global scale. Global climatic changes, along with changes to disturbance regimes, are considered to be the main drivers of this process. Particularly, many formerly open physiognomies of the Brazilian savanna have become encroached by woody species over the course of a few decades under fire suppression. In this scenario, many typical savanna species of the ground‐layer are reducing their above‐ground presence, possibly due to change in environmental filtering as a result of encroachment. Consequently, at encroachment sites, changes to microhabitats occur, such as less incident light to the soil surface, reduced red:far‐red ratios and soil surface temperatures, and increased litter deposition. These changes may hinder the regenerative capacity of ground‐layer savanna species. This study investigated the role of encroachment‐induced environmental changes as filters for the recruitment ability of ground‐layer savanna species. We examined the germination and seedling emergence of 12 species under controlled conditions, simulating natural aspects of encroached and non‐encroached sites of the Brazilian savanna. The germination and/or seedling emergence of all species examined were/was negatively affected by the simulated environmental filtering changes. Increased litter deposition reduced seedling emergence more than temperature and light affected germination. Filtering changes caused by woody encroachment represent a bottleneck for the regeneration from seeds of ground‐layer savanna species. Filtering changes by woody encroachment is one of the underlying mechanism explaining changes in species presence in savannas, and it ultimately leads to positive feedback loops wherein woody encroachment begets more woody encroachment. Abbreviated abstract summarising the article: We examined the germination responses of 12 savanna species under controlled conditions, simulating natural aspects of encroached and non‐encroached sites of a Brazilian savanna. The germination of all species examined was negatively affected by the simulated environmental filtering changes mainly by the increased litter deposition. Environmental filtering changes caused by woody encroachment represent a bottleneck for regeneration from seeds of ground‐layer savanna species.
... In the Cerrado, frequent fires have been present for at least four million years (Simon et al., 2009) and fire regimes are characterized by frequent (~3 to 5 years) surface fires of relatively low intensity fueled by grasses (Coutinho, 1982;Kauffman et al., 1994;Miranda et al., 2002Miranda et al., , 2009Pereira-Junior et al., 2014;Alvarado et al., 2017;Rissi et al., 2017). After fires, many woody and herbaceous species resprout from dormant buds (Coutinho, 1990;Medeiros & Miranda, 2008;Pausas et al., 2018;Pilon et al., 2020), but the role of post-fire seed germination as a regeneration mechanism in Cerrado remains unclear. Even though post-fire seed germination has been observed in grasslands and savannas that undergo surface fires (Overbeck & Pfadenhauer, 2007;Clarke et al., 2015;Ramos et al., 2019;Pilon et al., 2020), studies evaluating seed responses after heat shocks in the Cerrado have done so with few species Le Stradic et al., 2015;Fichino et al., 2016) or are restricted to certain clades (Ramos et al., 2016;Daibes et al., 2019;Zirondi, José, et al., 2019;Dairel & Fidelis, 2020), hindering the understanding of general postfire regeneration mechanisms at the community scale. ...
... After fires, many woody and herbaceous species resprout from dormant buds (Coutinho, 1990;Medeiros & Miranda, 2008;Pausas et al., 2018;Pilon et al., 2020), but the role of post-fire seed germination as a regeneration mechanism in Cerrado remains unclear. Even though post-fire seed germination has been observed in grasslands and savannas that undergo surface fires (Overbeck & Pfadenhauer, 2007;Clarke et al., 2015;Ramos et al., 2019;Pilon et al., 2020), studies evaluating seed responses after heat shocks in the Cerrado have done so with few species Le Stradic et al., 2015;Fichino et al., 2016) or are restricted to certain clades (Ramos et al., 2016;Daibes et al., 2019;Zirondi, José, et al., 2019;Dairel & Fidelis, 2020), hindering the understanding of general postfire regeneration mechanisms at the community scale. Moreover, few studies addressing fire-related seed responses in the Cerrado have taken into account plant resprouting ability following experimental fires (but see Pilon et al., 2020). ...
... Even though post-fire seed germination has been observed in grasslands and savannas that undergo surface fires (Overbeck & Pfadenhauer, 2007;Clarke et al., 2015;Ramos et al., 2019;Pilon et al., 2020), studies evaluating seed responses after heat shocks in the Cerrado have done so with few species Le Stradic et al., 2015;Fichino et al., 2016) or are restricted to certain clades (Ramos et al., 2016;Daibes et al., 2019;Zirondi, José, et al., 2019;Dairel & Fidelis, 2020), hindering the understanding of general postfire regeneration mechanisms at the community scale. Moreover, few studies addressing fire-related seed responses in the Cerrado have taken into account plant resprouting ability following experimental fires (but see Pilon et al., 2020). ...
Article
Aim Fire is a natural disturbance in many ecosystems throughout the world where plant populations can persist by the resprouting of individuals and/or by recruiting from seeds. We evaluated the post‐fire regeneration response for 41 coexisting species, including grasses, forbs, and shrubs, from an open Cerrado community (campo sujo) in Central Brazil. Location The study was conducted at the Reserva Natural Serra do Tombador (RNST) in Central Brazil. The vegetation of the study area is characterized by a continuous herbaceous layer dominated by grasses and scattered shrubs, which produces fine fuel loads that can burn frequently. Methods We examined both resprouting ability after experimental fires, accounting for bud location, and seed response to heat shocks caused by fire, where seeds were subjected to heat shocks of 100°C for one and three minutes, 200°C for one minute, and a control (untreated seeds). Results All species were able to resprout (R+) after fire, mainly from buds located in underground structures, but also from aerial and basal buds. Seeds of most species tolerated heat shocks of 100°C for one and three minutes, but heat treatments of 200°C decreased seed viability of nearly 50% of species. Seven species showed heat‐stimulated germination, all of which had dormant seeds. In sum, 81% of the community was classified as R + PT (resprouters with heat‐tolerant propagules) and 17% was R + PS (resprouters with heat‐stimulated propagules). The remaining 2% (one species) was classified as R + P‐, showing heat‐sensitive seeds. Conclusions Resprouting is the main post‐fire regeneration strategy in the Cerrado open savannas, while fire‐stimulated germination, although possible, is less common in comparison to other fire‐prone ecosystems. However, in Cerrado open savannas, heat tolerance is an important trait that enables germination when favorable conditions arise.
... The annual richness results may be an indicative of community resilience to disturbance and the post-burning vegetation recovery possibly due to adaptation strategies, such as the presence belowground organs and bud banks (APEZZATO- DA-GLÓRIA et al., 2008;BUISON et al., 2019;PILON et al., 2020). Resprouting (PAUSAS et al., 2018;PILON et al., 2020) and seed recruitment are also important post-fire regeneration mechanisms (SILVA et al., 2011;FIDELIS et al., 2014). ...
... The annual richness results may be an indicative of community resilience to disturbance and the post-burning vegetation recovery possibly due to adaptation strategies, such as the presence belowground organs and bud banks (APEZZATO- DA-GLÓRIA et al., 2008;BUISON et al., 2019;PILON et al., 2020). Resprouting (PAUSAS et al., 2018;PILON et al., 2020) and seed recruitment are also important post-fire regeneration mechanisms (SILVA et al., 2011;FIDELIS et al., 2014). The time of the year may have also influenced the results, as the type and the amount of the fuel load varies throughout the year (FIDELIS et al., 2013;RISSI et al., 2017) and many graminoids and herbs dry out the above-ground parts and allocate resources to underground organs in the dry season (FILGUEIRAS, 2002;FIDELIS et al., 2013;RISSI et al., 2017). ...
... In this work there was no significant difference between the two areas, but the monitoring was carried out only once a year, in the drought season. Some studies evidenced the importance of sampling throughout the year and observed that there is a trend of richness to approach pre-disturbance values in richness within a year after the fire (SILVA & NOGUEIRA, 1999;PILON et al., 2020). ...
Article
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Monitoring of vegetation on the herbaceous layer in a Cerrado sensu stricto in Planaltina (DF) was carried out eight times from 1988 to 1994 and in 2012, in two areas of 1.25 ha (Area 1, Area 2). Using the interception method on line, two transections of 100 m in length were defined, which were subdivided in sample units measuring one meter, totaling 200 units per area. In Area 1, prescribed burnings were applied in 1988, 1990 and in 1992. Area 2 was protected until July 1994, however an accidental fire hit the whole area in August the same year. Species of different habits up to a meter high were recorded in both areas. A number ranging between 92 and 134 species was observed from 1988 to 1994, and 115 species were recorded in 2012 in Area 1. Also, a number between 97 and 129 species was observed from 1988 to 1994, and 106 species were recorded in 2012 in Area 2. The results indicated the recovery and resiliency of the community after biennal burnnings. Biennal prescribed fires did not change the richness and diversity, but the community structure. The suppression of fire for 18 years did not promoted differences in the richness, but in the community diversity and structure. The exclusion of fire for 18 years also did not favored the floristic similarity between the two areas.
... 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). ...
... In such systems, belowground soil heating has been suggested to be the most useful parameter in predicting fire effects (Gagnon et al. 2015), given underground buds and seeds stored in the soil seed bank could be harmed when temperatures below the soil surface exceed a given lethal threshold (Neary et al. 1999;Stephan et al. 2010). Even though most species in Cerrado are resprouters and many resprout from underground buds (Pilon et al. 2021;Zupo et al. 2021), recruitment from seeds is still important and seeds dispersed in a given year need to survive fires to be able to germinate when environmental conditions are suitable (i.e., with the onset of the rainy season; Escobar et al. 2018). Therefore, temperatures reached in the soil are important to understand how fires could affect plant populations and communities. ...
... Although there are few seeders in Cerrado (Pilon et al. 2021;Zupo et al. 2021)-that is, species whose post-fire regeneration mechanism depends only on the recruitment of seeds stored in the seed bank (Pausas et al. 2004)-seeds of resprouting species that have been dispersed prior to a given fire episode need to survive the high temperatures caused by fires to ensure germination occurs when environmental conditions are suitable, usually with the onset of the rainy season (Escobar et al. 2018). Seeds from most Cerrado species can tolerate temperatures around 100°C (Fichino et al. 2016;Ramos et al. 2016;Zirondi et al. 2019;Daibes et al. 2019;Zupo et al. 2021; but see Paredes et al. 2018). ...
Article
Fire is a main disturbance structuring vegetation worldwide, but few studies have addressed differences in time since last fire and its relationship to fuel load characteristics and fire behavior in Neotropical savan-nas. We aimed to investigate fire behavior in a Cerrado open savanna of Central Brazil by conducting prescribed fires in areas with different fire-free intervals: one year (FI-1), two years (FI-2), and four years (FI-4). Specifically , we evaluated (1) the amount of live, dead, and total biomass (components of the fuel load); (2) fire behavior , including fire temperatures in three different heights (1 cm belowground, on the soil surface, and 50 cm aboveground), fire duration, residence time, fire intensity, rate of spread, and flame height; and (3) the relationship between soil heating, fuels, and fire by identifying the most important parameters driving soil heating. Total and dead fuel loads were greater in areas with longer fire-free intervals in comparison with areas burned the previous year, with the greatest increment to the fuel bed occurring in the first two years after fire. Greater fuel loads (consequently greater dead fuel loads) resulted in differences in belowground soil heating (-1 cm), where temperatures varied from 39 to 82°C in FI-2 plots and from 40 to 131°C in FI-4 plots; in FI-1 plots temperatures belowground varied from 29 to 68°C. Temperatures on the soil surface and 50 cm aboveground were also greater in plots with longer fire-free intervals, reaching over 400°C on the soil surface and exceeding 500°C 50 cm aboveground. Finally, amount of dead fuel was the best predictor of belowground soil heating, highlighting the importance of fuel loads, which is a key factor to be monitored in fire management plans of Cerrado open savannas.
... Changes in soil drainage can cause changes in its physicochemical and textural properties (Sigua et al. 2006), promoting encroachment by woody species and colonization by invasive species (Barbosa da Silva et al. 2016), and can also reduce the heterogeneity of microhabitats in the environment (Bleich et al. 2014). Although many studies show that fire frequency influences soil properties and vegetation, most of the studies on the effects of fire focus on dry savannas in the Cerrado (e.g., Silva and Batalha 2008;Pilon et al. 2021) and few have examined wet savannas (Araújo et al. 2013). ...
... Members of the family Poaceae are abundant in the Cerrado biome, predominantly in moist grasslands and in dry and moist savannas (Munhoz et al. 2008;Bijos et al. 2017;Souza et al. 2021). This growth form tends to form dense clusters or has rhizomes or stolons that increase the plants ability to establish themselves throughout the vegetation (Munhoz and Felfili 2006;Pilon et al. 2021). Besides, the fire suppression in the Cerrado favors woody species over herbaceous species (Durigan 2020), as well as found in the African savanna wet grassland (Luvuno et al. 2016). ...
Article
The vereda (Brazilian savanna palm swamp) has a distinguishable flora and high floristic beta diversity. The factors that influence dissimilarities among vereda floras have not been clearly elucidated. Here we investigated how key physicochemical soil factors modulate the species composition of this vegetation. Soil and plants were sampled from three veredas, species composition and diversity were compared among them. To investigate the effects of soil physicochemical properties on species richness and cover of each vereda, we fitted a linear mixed-effect model. The plant assemblages in the veredas diverged in terms of species composition but converged in two dominant species graminoids. We found significant differences in soil properties among the veredas, except in texture. Soil properties had significant effects on species richness and cover as a whole, and on richness and relative cover for the individual growth forms. Potential cation-exchange capacity alone negatively affected species richness, especially of graminoids and subshrubs. The cation-exchange capacity of soils and its complex interactions with phosphorus and organic matter were found to be the main drivers of species occurrence and vegetation cover in the veredas. The distinct flora of veredas is controlled by the interaction of species and its growth forms with soil filters.
... Moreover, the aboveground effects of these drivers (topkill, biomass removal, fuel provision and consumption) have an impact on the belowground makeup of these K E Y W O R D S belowground bud bank, climate seasonality, disturbance, frost in tropics, functional diversity, geoxyle, species diversity, tropical old-growth grassland, underground storage organ ecosystems at the community level, of which little is known. So far, a few studies have targeted the underground response of savanna tree species or that of geoxyles from the Cerrado (Appezzato-da- Glória et al., 2008;Pilon et al., 2021;Zupo et al., 2021) to herbivory, fire and soil properties. What is lacking are studies that relate the diversity and composition of Afrotropical geoxyles with their belowground functional traits, evolutionary ancestry, and environmental drivers. ...
... Multiple belowground functional types indicate that different persistence strategies co-occur (e.g. rhizomes for clonal propagation and tubers for high-capacity resprouting after disturbance), which is similar to findings from the Cerrado (Pilon et al., 2021). ...
Article
Aim Tropical old-growth grasslands are increasingly acknowledged as biodiverse ecosystems, but they are understudied in many aspects. Geoxyle species are a key component in many of these ecosystems, their belowground storage organs and bud banks are functionally diverse and contribute to the grasslands’ resilience. However, the drivers of the geoxyles’ evolution and (belowground) diversity are little understood. Thus, we combined analyses on the key aspects of diversity, belowground functionality, ancestry, and ecology of geoxyles to provide the first comprehensive understanding of this often overlooked growth form. Location Southern hemisphere Africa, particularly Angola as a part of the Zambezian phytochorion. Taxon Geoxyle species. Methods We assessed belowground bud bank types and biogeographic origins of geoxyles in grass-dominated vegetation types on the Angolan plateau, covering a broad altitudinal, climatic and geological range. Geoxyles were sampled extensively at three different sites, yielding 118 taxa covering about 59% of the Angolan geoxyle flora. Based on the current distribution of these species in Africa below the equator, we analysed their origins and environmental correlates in a taxonomic, functional and biogeographic context. Results Geoxyle species numbers and species communities differed strongly among sites, but functional types showed very similar spectra. Geoxyles evolved in multiple lineages and originated in different biomes, and functional types were unevenly associated with lineages and biomes. Furthermore, functional types correlate to specific environmental driver combinations. Main conclusions Functional diversity is not directly linked to species diversity, but is a result of multiple biogeographic origins that contributed functionally differently preadapted lineages to the Zambezian flora. Thus, geoxyles can occur under different environmental conditions, but require seasonal climates, and open grassy ecosystems subjected to fire, frost and likely herbivory. We highlight the importance of frost as a correlate of geoxyle diversity and emphasize the need for further studies to understand this important and complex growth form.
... The vegetative regeneration in disturbance-prone communities depends on a bud reserve, ready to be used when necessary and a diverse suite of belowground bud-bearing organs is determinant to system resilience (Clarke et al. 2013;Pilon et al. 2021). Despite regeneration from specialised belowground organs is described in neotropical savannas as the main regeneration strategy after disturbance (Pilon et al. 2021;Zupo et al. 2021), African savanna and grassy systems are dependent on regeneration from below-ground bud banks, as well as from a viable seed bank . ...
... The vegetative regeneration in disturbance-prone communities depends on a bud reserve, ready to be used when necessary and a diverse suite of belowground bud-bearing organs is determinant to system resilience (Clarke et al. 2013;Pilon et al. 2021). Despite regeneration from specialised belowground organs is described in neotropical savannas as the main regeneration strategy after disturbance (Pilon et al. 2021;Zupo et al. 2021), African savanna and grassy systems are dependent on regeneration from below-ground bud banks, as well as from a viable seed bank . Studies on seed banks are more common on the literature (O'Connor and Pickett 1992;Dreber 2011;Tessema et al. 2012Tessema et al. , 2016Oliveira et al. 2015); however, little is known about the composition of the belowground organs (White 1976;Bond andMidgley 2001, 2003;Maurin et al. 2014) and how disturbances affect their diversity and density (Wakeling and Bond 2007). ...
Article
Fire and herbivory are major drivers in tropical savanna ecosystems and they selected a flora composed of species able to cope with recurrent aboveground biomass removal. Renewal of the herbaceous stratum is made possible by resprouting, mostly through a belowground bud bank. Evaluating the impacts of disturbances on the bud bank can assist in predicting post-disturbance responses and system resilience. In a semi-arid savanna, we aimed to verify whether lower fire frequency, fire and herbivory exclusion could affect belowground bud bank and organs diversity and consequently, the resprouting potential. Lower fire frequency or suppression and absence of herbivory were expected to reduce the bud bank density, which was confirmed by our results. If the fire is suppressed or fire frequency is reduced, the total, graminoid and the shrub bud bank decreased, whereas herbivory exclusion resulted in total and a forb bud bank of lower densities. Belowground buds were identified in non-woody and woody rhizomes, stolons, root crowns, and bulbs or corms. Despite having bud banks of lower density, disturbance exclusion promoted belowground biomass accumulation. Our results indicated the importance of maintaining the endogenous disturbances to the preservation of the belowground community and regeneration strategy, guaranteeing resilience in semi-arid savanna communities.
... Classifying plants according to their flowering responses to fire might help to understand regeneration strategies and processes in tropical savannas, since plants are able to rapidly allocate resources for flowering after fire, which is an advantage in post-fire environments (Wigley et al., 2020). Although most tropical savanna species resprout after fire, a few species depend on seeds persisting after fire events (Pilon et al., 2021, Zupo et al. 2021. Therefore, if flowering is stimulated or dependent on fire, fire exclusion may significantly affect vegetation dynamics and composition, not only by changes caused to vegetation structure and diversity (Abreu et al., 2017), but also to the production of seeds and resources related to flowering and the associated fauna, especially regarding the diversity of pollinators (see Burkle et al.,2019;Carbone et al. 2019). ...
... The rapid flowering response to fire, even during the dry season, requires resources that can be rapidly allocated to the formation of flowers and vegetative aboveground parts. Most of the Cerrado species will resprout after fire (Pilon et al. 2021;Zupo et al. 2021), with the availability of resources through specialized structure (Appezzato-da- Glória et al., 2008;Pausas et al., 2018), mostly starch and fructans (Moraes et al., 2013;. Therefore, plants can rapidly allocate resources for plant regeneration (resprouting) and reproduction and thus, flowering responses to fire are fast. ...
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.
... Changes in soil drainage can cause changes in its physicochemical and textural properties (Sigua et al. 2006), promoting encroachment by woody species and colonization by invasive species (Barbosa da Silva et al. 2016), and can also reduce the heterogeneity of microhabitats in the environment (Bleich et al. 2014). Although many studies show that fire frequency influences soil properties and vegetation, most of the studies on the effects of fire focus on dry savannas in the Cerrado (e.g., Silva and Batalha 2008;Pilon et al. 2021) and few have examined wet savannas (Araújo et al. 2013). ...
... Members of the family Poaceae are abundant in the Cerrado biome, predominantly in moist grasslands and in dry and moist savannas (Munhoz et al. 2008;Bijos et al. 2017;Souza et al. 2021). This growth form tends to form dense clusters or has rhizomes or stolons that increase the plants ability to establish themselves throughout the vegetation (Munhoz and Felfili 2006;Pilon et al. 2021). Besides, the fire suppression in the Cerrado favors woody species over herbaceous species (Durigan 2020), as well as found in the African savanna wet grassland (Luvuno et al. 2016). ...
Article
The vereda (Brazilian savanna palm swamp) has a distinguishable flora and high floristic beta diversity. The factors that influence dissimilarities among vereda floras have not been clearly elucidated. Here we investigated how key physicochemical soil factors modulate the species composition of this vegetation. Soil and plants were sampled from three veredas, species composition and diversity were compared among them. To investigate the effects of soil physicochemical properties on species richness and cover of each vereda, we fitted a linear mixed-effect model. The plant assemblages in the veredas diverged in terms of species composition but converged in two dominant species graminoids. We found significant differences in soil properties among the veredas, except in texture. Soil properties had significant effects on species richness and cover as a whole, and on richness and relative cover for the individual growth forms. Potential cation-exchange capacity alone negatively affected species richness, especially of graminoids and subshrubs. The cation-exchange capacity of soils and its complex interactions with phosphorus and organic matter were found to be the main drivers of species occurrence and vegetation cover in the veredas. The distinct flora of veredas is controlled by the interaction of species and its growth forms with soil filters.
... For example, postfire recovery of woody ecosystems has resulted in increased plant diversity soon after fire due to an increase in grasses and annual plant diversity, followed by a reduction in biodiversity as woody cover increases over time (Giorgis et al. 2013;Maestre et al. 2016;Doherty et al. 2017). Similarly, the release of nutrients, the availability of light, and the temporary decrease of competition usually associated with the post-fire environments can maximize plant fitness of fast-growing and small-sized species (e.g., grasses and forbs) shortly after fire, which then decline as the forest canopy recovers Rostagno et al. 2006;Chapin III et al. 2011;Kunst et al. 2015;Pilon et al.. 2021). Along the same lines, increased soil nutrient pulses that occur immediately after fire might drop after some time due to soil erosion (Certini 2005). ...
... Biodiversity was not significantly affected by fire across any taxa group, climate type, or time since fire, indicating an overall high resilience at the analyzed spatial and temporal scales. This is in line with previous studies focused on specific semiarid regions, including two wellstudied large fire-prone ecosystems in South America (i.e., Cerrado and the Gran Chaco), which had shown post-fire recovery of biodiversity for different taxa groups, such as plants, birds, and insects (e.g., Kunst et al. 2003Kunst et al. , 2015Kowaljow et al. 2019;Durigan et al. 2020;Pilon et al. 2021). However, these responses may certainly involve context-dependent changes in species composition (Durigan et al. 2020;McLauchlan et al. 2020), which could not be captured in our quantitative synthesis. ...
Article
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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.
... The most species-rich families found in the shrub grassland and savanna belonged to Myrtaceae, Euphorbiaceae, Asteraceae and Fabaceae, which are well represented in floristic surveys in the Cerrado (e.g., Batalha and Mantovani 2001;Antar and Sano 2019). Species from these families in the Cerrado store reserves and biomass in a great diversity of thickened underground organs that can support regeneration of individual plants after seasonal droughts or fire (Simon et al. 2009;Pausas et al. 2018;Pilon et al. 2020). Poaceae and Cyperaceae, the families with highest richness and cover in the moist grassland, are usually the richest families in wet open grassland ecosystems in the Cerrado (Amorim and Batalha 2007;Munhoz et al. 2008;Bijos et al. 2017). ...
... Many species of Poaceae and Cyperaceae form dense clumps or rhizomatous individuals widely scattered in the vegetation, which increases their capacity to colonize and cover the soil (Filgueiras 2002). In addition, many grasses species occurring in fire-prone savannas present adaptations such as below ground rhizome buds that resprout after a fire in which aboveground matter is consumed, increasing their survival rate in areas with that kind of disturbance (Choczynska and Johnson 2009;Pilon et al. 2020). Furthermore, the high occupancy rate of Poaceae individuals is due to the fact that most of these species are C 4 grasses adapted to direct incidence of sunlight, a condition found in open areas, which are ideal places for their establishment (Jacobs et al. 1999;Parr et al. 2014). ...
Article
The Cerrado biome comprises a mosaic of different vegetation types such as grasslands, savannas and forests. We studied soil properties and the herbaceous-shrub layer vegetation in moist grassland, shrub grassland and savanna. We assume that the moist grassland will present a distinct species composition from the other vegetation types, as waterlogging leads to changes in soil features that act as a filter of species that are adapted to this condition. The results showed that the soil in the moist grassland was distinct from the ones in savanna and shrub grassland. We found that the soil organic matter and the proportion of clay particles determined the variation in composition/cover and richness in the herbaceous-shrub layer in the three vegetation types. Higher organic matter content and smaller proportion of clay particles explained the larger distinction in richness and cover in moist grassland (lowest one) compared to shrub grassland and savanna sites. A total of 228 species in 47 families were sampled in the three vegetation types, and only five species were common to all three. The results revealed that, on a local scale, adjacent vegetation types of Cerrado with differences in soil organic matter and clay vary greatly in terms of growth forms, species composition and cover in the herbaceous-shrub layer. Understanding how herbaceous-shrub species richness and cover is related to soil nutrients, and texture heterogeneity in the mosaic of the vegetation types of the Cerrado may be useful in maintaining plant species structure and diversity.
... Woody plants evolved a set of strategies to tolerate fire or escape its effects, such as investing in a thick outer bark and therefore insulating the living tissues of the wood; or growing taller and saving the canopy from flames and from the heat (Keeley et al., 2011;Scalon et al., 2020). However, savanna ground layer plants are shorter, and its different growth forms such as herbs, subshrubs and grasses are certainly the most affected functional groups within the plant community in terms of biomass loss (Kauffman et al., 1998;Pilon et al., 2021). Aboveground biomass of ground layer species is mainly composed by photosynthetic organs (Augustine et al., 2010), therefore these plants need to produce new leaves promptly after each fire event in order to maintain their acquisitive metabolism. ...
... Many ground layer species are perennials and evolved under fire regimes that lead to the selection of specific traits to deal with the loss of aboveground biomass (McIntyre et al., 1995;Pilon et al., 2021). These fire-adapted traits are mainly located in their well-developed underground organs (Appezzato-da-Glória et al., 2008), which have a high number of protected buds (Fidelis et al., 2014;Filartiga et al., 2017) that result in the capacity to resprout after fire events. ...
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.
... However, it is likely that also for this group of species, traditional fire and grazing management contribute to the rich biodiversity, potentially including species with optima at higher altitudes that benefit from decreased competition. There is a need to investigate the dynamics of all kinds of organisms in an ecosystem, to get a more holistic picture of possible outcomes of management policy (Van Mantgem et al., 2015;Bhaskar et al., 2019;Pilon et al., 2020). Fire is often regarded as destructive, even when it has shaped the ecosystem for a long time. ...
Article
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Questions In some fire‐prone ecosystems, bryophytes play a crucial role by providing the surface fuel that controls the fire return interval. Afroalpine heathlands are such an ecosystem, yet almost nothing is known about the bryophytes in this system. We do not know the level of species richness, or if there is a successive accumulation of species over time, or if some species are adapted to specific phases along the successional gradient, for example early‐successional species sensitive to competition. Location Afroalpine heathlands in Ethiopia. Methods We made an inventory of all bryophytes in 48 plots of 5 m × 5 m, distributed along a chronosequence from 1 to 25 years post fire. The heathlands are located between 3500 m and 3800 m a.s.l. and are managed by traditional pasture burning with fire intervals of 8–20 years. Results We found in total 111 taxa of bryophytes. Post‐fire mortality was almost 100%. The youngest plots had only a few cosmopolitan species often found after fire. Initially, species richness increased monotonically while starting to level off around 15 years after fire, when many plots had around 30 species and a high cover of Breutelia diffracta, which is a key ground‐living species, important as surface fuel. Most species were found with sporophytes, a pattern even stronger for the most frequent species. Conclusions Interestingly, bryophyte diversity is already remarkably high by only 15 years after total eradication. The relatively slow accumulation of species in the first years after fire suggests that dispersal in space, and not time, is the major mechanism by which sites regain their diversity (i.e. spore banks play a smaller role than colonization of wind‐borne spores). This indicates that the high species richness is built up through colonization from surrounding heathlands, and perhaps also from higher‐altitude alpine grasslands and lower‐altitude forests, and that the bryophyte diversity in this system is maintained by the traditional fire and grazing management.
... The Cerrado herbaceous layer has high resilience and recovers quickly after a fire (Loiola et al., 2010). In just eight months after the fire, Pilon et al. (2020) registered the diversity and ground cover recovery of 86% of the herbaceous and forb species to a pre-fire condition. The Cerrado landscapes high heterogeneity with the different plant formations in proximity is a challenge for fire management over large areas. ...
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.
... Keeping buds below ground is a strategy for individuals to persist in disturbance-prone ecosystems (Rosenvald and Lõhmus, 2008;Fidelis et al., 2014;Pausas et al., 2018;Ott et al., 2019). Savanna species tend to have underground organs capable of surviving for decades dormant, allowing savanna species to persist in the ecosystem and re-emerge when conditions are favourable again (Bardgett et al., 2014;Bond and Midgley, 2001;De Moraes et al., 2016;Ott et al., 2019;Pausas et al., 2018;Pilon et al., 2020). In our experimental system, these underground organs may have remained dormant for a long time until canopy opening by clear-cutting allowed light reaches the soil surface, enabling rapid regeneration and recovery of herb and shrub populations, commonly found in savannas. ...
Article
Humans have changed vegetation dynamics in Neotropical savannas by suppressing fires, allowing trees and shrubs to expand into ancient savanna landscapes in a process known as woody encroachment. This woody encroachment drives the loss of biodiversity and modifies the functioning of savanna ecosystems. Here we combine satellite data analysis with an experimental approach to test the hypothesis that long-term management by clear-cutting helps restore the diversity and functional composition of open savannas. First, we used Landsat time series of the Normalized Difference Water Index, to assess changes in vegetation structure, comparing experimental areas with open savannas in the same region. We then obtained field experimental evidence comparing areas managed during 30 years versus unmanaged areas, including data on vegetation structure and composition. Our results from satellite image analyses indicate that, before the first clear-cutting, vegetation structure was similar in managed and unmanaged sites, and both differed from open savanna. When clear-cutting manipulation started, NDWI of managed areas became persistently lower than that of unmanaged control areas. In the field, we found that in managed areas, species diversity and richness of typical savanna species had increased, and that species composition had changed to become more similar to open savannas. We also observed the recovery of savanna functional composition, suggesting that ecosystem processes were restored by clear-cutting management. Our findings reveal that the repeated removal of dominant woody species by clear-cutting has contributed to maintain the diversity and functioning of savannas degraded by forest encroachment.
... As espécies foram classificadas em baixa, média, alta e muito alta, de acordo com a frequência relativa mais a densidade relativa de regenerantes encontrados em 109 pastagens de diferentes regiões do Cerrado. Especifica-se também a forma (predominante) como ocorre a regeneração, por sementes dispersas ou por rebrota de raízes, caules e propágulos armazenados no solo [118][119][120][121] . ...
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Os sistemas silvipastoris combinam silvicultura e pecuária para gerar produção complementar e interação positiva entre árvores, capim e gado. No Cerrado encontramos alta regeneração e diversidade de árvores nativas em pastagens. Encontramos também pecuaristas que conhecem e reconhecem o valor das árvores. Este livro traz caminhos para a implantação de Sistemas Silvipastoris com árvores nativas no Cerrado: sua definição, importância, experiências em andamento, métodos de cultivo, incentivos e oportunidades. Trazemos 23 espécies de árvores frequentes nas pastagens do Cerrado e suas características.
... However, because of these departures, further studies spanning longer sampling periods will yield further information about the phenological responses to both climate and soils. Future studies also need to assess how these three vegetation types respond phenologically to fire events, which is a potential abiotic driver of phenology in tropical savannas (Pilon et al., 2020). Addressing these issues will be important for understanding vegetation dynamics in megadiverse tropical gradients, especially under the projected climate change scenarios. ...
Article
Question - Climate, particularly precipitation, is the primary factor driving tropical plant phenology because of its relevant role in regulating water availability. However, differences in soil physicochemical properties can also drive resource availability, potentially affecting plant phenology, especially under similar rainfall regime environments. We determined whether seasonality and synchrony of vegetative and reproductive phenophases differ along a grassland-savanna-forest gradient under the same climate regime in a Neotropical seasonal ecosystem. We hypothesized that species growing on shallow, nutrient-impoverished soils have a higher capacity to respond to precipitation pulses than rich soils. Location - Serra do Cipó, southeastern Brazil. Methods - We quantified soil physicochemical properties associated with fertility and water retention of the grassland (campo rupestre), savanna (cerrado) and forest, and determined phenological strategies of species across the three vegetations types by monitoring vegetative and reproductive phenophases over one year. For each phenophase, in each vegetation type, we evaluated seasonality and synchrony of phenological patterns. We quantified the phylogenetic signal for phenophases to disentangle the relative roles of historical versus ecological drivers of plant phenology. Results - Soils from campo rupestre were more nutrient- and water-limited than those of cerrado and forest. Cerrado and forest communities had similar phenological strategies, whereas species from campo rupestre showed strategies that maximize resource acquisition and conservation. In the cerrado and forest, leafing and flowering patterns were seasonal, with leaf flushing and flowering peak at the onset of the rainy season and leaf senescence in the dry season. Conversely, species from campo rupestre showed continuous leafing and flowering patterns, while fruiting was seasonal. Phenophases did not show phylogenetic signal. Conclusions - We demonstrated changes in vegetative and reproductive phenology that are likely associated with variation in soil physicochemical properties. We argue that more severe edaphic filters may have shaped different phenological patterns in campo rupestre.
... Most of the species forming the herbaceous stratum in grassy ecosystems have traits that allow rather quick regeneration after disturbances such as fire and grazing (Archibald et al., 2019), including protected meristems (i.e. rhizomatous and rosette species), clonality, presence of bud banks and below-ground storage organs (Pilon et al., 2020;Fidelis et al., 2010). However, grazing itself influences the functional characteristics of the plant communities: heavier grazing will lead to the selection for plant species with the capacity to quick recovery of their aboveground biomass, i.e., resource-acquisitive species, while low grazing intensities, or even absence, will lead to the selection of resource-conservative species, such as tussock grasses (Cruz et al., 2010). ...
Article
Differently from commonly used forest conservation strategies, the absence of disturbance in non-forest-ecosystems can result in loss of biodiversity. Grassy ecosystems characterize extensive areas in all biomes in Brazil, offering great contribution to biological diversity and providing ecosystem services on which society depends. Palaeoecological evidence indicates these ecosystems evolved under the influence of grazing and fire, and these disturbances have been essential for controlling the dominance of woody vegetation. While the need for fire to maintain grassy biomes has been recently discussed, grazing as a management tool for conservation is still little accepted by the local scientific community and by decision-makers. Here we provide a comprehensive analysis of the current literature on grazing management and its effects on grassy ecosystems in Brazil. Based on a review of the role of grazers prior and after European colonization, and a synthesis on grazing effects across different systems, we call for the evaluation of grazing as a management tool for biodiversity conservation in Brazil’s grassy systems. Grazing should be an interesting management strategy especially in Legal Reserves with grassy vegetation types, as it can ally conservation with livestock production. To achieve these potentially complementary objectives, a research agenda needs to be developed to devise adaptive management strategies for Legal Reserves. In this, relevant stakeholders should be included and both the ecological conditions of the ecosystem in question and the socioeconomic determinants considered.
... From an evolutionary perspective, the flammability of plants is considered to be a characteristic that promotes periodical fires, and thus favors the selection of fire-adapted plants in a feedback scheme (Bond and Keeley, 2005). Thus, the structure and functioning of fire-dependent ecosystems is the result of a long history where fire has a pivotal role in selecting species and influencing ecological processes (e.g., Pilon et al., 2021). In the so-called fire-independent ecosystems, fire rarely occurs either because of unfavorable climatic conditions (very humid, very dry, or very cold) or for the lack of fuel (plant biomass) to carry a fire. ...
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Brazil has experienced unprecedented wildfires in the last decade. Images of immense burnt areas or deadanimals that failed to escape the 2020 wildfires have shocked the world. To prevent or minimize furthersimilar disasters we must understand the factors that have led to these catastrophic events. The causes andconsequences of wildfires entail complex interactions between the biophysical and sociocultural spheres,and suitable management decisions require a sound scientific base. We present the recent panoramaof increasing fire outbreaks in the Brazilian biomes, and discuss the causes that have contributed tosuch fires, their impacts on the environment and overall consequences for human well-being, based onreviewing the extensive specialist literature, on authors’ expert knowledge and information providedby environmental managers, researchers and politicians during a workshop organized to debate the wildfire issue in Brazil. Our up-to-date review is aimed at the academic public, environmental managersand decision- and policy-makers. First, we present evidence on the contrasting effects of fire on differentecosystems. Second, we outline the historic perceptions and policies related to fire use and managementin Brazil since its colonization to the present date. Third, we propose means to advance fire preventionand develop successful management strategies. Finally, we answer frequently asked questions to clarifyand/or demystify some fire-related issues not always properly addressed in the media.
... The vegetation occurs forming mosaics of grasslands, savannas, and forests, which create a gradient of fire-prone to fire-sensitive vegetation types and allow for exploring the effects of fire under the same climatic conditions. Unlike other savannas worldwide, the Cerrado lacks large mammalian herbivores, indicating that plant-fire feedback is mainly responsible for maintaining the vegetation in an open savanna state (Dantas et al., 2016;but see de Assis et al., 2011, andHoffmann et al., 2019, for influences of water availability and Accepted Article frost events on a local scale). Where there are no edaphic constraints, fire suppression leads to shifts in community structure and composition, enhancing woody encroachment and loss of savanna species (Abreu et al., 2017;Rosan et al., 2019). ...
Article
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 analyzed 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 aboveground 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, 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.
... Regeneration of plants is a complex process that includes both vegetative and reproductive strategies (Larson and Funk, 2016). Both resprouting and seeding are important post-fire regeneration strategies in species from fire-prone ecosystems (Pilon et al., 2021). Many contributions in the SI address the several steps of vegetation recovery after fires, often on the community level, but also focusing on specific species (Ferraro et al., 2021). ...
Article
Fires are widespread disturbance events with many implications for different aspects of plant persistence and vegetation properties. Changing fire regimes canprofoundly affect vegetation dynamics and ecosystem properties. Recent steep increases in the frequency of fires worldwide and the occurrence of megafires have caught the attention of scientists, policymakers, and the media. The FLORA Special Issue on Fire and Vegetation unites five invited Opinion Papers with emphasis on South America and nineteen research papers, including one review, on different aspects of the fire–vegetation interaction. The studies contribute both to the discussion of how to better manage fire in ecosystems and to improve our understanding of fire effects on organisms, communities, and ecosystems. Our expectation is that the Special Issue stimulates further research and, ultimately, helps to inform fire management practice to improve human well-being, to ensure the sustainability of resource use, and perhaps most important, biodiversity conservation and climate change mitigation
... Nevertheless, in savanna vegetation, the resprouting capacity of species is the primary source of post-fire regeneration (Pilon et al., 2021). ...
Article
1. Indigenous peoples have been managing fire‐prone landscapes for millennia, especially in tropical savannas, thereby maintaining carbon stocks and pyrodiversity and ensuring food security. In some indigenous lands in Brazil, fire brigades are composed of indigenous people, integrating their traditional knowledge in Brazilian fire management policies; however, the effectiveness of their management is largely undocumented. Nevertheless, we need to know the effectiveness of indigenous fire brigades and their influence on fire patterns. 2. Here, we evaluate an 18‐year historical series of fire patterns and burn scars, comparing periods with and without indigenous brigade activity, to describe the role of indigenous fire brigades in the Kadiwéu Indigenous Territory. In this Indigenous Territory, fire brigades composed of indigenous people have been instituted, trained and maintained by the National Center of Prevention and Combat of Wildfire (PREVFOGO/IBAMA) since 2009. These brigades are responsible for fire management throughout the Kadiwéu Indigenous Territory using controlled burning, prescribed burning, and combating wildfires. 3. We found that fire management by the indigenous brigades has reduced fire frequency by 80% in the areas with high fire frequency (over 70% of the analyzed time). Management also reduced the size of the area burned by 53% and the influence of climate over the total area burned. According to our models, the area affected by fires is mainly influenced by annual rainfall in the absence of indigenous brigades; in contrast, climatic factors could not explain the variation in the burned area in the period without indigenous brigades. 4. Synthesis and applications — The fire management realized by the indigenous brigades can modify the fire regime. These changes in the fire regime can include: changes in spatial patterns, the magnitude of fires, and reduction in the influence of climate on fire regimes. Hence, the management carried out by the indigenous brigades can be considered an important tool for fire management. In addition, demonstrates the importance of programs that integrate traditional indigenous knowledge with fire management policies, such as the Integrated Fire Management (IFM), to construct effective management strategies.
... Even in seasonally dry forests, where fire is fundamental for maintaining vegetation structure over long time scales, human alteration of fire regimes can result in transitions to treeless landscapes (Driscoll et al. 2010;Pausas and Bond 2020;Pilon et al. 2021;Giorgis et al. 2021). For instance, the increase in fire frequency in Mediterranean chaparral (California) favours the dominance of highly competitive non-native grasses over native woody species recruiting from the seed bank, which promotes a further increase in fire frequency that redirects the system towards a trajectory of higher dominance of grasses (Keeley 2012;Keeley and Pausas 2019). ...
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The transformation of forests to treeless landscapes as a result of disturbances (deforestation transitions) is an ongoing process in many regions of the world. Here we first revise the historical context of these transformations and then, we focus on its consequences for li􀄴er decomposition. We also present a case study, based on four ecosystems of central Argentina (Sub-Andean, Mountain Chaco, Espinal and Arid Chaco), evaluating how deforestation transitions can modify ecosystem decomposition by altering its main controls. Although there is evidence of consequences of deforestation transitions on the local environment for decomposition and on leaf litter quality it is not clear how those changes would impact the decomposition of natural mixed litter in the field. In our study case, we show that the deforestation transitions evaluated across four ecosystems resulted in no consistent changes in standard substrate decomposition but a consistent increase in the litter mixtures’ decomposability and quality. Likely as a consequence of this patern, the loss of trees resulted in a consistent increase in the in situ mixtures decomposition across the ecosystems studied. Beyond our particular findings, our analysis highlights how the accurate prediction of the consequences of deforestation transition on changes in carbon and nutrient cycling needs to understand the behaviour of its controls. Only through this understanding, we will be able to interpret the payerns of in situ mixtures decomposition and predict the consequences of deforestation transitions adequately on carbon (C) and nutrient cycling. Additionally, the recent literature, in coincidence with our results, gives evidence that the presence of non-leafy plant debris and local-scale variation in the local environment may play a stronger role than previously thought in C and nutrient cycling.
... Despite the recent science and media attention to the savannas, they are threatened all around the world by land conversion, biological invasions and fire suppression (Durigan and Ratter, 2006;Parr et al., 2014). Land conversion to agricultural and silvicultural practices usually involves extensive soil management, damaging the underground bud-bearing organs that are the main source of resilience in savannas (Clarke et al., 2013;Pausas et al., 2018;Pilon et al., 2021).Once the belowground biomass is eliminated, it is really difficult to recover degraded savannas (Zaloumis and Bond, 2011). ...
Article
The Cerrado, the most biodiverse savanna, has been losing its natural areas through conversion to agricultural land. In the Santa Barbara Ecological Station (SBES), more than 136.4 ha of open Cerrado vegetation were converted into pine plantations in the 1960s-1970s. Nonetheless, nowadays techniques such as clear-cutting pine trees and burning of the remaining material have been used to recover the native vegetation in those areas. In one of these recovering areas, some native species have resprouted, particularly Psidium grandifolium, which naturally occurs in open Cerrado vegetation. Here, we aimed to elucidate which attributes ensured the resilience of this species after decades of afforestation. To do so, we compare the belowground systems, bud banks, chemical contents of roots and vessel characteristics of P. grandifolium occurring in a natural open Cerrado area and an area under regeneration after the clear-cutting of pine and later burning at SBES. In both study areas, plants showed xylopodium whose upper parts consisted of a thin cauline axis joined to a lignified tuberous root with fusiform morphology. In the natural area, the xylopodia were orientated vertically on the ground, while in the regenerating area, there was a curvature in the cauline axis, changing the xylopodia orientation to a horizontal position. The belowground bud bank was three times greater in the area under regeneration. Roots presented significant differences in the concentrations of total soluble carbohydrates and flavonoids between study areas. Our results also demonstrated that plants with thickened bud-bearing belowground systems held great resilience capacity, even when the structures were damaged by soil management before pine planting. Individuals of P. grandifolium managed to remain dormant in the plantations for decades until the conditions for resprouting were adequate. This work showed a series of plastic responses that Cerrado species present when submitted to afforestation and different growing conditions.
... Depending on its intensity and recurrence, fire has various effects on vegetation dynamics. Low-intensity fire can stimulate the germination of some species, a process that can play an important role in the ecological restoration of habitats (Armesto et al., 2009;Pilon et al., 2021;Shi et al., 2022), however high-intensity fires can damage the seeds and inhibit germination (Pyke et al., 2010). The role of soil seed bank in post-fire regeneration is particularly marked for species that have an avoidance strategy in response to fire (i.e., fire-intolerant species) (Zida et al., 2020). ...
Article
Soil seed bank is an important driver of vegetation dynamics, particularly in fire-prone Mediterranean ecosystems. In this study, we disentangle the effects of fire-related cues on the dynamics of the soil seed bank in semiarid oak forests of western Iran. Soil samples were collected in two types of forests: below closed canopy or below the open canopy of more intensively used forests. In a greenhouse experiment, the effects of five treatments were tested: application of ash (Ash), smoke (Smoke), 50°C temperature (Heat50), 100°C temperature (Heat100) and control. Soil samples were regularly monitored and the number of germinated seeds (seedlings) by species were recorded in each treatment. Diversity indices were also computed. We identified 18 species from 16 genera and 9 families. 56% of the seedlings emerged from the closed canopy forest soils and 44% from the open canopy forests. Seedling density and diversity values were the lowest in the Heat100 treatment. No annual grasses and tree species were recorded in this treatment. In contrast, the influence of the other fire-related cues was mediated by the forest type covertype of forest cover: the number of emerged seedlings was the highest in Smoke and Heat50 in the open canopy and closed canopy, respectively. This mediation effect was also reflected in the composition of the control as tree species were only present in the closed canopy and annual forbs were less abundant there compared to the open canopy type. Considering all fire treatments together, the seedling density was significantly higher in the closed canopy type than in the open canopy (309.6 ± 28.03 vs. 240.8 ± 20.78 seeds/m2). Our results showed that intense fires leading to high soil temperatures are largely detrimental to soil seed bank germination and species diversity, whereas less intense fires can be favourable depending on species life form and the type of forest. Our findings highlight that post-fire regeneration from the soil seed bank is more promising in closed forests than in forests with an open canopy in the studied ecosystem.
... 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.
... The native species of the Cerrado have adaptations that allow their survival after natural disturbances, including fire events, which remove and / or cause injuries to aerial organs. Resprouting is the main mechanism of vegetation regeneration after such disturbances, and is mediated by the underground organs that store reserve compounds (Appezzato-da-Glória, 2015;Clarke et al., 2010;de Moraes et al., 2016;Pausas et al., 2018;Pilon et al., 2021) and well-developed bud banks (Aubert and Oliveira-Filho, 1994;Clarke et al., 2013;Ferraro et al., 2020). However, in the face of unnatural disturbances, many species are suppressed, as they cannot survive in environments that present adverse conditions, for example, exotic species cultivation areas (de Abreu and Ferraro et al., 2020). ...
Article
The Allagoptera campestris palm occurs naturally in open areas of the Brazilian Cerrado. The species grows in the pine understory and in areas under regeneration, where pine trees were removed, and the remaining material was burned. To verify if the persistence of this palm species in disturbed environments is related to its leaf phenotypic variation, we collected leaf samples of 10 plants from a natural Cerrado area, from a pine understory, and from an area under regeneration. In all sites, the leaves presented raphide‐containing idioblasts, which are described here for the first time for the Allagoptera genus. The plasticity index was high for all leaf traits analyzed. In pine understory, the plants have longer, slender leaves, with a lower stomatal index and lower values of net CO2 assimilation. In contrast, in the area under regeneration, plants fully exposed to sunlight form a larger number of smaller leaves with a thicker leaf blade and a higher stomatal index. The variations of leaf morphology and physiology support our hypothesis that the persistence of A. campestris relates to leaf adjustments to suit changes in light availability in the two unnatural Cerrado environments.
... Disregarding reference data that may have burned over the imagery period marginally improved classification accuracies for the savanna and grassland formations. This quality control step may have prevented bare ground pixels and recovering post-burn vegetation pixels from being included in the training dataset ( Fig. 2) 80,130 . The impact of vegetation burning on the collection of reliable ground reference data and the subsequent effect burn events have on classification accuracies will likely vary across the Cerrado, as natural and anthropogenic fire regimes differ 131 . ...
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Native vegetation across the Brazilian Cerrado is highly heterogeneous and biodiverse and provides important ecosystem services, including carbon and water balance regulation, however, land-use changes have been extensive. Conservation and restoration of native vegetation is essential and could be facilitated by detailed landcover maps. Here, across a large case study region in Goiás State, Brazil (1.1 Mha), we produced physiognomy level maps of native vegetation (n = 8) and other landcover types (n = 5). Seven different classification schemes using different combinations of input satellite imagery were used, with a Random Forest classifier and 2-stage approach implemented within Google Earth Engine. Overall classification accuracies ranged from 88.6–92.6% for native and non-native vegetation at the formation level (stage-1), and 70.7–77.9% for native vegetation at the physiognomy level (stage-2), across the seven different classifications schemes. The differences in classification accuracy resulting from varying the input imagery combination and quality control procedures used were small. However, a combination of seasonal Sentinel-1 (C-band synthetic aperture radar) and Sentinel-2 (surface reflectance) imagery resulted in the most accurate classification at a spatial resolution of 20 m. Classification accuracies when using Landsat-8 imagery were marginally lower, but still reasonable. Quality control procedures that account for vegetation burning when selecting vegetation reference data may also improve classification accuracy for some native vegetation types. Detailed landcover maps, produced using freely available satellite imagery and upscalable techniques, will be important tools for understanding vegetation functioning at the landscape scale and for implementing restoration projects.
... Most living above-ground biomass of grasses dries during the dry season and the dead biomass remains attached to the plant (Pilon et al., 2021). However, many savanna grasses remain physiologically active, maintaining their culms, rhizomes, and superficial roots active at the peak of the dry season, as they maintain their green culms below a dry and brown sheet cover and their diurnal changes in leaf water potentials (Rossatto et al., 2013). ...
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.
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.
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Prescribed burning (PB), the planned and controlled application of fire is a well-established tool for biodiversity conservation in a plethora of habitats globally. In European grasslands that are threatened hotspots of biodiversity, PB has the potential to address challenges related to several threats such as abandonment, climate change or invasive species. However, its potential is seldom realized both in experimental and real-world conditions. To increase the potential of PB in the management of European grasslands, we suggest adapting the fire regime concept in future studies and to determine optimal PB regimes based on experimental approaches, paleo-data and the disappearing traditional ecological knowledge. For the evidence-based evaluation of PB applicability, a decision support framework is suggested.
Chapter
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.
Article
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.
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O presente trabalho dá continuidade aos mapeamentos da cobertura vegetal que o Instituto Florestal tem produzido para todo o estado de São Paulo, quantificando a área dos remanescentes de vegetação nativa e avaliando suas alterações e estado de conservação. Os resultados do mapeamento são apresentados através dos seguintes recortes territoriais: Bacia Hidrográfica, Unidade de Gerenciamento de Recursos Hídricos e Município, Região Fitoecológica e Unidade de Conservação.
Article
The fire regime is essential in creating a mosaic of plant structure and diversity in South American open savannas, especially favouring herbs. However, studies investigating diversity patterns in Neotropical savannas rarely focus on the herb–subshrub layer. This study investigated the variation of the herb–subshrub layer under contrasting fire regimes in the most conserved site within the Cerrado Domain, the Jalapão region, Brazil. We selected four sites of open savanna physiognomy with similar topographic, climatic and edaphic features: three burned every 2 years, while the fourth site has remained unburned for at least the last 10 years. We randomly distributed 15 plots of 4 m ² in each site and identified all herbs and subshrubs in each plot to estimate density, richness, alpha diversity and species composition. The unburned site had lower herb–subshrub density, richness and diversity than the frequently burned sites. Species composition varied between frequently burned and unburned sites, partially explained by the fire frequency across sites. Although other ecological factors may explain the patterns detected, we cannot rule out the importance of fire in structuring plant communities in the Jalapão region. As in other savannas, our study in the Cerrado Domain reinforces the essential role of the fire regimes in modifying and maintaining the diversity of herbaceous plants at the landscape scale.
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Species loss leads to changes in ecosystem function and services, impacting human well-being. Although biodiversity restoration is pivotal to circumvent this situation, the techniques for restoring old-growth savannas are still limited and the restoration outcomes remain unpredictable. Here, we use a trait-based approach to understand the functional outcomes of ecological restoration via direct seeding in a Brazilian savanna (cerrado, hereafter neotropical savanna). We compared the functional composition from woody and non-woody component, total biomass and biomass allocation of a restored relative to a degraded savanna (abandoned pasture) dominated by exotic grasses and a well-preserved old-growth native savanna. We found that the functional composition of restored communities was very similar to those dominated by exotic grasses, both characterized by a greater dominance of species with acquisitive traits, higher above-ground biomass, and lower investment in root biomass. In contrast, the native vegetation exhibited a dominance of conservative traits and higher investment in belowground rather than aboveground biomass. Even though the acquisitive traits in the restored savanna allow a fast aboveground biomass accumulation and soil cover, the lower belowground biomass investment in the restored savanna may limit its resistance and resilience to droughts and fires. Our findings suggest that restoration efforts in neotropical savanna should focus on fostering the establishment of slow-growing species to recover the ecosystem properties provided by the high biodiversity in neotropical savannas. This article is protected by copyright. All rights reserved.
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Key message Although all populations show extensive pollen immigration, the occurrence of spatial genetic structure and biparental inbreeding decreased genetic diversity and effective population size. Abstract The Brazilian savanna is the second largest Neotropical biome, and a globally important biodiversity hotspot. Basic knowledge of the ecology and genetics of its species can help conserve this important biome. We investigated genetic diversity, spatial genetic structure (SGS), pollen dispersal, and mating system in three Hymenaea stigonocarpa populations (AS, PE, IT) in the Brazilian savanna, using microsatellite loci and samples of adult trees from all populations and seeds from the IT population. As a result of the long geographic distance between populations, the genetic differentiation among them was high (0.397). Individuals of the IT population presented a grouped distribution due to root propagation, resulting in low genotypic richness (GR\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathrm{GR}$$\end{document} = 0.194) and allelic richness (R\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$R$$\end{document} = 4), and high SGS (Sp\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathrm{Sp}$$\end{document} = 0.064) compared to AS and PE (GR\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathrm{GR}$$\end{document} > 0.98, R > 5, Sp\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathrm{Sp}$$\end{document} < 0.026) populations. The IT population showed high pollen immigration (46.4%), pollen dispersal distance (up to 3.57 km), and outcrossing rate (0.934–1.0), but matings were correlated (0.01–1), and some occurred among relatives (up to 0.098), resulting in some inbred seeds (0.140), a lower variance effective population size (Ne\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${N}_{e}$$\end{document} = 3.02) than expected with random mating, and an estimate of 50 seed-trees required to retain an Ne\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${N}_{e}$$\end{document} of 150 in samples of maternal progeny. The estimated minimum viable area to retain a reference (Ner\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${N}_{\mathrm{er}}$$\end{document}) of 1000 indicates that the current AS and IT population areas are insufficient to maintain viable populations in the long-term, demonstrating the importance of maintaining surrounding areas for conservation of these H. stigonocarpa populations.
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Fire is a fundamental ecological factor in savannas because it affects vegetation dynamics and ecosystem functioning. However, the effects of fire on belowground compartments, including biomass and root traits, and their regeneration remain poorly understood. In this study, we assess the variation of above‐ and belowground plant components along fire‐history gradients in Brazilian open savannas and investigate whether changes in vegetation and soil properties are associated with the responses of belowground biomass and root traits. The study was conducted in eight sampling areas of open savanna (campo sujo, i.e., vegetation having low woody cover) within the Cerrado (Brazilian savannas), located along a gradient of time since the last fire (1–34 years); the number of fires that occurred within the past 34 years (0–9 fires) varied by sampling area. In each sampling area, we measured above‐ and belowground biomass, root depth distribution, root functional parameters, and nutrient levels in the upper soil layers (0–10 cm). Rapid recovery of aboveground live biomass after a fire was primarily due to resprouting of graminoids. This recovery was associated with an increase in absorptive root biomass in the upper soil layer in the most recently burnt sites, whereas root biomass was unaffected in deeper layers. Root parameters remained constant regardless of fire history but responded to variations in vegetation structure and soil properties. Specific root length (SRL) decreased with K, Mg2+, Al3+, N, and C and increased with P concentration. In contrast, root tissue density (RTD) and absorptive root proportion were negatively correlated with soil P. RTD was strongly associated with the aboveground biomass of graminoids. Soil texture impacted the root system: the proportion of absorptive roots increased with fine sand content in the soil, inversely to transport root biomass. The relationship between fire and soil properties was insignificant. Synthesis. In savannas, fire stimulates absorptive root biomass in response to the higher demand for belowground resources. This response is correlated with shoot regrowth after a fire. Variations in morphological root parameters are not directly associated with fire history; instead, they reflect differences in soil chemistry, especially soil P and graminoid biomass changes.
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Vegetation‐fire feedbacks are important for determining the distribution of forest and savanna. To understand how vegetation structure controls these feedbacks, we quantified flammability across gradients of tree density from grassland to forest in the Brazilian Cerrado. We experimentally burned 102 plots, for which we measured vegetation structure, fuels, microclimate, ignition success, and fire behavior. Tree density had strong negative effects on ignition success, rate of spread, fire‐line intensity, and flame height. Declining grass biomass was the principal cause of this decline in flammability as tree density increased, but increasing fuel moisture contributed. Although the response of flammability to tree cover is often portrayed as an abrupt, largely invariant threshold, we found the response to be gradual, with considerable variability driven largely by temporal changes in atmospheric humidity. Even when accounting for humidity, flammability at intermediate tree densities cannot be reliably predicted. Fire spread in savanna‐forest mosaics is not as deterministic as often assumed, though may appear deterministic where vegetation boundaries are already sharp. Where transitions are diffuse, fire spread is difficult to predict, but should become increasingly predictable over multiple fire cycles, as boundaries are progressively sharpened until flammability appears to respond in a threshold‐like manner.
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Savannas are commonly described as a vegetation type with a grass layer interspersed with a discontinuous tree or shrub layer. On the contrary, forbs, a plant life form that can include any nongraminoid herbaceous vascular plant, are poorly represented in definitions of savannas worldwide. While forbs have been acknowledged as a diverse component of the herbaceous layer in savanna ecosystems and valued for the ecosystem services and functions they provide, they have not been the primary focus in most savanna vegetation studies. We performed a systematic review of scientific literature to establish the extent to which forbs are implicitly or explicitly considered as a discrete vegetation component in savanna research. The overall aims were to summarize knowledge on forb ecology, identify knowledge gaps, and derive new perspectives for savanna research and management with a special focus on arid and semiarid ecosystems in Africa. We synthesize and discuss our findings in the context of different overarching research themes: (a) functional organization and spatial patterning, (b) land degradation and range management, (c) conservation and reserve management, (d) resource use and forage patterning, and (e) germination and recruitment. Our results revealed biases in published research with respect to study origin (country coverage in Africa), climate (more semiarid than arid systems), spatial scale (more local than landscape scale), the level at which responses or resource potential was analyzed (primarily plant functional groups rather than species), and the focus on interactions between life forms (rather seldom between forbs and grasses and/or trees). We conclude that the understanding of African savanna community responses to drivers of global environmental change requires knowledge beyond interactions between trees and grasses only and beyond the plant functional group level. Despite multifaceted evidence of our current understanding of forbs in dry savannas, there appear to be knowledge gaps, specifically in linking drivers of environmental change to forb community responses. We therefore propose that more attention be given to forbs as an additional ecologically important plant life form in the conventional tree–grass paradigm of savannas. Through this systematic review on forb ecology, we evaluate and summarize current knowledge of forbs in dry African savanna ecosystems and conclude that the ecological understanding of savanna community responses to drivers of global environmental change requires knowledge beyond the plant functional group level. Here, we highlight important findings and summarize knowledge gaps and future perspectives for including forbs as an additional ecologically important plant life form in the conventional tree–grass paradigm of savannas.
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Forest-savanna mosaics are maintained by fire-mediated positive feedbacks; whereby forest is fire suppressive and savanna is fire promoting. Forest-savanna transitions therefore represent the interface of opposing fire regimes. Within the transition there is a threshold point at which tree canopy cover becomes sufficiently dense to shade out grasses and thus suppress fire. Prior to reaching this threshold, changes in fire behavior may already be occurring within the savanna. Such changes are neither empirically described nor their drivers understood. Fire behavior is largely driven by fuel flammability. Flammability can vary significantly between grass species and grass species composition can change near forest-savanna transitions. This study measured fire behavior changes at eighteen forest-savanna transition sites in a vegetation mosaic in Lopé National Park in Gabon, central Africa. The extent to which these changes could be attributed to changes in grass flammability was determined using species-specific flammability traits. Results showed simultaneous suppression of fire and grass biomass when tree canopy leaf area index (LAI) reached a value of 3, indicating that a fire suppression threshold existed within the forest-savanna transition. Fires became less intense and less hot prior to reaching this fire suppression threshold. These changes were associated with higher LAI values, which induced a change in the grass community, from one dominated by the highly flammable Anadelphia afzeliana to one dominated by the less flammable Hyparrhenia diplandra. Changes in fire behavior were not associated with changes in total grass biomass. This study demonstrated not only the presence of a fire suppression threshold but the mechanism of its action. Grass composition mediated fire-behavior within the savanna prior to reaching the suppression threshold, and grass species composition was mediated by tree canopy cover which was in turn mediated by fire-behavior. These findings highlight how biotic and abiotic controls interact and amplify each other in this mosaicked landscape to facilitate forest and savanna co-existence.
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Neotropical grasslands have undergone intensive degradation by land conversion or biological invasion, but their restoration is still challenging. Here, we integrated two approaches to i) assessing the resilience of pristine dry and wet cerrado grasslands after removal of plants and topsoil and ii) evaluating the effectiveness of different treatments based on the material extracted from pristine grasslands to restore degraded dry and wet grasslands after pine invasion. We used old‐growth cerrado grasslands in southeastern Brazil as donor ecosystems and assessed their resilience after the removal of all plants and the upper 5‐cm soil layer. To restore both wet and dry grasslands, we tested topsoil translocation, plant transplantation, direct seeding, topsoil translocation + direct seeding, and needle layer removal. Wet and dry grasslands were both resilient to plants and topsoil removal, as evidenced by their fast recovery. The major mechanisms promoting resilience were seed germination in the wet grasslands and resprouting from underground organs in the dry grasslands. Transplantation was the most successful treatment to restore vegetation cover, species richness and composition in both wet and dry grasslands, especially for herbaceous species. Restoration of the herbaceous layer of cerrado grasslands can be successful using natural ecosystems as donor sites without impairing their resilience in the studied scale. Improving the resilience of degraded dry and wet cerrado grasslands depends on re‐establishing the condition to seed germination in the wet grasslands and reintroducing species able to resprout after disturbance in the dry grasslands, attributes that explained the quick recovery of the donor ecosystems. This article is protected by copyright. All rights reserved.
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Long-term herbaceous vegetation data collected from herbivore and fire exclusion treatments in a nutrient-rich system in the Kruger National Park (KNP), South Africa were used to compare the response patterns of forbs and grasses to varying rainfall conditions. Palatable annual forbs consistently dominated over palatable annual grasses, whereas unpalatable perennial forbs seem to be adapted to herbivory pressure, but not to long-term herbivore exclusion. Above-average rainfall conditions enhanced palatable perennial grass abundances, whereas drought conditions did not favour one palatable perennial life form over the other. This highlights that palatable perennial functional groups, and not grasses alone, provide important ecosystem functions, such as forage stability and hence functional redundancy to absorb disturbances such as droughts. Furthermore, this study did not support previous findings that conditions such as drought, fire and herbivory increase the abundance of unfavourable functional groups at the expense of palatable perennial grasses, as they remained the dominant functional group in this ecosystem type. These observations provide evidence of a dynamic coexistence between grasses and forbs. (Shortened version of the original published abstract)
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1.In recent years belowground plant ecology has experienced a booming interest. This has resulted in major advances towards a greater understanding of belowground plant and ecosystem functioning focused on fine roots, mycorrhizal associations and nutrient acquisition. 2.Despite this, other important functions (e.g., on‐spot persistence, space occupancy, resprouting after biomass removal) exerted by different belowground plant organs (e.g., roots, rhizomes, bulbs) remain largely unexplored. 3.Here, we propose a framework providing a comprehensive perspective on the entire set of belowground plant organs and functions. We suggest a compartment‐based approach. We identify two major belowground compartments, that is, acquisitive and non‐acquisitive, associated with biomass allocation into these functions. Also, we recommend the non‐acquisitive compartment to be divided in structural (e.g., functional roles carried out by rhizomes, such as sharing of resources, space occupancy) and non‐structural (e.g., functional roles exerted by carbohydrates reserve affecting resprouting ability, protection against climate adversity) sub‐compartments. We discuss methodological challenges – and their possible solutions – posed by changes in biomass allocation across growth forms and ontogenetic stages, and in relation to biomass partitioning and turnover. 4.We urge the implementation of methods and approaches considering all the belowground plant compartments. This way, we would make sure that key, yet less‐studied functions would be incorporated into the belowground plant ecology research‐agenda. The framework has potential to advance the understanding of belowground plant and ecosystem functioning by considering relations and tradeoffs between different plant functions and organs. Finally, we identify four major areas where using the proposed compartment‐based approach would be particularly important, namely i) biomass scaling, ii) clonality‐resource acquisition relations, iii) linkages between resprouting and changing environmental conditions, and iv) carbon sequestration.
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Several decades of frustrated attempts to prevent fires in the Brazilian savanna (Cerrado) have led to deleterious ecological and management consequences. In 2014, the first Integrated Fire Management (IFM) programme was launched in three protected areas (PA). 2.The IFM program considers local practices, ecological information, management options, and aims to create landscape mosaics of different fire histories to conserve biodiversity, reduce the prevalence of late-dry season (LDS) wildfires, protect fire-sensitive vegetation, and reduce conflicts between PA managers and local communities. 3.The first three years of imposed fire management regimes led to 40-57% reduction in LDS fires, improved dialogue between researchers, managers and local communities, generating fire management learning communities. 4.Synthesis and applications. This Integrated Fire Management programme represents a major advance in Cerrado management and conservation, by actively managing fires and decreasing the proportion of areas burnt by late-dry season wildfires. It can contribute to protected areas’ management in the Cerrado and other South American fire-prone ecosystems. Long-term monitoring and research are essential to understand the ecological implications and to improve fire management practices. This article is protected by copyright. All rights reserved.
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The fine-scale effects of fire and the consequences for seed survival are poorly understood, especially in the Cerrado (Brazilian savannas). Thus, we investigated whether vegetation gaps (bare soil patches) influence the survival of exposed seeds during fire events in the Cerrado by serving as safe sites.Weperformed field fire experiments in Central Brazil to examine how gap size (% of bare soil) influences fire heat (fire temperatures and residence time) and seed survival (Experiment 1) and to determine how seed survival is affected by fixed conditions: gaps vs grass tussocks during fires (Experiment 2). We used seeds of two common Cerrado legumes, Mimosa leiocephala Benth. and Harpalyce brasiliana Benth. Seed survival was analysed using GLMMs with a binomial distribution. In Experiment 1, seeds survived (38 and 35% for M. leiocephala and H. brasiliana respectively) only when the gaps had >40% of bare soil. In Experiment 2, all seeds under grass tussocks died when exposed to fire, whereas up to 40% of seeds survived in vegetation gaps, relative to their respective controls. Because vegetation gaps influence fire heat, they are important as safe sites for seed survival in the Cerrado, allowing a significant proportion of seeds to survive when exposed at the soil surface.
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Roughly 3% of the Earth’s land surface burns annually, representing a critical exchange of energy and matter between the land and atmosphere via combustion. Fires range from slow smouldering peat fires, to low-intensity surface fires, to intense crown fires, depending on vegetation structure, fuel moisture, prevailing climate, and weather conditions. While the links between biogeochemistry, climate and fire are widely studied within Earth system science, these relationships are also mediated by fuels – namely plants and their litter – which are the product of evolutionary and ecological processes. Fire is a powerful selective force and, over their evolutionary history, plants across diverse clades have evolved numerous traits that either tolerate or promote fire. Here we outline a conceptual framework of how plant traits determine the flammability of ecosystems and interact with climate and weather to influence fire regimes. We explore how these evolutionary and ecological processes scale to impact biogeochemistry and Earth system processes. Finally, we outline several research challenges that, when resolved, will improve our understanding of the role of plant evolution in mediating the fire feedbacks driving Earth system processes. Understanding current patterns of fire and vegetation, as well as patterns of fire over geological time, requires research that incorporates evolutionary biology, ecology, biogeography, and the biogeosciences
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Tropical savannas have been increasingly viewed as an opportunity for carbon sequestration through fire suppression and afforestation, but insufficient attention has been given to the consequences for biodiversity. To evaluate the biodiversity costs of increasing carbon sequestration, we quantified changes in ecosystem carbon stocks and the associated changes in communities of plants and ants resulting from fire suppression in savannas of the Brazilian Cerrado, a global biodiversity hotspot. Fire suppression resulted in increased carbon stocks of 1.2 Mg ha⁻¹ year⁻¹ since 1986 but was associated with acute species loss. In sites fully encroached by forest, plant species richness declined by 27%, and ant richness declined by 35%. Richness of savanna specialists, the species most at risk of local extinction due to forest encroachment, declined by 67% for plants and 86% for ants. This loss highlights the important role of fire in maintaining biodiversity in tropical savannas, a role that is not reflected in current policies of fire suppression throughout the Brazilian Cerrado. In tropical grasslands and savannas throughout the tropics, carbon mitigation programs that promote forest cover cannot be assumed to provide net benefits for conservation.
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The coexistence of grasses, herbs, shrubs and trees characterizes savannas; therefore, to restore such ecosystems one should consider re-introducing all these growth forms. Currently, little is known about field establishment of most “Cerrado” (Brazilian savanna) species that could be used for restoration purposes. Most knowledge on restoration is focused on planting seedlings of tree species from forest physiognomies. Alternatively, direct seeding can be an appropriate method to re-introduce plants of different life forms to restore savannas. We evaluated the initial establishment success under field conditions of 75 “Cerrado” native species (50 trees, 13 shrubs, and 12 grasses) in direct seeding experiments in four sites in Central Brazil for 2.5 years. For that, we tagged and measured tree and larger shrub species and estimated ground cover by small shrub and grass species. Sixty-two species became established (42 trees, 11 shrubs and 9 grasses) under field conditions. Thirty-eight of the 48 tagged species had relatively high emergence rates (>10%) and 41 had high seedling survival (>60%) in the first year. Among grasses and small shrub species, Andropogon fastigiatus Sw., Aristida riparia Trin., Schizachyrium sanguineum (Retz.) Alston, Lepidaploa aurea (Mart. ex DC.) H.Rob., Stylosanthes capitata Vogel, S. macrocephala M.B.Ferreira & Sousa Costa, Achyrocline satureioides (Lam.) DC. and Trachypogon spicatus (L.f.) Kuntze had the greatest initial establishment success (up to 30% soil cover). The data on harvesting period, processing mode and field establishment for these 75 species can be readily used in restoration efforts in the “Cerrado”.
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Few studies address the ecology of herbs of Cerrado grasslands, which are ecosystems where the long dry season, high temperatures, insolation, fire and invasive grasses greatly influencing germination and the establishment of plants. We assessed germination of 13 species of Poaceae from Cerrado grasslands under nursery conditions or in germination chambers, the latter with i) recently collected seeds and seeds after six months storage, ii) under constant and alternating temperatures, and iii) in the presence and absence of light. Germinability, mean germination time (MGT) and required light were quantified to elucidate factors involved in successful germination. Germinability was low for most grasses, probably because of low seed viability. For most species, germinability and MGT were not altered by seed storage. Germination percentages were higher at alternating temperatures and in the presence of light, factors that are more similar to natural environmental situations compared with constant temperature or the absence of light. Our findings indicate that alternating temperatures and light incidence are key factors for germination of species of Poaceae. The maintenance of these environmental factors, which are crucial for the conservation of Cerrado grasslands, depends on appropriate management interventions, such as fire management and the control of biological invasion.