The multiple roles of trichomes in two Croton species.

Trichomes are common in plants from dry environments, and despite their recognized role in protection and defense, little is known about their role as absorptive structures and in other aspects of leaf ecophysiology. We combine anatomical and ecophysiological data to evaluate how trichomes affect leaf gas exchange and water balance during drought. We studied two congeneric species with pubescent leaves which co-occur in Brazilian Caatinga: Croton blanchetianus (dense trichomes) and Croton adenocalyx (sparse trichomes). We found a novel foliar water uptake (FWU) pathway in C. blanchetianus composed of stellate trichomes and underlying epidermal cells and sclereids that interconnect the trichomes from both leaf surfaces. The water absorbed by these trichomes is redistributed laterally by pectin protuberances on mesophyll cell walls. This mechanism enables C. blanchetianus leaves to absorb water more efficiently than C. adenocalyx. Consequently, the exposure of C. blanchetianus to dew during drought improved its leaf gas exchange and water status more than C. adenocalyx. C. blanchetianus trichomes also increase their leaf capacity to reflect light and maintain lower temperatures during drought. Our results emphasize the multiple roles that trichomes might have on plant functioning and the importance of FWU for the ecophysiology of Caatinga plants during drought.

Landsat data respond to variations in the structure of Caatinga plant communities along a successional gradient.

Plant community succession is generally approached with phytosociological methods, but field surveys are time-consuming, expensive, and limited to several of sites. Remote sensing offers an efficient and economical way to analyze vegetation on large extensions and in inaccessible areas. Most studies addressing remote sensing and tree community succession refer to forest physiognomies. We investigated whether structural changes that occur in non-forest physiognomies are identified by multispectral sensor images (OLI-Landsat). Thirteen 0.1-ha plots were set up in Caatinga fragments aging 10-15, 20-25, 30-35, 40-45 and >50 years to calculate the total density of individuals (TD), mean canopy height (H), total basal area (G) and total aboveground biomass (AGB). We performed correlation analyses between these structural descriptors and eight remote sensing variables (reflectance data and spectral indices) obtained from Landsat images at the end of the rainy season and during the dry season. Blue and short-wave infrared reflectances were negatively correlated with mean height, basal area and biomass, regardless of the analyzed scene (coefficients between -0.58 and -0.79). The litter layer (a non-photosynthetic vegetation component) and the soil exposure are important factors influencing the spectral data.

Costs and benefits of gas inside wood and its relationship with anatomical traits: a contrast between trees and lianas.

Gas inside wood plays an important role in plant functioning, but there has been no study examining the adaptive nature of gas inside wood across plants differing in biomechanical demands. Using a comparative approach, we measured gas volumetric content, xylem's anatomical traits and wood density of 15 tree and 16 liana species, to test whether gas content varies between these plant types strongly differing in their biomechanical demands. We asked (i) whether trees and lianas differ in gas content and (ii) how anatomical traits and wood density are related to gas content. Lianas had significantly less gas content in their branches compared with tree species. In tree species, gas content scaled positively with fiber, vessel and xylem cross-sectional area and fiber and vessel diameter, and negatively with dry-mass density. When pooling trees and lianas together, fiber cross-sectional area was the strongest predictor of gas content, with higher xylem cross-sectional area of fiber associated with higher gas content. In addition, we showed, through a simple analytical model, that gas inside wood increases the minimum branch diameter needed to prevent rupture, and this effect was stronger on trees compared with lianas. Our results support the view that gas inside wood plays an important role in the evolution of biomechanical functioning in different plant forms. Gas inside wood may also play an important role in physiological activities such as water transport, storage, photosynthesis and respiration, but it is still unknown whether these roles are or are not secondary to the mechanical support.

Assembly rules in a resource gradient: Competition and abiotic filtering determine the structuring of plant communities in stressful environments.

The relative importance of different community assembly mechanisms varies depending on the environment. According to the stress-dominance hypothesis (SDH), assembly mechanisms range from strong abiotic filtering to competition as the environment becomes more favourable. Most evidence for the SDH comes from studies in gradients of conditions (i.e. abiotic environmental factors that influence the functioning of organisms but are not consumed by them). However, we hypothesized that in resource gradients, competition increases as abiotic filtering becomes stronger. To test our hypothesis, we set up eight plots at different sites along an abiotic severity gradient in the Brazilian semi-arid region (BSAR). In each plot, we identified and measured each woody plant species found, and we recorded 11 functional traits of the main species, dividing the traits into alpha (competition effects) and beta (abiotic filtering effects). We investigated the presence of phylogenetic signal in the traits, the community phylogenetic and phenotypic patterns, and associated the variation in these patterns with the availability of water and soil nutrients. We found phylogenetic signal for most (91%) of the traits analysed. The phylogenetic patterns varied from clustered in stressful sites to random or overdispersed in favourable sites, and we concluded that these phylogenetic patterns were the result of historical processes influencing community assembly in different environments in the BSAR. In general, the phenotypic patterns varied from clustered at the most stressful end to random at less stressful sites. Our results show that in resource gradients, any restriction of the resource (hydric or edaphic) intensifies abiotic filtering and, at the same time, increases the competitive hierarchy among species. On the other hand, stochastic processes seem to have a stronger influence under more favourable abiotic conditions, where abiotic filtering and competition are weaker. Thus, we conclude that the SDH is not supported in resource gradients.

The role of edaphic environment and climate in structuring phylogenetic pattern in seasonally dry tropical plant communities.

Seasonally dry tropical plant formations (SDTF) are likely to exhibit phylogenetic clustering owing to niche conservatism driven by a strong environmental filter (water stress), but heterogeneous edaphic environments and life histories may result in heterogeneity in degree of phylogenetic clustering. We investigated phylogenetic patterns across ecological gradients related to water availability (edaphic environment and climate) in the Caatinga, a SDTF in Brazil. Caatinga is characterized by semiarid climate and three distinct edaphic environments - sedimentary, crystalline, and inselberg -representing a decreasing gradient in soil water availability. We used two measures of phylogenetic diversity: Net Relatedness Index based on the entire phylogeny among species present in a site, reflecting long-term diversification; and Nearest Taxon Index based on the tips of the phylogeny, reflecting more recent diversification. We also evaluated woody species in contrast to herbaceous species. The main climatic variable influencing phylogenetic pattern was precipitation in the driest quarter, particularly for herbaceous species, suggesting that environmental filtering related to minimal periods of precipitation is an important driver of Caatinga biodiversity, as one might expect for a SDTF. Woody species tended to show phylogenetic clustering whereas herbaceous species tended towards phylogenetic overdispersion. We also found phylogenetic clustering in two edaphic environments (sedimentary and crystalline) in contrast to phylogenetic overdispersion in the third (inselberg). We conclude that while niche conservatism is evident in phylogenetic clustering in the Caatinga, this is not a universal pattern likely due to heterogeneity in the degree of realized environmental filtering across edaphic environments. Thus, SDTF, in spite of a strong shared environmental filter, are potentially heterogeneous in phylogenetic structuring. Our results support the need for scientifically informed conservation strategies in the Caatinga and other SDTF regions that have not previously been prioritized for conservation in order to take into account this heterogeneity.

Does climate influence spatial variation of tree species alpha diversity in the Brazilian Atlantic rainforest? / O clima influencia a variação espacial da diversidade alfa de espécies arbóreas na floresta pluvial Atlântica do Brasil?

We tested the hypothesis that the variation in tree species alpha diversity is driven by climate in the Brazilian Atlantic Rainforest (ARF). Considering 139 samples of trees with DBH ≥ 4.8 cm, we correlated alpha diversity measures (Shannon heterogeneity index H', Chao I richness estimator, and Simpson concentration index C) with climate variables (perhumidity index, mean annual rainfall, and mean annual temperature) and spatial variables (latitude, longitude, and altitude). Using CCA, multiple regression analysis and RDA procedures, we found a positive relationship between latitude, longitude, and altitude with Shannon's diversity index and Chao I richness estimator, and a negative relationship with Simpson concentration index. Over 75% of the variation remained unexplained and were attributed to stochastic processes. These results indicate that climate has a very weak influence on tree species alpha diversity, which is more influenced by spatial variation in the ARF. We propose that the current tree species alpha diversity could be a result of the history of the ARF during the Cenozoic, when geological events and climate oscillations could have triggered biogeographic processes, such as alternating episodes of vicariance and dispersal, which would have lead to the great diversity of species and heterogeneity across the geographic space observed today.

Investigamos a hipótese de que a variação da diversidade alfa de espécies de árvores é determinada pelo clima na Floresta Pluvial Atlântica brasileira (FPA). Considerando 139 amostras de árvores com DAP ≥ 4,8 cm, correlacionamos medidas de diversidade alfa (heterogeneidade de Shannon H', riqueza Chao I e concentração de Simpson C) com variáveis climáticas (índice de perumidade, precipitação total média anual e temperatura anual média) e variáveis espaciais (latitude, longitude e altitude). Aplicando CCA, análise de regressão múltipla e RDA, encontramos correlação positiva da latitude, longitude e altitude com H' e Chao I e uma correlação negativa com a concentração de Simpson. Mais de 75% das variações permaneceram inexplicadas e foram atribuídas a processos estocásticos. Esses resultados indicam que o clima tem uma fraca influência sobre a diversidade alfa de espécies arbóreas, a qual é mais influenciada pela variação do espaço na FPA. Propomos que a atual diversidade de espécies de árvores poderia ser um resultado da história da FPA durante o Cenozoico, quando eventos geológicos e oscilações climáticas poderiam ter desencadeado processos biogeográficos como episódios alternados de vicariância e dispersão, os quais poderiam ter levado à grande diversificação de espécies e sua heterogeneidade no espaço geográfico que se observa atualmente.

Florística e fitossociologia em parcelas permanentes da Mata Atlântica do sudeste do Brasil ao longo de um gradiente altitudinal / Floristic and phytosociology in permanent plots of the Atlantic Rainforest along an altitudinal gradient in southeastern Brazil

Este trabalho resume os dados de florística e fitossociologia de 11, das 14 parcelas de 1 ha, alocadas ao longo do gradiente altitudinal da Serra do Mar, São Paulo, Brasil. As parcelas começam na cota 10 m (Floresta de Restinga da Praia da Fazenda, município de Ubatuba) e estão distribuídas até a cota 1100 m (Floresta Ombrófila Densa Montana da Trilha do rio Itamambuca, município de São Luis do Paraitinga) abrangendo os Núcleos Picinguaba e Santa Virgínia do Parque Estadual da Serra do Mar. Na Restinga o solo é Neossolo Quartzarênico francamente arenoso, enquanto que na encosta o solo é um Cambisolo Háplico Distrófico argilo-arenoso, sendo que todas as parcelas apresentaram solo ácido (pH 3 - 4) com alta diluição de nutrientes e alta saturação de alumínio. Na Restinga e no sopé da encosta o clima é Tropical/Subtropical Úmido (Af/Cfa), sem estação seca, com precipitação média anual superior a 2.200 mm e temperatura média anual de 22 ºC. Subindo a encosta mantêm-se a média de precipitação, mas há um gradativo resfriamento, de forma que a 1.100 m o clima é Subtropical Úmido (Cfa/Cfb), sem estação seca, com temperatura média anual de 17 ºC. Destaca-se ainda que, quase diariamente, a parte superior da encosta, geralmente acima de 400 m, é coberta por uma densa neblina. Nas 14 parcelas foram marcados, medidos e amostrados 21.733 indivíduos com DAP > 4,8 cm, incluindo árvores, palmeiras e fetos arborescentes. O número médio de indivíduos amostrados nas 14 parcelas foi de 1.264 ind.ha-1 (± 218 EP de 95%). Dentro dos parâmetros considerados predominaram as árvores (71% FOD Montana a 90% na Restinga), seguidas de palmeiras (10% na Restinga a 25% na FOD Montana) e fetos arborescentes (0% na Restinga a 4% na FOD Montana). Neste aspecto destaca-se a FOD Terras Baixas Exploradas com apenas 1,8% de palmeiras e surpreendentes 10% de fetos arborescentes. O dossel é irregular, com altura variando de 7 a 9 m, raramente as árvores emergentes chegam a 18 m, e a irregularidade do dossel permite a entrada de luz suficiente para o desenvolvimento de centenas de espécies epífitas. Com exceção da FOD Montana, onde o número de mortos foi superior a 5% dos indivíduos amostrados, nas demais fitofisionomias este valor ficou abaixo de 2,5%. Nas 11 parcelas onde foi realizado o estudo florístico foram encontradas 562 espécies distribuídas em 195 gêneros e 68 famílias. Apenas sete espécies - Euterpe edulis Mart. (Arecaceae), Calyptranthes lucida Mart. ex DC. e Marlierea tomentosa Cambess (ambas Myrtaceae), Guapira opposita (Vell.) Reitz (Nyctaginaceae), Cupania oblongifolia Mart. (Sapindaceae) e as Urticaceae Cecropia glaziovii Snethl. e Coussapoa microcarpa (Schott) Rizzini - ocorreram da Floresta de Restinga à FOD Montana, enquanto outras 12 espécies só não ocorreram na Floresta de Restinga. As famílias com o maior número de espécies são Myrtaceae (133 spp), Fabaceae (47 spp), Rubiaceae (49) e Lauraceae (49) ao longo de todo gradiente da FOD e Monimiaceae (21) especificamente nas parcelas da FOD Montana. Em termos de número de indivíduos as famílias mais importantes foram Arecaceae, Rubiaceae, Myrtaceae, Sapotaceae, Lauraceae e na FOD Montana, Monimiaceae. Somente na parcela F, onde ocorreu exploração de madeira entre 1960 e 1985, a abundância de palmeiras foi substituída pelas Cyatheaceae. O gradiente estudado apresenta um pico da diversidade e riqueza nas altitudes intermediárias (300 a 400 m) ao longo da encosta (índice de Shannon-Weiner - H' - variando de 3,96 a 4,48 nats.indivíduo -1). Diversas explicações para este resultado são apresentadas neste trabalho, incluindo o fato dessas altitudes estarem nos limites das expansões e retrações das diferentes fitofisionomias da FOD Atlântica durante as flutuações climáticas do Pleistoceno. Os dados aqui apresentados demonstram a extraordinária riqueza de espécies arbóreas da Floresta Ombrófila Densa Atlântica dos Núcleos Picinguaba e Santa Virgínia do Parque Estadual da Serra do Mar, reforçando a importância de sua conservação ao longo de todo o gradiente altitudinal. A diversidade desta floresta justifica também o investimento de longo prazo, através de parcelas permanentes, para compreender sua dinâmica e funcionamento, bem como monitorar o impacto das mudanças climáticas nessa vegetação.

This paper summarizes floristic and phytossociology data of 11, out of 14 plots of 1 ha, allocated along an altitudinal gradient in the Serra do Mar, São Paulo, Brazil. The study was conducted at Serra do Mar State Park and the plots start at the sea level (10 m - plot of Restinga Forest that occurs at Praia da Fazenda, Picinguaba, municipality of Ubatuba) up to 1100 m above sea level (the Montane Ombrophilous Dense occurs alongside the Itamambuca Trail, municipality of São Luis do Paraitinga). The Restinga Forest occurs in Pleistocenic Coastal Plain where the soil is classified as a sandy Quartzipsamment (Quartzenic Neosol), while along the slopes of the Serra do Mar, the Ombrophylus Dense Forest grows on the top of a pre-Cambrian crystalline basement with granitic rocks, where the soil is a sandy-loam Dystrophic Inceptisol (Cambisol/Latosol). In all 14 plots soils are acidic (pH 3 - 4), chemically poor, with high dilution of nutrients and high saturation of aluminum. In the Restinga and at the foot of the slope the climate is Tropical/Subtropical Humid (Af/Cfa), with no dry season, an average annual rainfall over 2,200 mm and an average annual temperature of 22 ºC. Towards the top of the Serra do Mar there is a gradual cooling along the slope, but there is no reduction in rainfall, so at 1,100 m above sea level the climate is classified as Humid Subtropical (Cfa/Cfb), with no dry season and an average annual temperature of 17 ºC. It is important to remark that, almost daily, from 400 m above sea level up to the top of slopes the mountains are covered by a dense fog. In the 14 plots 21,733 individuals with DBH > 4.8 cm, including trees, palms and ferns, were marked, measured and sampled. The average number of individuals sampled in each plot was 1264 ind.ha-1(± 218 SE 95%). Within the parameters considered trees prevailed (71% in the Montane ODF to 90% in the Restinga Forest), followed by palms (10% in the RF and 25% in the Montane Ombrophilous Dense Forest/ODF) and ferns (0% % in the RF and 4% in the Montane ODF). Regarding these proportions the Exploited Lowlands ODF differs from the others with only 1.8% of palm trees and striking 10% of ferns. The forest canopy is irregular with heights ranging from 7 to 9 m, rarely emergent trees reach 18 m, and due to this irregularity of the canopy the amount of light that gets through sets conditions for the development of hundreds of epiphytic species. Aside from Montana ODF, where the number of dead trees was more than 5% of individuals sampled, in the other phytophysiognomies this value was below 2.5%. In the 11 plots where the floristic study was conducted we found 562 species in 195 genera and 68 families. Only seven species - Euterpe edulis Mart. (Arecaceae), Calyptranthes lucida Mart. ex DC. and Marlierea tomentosa Cambess (both Myrtaceae), Guapira opposita (Vell.) Reitz (Nyctaginaceae), Cupania oblongifolia Mart. (Sapindaceae), Cecropia glaziovii Snethl. and Coussapoa microcarpa (Schott) Rizzini (both Urticaceae) - occurred from Restinga to Montane ODF, while 12 other species did not occur only in the Restinga Forest. Families with the greatest number of species are Myrtaceae (133 spp), Fabaceae (47 spp), Rubiaceae (49) and Lauraceae (49) throughout the gradient and Monimiaceae (21) specifically in portions Montane ODF. Only in the F plot, where logging has occurred between 1950 and 1985, the abundance of palm trees has been replaced by Cyatheaceae. The study shows a peak of diversity and richness, Shannon-Weiner index (H') ranging from 3.96 to 4.48 nats.ind-1, in the intermediate altitudes (300 to 400 m) along the slope. Several explanations for this result are raised here, including the fact that these elevations are within the limits expansions and retractions of the different phytophysiognomies of the Atlantic ODF due to climate fluctuations during the Pleistocene. The results presented in this paper demonstrate the extraordinary richness of tree species of the Atlantic Rainforest from the northeastern coast of the State of Sao Paulo, reinforcing the importance of its conservation throughout the altitudinal gradient. The richness of this forest justifies a long term commitment to study its dynamics and functioning through permanent plots, and monitor the impacts of climate change in this vegetation.

Florística e estrutura de um trecho de Floresta Ombrófila Densa Atlântica Submontana no Parque Estadual da Serra do Mar, em Ubatuba/SP, Brasil / Tree community structure in an Atlantic forest fragment at Serra do Mar State Park, southeastern Brazil

This work describes the tree community structure and composition in a 1 ha plot of undisturbed Atlantic Forest located at the north coast (S 23° 21' 59.8" - W 45° 05' 02.8") of São Paulo state and relates its floristic composition in a regional context. We sampled all stems with diameter at breast height (dbh) > 4.8 cm in 100 contiguous 10 × 10 m plots. We found 1881 individuals distributed in 206 species, 102 genera and 48 families. 1578 stems were trees (83.9 percent), 237 palms (12.6 percent), eight ferns (0.42 percent) and 58 standing dead trees (3.08 percent). Myrtaceae (43), Rubiaceae (18), Lauraceae (16), and Fabaceae (13) were the families with the greatest number of species, respectively. Rubiaceae, Myrtaceae, Arecaceae, and Sapotaceae had the greatest number of individuals, respectively, summing 946 stems (50.29 percent). Euterpe edulis Mart. had the highest importance value (iv) and stem density (9.5 percent). We found two new species and two other species had their first record in São Paulo state. The species richness (206) and diversity (H' = 4.48 nats.indivíduo-1) are among the highest ever recorded in Brazilian forests.

Este trabalho descreve a composição e a estrutura da comunidade arbórea de 1 ha de Floresta Ombrófila Densa Atlântica Submontana primária localizado no litoral norte do estado de São Paulo (S 23° 21'59.8" - O 45° 05'02.8") e relaciona sua flora em um contexto regional. Todos os indivíduos arbóreos com perímetro a altura do peito (pap) > 15 cm foram amostrados em 100 parcelas (10 × 10 m) contíguas. Foram encontrados 1881 indivíduos de 206 espécies, 102 gêneros e 48 famílias, sendo 1578 árvores (83,9 por cento), 237 palmeiras (12,6 por cento), 8 samambaias arborescentes (0,42 por cento) e 58 mortos (3,08 por cento). Myrtaceae (43), Rubiaceae (18), Lauraceae (16) e Fabaceae (13) foram as famílias de maior riqueza e Rubiaceae, Myrtaceae, Arecaceae e Sapotaceae foram as famílias de maior densidade, somando 946 indivíduos (50,29 por cento). Euterpe edulis Mart. obteve o maior índice de valor de importância (ivi) e a maior densidade (9,5 por cento). Foram registradas duas espécies novas e duas espécies tiveram seu primeiro registro para o estado de São Paulo. A diversidade (H' = 4,48 nats.indivíduo-1) e a riqueza da área (206 espécies) estão entre as maiores registradas em levantamentos de florestas brasileiras.

Florestas de restinga e de terras baixas na planície costeira do sudeste do Brasil: vegetação e heterogeneidade ambiental / Restinga and Lowland forests in coastal plain of southeastern Brazil: vegetation and environmental heterogeneity

Foram avaliadas semelhanças florísticas entre duas fisionomias de Floresta Atlântica na região costeira do Brasil, denominadas Floresta de Restinga e Floresta das Terras Baixas. A hipótese era que, devido à diferença nos processos geomorfológicos, essas duas florestas difeririam em variáveis físico-químicas dos solos, composição florística, biomassa aérea e produção de serapilheira. O trabalho foi conduzido em uma área de 1 ha (100 × 100 m) em cada tipo de floresta, no município de Ubatuba, São Paulo. Foram registrados e medidos todos os indivíduos arbóreos com DAP > 4,8 cm e coletadas amostras de solo e serapilheira. As análises de agrupamento e de ordenação indicaram que os solos e principalmente a flora distribuem-se como grupos bem definidos, concordando com a hipótese de distinção entre as duas florestas. A diversidade de espécies foi maior (p < 0.0001) na Floresta de Terras Baixas (H' = 4,00 nats.indivíduo-1) do que na Restinga (H' = 3,38 nats.indivíduo-1). No entanto, a produção de serapilheira e a biomassa não diferiram (p > 0,05) entre as duas florestas. Esse aparente paradoxo poderia ser explicado supondo-se que, uma vez que espécies diferentes consigam se estabelecer na Restinga ou nas Terras Baixas e encontrem um espectro favorável de condições e recursos, elas tenderiam a persistir e se desenvolver naquele local; nesse caso, embora as condições edáficas difiram entre as duas áreas, cada espécie responderia de modo particular a essas variações, de modo que as florestas poderiam atingir valores semelhantes de biomassa e produção de serapilheira. É provável que o filtro ambiental condicionado pelos solos esteja sendo importante para a forte separação florística entre essas duas florestas.

It was evaluated the floristic similarity between two Atlantic Rainforest physiognomies in Brazilian coast area, herein called Restinga and Lowland forests. The hypothesis was that, due the differences in geomorphologic processes, these forests would differ on soil physical and chemical properties, floristic composition, live above-ground biomass and litterfall production. It was sampled 1 ha (100 × 100 m) for each site located in Ubatuba, São Paulo state, SE Brazil. Within each hectare it was recorded trees with DBH > 4.8 cm in all 10 × 10 m contiguous plots, and collected soil and litterfall samples. The cluster and ordination analyses indicated the two communities as distinct groups considering soil and floristic composition, agreeing with the initial hypothesis. Species diversity was higher (p < 0.0001) in the Lowland forest (H' = 4.00 nats.individual-1) than in the Restinga (H' = 3.38 nats.individual-1). However, litterfall production and biomass did not differ (p > 0.05) between the two forests. This apparent paradox could be explained assuming that, since different species establish themselves in the Restinga or Lowland forests and find a favorable spectrum of conditions and resources, they would tend to persist and to develop in that place; even so the edaphic conditions differ between the Restinga and Lowland forests, each species could respond in a particular way to these variations, and then both forests could reach similar values of biomass and litterfall production. It is probable that the environmental filter conditioned by soils has being important for the strong floristic segregation between these two forests.

The vascular flora of the cerrado in Emas National Park (Central Brazil): a savanna flora summarized

The Brazilian cerrado may be divided in two main phytogeographic sectors: one characterized by Piptocarpha rotundifolia, in which the Emas National Park (ENP) is located, and other characterized by Curatella americana. We carried out a floristic survey in ENP, which allowed an assessment of the taxonomic composition, taxa size, and similarity with other sites for the ENP's vascular flora. We compared the ENP's flora with southeastern outlying cerrado sites, also in the Piptocarpha sector, and with general floristic patterns in the cerrado vegetation. The distribution of species per family in ENP was significantly different from that obtained for each component of the general cerrado flora. The herbaceous component was characterized by an overproportion of Myrtaceae and an underproportion of Orchidaceae and Lythraceae; and the woody component, by an overproportion of Myrtaceae and Nyctaginaceae. When compared with outlying cerrado sites, the ENP was quite distinct, not only at species level, but also at family level.

O cerrado pode ser dividido em dois principais setores fitogeográficos: um caracterizado por Piptocarpha rotundifolia, em que o Parque Nacional das Emas (PNE) está localizado, e outro caracterizado por Curatella americana. Realizamos um levantamento florístico no PNE, que nos permitiu determinar a composição taxonômica de sua flora vascular e sua similaridade com outros sítios. Comparamos a flora do PNE com sítios disjuntos de cerrado, também no setor Piptocarpha, e com padrões florísticos gerais do cerrado. A distribuição de espécies por família foi significativamente diferente daquela obtida para cada componente da flora do cerrado. O componente herbáceo-subarbustivo se caracterizou pela super-representação de Myrtaceae e pela sub-representação de Orchidaceae e Lythraceae; e o componente arbustivo-arbóreo, pela super-representação de Myrtaceae e Nyctaginaceae. Quando comparado aos sítios disjuntos, o PNE se mostrou distinto, não só em nível específico, mas também em nível de famílias.