@article{neves_santos_schultz_gotzek_abreu_durigan_vasconcelos_2023, title={Woody encroachment affects multiple dimensions of ant diversity in a neotropical savanna}, ISSN={["1752-4598"]}, DOI={10.1111/icad.12633}, abstractNote={Abstract
Although savanna woody encroachment has become a global phenomenon, relatively little is known about its effects on multiple dimensions and levels of savanna biodiversity.
Using a combination of field surveys, a species‐level phylogeny, and functional metrics drawn from a morphological dataset, we evaluated how the progressive increase in tree cover in a fire‐suppressed savanna landscape affects the taxonomic, functional, and phylogenetic diversity of neotropical ant communities, at both the alpha and beta levels. Ants were sampled along an extensive tree cover gradient, ranging from open savannas to forests established in former savanna areas.
Variation in tree cover had a significant influence on all facets of diversity at the beta level, whereas at the alpha level tree cover variation affected the taxonomic and functional but not the phylogenetic diversity of the ant communities.
In general, ant community responses to variation in tree cover were largely non‐linear as differences in taxonomic alpha diversity and in the taxonomic, functional, and phylogenetic composition of the sampled communities were often much stronger at the savanna/forest transition than at any other part of the gradient. This indicates that savanna ant communities switch rapidly to an alternative state once the savanna turns into forest.
Ant communities in the newly formed forest areas lacked many of the species typical of the savanna habitats, suggesting that the maintenance of a fire suppression policy is likely to result in a decrease in ant diversity and in the homogenisation of the ant fauna at the landscape scale.
}, journal={INSECT CONSERVATION AND DIVERSITY}, author={Neves, K. and Santos, B. and Schultz, T. and Gotzek, D. and Abreu, R. C. R. and Durigan, G. and Vasconcelos, H. L.}, year={2023}, month={Feb} }
 @article{flake_abreu_durigan_hoffmann_2021, title={Savannas are not old fields: Functional trajectories of forest expansion in a fire-suppressed Brazilian savanna are driven by habitat generalists}, ISSN={["1365-2435"]}, DOI={10.1111/1365-2435.13818}, abstractNote={Abstract


Under fire suppression, many tropical savannas transform into forests. Forest expansion entails changes in environmental variables and plant community structure. We hypothesized that forest expansion into savanna results in a shift in community‐weighted mean functional traits from stress tolerance to competitiveness, with generalist species having trait values intermediate between those of specialists of savanna and forest habitats.

We studied 30 plots distributed over three savanna–forest boundaries undergoing forest expansion in the Brazilian Cerrado, capturing a gradient from open savanna to recently formed forest. We measured functional traits of 116 woody species of savanna specialist, generalist and forest specialist functional groups and quantified changes in species composition and mean traits across the basal area gradient.

We identified two main axes of species traits. The first separated forest and generalist species from savanna specialists, with the latter possessing traits associated with resistance to disturbance and stress— such as thick leaves, thick bark, slower height growth and lower shade tolerance. Our second trait axis separated shrubs and understorey trees from pioneer species. Generalist species’ traits did not differ substantially from forest species, nor did they tend to have a typical pioneer strategy.

Community‐weighted trait means changed linearly with forest development. There was a steady increase in traits associated with competitive dominance rather than stress tolerance and fire resistance, indicating a wholesale shift in the selective environment. Several of these patterns—for example, increasing height and decreasing light requirements—are common in old‐field succession. In contrast to old‐field succession, we found that SLA increased, leaf thickness decreased and wood density stayed constant.

The assembly of forests appears to be shaped by environmental filters that contribute to a functional trajectory distinct from most other studied ecosystems. Our results highlight the importance of the functional composition of the early community and of the early colonizers of the open environment. Differences between savanna and forest specialists reflect the selective effects of the contrasting environments, while the traits of generalists—and their interaction with environmental filters—drive the dynamics of forest expansion.

A free Plain Language Summary can be found within the Supporting Information of this article.}, journal={FUNCTIONAL ECOLOGY}, author={Flake, Samuel W. and Abreu, Rodolfo C. R. and Durigan, Giselda and Hoffmann, William A.}, year={2021}, month={May} }
 @article{newberry_power_abreu_durigan_rossatto_hoffmann_2020, title={Flammability thresholds or flammability gradients? Determinants of fire across savanna-forest transitions}, volume={228}, ISSN={["1469-8137"]}, DOI={10.1111/nph.16742}, abstractNote={Summary


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 often is 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 predicted reliably.

Fire spread in savanna–forest mosaics is not as deterministic as often assumed, but may appear so 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.

}, number={3}, journal={NEW PHYTOLOGIST}, author={Newberry, Brooklynn M. and Power, Collin R. and Abreu, Rodolfo C. R. and Durigan, Giselda and Rossatto, Davi R. and Hoffmann, William A.}, year={2020}, month={Nov}, pages={910–921} }
 @article{durigan_pilon_abreu_hoffmann_martins_fiorillo_antunes_carmignotto_maravalhas_vieira_et al._2020, title={No Net Loss of Species Diversity After Prescribed Fires in the Brazilian Savanna}, volume={3}, ISSN={["2624-893X"]}, DOI={10.3389/ffgc.2020.00013}, abstractNote={Although savannas are fire-adapted ecosystems, prescribing fire for biodiversity conservation remains controversial at least in some regions where savannas occur. Faced with uncertainty, many decision makers and even scientists are still reluctant to prescribe fire for conservation purposes in fire-prone ecosystems, invoking the precautionary principle. Knowledge gaps on the ideal fire regime, such as how and when to burn, and especially the fear of biodiversity losses, are among the main arguments against fire management applied to remnants of native savanna vegetation. To inform this debate, we assessed the impact of prescribed fires on diversity of plants (different growth forms), ants, frogs, lizards, birds, and small mammals, in savannas and grasslands of the Brazilian Cerrado. We assessed the existing species richness, composition, and abundance in areas subjected to long periods of fire suppression and compared to that observed over a short period after prescribed dry-season fires, within each group of plants and animals. Whenever possible, we carried out separate analyses for grassland and savanna. Burning did not significantly reduce species richness of any of the groups analyzed, but had a positive effect on richness of graminoids in grassland. When analyzed at the species level, abundance of most animal groups did not show consistent responses to fire, except for a decrease in some frog populations in grasslands. Forbs, graminoids, and subshrubs increased in abundance after fire in grassland areas, though in savanna areas, abundance of forbs, and subshrubs tended to decline after fire. Species composition changed little in response to fire as indicated by low levels of dissimilarity between burned and unburned areas. These results confirm the high resilience of Cerrado biota to fire, as expected for savanna ecosystems in general. Besides, we demonstrate here that the risk of biodiversity losses cannot justify the objections to the use of prescribed fire for conservation purposes in the Cerrado.}, journal={FRONTIERS IN FORESTS AND GLOBAL CHANGE}, author={Durigan, Giselda and Pilon, Natashi A. L. and Abreu, Rodolfo C. R. and Hoffmann, William A. and Martins, Marcio and Fiorillo, Bruno F. and Antunes, Alexsander Z. and Carmignotto, Ana Paula and Maravalhas, Jonas B. and Vieira, Jesica and et al.}, year={2020}, month={Feb} }
 @article{pilon_cava_hoffmann_abreu_fidelis_durigan_2021, title={The diversity of post-fire regeneration strategies in the cerrado ground layer}, volume={109}, ISSN={["1365-2745"]}, DOI={10.1111/1365-2745.13456}, abstractNote={Abstract


Disentangling species strategies that confer resilience to natural disturbances is key to conserving and restoring savanna ecosystems. Fire is a recurrent disturbance in savannas, and savanna vegetation is highly adapted to and often dependent on fire. However, although the woody component of tropical savannas is well studied, we still do not understand how ground‐layer plant communities respond to fire, limiting conservation and management actions.

We investigated the effects of prescribed fire on community structure and composition, and evaluated which traits are involved in plant community regeneration after fire in the cerrado ground layer. We assessed traits related to species persistence and colonization capacity after fire, including resprouter type, underground structure, fire‐induced flowering, regeneration strategy and growth form. We searched for functional groups related to response to fire, to shed light on the main strategies of post‐fire recovery among species in the ground layer.

Fire changed ground‐layer community structure and composition in the short term, leading to greater plant species richness, population densities and increasing bare soil, compared with unburned communities. Eight months after fire, species abundance did not differ from pre‐disturbance values for 86% of the species, demonstrating the resilience of this layer to fire. Only one ruderal species was disadvantaged by fire and 13% of the species benefited. Rapid recovery of soil cover by native vegetation in burned areas was driven by species with high capacity to resprout and spread vegetatively. Recovery of the savanna ground‐layer community, as a whole, resulted from a combination of different species traits. We summarized these traits into five large groups, encompassing key strategies involved in ground‐layer regeneration after fire.

Synthesis. Fire dramatically changes the ground layer of savanna vegetation in the short term, but the system is highly resilient, quickly recovering the pre‐fire state. Recovery involves different strategies, which we categorized into five functional groups of plant species: grasses, seeders, bloomers, undergrounders and resprouters. Knowledge of these diverse strategies should be used as a tool to assess conservation and restoration status of fire‐resilient ecosystems in the cerrado.

}, number={1}, journal={JOURNAL OF ECOLOGY}, author={Pilon, Natashi A. L. and Cava, Mario G. B. and Hoffmann, William A. and Abreu, Rodolfo C. R. and Fidelis, Alessandra and Durigan, Giselda}, year={2021}, month={Jan}, pages={154–166} }
 @article{brandes_albuquerque_domingues_barros_durigan_abreu_2020, title={Dendroecology of Pinus elliottii Engelm. reveals waves of invasion in a neotropical savanna}, volume={22}, ISSN={["1573-1464"]}, DOI={10.1007/s10530-019-02099-2}, number={2}, journal={BIOLOGICAL INVASIONS}, author={Brandes, Arno Fritz das Neves and Albuquerque, Rafael Perpetuo and Domingues, Gustavo de Assis Fores and Barros, Claudia Franca and Durigan, Giselda and Abreu, Rodolfo Cesar Real}, year={2020}, month={Feb}, pages={403–419} }
 @article{pilon_hoffmann_abreu_durigan_2018, title={Quantifying the short-term flowering after fire in some plant communities of a cerrado grassland}, volume={11}, ISSN={["1755-1668"]}, DOI={10.1080/17550874.2018.1517396}, abstractNote={ABSTRACT Background: Fire has been reported to trigger the production of flowers and fruits in many fire-prone ecosystems around the world. However, for tropical savannas, little is known about the effects of fire on flower production at community and species scale, especially for the ground-layer. Aims: We assessed the role of fire as a trigger to short-term flowering in cerrado grassland, compared with unburned vegetation. Methods: We recorded the presence of flowers or fruits in 2,441 individuals from 47 plant species (grasses, forbs and subshrubs), during 6 months after fire, in burned and unburned areas of cerrado grasslands, in south-eastern Brazil. Results: In the burned areas, 63% of individuals sampled flowered, in contrast to 19% in unburned areas, demonstrating a strong and positive effect of fire on plant communities of cerrado grasslands. Fire significantly induced flowering in 79% of the studied species, of which 20 species flowered only after fire (nine grasses, seven subshrubs and four forbs). Conclusions: These results highlight the role of fire triggering important ecological processes in the cerrado grasslands, potentially benefiting seed production and genetic diversity of many species. Fire is a crucial factor to be maintained for conservation of these ecosystems and their biodiversity.}, number={3}, journal={PLANT ECOLOGY & DIVERSITY}, author={Pilon, Natashi A. L. and Hoffmann, William A. and Abreu, Rodolfo C. R. and Durigan, Giselda}, year={2018}, pages={259–266} }
 @article{hoffmann_flake_abreu_pilon_rossatto_durigan_2019, title={Rare frost events reinforce tropical savanna-forest boundaries}, volume={107}, ISSN={["1365-2745"]}, DOI={10.1111/1365-2745.13047}, abstractNote={Abstract


The ability of vegetation to ameliorate or exacerbate environmental extremes can generate feedbacks that mediate the distribution of biomes. It has been suggested that feedbacks between vegetation and frost damage may be important for maintaining savanna, particularly at the edge of the tropics.

We quantified frost damage and air temperature across a network of 30 permanent plots distributed across tropical savanna–forest boundaries in Brazil during an uncommonly hard frost.

Tree cover strongly buffered temperatures during frost events, such that forest sites were up to 5°C warmer than nearby sites occupied by open shrub savanna. Consequently, in forest, woody plants were not damaged, but in savanna, there was extensive dieback of trees and shrubs. Within savanna, frost had disproportionately large effects on small individuals, likely due to colder temperatures near the ground and the lower thermal mass of thin stems. Across species, frost tolerance was strongly correlated with latitudinal range limit, revealing the importance of minimum temperature as a species filter at the regional scale. Counterintuitively, savanna species, which are adapted to open habitats where frost is more likely, were more vulnerable to cold than were forest species and experienced more than twice the amount of leaf damage as co‐occurring forest species.

Synthesis. Frost reinforces the effects of fire on vegetation structure by preferentially damaging trees in open environments and generating high loads of dead, flammable fuels. However, frost does not currently occur with sufficient frequency in the region to maintain open savanna by itself. Nevertheless, it occurs with sufficient frequency and severity that it likely acts as an environmental filter and evolutionary selective factor for some of the most frost‐sensitive species.

}, number={1}, journal={JOURNAL OF ECOLOGY}, author={Hoffmann, William A. and Flake, Samuel W. and Abreu, Rodolfo C. R. and Pilon, Natashi A. L. and Rossatto, Davi R. and Durigan, Giselda}, year={2019}, month={Jan}, pages={468–477} }
 @article{abreu_hoffmann_vasconcelos_pilon_rossatto_durigan_2017, title={The biodiversity cost of carbon sequestration in tropical savanna}, volume={3}, ISSN={["2375-2548"]}, DOI={10.1126/sciadv.1701284}, abstractNote={Forest expansion into Brazilian savanna due to fire suppression causes precipitous species loss.}, number={8}, journal={SCIENCE ADVANCES}, author={Abreu, Rodolfo C. R. and Hoffmann, William A. and Vasconcelos, Heraldo L. and Pilon, Natashi A. and Rossatto, Davi R. and Durigan, Giselda}, year={2017}, month={Aug} }