Dissecting the difference in tree species richness between Africa and South America.

SignificanceOur full-scale comparison of Africa and South America's lowland tropical tree floras shows that both Africa and South America's moist and dry tree floras are organized similarly: plant families that are rich in tree species on one continent are also rich in tree species on the other continent, and these patterns hold across moist and dry environments. Moreover, we confirm that there is an important difference in tree species richness between the two continents, which is linked to a few families that are exceptionally diverse in South American moist forests, although dry formations also contribute to this difference. Plant families only present on one of the two continents do not contribute substantially to differences in tree species richness.

Climate and evolutionary history define the phylogenetic diversity of vegetation types in the central region of South America.

In South America the biogeographic history has produced different biomes with different vegetation types and distinct floras. As these vegetation types may diverge in evolutionary histories, we analysed how alpha and beta phylogenetic diversity vary across them and determine the main drivers of variation in phylogenetic diversity. To this end, we compiled a list of 205 sites and 1222 tree species spread over four biomes and eight vegetation types in central South America. For each site we evaluated six measures of evolutionary alpha diversity (species richness, phylogenetic diversity sensu stricto and the standardized effect size of phylogenetic diversity, mean phylogenetic distance and mean nearest taxon distance) and beta diversity (phylogenetic Sorensen's similarity). We checked the influence of spatial and environmental variables using generalized least squares models. The greatest phylogenetic differentiation was found between west and east of central South America, mainly between the Chaco communities and the other vegetation types, suggesting that species found in this biome come from different lineages, comparing with the others vegetation types. Our results also showed a clustered phylogenetic structure for the Dry Chaco woodlands, which may be associated with harsh environmental conditions. In addition to historical process, climatic conditions are the main drivers shaping phylogenetic patterns among the distinct vegetation types. Understanding patterns of phylogenetic diversity and distribution can greatly improve conservation planning and management since it allows the conservation of unique biome characteristics.

Long-term monitoring of diversity and structure of two stands of an Atlantic Tropical Forest.

BACKGROUND: This study aimed to report the long-term monitoring of diversity and structure of the tree community in a protected semideciduous Atlantic Forest in the South of Minas Gerais State, Southeast Brazil. The study was conducted in two stands (B and C), each with 26 and 38 10 m x 30 m plots. Censuses of stand B were conducted in 2000, 2005 and 2011, and stand C in 2001, 2006 and 2011. In both stands, the most abundant and important species for biomass accumulation over the inventories were trees larger than 20 cm of diameter, which characterize advanced successional stage within the forest. NEW INFORMATION: The two surveyed stands within the studied forest presented differences in structure, diversity and species richness over the time.

Human impacts affect tree community features of 20 forest fragments of a vanishing neotropical hotspot.

The loss in forest area due to human occupancy is not the only threat to the remaining biodiversity: forest fragments are susceptible to additional human impact. Our aim was to investigate the effect of human impact on tree community features (species composition and abundance, and structural descriptors) and check if there was a decrease in the number of slender trees, an increase in the amount of large trees, and also a reduction in the number of tree species that occur in 20 fragments of Atlantic montane semideciduous forest in southeastern Brazil. We produced digital maps of each forest fragment using Landsat 7 satellite images and processed the maps to obtain morphometric variables. We used investigative questionnaires and field observations to survey the history of human impact. We then converted the information into scores given to the extent, severity, and duration of each impact, including proportional border area, fire, trails, coppicing, logging, and cattle, and converted these scores into categorical levels. We used linear models to assess the effect of impacts on tree species abundance distribution and stand structural descriptors. Part of the variation in floristic patterns was significantly correlated to the impacts of fire, logging, and proportional border area. Structural descriptors were influenced by cattle and outer roads. Our results provided, for the first time, strong evidence that tree species occurrence and abundance, and forest structure of Atlantic seasonal forest fragments respond differently to various modes of disturbance by humans.

Estrutura fitossociológica de um fragmento natural de floresta inundável em área de Campo Sujo, Lagoa da Confusão, Tocantins / Phytosociological structure of a natural fragment of floodplain forest in area of Campo Sujo, municipal district of Lagoa da Confusão, Tocantins, Brazil

Fragmentos de florestas inundáveis localizam-se naturalmente na Planície do Araguaia entre os estados de Tocantins e Mato Grosso nas áreas de Cerrado. Ocorrem sob a forma de depressões naturais, que no estado do Tocantins estão situados nas áreas de planícies de inundação, que favorecem seu alagamento, conseqüentemente, o maior tempo de retenção da água em épocas de elevada precipitação. Este estudo teve como objetivo caracterizar a estrutura de um fragmento de floresta inundável de aproximadamente um hectare, inserido em área de Campo Sujo, no município de Lagoa da Confusão, TO. Foram amostrados todos os indivíduos arbustivo-arbóreos com circunferência 1,30m do solo (CAP) > 15 cm. Ao todo, foram encontrados 665 indivíduos, 34 famílias e 49 espécies. As espécies com maior valor de cobertura, em ordem decrescente, foram Sclerolobium paniculatum var. rubiginosum (Mart. ex Tul.) Benth., Calophyllum brasiliense Cambess. e Licania apetala (E. Mey.) Fritsch. As famílias mais ricas foram Fabaceae (8), Arecaceae, Chrysobalanaceae e Vochysiaceae (3). O índice de diversidade de Shannon (H') foi de 2,97nats/ind. A distribuição de classes de diâmetro apresentou curva na forma de "J" invertido estando a maioria dos indivíduos nas sete primeiras classes.

Fragments of floodplain forests occur naturally in the Araguaia plain between the states of Tocantins and Mato Grosso on the ares of Cerrado. These fragments happen in form of natural depressions, which are located in areas of floodplains in the State of Tocantins, which favors its flooding and, consequently, the largest period of water retention during periods of high precipitation. The objective of this study was to characterize the structure of a fragment of floodplain forest of approximately one hectare, inserted in area of Campo Sujo, in Lagoa da Confusão, TO. Were sampled all the tree/shrub individuals with circumference at 1,30m of the soil (CAB) > 15 cm. On the whole, 665 individuals, 34 families and 49 species were found. The species with larger cover value, in descending order, were Sclerolobium paniculatum var. rubiginosum (Mart. former Tul.) Benth., Calophyllum brasiliense Cambess. and Licania apetala (E. Mey.) Fritsch.. The richest families were Fabaceae (8), Arecaceae, Chrysobalanaceae and Vochysiaceae (3). The Shannon diversity index (H') was 2,97 nats/ind. The distribution of diameter classes showed an inverted "J" curve.