Scielo RSS <![CDATA[Acta Botanica Brasilica]]> vol. 30 num. 3 lang. en <![CDATA[SciELO Logo]]> <![CDATA[Effects of forest structure on litter production, soil chemical composition and litter-soil interactions]]> ABSTRACT Litter production in forest ecosystems is a major indicator of primary productivity because litter helps incorporate carbon and nutrients from plants into the soil and is directly involved in plant-soil interactions. To our knowledge, few studies have investigated the relationship between species diversity and ecosystem processes in subtropical forest fragments. In this work, we determined forest structural parameters and assessed seasonal leaf litter input, leaf decomposition rate, litter quality and soil characteristics in two subtropical Atlantic Forest fragments. Litter production was greater in the native fragment with the higher species diversity (FN1). The two native fragments (FN1 and FN2) differed in basal area, volume and dominance in the upper stratum, which were positively correlated with litter production in FN1 but negatively correlated in FN2. Soil in FN1 exhibited higher contents of organic C, available phosphorus and exchangeable calcium, and the leaf litter had a higher C:N ratio. Although these results are consistent with a plant-soil feedback, which suggests the presence of a complementary effect, the dominance of certain families in subtropical forest fragments results in a selection effect on litter productivity and decomposition. <![CDATA[The scaly tree ferns (Cyatheaceae-Polypodiopsida) of Brazil]]> ABSTRACT A synopsis of all scaly tree fern species (Cyatheaceae) occurring in Brazil is presented. We recognize 51 species in three genera [Sphaeropteris one species, Alsophila four species (one subspecies, two varieties), and Cyathea 45 species (one variety) ] with 17 taxa being endemic to Brazil. One hybrid endemic to Brazil is recognized. Further included are five species that have not yet been recorded in Brazil, but are expected here because they are found in adjacent countries and occur literally on the border with Brazil. We present the first key covering the family for the whole territory of Brazil. <![CDATA[Pollen and spores from surface samples in the <em>campos</em> region of Uruguay and their paleoecological implications]]> ABSTRACT In this study we describe and illustrate pollen and spores that have been identified as significant in modern and fossil samples from the campos region of Uruguay. We provide new information about modern pollen assemblages and their relationship to the vegetation types of this region. We discuss the taxonomic limitations of pollen and spores and their representation in both modern and fossil samples. We highlight the importance of identifying both silent and key indicator taxa for making accurate paleoecological interpretations. We also emphasize the importance of knowing the pollination strategies of parental plants because many of them are zoophilous, and so small changes in the proportions of their pollen grains in fossil assemblages could reflect important changes in vegetation. This study presents a practical approach to paleoecological research, which not only produces robust results in studies of the campos region, but can be applied to other grassland ecosystems, including those in temperate regions. <![CDATA[A Synopsis of <strong><em>Sloanea</em></strong> (Elaeocarpaceae) in the Neotropical extra-Amazonian Region]]> ABSTRACT The genus Sloanea is comprised of 150 species, of which about 50 occur in Brazil among several vegetation types but mainly the Amazon and Atlantic forests. The present work provides a synopsis of the Neotropical species of Sloanea in the extra-Amazonian region based on a recent revision of the genus. In general, morphologically Sloanea comprises large trees endowed with buttressed roots; simple leaves; flowers with sepals that may or may not cover the reproductive organs in pre-anthesis phases; stamens with the connective prolonged into an awn that is acuminate, acute or aristate and fruit covered with rigid or flexible bristles or sometimes unarmed. This synopsis describes 17 species, and provides an identification key, illustrations and comments on their diagnostic characters, geographical distribution and main bibliographic references. <![CDATA[Annual tree rings in <strong><em>Piptadenia gonoacantha</em></strong> (Mart.) J.F.Macbr. in a restoration experiment in the Atlantic Forest: potential for dendroecological research]]> ABSTRACT The tree Piptadenia gonoachantha is widely used in forestry and in forest restoration projects, which require methods for evaluating tree growth. Long-term studies are necessary to determine patterns and detect changes in species growth rhythms. Tree ring analysis provides a precise method for determining age and documenting long-term growth trends in tropical tree species. The present study evaluated the periodicity of tree ring formation and radial growth dynamics of P. gonoachantha from a population of known age in the Poço das Antas Biological Reserve. Two radii from six trees were sampled using non-destructive methods. Tree rings were counted and measured to estimate age and to calculate diametric increment. All samples had 16 tree rings, which matched the known plantation age and confirmed the annual formation of rings. The individuals sampled had a mean annual diametric increment of 9.5 mm / year. Results showed a trend towards decreasing growth rate with increasing age. Individuals of P. gonoachantha in Ombrophilous Dense Forest produce annual tree rings, which holds potential for future dendroecological studies. <![CDATA[Stamen morphoanatomy of <strong><em>Dyckia</em></strong> Schult.f. (Bromeliaceae, Pitcairnioideae) species: new data for taxonomic use]]> ABSTRACT This study presents a morphoanatomical analysis of Dyckia ibicuiensis , D. polyclada and D. racinae stamens. Flowers at anthesis were desiccated and their stamens were processed using common light microscopic techniques. Morphologically, the androecium in these species is differentiated by the disposition of the stamens around the gynoecium and by general anther characteristics. Included stamens, with antesepalous filaments different from those of the antepetalous, anthers in a radial disposition, always curved, and sporangia facing the gynoecium characterize D. ibicuiensis and D. racinae . This configuration results from the filament connation, as well as special anatomical characteristics of the anthers, such as the connective with thickenings. In addition, these species are differentiated by the U-shaped thickening in the endothecium. D. polyclada is characterized by its small, free and exserted stamens, with a very short common tube, its anthers, that are not curved or organized around the gynoecium, and its divergent sporangia. The anatomical and morphological characteristics identified here are important for characterization of these species. Considering that the androecium is important in the delimitation of Dyckia , the increased use of these data should be equally important for other species and infrageneric groupings. <![CDATA[Effect of rosette size, clonality and spatial distribution on the reproduction of <strong> <em>Vriesea carinata</em></strong> (Bromeliaceae) in the Atlantic Forest of Paraná, southern Brazil]]> ABSTRACT Plant size and clonality are important traits for explaining the reproductive effort of clonal plants. Larger plants can invest more resources into reproduction, and clonality is known to increase reproductive effort. Moreover, reproductive effort is influenced by environmental variation, and so the spatial distribution of plants may affect plant reproductive effort. We investigated the effect of plant size, clonality and spatial distribution on the reproductive effort of Vriesea carinata in the Atlantic Forest in the state of Paraná, Brazil. We marked twenty individual plants and measured their rosette size, biomass and number, as well as rosette reproductive effort (number of flowers, fruits and seeds). We also evaluated the relationship between reproductive effort and spatial distribution of plants. Reproductive effort did not correlate with size, whereas greater clonal growth contributed to a lower reproductive effort because rosettes within clones that had more rosettes set fewer flowers. We found that plants growing closer to each other exhibited similar reproductive efforts independently of vegetative traits, because reproductive traits were spatially autocorrelated. In Vriesea carinata, the main drivers of reproductive effort are clonality, which decreases flower production, and spatial factors, which result in greater similarity in reproductive efforts among more proximate plants. <![CDATA[Root fungal associations in some non-orchidaceous vascular lithophytes]]> ABSTRACT Plant roots in natural ecosystems are colonized by a diverse group of fungi among which the most common and widespread are arbuscular mycorrhizal (AM) and dark septate endophyte (DSE) fungi. Though AM and DSE fungal associations are well reported for terricolous plant species, they are rather poorly known for lithophytic plant species. In this study, we examined AM and DSE fungal association in 72 non-orchidaceous vascular plant species growing as lithophytes in Siruvani Hills, Western Ghats of Tamilnadu, India. Sixty-nine plant species had AM and 58 species had DSE fungal associations. To our knowledge, we report AM fungal association in 42 and DSE fungal association in 53 plant species for the first time. There were significant differences in total root length colonization and root length colonized by different AM and DSE fungal structures among plant species. In contrast, the differences in AM and DSE fungal colonization among plants in various life-forms and lifecycles were not significant. AM morphology reported for the first time in 56 plant species was dominated by intermediate type AM morphology. A significant negative relationship existed between total root length colonized by AM and DSE fungi. These results clearly suggest that AM and DSE fungal associations are widespread in lithophytes. <![CDATA[Vascular epiphytic flora of a high montane environment of Brazilian Atlantic Forest: composition and floristic relationships with other ombrophilous forests]]> ABSTRACT Only a few studies regarding vascular epiphytes have been conducted in mixed ombrophilous forests (MOF) in Serra da Mantiqueira, a mountainous environment in the Brazilian Atlantic Forest, where the relationships of epiphytic flora with other physiognomies are unknown. This study aimed to survey the epiphytes of a MOF remnant located in Serra da Mantiqueira, and to analyze the floristic relationships with ombrophilous forests of the Southern and Southeastern regions of Brazil. The checklist was compared with 51 other areas composed of ombrophilous forests and/or ecotones with other physiognomies using UPGMA (with Sørensen index), and canonical correspondence analysis (CCA). We recorded 138 species, and Orchidaceae and Polypodiaceae were the richest families (51 and 23 species, respectively). The UPGMA showed the importance of physiognomy and elevation in the floristic relationships, and CCA reinforced the influence of elevation, in addition to the shortest distance to the ocean and minimum annual temperature; however, in this analysis, the physiognomies showed little influence on the relationships. The epiphytic flora of MOF of Southern and Southeastern regions of Brazil has different relationships compared with the data available for shrubs and trees, suggesting a greater importance of phorophytic species than geographical distance and, to some extent, environmental variables. <![CDATA[Enzyme activity and reserve mobilization during Macaw palm (<strong> <em>Acrocomia aculeata</em></strong> ) seed germination]]> ABSTRACT Reserve mobilization in seeds occurs after visible germination, which is marked by the protrusion of the radicle or cotyledonary petiole, as in species of Arecaceae. Acrocomia aculeata (macaw palm), usually produces hard seeds whose endosperm has mannan-rich cell walls. We investigated the composition of storage compounds in macaw palm seed and the roles of two enzymes (endo-β-mannanase, α-galactosidase) during and after germination. The seeds were firstly submitted to pre-established protocol to overcome dormancy and promote germination. Enzyme activity in both embryo and endosperm were assayed from the initiation of germinative activities until leaf sheath appearance, and the status of seed structures and reserve compounds were evaluated. Protein content of the embryo decreased with the initiation of imbibition while the lipid content began decreasing six days after removal of the operculum. Increases in enzyme activity and starch content were both observed after visible germination. We suggest that endo-β-mannanase and α-galactosidase become active immediately at germination, facilitating haustorium expansion and providing carbohydrates for initial seedling development. Protein is the first storage compound mobilized during early imbibition, and the observed increase in the starch content of the haustorium was related to lipid degradation in that organ and mannan degradation in the adjacent endosperm. <![CDATA[Intraspecific variation in alkaline phosphatase activity in <strong><em>Phaeodactylum tricornutum</em></strong> (Bacillariophyceae, Bohlin)]]> ABSTRACT To describe potential intraspecific variation in phosphorus incorporation in two strains of Phaeodactylum tricornutum (Bohlin), Ub3 and Ub7, alkaline phosphatase (AP) activity was evaluated via enzyme-labeled fluorescence assay. Analysis using the probe ELF-97(r) provides individual evaluation, and therefore can determine the nutritional status of inorganic phosphorus in phytoplanktonic cells. Bioassays compared the control treatment to both phosphate-enriched and phosphate-depleted treatments by varying only the phosphate concentration in the media. The P. tricornutum strains exhibited differences in their development when incubated in the phosphate-enriched media. The development of the Ub7 strain differed by exhibiting "luxury uptake" and utilization of organic phosphorus, and the alkaline phosphatase analysis indicated limitations of this clone under such conditions. The Ub7 strain showed higher AP activity, when compared to Ub3, in the P-enriched condition. P. tricornutum presented increases in AP activity and low variation in Surface/Volume ratio, by increasing biovolume and its maximum linear dimension, as strategies for phosphate incorporation. Our results highlight intraspecific differences in alkaline phosphatase activity, and hence differences in the incorporation of organic phosphorus, as the tested species regulated enzymatic activity under different external phosphate concentrations. <![CDATA[Bryophyte communities of restingas in Northeastern Brazil and their similarity to those of other restingas in the country]]> ABSTRACT Restingas are a coastal component of the Atlantic Forest. They experience high temperatures and possess soils with a low capacity to retain water, low nutrient content and high salt concentrations. Studies on bryophytes of restingas have been mostly conducted in Southeastern Brazil, and so we aimed to characterize the bryophyte flora of seven areas of restinga in the Northeastern Region and to establish their floristic affinities with other restingas in Brazil. Fifty-five species were found in the studied restingas, the vast majority of which are generalist species with life forms of intermediate tolerance to desiccation and of corticicolous and terrestrial habitat. The number of species per area is low compared to the species richness of other restingas in Brazil. A cluster analysis, although based on low similarity, showed that the bryoflora from the surveyed areas is distinct from those of restingas from Bahia, Espírito Santo and Rio de Janeiro, which all form a group, and those of the coast of São Paulo, which also comprised a cluster. The heterogeneous climate, soils and vegetation structure of the studied restingas, in comparison those of the Southeast, act as selective filters for the species, thereby contributing to the distinction observed in those communities. <![CDATA[Can regional and local filters explain epiphytic bryophyte distributions in the Atlantic Forest of southeastern Brazil?]]> ABSTRACT Environmental conditions in distinct tropical rainforest phytophysiognomies can act as regional filters in determining the distribution of montane bryoflora likewise, local filters inherent to phorophyte species can have modulating influences. We analyzed the bryophyte communities in three phytophysiognomies of Atlantic Forest, in order to examine the influences of local (phorophyte species) and regional (forest phytophysiognomies) filters on their distributions. The study was undertaken in the Serra do Mar State Park, Ubatuba, SP, Brazil, using 1 ha plots in three forest phytophysiognomies along an elevational gradient. Four phorophyte species were selected, with three to seven replicates each. The line-intercept method was used on each phorophyte for collecting botanical material. Multivariate analyses were used to correlate species distributions with environmental filters. A total of 71 taxa were identified. Mean bryophyte coverage did not vary among the different phytophysiognomies, and although their species compositions were markedly distinct, no cohesive or isolated groups were found. Among the local filters examined, phorophyte DBH was found to be correlated with bryophyte coverage; the pH of the bark of Euterpe edulis and the high rugosity of the trunk of the Cyatheaceae influenced species compositions. Other filters not evaluated here may also be relevant for determining species distributions. <![CDATA[Late Holocene paleoenvironments of the floodplain of the Solimões River, Central Amazonia, based on the palynological record of Lake Cabaliana]]> ABSTRACT The core PD-67 of 160 cm depth was collected from the delta of Lake Cabaliana situated on the Solimões River. Seventeen samples were removed for palynological and sedimentological analysis and three for radiocarbon analysis. Two dry periods, both in the Late Holocene, were observed (2800-2550 cal yr BP, 1450-550 cal yr BP) separated by a wetter phase (2550-1450 cal yr BP). In 2800-2550 cal yr BP, varzea forests of Alchornea, Symmeria, Cecropia, Alternanthera and Asteraceae were predominant. Beginning in 2,550-1450 cal yr BP, the varzea was characterized by pioneer elements, such as Cassia, Laetia, Mabea, Symmeria and Cecropia, and by the expansion of Poaceae, Cyperaceae, Sagittaria, Montrichardia and Asteraceae. In 1450-550 cal yr BP the succession of varzea continued with Pseudobombax, Laetia, Luehea/Lueheopsis and Ryanaea increasing simultaneously with the terra firme vegetation of Rutaceae, Sapotaceae, Styrax, Scleronema, Anthurium, Araceae, pteridophytes and Pariana. The successional dynamics at Lake Cabaliana indicated that the local varzea had become established recently, and is composed of a mosaic of different successional stages of vegetation influenced mainly by flood pulse and variation in rainfall. It is therefore possible to propose that the recent climate history of Central Amazonia reflects changes in rainfall patterns in the basin. <![CDATA[Isolated trees with high crown coverage and densities increase pasture seed rain]]> ABSTRACT Pasture and crop lands restrict seed dispersal near remnant forest fragments, especially by restricting the movements of dispersal agents and limiting propagule dispersal. Some factors can improve seed dispersal in open areas, such as the presence of high numbers of isolated trees in close proximity to forest fragments. We sought to determine if: (i) the structural characteristics and (ii) densities of isolated trees in pasture lands, and (iii) their distances from the forest fragments, influence seed dispersal. We installed 18 seed traps in each of six pastures (total=108 traps) bordering forest fragments distributed over 6 distance classes from the forest edges (0, 5, 10, 20, 40 and 80 m). We determined the characteristics of the plants surrounding the traps. GLM and GLMer analyses were performed and the best model was selected by AIC. We collected 8162 seeds (4722 anemochorous, 3304 epizoochorous, 72 autochorous, and 64 endozoochorous) belonging to 26 species. Our results showed that plants with high crown coverage close to forest fragments and at high densities in the pastures increased seed dispersal. These results may aid future restoration of pasture lands by improving seed dispersal in this harsh habitat and promoting better connectivity between forest fragments. <![CDATA[Fruits and frugivores of the Brazilian Cerrado: ecological and phylogenetic considerations]]> ABSTRACT Knowing the morphological and phylogenetic patterns of fruits of a plant community may elucidate plant-frugivore interactions, and analysis of dispersal syndromes is a practical approach to understanding these mutualisms. We investigated different zoochorous fruits and frugivorous animals among Cerrado formations (forest, savanna and grassland), mapped dispersal syndromes on a Cerrado angiosperm phylogeny and tested for phylogenetic signal. For a core region in Cerrado, we found that, among almost a thousand fruit species and 258 fruit-eating vertebrates, 60% of the fruits had an ornithochorous syndrome and that 70% of the frugivores were birds. Most fruit and frugivorous species (~80%) inhabit forest formations, but many of them also occurred in more than one Cerrado formation. The zoochorous syndromes were found to have little phylogenetic signal, with many plant families exhibiting more than one fruit syndrome, and with ornithochory being widely distributed throughout the phylogeny. Our results suggest that plant-frugivore interactions tend to be evolutionarily labile in this Neotropical region, although birds have had a prominent role in fruit evolution. Furthermore, we found that all three Cerrado formations seem to be interrelated in maintaining functional stability of the plant-frugivore mutualisms in the Cerrado biome. <![CDATA[Phenodynamics of five orchids species growing on rock outcrops in the Chapada Diamantina Mountains in northeastern Brazil]]> ABSTRACT We evaluated the vegetative and reproductive phenological patterns of the orchids Cattleya elongata, Cyrtopodium aliciae, Epidendrum orchidiflorum, Epistephium lucidum, and Sobralia liliastrum (Orchidaceae) growing on sandstone outcrops in the Chapada Diamantina Mountains in northeastern Brazil. Phenological events were associated with abiotic factors, leaf longevity, life form, plant growth pattern, and pollination syndrome. Phenological observations were made for 18 months and followed the phenophases of: stem/pseudobulb emission, leaf flush, leaf fall, flowering, immature fruit and mature fruit. Seasonality, synchrony, and correlations between phenophases and environmental variables were tested. The orchid species demonstrated aseasonal vegetative phenologies, except for pseudobulb emission. Reproductive events were seasonal, except for flowering in E. orchidiflorum. There was high flowering overlap between the species pairs S. liliastrum and C. aliciae (dry season) and C. elongata and E. lucidum (rainy season). Dispersal occurred during both the rainy and dry seasons. The vegetative phenophases exhibited low synchrony, and were related to certain morphofunctional characters (stems/pseudobulbs, CAM metabolism). The reproductive phenophases showed high synchrony consistent with the deceit pollination strategy usually associated with the group. <![CDATA[The effect of simulated heat-shock and daily temperature fluctuations on seed germination of four species from fire-prone ecosystems]]> ABSTRACT Seed germination in many species from fire-prone ecosystems may be triggered by heat shock and/or temperature fluctuation, and how species respond to such fire-related cues is important to understand post-fire regeneration strategies. Thus, we tested how heat shock and daily temperature fluctuations affect the germination of four species from fire-prone ecosystems; two from the Cerrado and two from the Mediterranean Basin. Seeds of all four species were subjected to four treatments: Fire (F), temperature fluctuations (TF), fire+temperature fluctuations (F+TF) and control (C). After treatments, seeds were put to germinate for 60 days at 25ºC (dark). Responses differed according to species and native ecosystem. Germination percentage for the Cerrado species did not increase with any of the treatments, while germination of one Mediterranean species increased with all treatments and the other only with treatments that included fire. Although the Cerrado species did not respond to the treatments used in this study, their seeds survived the exposure to heat shock, which suggests they possess tolerance to fire. Fire frequency in the Cerrado is higher than that in Mediterranean ecosystems, thus traits related to fire-resistance would be more advantageous than traits related to post-fire recruitment, which are widespread among Mediterranean species.