Rubens Manoel dos Santos

Identity and relationships of the Arboreal Caatinga among other floristic units of seasonally dry tropical forests (SDTFs) of north-eastern and Central Brazil

The tree species composition of seasonally dry tropical forests (SDTF) in north-eastern and central Brazil is analyzed to address the following hypotheses: (1) variations in species composition are related to both environment (climate and substrate) and spatial proximity; (2) SDTF floristic units may be recognized based on peculiar composition and environment; and (3) the Arboreal Caatinga, a deciduous forest occurring along the hinterland borders of the Caatinga Domain, is one of these units and its flora is more strongly related to the caatinga vegetation than to outlying forests. The study region is framed by the Brazilian coastline, 50th meridian west and 21st parallel south, including the Caatinga Domain and extensions into the Atlantic Forest and Cerrado Domains. Multivariate and geostatistic analyses were performed on a database containing 16,226 occurrence records of 1332 tree species in 187 georeferenced SDTF areas and respective environmental variables. Tree species composition varied significantly with both environmental variables and spatial proximity. Eight SDTF floristic units were recognized in the region, including the Arboreal Caatinga. In terms of species composition, its tree flora showed a stronger link with that of the Cerrado Dry Forest Enclaves. On the other hand, in terms of species frequency across sample areas, the links were stronger with two other units: Rock Outcrops Caatinga and Agreste and Brejo Dry Forests. There is a role for niche-based control of tree species composition across the SDTFs of the region determined primarily by the availability of ground water across time and secondarily by the amount of soil mineral nutrients. Spatial proximity also contributes significantly to the floristic cohesion of SDTF units suggesting a highly dispersal-limited tree flora. These units should be given the status of eco-regions to help driving the conservation policy regarding the protection of their biodiversity.

Riqueza e similaridade florística de oito remanescentes florestais no norte de Minas Gerais, Brasil

n The objective of this study was to characterize and compare the floristic composition of eight fragments of Calcareous Dry Forest and Arboreal Caatinga in the north of Minas Gerais State, Brazil. The survey of the tree species was performed by periodic visits to the fragments. We found 114 tree species belonging to 40 botanical families in the eight fragments. Of a total of 89 species found in the Calcareous Dry Forest fragments, 37 (42%) were typical of this formation. On the other hand, from the 75 species sampled in the Arboreal Caatinga remnants, 25 species (33%) occurred only in these fragments. The cluster analysis suggested that the floristic composition of the fragments was affected by the phytophysiognomy and by local bioecological conditions. The observed relationship between remnant area and tree species richness suggests that area was a good indicator of species richness in the forest fragments. The results of this study indicate that both historical (phytophysiognomy) and ecological (e.g., remnant area and occurrence of human disturbance) factors constitute important elements that determine the composition and richness of tree species of forest fragments in the north of Minas Gerais State.

Dinâmica da comunidade e populações arbóreas da borda e interior de um remanescente florestal na Serra da Mantiqueira, Minas Gerais, em um intervalo de cinco anos (1999-2004)

The dynamics of the tree community and 26 component populations was investigated in a fragment of tropical semideciduous forest in Piedade do Rio Grande, SE Brazil, based on surveys done in 1999 and 2004 in 30 400 m2 plots, 12 of which were located on the edge of the fragment and 18 in its interior. The purpose was to assess whether the tree community and populations (a) were stable in the period, and (b) showed a more accelerated dynamics on the fragment edge than in its interior. Rates of mortality and recruitment of trees and gain and loss of basal area were obtained for the whole sample, its two sectors, diameter classes and tree populations. The stability hypotheses was rejected because, in both the edge and interior, mortality rates surpassed recruitment rates, gain rates of basal area surpassed loss rates, and size distributions changed, with declining density of smaller trees. These overall changes were possibly related to (a) ongoing long-lasting fragmentation effects, (b) a particular phase of a rhythmic forest cycle and, or (c) the alleged recent global acceleration of forest turnover due to increased CO2 in the atmosphere. The two sectors did differ in their turnover rates higher on the edge than in the forest interior, probably because of more abundant light at the edge, but also because tree populations of fast-growing pioneer and light-demanding species are more abundant at the edge.

Gall inducing arthropods from a seasonally dry tropical forest in Serra do Cipó, Brazil

Highly diverse forms of galling arthropods can be identified in much of southeastern Brazils vegetation. Three fragments of a Seasonally Dry Tropical Forest (SDTF) located in the southern range of the Espinhaco Mountains were selected for study in the first survey of galling organisms in such tropical vegetation. Investigators found 92 distinct gall morphotypes on several organs of 51 host plant species of 19 families. Cecidomyiidae (Diptera) was the most prolific gall-inducing species, responsible for the largest proportion of galls (77%) observed. Leaves were the most frequently galled plant organ (63%), while the most common gall morphotype was of a spherical shape (30%). The two plant species, Baccharis dracunculifolia (Asteraceae) and Celtis brasiliensis (Cannabaceae), presented the highest number of gall morphtypes, displaying an average of 5 gall morphotypes each. This is the first study of gall-inducing arthropods and their host plant species ever undertaken in a Brazilian SDTF ecosystem. Given the intense human pressure on SDTFs, the high richness of galling arthropods, and implied floral host diversity found in this study indicates the need for an increased effort to catalogue the corresponding flora and fauna, observe their intricate associations and further understand the implications of such rich diversity in these stressed and vulnerable ecosystems.

Amazon plant diversity revealed by a taxonomically verified species list

Significance Large floristic datasets that purportedly represent the diversity and composition of the Amazon tree flora are being widely used to draw conclusions about the patterns and evolution of Amazon plant diversity, but these datasets are fundamentally flawed in both their methodology and the resulting content. We have assembled a comprehensive dataset of Amazonian seed plant species from published sources that includes falsifiable data based on voucher specimens identified by taxonomic specialists. This growing list should serve as a basis for addressing the long-standing debate on the number of plant species in the Amazon, as well as for downstream ecological and evolutionary analyses aimed at understanding the origin and function of the exceptional biodiversity of the vast Amazonian forests. Recent debates on the number of plant species in the vast lowland rain forests of the Amazon have been based largely on model estimates, neglecting published checklists based on verified voucher data. Here we collate taxonomically verified checklists to present a list of seed plant species from lowland Amazon rain forests. Our list comprises 14,003 species, of which 6,727 are trees. These figures are similar to estimates derived from nonparametric ecological models, but they contrast strongly with predictions of much higher tree diversity derived from parametric models. Based on the known proportion of tree species in neotropical lowland rain forest communities as measured in complete plot censuses, and on overall estimates of seed plant diversity in Brazil and in the neotropics in general, it is more likely that tree diversity in the Amazon is closer to the lower estimates derived from nonparametric models. Much remains unknown about Amazonian plant diversity, but this taxonomically verified dataset provides a valid starting point for macroecological and evolutionary studies aimed at understanding the origin, evolution, and ecology of the exceptional biodiversity of Amazonian forests.

Dinâmica da comunidade arbórea em um fragmento de floresta estacional semidecidual montana em Lavras, Minas Gerais, em diferentes classes de solos

In order to analyze the existence of structural changes and the influence of different soils classes on tree community dynamics rates, a fragment of tropical montane seasonal semi-deciduous forest (8,7 ha) in SE Brazil was studied in a 5 years period (2000-2005). Data were collected in 47, 20 × 20 m, plots arranged in two 80 m distant transect, crossing the study area toward its widest length. In 2000, were surveyed all individuals with DBH > 5 cm. Species botanical identification were provided and diameters at breast height (DBH) were collected for each tree individual. In 2005, all dead trees were recorded, the surviving trees were remeasured and the recruits were measured and identified (DBH > 5 cm). Mortality, recruitments, basal area loss and gain rates were calculated for each plot, for the total area and for each soil class (Nitosols, Oxysols and Cambisols). The overall pattern in the fragment indicated reduction in number of individuals

Composição florística e análise fitogeográfica de uma floresta semidecídua na Bahia, Brasil

Resumo (Composicâo floristica e analise fitogeografica de urna floresta semidecidua na Bahia, Brasil) As florestas semideciduas na Bahia mostram-se bastante fragmentadas e tem sido pouco estudadas em relacâo a floristica e a fitogeografia. Estas florestas estâo situadas principalmente no semi-arido e isoladas da Mata Atlantica costeira por extensas areas de caatinga. Este trabalho apresenta o levantamento floristico de um fragmento de floresta semidecidua na Serra da Fazenda Retiro (SFR), localizada no municipio de Feira de Santana, Bahia, com o objetivo principal de avahar a sua posicâo fitogeografica em relacâo as caatingas e a Mata Atlantica. Foram amostradas 173 especies incluidas em 143 generos e 59 familias. Myrtaceae foi a familia que apresentou o maior numero de especies (15 spp.), seguida por Euphorbiaceae (13), Leguminosae (12), Malvaceae (7), Orchidaceae (7) e Rubiaceae (7). Alem disso, foram coletadas tres novas especies dos generos Neomarica (Iridaceae), Pseudobombax (Malvaceae) e Solarium (Solanaceae). As analises de agrupamento pelo metodo UPGMA e de composicâo de especies da SFR mostram que a area, apesar de estar situada dentro do Bioma Caatinga, apresenta urna maior relacâo floristica com as florestas semideciduas do Dominio da Floresta Atlantica. Palavras-chave: fitogeograna, flora, florestas secas, Mata Atlantica, semi-arido. Abstract (Floristic composition andphytogeographical analysis of a semideciduous forest in Bahia State, Brazil) The semideciduous forests of Bahia occur as highly fragmented areas and have only received a little attention from floristic and phytogeographical studies. These areas are mainly situated within the semi-arid region and isolated from the Coastal Atlantic Forest by the surrounding dry vegetation of the caatinga domain. This paper presents a floristic survey of a semideciduous forest fragment at Serra da Fazenda Retiro (SFR), Feira de Santana, Bahia State, in order to assess its phytogeographical relationships in comparison to caatinga vegetation and Atlantic Forest. The survey identified 173 species belonging to 143 genera and 59 families. Myrtaceae presented the highest species number (15 spp.), followed by Euphorbiaceae (13), Leguminosae (12), Malvaceae (7), Orchidaceae (7), and Rubiaceae (7). Additionally, three new species of the genera Neomarica (Iridaceae), Pseudobombax (Malvaceae), and Solarium (Solanaceae) were sampled. In spite of the studied area being located within the circumscription of the Caatinga Biome, analysis of similarity (UPGMA) and of the SFR species composition showed that it is more floristically related to semideciduous forest of the Atlantic Forest domain rather than to caatinga vegetation.

Floristic Variation within Seasonally Dry Tropical Forests of the Caatinga Biogeographic Domain, Brazil, and Its Conservation Implications

SUMMARY Seasonally Dry Tropical Forests (SDTF) are gaining recognition as a significant biome and poorly conserved tropical biodiversity refuge. Understanding floristic relationships within SDTF is essential for their effective conservation. This study examines the floristic variation within SDTF of the Caatinga Biogeographic Domain, in north-eastern Brazil. SDTF trees, shrubs and arborescent cacti were sampled in six localities in the Brazilian states of Minas Gerais and Bahia. A number of soil chemical attributes were also measured to analyse vegetation-soil relationships across the study sites. Five floristically distinct SDTF communities were delineated. Differences in these communities are attributable to influences from adjacent savanna and rain forest surrounding the study sites, and also to soil properties such as Al3+, base saturation and gravel content. The high species richness of, and species dissimilarity between communities reflect the need for judicious conservation planning for SDTF that account for biodiversity values and forest structural integrity.

Functional Traits and Water Transport Strategies in Lowland Tropical Rainforest Trees

Understanding how tropical rainforest trees may respond to the precipitation extremes predicted in future climate change scenarios is paramount for their conservation and management. Tree species clearly differ in drought susceptibility, suggesting that variable water transport strategies exist. Using a multi-disciplinary approach, we examined the hydraulic variability in trees in a lowland tropical rainforest in north-eastern Australia. We studied eight tree species representing broad plant functional groups (one palm and seven eudicot mature-phase, and early-successional trees). We characterised the species’ hydraulic system through maximum rates of volumetric sap flow and velocities using the heat ratio method, and measured rates of tree growth and several stem, vessel, and leaf traits. Sap flow measures exhibited limited variability across species, although early-successional species and palms had high mean sap velocities relative to most mature-phase species. Stem, vessel, and leaf traits were poor predictors of sap flow measures. However, these traits exhibited different associations in multivariate analysis, revealing gradients in some traits across species and alternative hydraulic strategies in others. Trait differences across and within tree functional groups reflect variation in water transport and drought resistance strategies. These varying strategies will help in our understanding of changing species distributions under predicted drought scenarios.

Spatial Pattern and Fine-Scale Genetic Structure Indicating Recent Colonization of the Palm Euterpe edulis in a Brazilian Atlantic Forest Fragment

Rainforests worldwide are subject to increasing amounts of external pressure and degradation that dissect continuous species distributions into small and isolated fragments (Whitmore 1997). This spatial isolation and reduction of natural populations negatively affects the reproductive success of many tropical plants (Fuchs et al. 2003; Quesada et al. 2004). A reduction in the number of reproductive individuals in a population represents a decrease in the number of pollen/ovary donors and in the quantity of pollen deposited (Aizen and Feinsinger 1994). This may be accompanied by a decrease in the abundance of pollinators and selection for self-compatibility (Stephenson et al. 2000). Subsequently, such impacts can lead to