Resumo A contribuição do estrato herbáceo para a diversidade de plantas tropicais é considerável, mas esse componente permanece subamostrado. Investigamos questões florísticas, estruturais, ecológicas e de conservação relacionadas ao componente herbáceo de uma floresta estacional decidual associada a afloramentos rochosos graníticos na região do Cristalino, que é uma área chave para a conservação da biodiversidade na Amazônia brasileira. Instalamos um plot permanente de 1 ha, alocando 10 linhas de 20 m cada. Identificamos os indivíduos amostrados, medimos altura e projeção e verificamos cobertura e frequência por espécie, gênero e família. Registramos 86 espécies, 62 gêneros e 25 famílias, sendo Orchidaceae a família com maior riqueza de espécies. Entre as 26 novas espécies adicionadas à Flora do Cristalino, incluímos Philodendron deflexum Poepp ex Schott e Griffinia nocturna Ravenna, esta última ‘Criticamente Ameaçada’. Além disso, a ocorrência de G. nocturna em uma matriz florestal amazônica é uma novidade neste estudo. A estimativa da diversidade de espécies de acordo com Shannon-Wiener (H ‘) foi 2,43 nats / ind.-1 (equivalente a 11,37 ± 0,90 IC95% espécies igualmente comuns), e de acordo com Simpson (1/D), 6,82 (± 0,648 IC95%). As curvas de rarefação e extrapolação para as estimativas de diversidade tenderam à estabilização. Embora a vegetação associada a afloramentos rochosos em geral apresente um elevado número de espécies endêmicas, esse padrão não foi encontrado para a nossa área de estudo, o que pode ser explicado pela sua ocorrência contínua à matriz florestal. O sub-bosque da nossa área de estudo apresenta mistura de floras, sendo composto principalmente por espécies dos biomas Amazônia e/ou Cerrado. Diante das pressões antrópicas existentes no sul da Amazônia, reforçamos a importância da realização de inventários das comunidades herbáceas desse bioma, já que o risco de perda de espécies é ainda mais alarmante quando consideramos a subamostragem desse componente.

Abstract The contribution of the herbaceous stratum to tropical plant diversity is considerable, however this component remains undersampled. We investigated floristic, structural, ecological and conservation issues concerning the herbaceous component of a seasonal deciduous forest associated with granitic rock outcrops in the Cristalino Region, a key area for biodiversity conservation in the Brazilian Amazon. We installed a permanent plot of 1 ha, allocating 10 transect-lines of 20 m each. We identified the sampled individuals, measured height and projection, and verified cover and frequency per species, genera and family. We recorded 86 species, 62 genera and 25 families, with Orchidaceae being the family with the highest species richness. Among the 26 new species added to Cristalino Flora, we included Philodendron deflexum Poepp. ex Schott and Griffinia nocturna Ravenna, the latter ‘Critically Endangered’. Furthermore, the occurrence of G. nocturna in an Amazonian forest matrix is a novelty in this study. The estimate of species diversity according to Shannon-Wiener (H’) was 2.43 nats.ind.-1 (equivalent to 11.37 ± 0.90 IC95% equally common species), and according to Simpson (1/D), 6.82 (± 0.648 IC95%). The rarefaction and extrapolation curves for the diversity estimates tended to stabilize. Although the vegetation on rock outcrops usually presents a high number of endemic species, this pattern was not found in our study area, which can be explained by its continuous occurrence in the forest matrix. The understory of our study area consists in a mixture of floras, being composed mainly of species from the Amazon and/or Cerrado biomes. In view of the current anthropic pressure faced by the southern Amazon, we reinforce the importance of carrying out inventories of its herbaceous communities, since the risk of species loss is even more alarming when considering present undersampling of this component.

ABSTRACT Ecological transitions usually represent vulnerable ecosystems and high biodiversity. Investigating their drivers is important from both biogeographic and conservationist perspectives. One of these transitions is situated between the two largest biogeographic domains of South America - the Amazon and the Cerrado. We evaluated variation in tree floristic composition throughout this transition and assessed which factors explain this variation. We used 17,240 records of occurrences of 2,530 tree species from the NeotropTree database. We investigated variation in floristic composition using UPGMA cluster analysis with bootstrap resampling and NMDS ordination, and modeled the distribution of species in relation to environmental and spatial predictors by means of transformation-based Redundancy Canonical Analysis (tb-RDA) and variance partitioning. We found four general floristic groups: 1) flooded forests; 2) white sand dwarf-forests; 3) savannic and dwarf forests; and 4) non-flooded forest types. Floristic variation along the transition was influenced by the environment, especially variables related to fire and soil moisture, and by space, especially variables acting on broader scales. Correspondence between the environmental heterogeneity found throughout the transition and our results demonstrates once again the importance of conserving biogeographical transition zones in general, and the most comprehensive of South America in particular.

ABSTRACT We present a summary of floristic variation and distribution of richness of tree and tree-like taxa (i.e., freestanding plants that reach at least 3m in height) in Brazil. We investigated composition patterns throughout phytogeographic domains and vegetation types based on 698,490 occurrence records obtained from the NeoTropTree (NTT) database, and used rarefaction and extrapolation methods to compare species richness. We delimited areas of high taxa richness in Brazil by applying the Geographic Interpolation of Endemism method. There are 9,108 tree species catalogued in NTT for Brazil, but our extrapolations indicate that the total could reach 9,525 species. Predominantly forested domains showed the greatest richness of taxa with the Amazon domain having the highest number of exclusive taxa. Fabaceae and Myrtaceae were the most represented families. The richest vegetation types were Rain Evergreen Forest and Seasonally Semideciduous Forest. Distribution patterns of richness in Brazil and among its domains were found to be controlled by different spatial scales for each taxon. Transition zones had high species richness. The patterns found here can help to identify priority areas for biodiversity conservation in Brazil.

Resumo: A vegetação que se associa a afloramentos rochosos é responsável por incrementar a diversidade florística e de paisagens, uma vez que a flora pode ser distinta da paisagem circundante. Nosso objetivo foi caracterizar a vegetação lenhosa sobre o afloramento rochoso da RPPN Mirante da Serra, região do Cristalino, estado de Mato Grosso, Brasil. Em uma Floresta Estacional Decidual associada a afloramento granítico, demarcamos uma parcela de 1 ha. Realizamos coletas nesse plot, instalado para a realização de estudos de monitoramento e, ainda, coletas aleatórias em trilhas próximas da parcela para melhor representar a flora do afloramento. A amostragem resultou em um total de 126 espécies, 95 gêneros e 39 famílias. Ao todo, 18 espécies foram incrementadas à Flora do Cristalino, das quais sete são novos registros à flora do estado de Mato Grosso e quatro ao Domínio da Amazônia. Encontramos duas espécies ameaçadas e 17 endêmicas do Brasil. O afloramento rochoso presente na RPPN Mirante da Serra é uma importante área de conservação para uma contínua realização de estudos florísticos de modo a possibilitar um programa de monitoramento da área, considerando os novos registros de ocorrência e, também, por conter espécies ameaçadas.

Abstract: Vegetation associated with rocky outcrops is responsible for increasing floristic and landscape diversity, since its flora can be different from the adjacent landscape. Our objective was to characterize the woody vegetation associated with the rocky outcrop of the RPPN Mirante da Serra, Cristalino region, Mato Grosso State, Brazil. In a Deciduous Seasonal Forest associated with granite outcrops, we demarcated a plot of 1ha. We performed collections on this plot, installed for conducting monitoring studies, and also random collections on trails near the plot to better represent the outcrop flora. We totaled 126 species, 95 genera and 39 families. Overall, 18 species were increased to the Flora of Cristalino - with seven new records to the flora of Mato Grosso and four new records to the Amazon Domain. We found two threatened and 17 Brazilian endemic species. The rocky outcrop present in the RPPN Mirante da Serra is an important conservation area for a continuous execution of floristic studies in a manner to enable a monitoring program of the area, considering the new occurrence records and also because it contains threatened species.

ABSTRACT The effect of environmental variables on the plant species distribution in the Atlantic Forest raises the interest of researchers, but few studies, mainly at local scales, analyzed the influence of spatial factors on the environment and species distribution. Linear models and spatial correlograms were used to evaluate whether environment and space may predict variations in species composition of trees and shrubs in a Subtropical Rainforest remnant. The study area was divided in 25 plots of 400 m², systematically distributed, where individuals with DBH ≥ 5 cm were measured. Elevation and slope were the most important predictors of the floristic variations, but space, generally neglected in researches on South American's vegetation, had a relevant influence, as a structural component, in terms of environmental variables, and as intrinsic biological component, here probably as result of constraints in species dispersion. Although the origin of great part of the variation in species composition remained unknown, which is common in studies on vegetation, results indicated, for the first time, the complex role of spatial and environmental variables in the composition of trees and shrub species in a Subtropical Rainforest of Brazil.

ABSTRACT Estimating species richness with herbarium data and new collections allows us to understand the distribution of diversity. We investigated the accuracy of lycophyte and fern sampling along a vegetation gradient in the subtropical Atlantic Forest in southern Brazil. We compiled lycophyte and fern collection metadata and estimated species richness and assessed sampling accuracy for sixty 50 x 50 km units using ACE, Chao 1, Chao 2, Jackknife 1 and Jackknife 2 estimators. We compiled data for 12,779 fern specimens of 441 species, 67 of which were sampled in only one unit (singletons) and 35 in two units (duplicates). Of the 60 units examined, only 11 had observed values that were above 70% of their estimated values, and 14 had observed levels between 65-70% of the estimated values, meaning that 35 units had a sampling accuracy of less than 65%. In spite of the long history of lycophyte and fern collecting in the study area, there remain units with a lower than expected sampling accuracy for a subtropical forest. This finding indicates that a sizeable collection effort is needed in order to discover the actual distribution of species before the effects of fragmentation and deforestation become permanent.

RESUMO Nós submetemos dados geoclimáticos e de ocorrência de espécies arbóreas de 59 sítios em uma bacia hidrográfica na Mata Atlântica do sudeste do Brasil a análises de ordenação, ANOVA e agrupamento com os objetivos de investigar as causas dos padrões fitogeográficos e determinar se as seis sub-regiões reconhecidas constituem unidades florísticas distintas. Nós descobrimos que clima e espaço foram significativamente (p ≤ 0,05) importantes na explicação dos padrões fitogeográficos. As variações florísticas seguem gradientes térmicos ligados à altitude tanto em sub-regiões costeiras como interioranas. Um gradiente de sazonalidade da precipitação esteve relacionado com a variação florística até 100 km para o interior a partir do oceano. A temperatura no trimestre mais quente e a precipitação durante o trimestre mais frio foram os principais preditores. As sub-regiões Planície Arenosa Costeira, Terra Baixa Costeira, Montanha Costeira, e Depressão Central foram reconhecidas como unidades florísticas distintas. Diferenças significativas não foram encontradas entre Montanha do Interior e Cadeia do Espinhaço, indicando que essas sub-regiões devem compor uma única unidade florística abrangendo todas as áreas elevadas do interior. Por causa de suas peculiaridades ecológicas, os campos ferruginosos no interior da Cadeia do Espinhaço podem constituir uma unidade especial. As unidades florísticas aqui propostas fornecerão informações importantes para o sábio planejamento da conservação no hotspot Mata Atlântica.

ABSTRACT We submitted tree species occurrence and geoclimatic data from 59 sites in a river basin in the Atlantic Forest of southeastern Brazil to ordination, ANOVA, and cluster analyses with the goals of investigating the causes of phytogeographic patterns and determining whether the six recognized subregions represent distinct floristic units. We found that both climate and space were significantly (p ≤ 0.05) important in the explanation of phytogeographic patterns. Floristic variations follow thermal gradients linked to elevation in both coastal and inland subregions. A gradient of precipitation seasonality was found to be related to floristic variation up to 100 km inland from the ocean. The temperature of the warmest quarter and the precipitation during the coldest quarter were the main predictors. The subregions Sandy Coastal Plain, Coastal Lowland, Coastal Highland, and Central Depression were recognized as distinct floristic units. Significant differences were not found between the Inland Highland and the Espinhaço Range, indicating that these subregions should compose a single floristic unit encompassing all interior highlands. Because of their ecological peculiarities, the ferric outcrops within the Espinhaço Range may constitute a special unit. The floristic units proposed here will provide important information for wiser conservation planning in the Atlantic Forest hotspot.

Accurate knowledge of floristic composition is crucial when planning and designing research projects and public policies. In this study, our goal was to assess tree sampling accuracy and to identify sites with higher concentrations of rare tree species, as well as those with the highest tree species richness, in the state of Santa Catarina, Brazil. We determined sampling accuracy using the first-order jackknife and Chao 2 estimators, calculated the number of rare species (singletons and doubletons) and applied sampled-based rarefaction. We found that sample accuracy (estimated vs. observed values) was over 90% for the state as a whole, the best estimates having been obtained for the areas of rain forest (first-order jackknife: 91%; Chao 2: 95%). Of the tree species identified, 16.6% were considered rare in the state and only 4% were found in all forest types. Among the various forest types, semideciduous forests showed the highest proportions of rare tree species. Tree species richness was highest in the rain forests and lowest in the dwarf cloud forests. Our results make an important contribution to the conservation of tree species within one of the "hottest" biodiversity hotspots in the world.