Ecologists have long sought to understand the factors controlling the structure of savanna vegetation. Using data from 2154 sites in savannas across Africa, Australia, and South America, we found that increasing moisture availability drives increases in fire and tree basal area, whereas fire reduces tree basal area. However, among continents, the magnitude of these effects varied substantially, so that a single model cannot adequately represent savanna woody biomass across these regions. Historical and environmental differences drive the regional variation in the functional relationships between woody vegetation, fire, and climate. These same differences will determine the regional responses of vegetation to future climates, with implications for global carbon stocks.

Biological knowledge is important for guidance of conservation polices. In the Cerrado, an extremely diverse biome, the last synthesis of floristic knowledge has more than ten years. To understand the progress on the information, our aim was quantify the tree species of the Cerrado, and assess their distribution. We compiled 167 inventories and rapid surveys of tree species, corresponding to 625 sites. We accessed the species distributions in the Brazilian biomes, and estimated the number of species in the savannas of Cerrado using four algorithms. We observed a greater local richness in more central regions of the biome, but due to high beta diversity, more peripheral regions presented a greater cumulative richness. The Atlantic Forest was the most important neighbouring biome, influencing the floristic composition of the Cerrado. The proportion of typical Cerrado species was 16%. The highest proportion of endemic species is possibly found in other life forms, and it is crucial that these species are included in inventories and floristic surveys. To guide new studies and help supplement the knowledge of the Cerrado's flora, we identified the main sampling gaps, located mainly in ecotonal regions, which are responsible for the largest number of species recorded in studies of the Cerrado.

Mound fields are a common landscape throughout the world and much of the evidence for their origin has been of a circumstantial nature. It has been hypothesized that earth mounds emerge over grasslands by termite activity; alternatively, they might be formed after erosion. We tested whether a mound field in central Brazil was generated by termite activity or erosion. We used soil organic matter isotopic composition, soil chemical, physical and floristic composition to determine the origin of a mound field. If the mounds emerged by termite activity in an established grassland the soil organic matter below the mound should have the isotopic signature of C 4 dominated grassland, which contrasts with savanna C 3 + C 4 signature. Additionally, soil traits should resemble those of the grassland. All markers indicate that the mounds were formed by erosion. The soil isotopic composition, chemical traits and texture below the mound resembled those of the savanna and not those of the grassland. Moreover, most of the species present in the mound were typical of savanna. Concrete evidence is provided that mound fields in the studied area were produced by erosion of a savanna ecosystem and not termite activity. The use of the techniques applied here would improve the assessments of whether analogous landscapes are of a biogenic nature or not.

O objetivo deste estudo foi descrever a riqueza, estrutura e diversidade de espécies arbóreas em áreas de Floresta Estacional e ecótono (Floresta Estacional/Floresta Ombrófila) no estado do Tocantins, buscando subsídios para a conservação, manejo florestal, compensação de reserva legal e recuperação ambiental, além de discutir as identidades fitogeográficas em comparação com outras florestas do Brasil. Em 18 bacias hidrográficas, conduziu-se amostragem da vegetação arbórea (DAP > 5 cm) de 22 áreas (amostras) por meio do inventário de 477 parcelas de 400 m². Foram elaboradas análises de classificação pelo método TWINSPAN, em duas escalas distintas. A primeira avaliou a diversidade beta entre as parcelas amostradas no estado do Tocantins e a segunda buscou analisar a similaridade das florestas do Tocantins em relação a outras florestas do bioma Cerrado e suas áreas de tensão ecológica. As florestas amostradas apresentaram ampla variação em termos de riqueza (33 a 243 espécies), densidade (486 a 1.179 ind.ha-1), área basal (14,04 e 37,49 m².ha-1), índices de diversidade (H´ = 2,75 a 4,59) e de equabilidade (J´= 0,72 a 0,86). As análises de classificação convergiram para resultados comuns, identificando quatro ambientes dissimilares em termos florísticos e estruturais no estado do Tocantins: Floresta Estacional Decidual, Floresta Estacional Semidecidual, ecótono Floresta Estacional Semidecidual/Floresta Ombrófila e ecótono Floresta Estacional Decidual/Floresta Ombrófila. A fim de manter a diversidade de plantas e de ambientes na região de transição Floresta Amazônica e Cerrado, sugere-se que o processo de criação de unidades de conservação no estado do Tocantins deva ser intensificado e tenha como base para seleção das áreas critérios biogeográficos.

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Cerrado is the second largest biome in South America and accounted for the second largest contribution to carbon emissions in Brazil for the last 10 years, mainly due to land-use changes. It comprises approximately 2 million km2 and is divided into 22 ecoregions, based on environmental conditions and vegetation. The most dominant vegetation type is cerrado sensu stricto (cerrado ss), a savanna woodland. Quantifying variation of biomass density of this vegetation is crucial for climate change mitigation policies. Integrating remote sensing data with adequate allometric equations and field-based data sets can provide large-scale estimates of biomass. We developed individual-tree aboveground biomass (AGB) allometric models to compare different regression techniques and explanatory variables. We applied the model with the strongest fit to a comprehensive ground-based data set (77 sites, 893 plots, and 95,484 trees) to describe AGB density variation of cerrado ss. We also investigated the influence of physiographic and climatological variables on AGB density; this analysis was restricted to 68 sites because eight sites could not be classified into a specific ecoregion, and one site had no soil texture data. In addition, we developed two models to estimate plot AGB density based on plot basal area. Our data show that for individual-tree AGB models a) log-log linear models provided better estimates than nonlinear power models; b) including species as a random effect improved model fit; c) diameter at 30 cm above ground was a reliable predictor for individual-tree AGB, and although height significantly improved model fit, species wood density did not. Mean tree AGB density in cerrado ss was 22.9 tons ha-1 (95% confidence interval = ± 2.2) and varied widely between ecoregions (8.8 to 42.2 tons ha-1), within ecoregions (e.g. 4.8 to 39.5 tons ha-1), and even within sites (24.3 to 69.9 tons ha-1). Biomass density tended to be higher in sites close to the Amazon. Ecoregion explained 42% of biomass variation between the 68 sites (P < 0.01) and shows strong potential as a parameter for classifying regional biomass variation in the Cerrado.

A large ecological area on the earth's surface, with fauna and flora (animals and plants) adapting to their environment. A biome also defined by its non-living factors, such as climate, geology, soil, and vegetation.

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