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Leaves of 208 trees were collected for isotopic analysis together with wood from 36 tree boles and 18 samples of fine litter from a terra-firme forest located at Samuel Ecological Reserve, Rondônia State, in the southwestern Amazon region. The range of δC values in leaves was from -28 to -36‰, with an average (±1 SD) of -32.1 ± 1.5‰, which was more negative than the δC values of bole samples (-28.4 ± 2.0‰) and fine litter (-28.7 ± 2.0‰). These values are within the range found for tropical and subtropical forests. Pooling the δC values for leaf samples from trees of the same height gave averages which were positively correlated with plant height at a highly significant level, with a slope of 0.06 and an intercept of -33.3‰ and a correlation coefficient r =0.70 (P<0.001).

Foi realizado um levantamento florístico de três remanescentes de floresta montana localizados na Mata Atlântica do sul da Bahia. Durante os anos de 2004 a 2008 foram feitas coletas periódicas de material botânico, principalmente ao longo de trilhas no interior dos fragmentos das áreas: Reserva Serra da Pedra Lascada - SPL, Reserva Serra das Lontras - SLO e Reserva Particular do Patrimônio Natural Serra Bonita - SBO. A riqueza florística em cada área foi comparada entre si e com outras áreas de Mata Atlântica na Bahia e no Sudeste do Brasil. Foi registrado um total de 1.129 espécies em 467 gêneros e 124 famílias. O hábito arbóreo representou 46,9% das espécies, seguido de herbáceas (20,1%), epífitas (19,5%) e trepadeiras (13,5%). As famílias Araceae, Asteraceae, Bromeliaceae, Fabaceae, Lauraceae, Melastomataceae, Myrtaceae, Orchidaceae, Piperaceae, Poaceae, Rubiaceae e Solanaceae apresentaram a maior riqueza florística nas três áreas em conjunto. O gênero Psychotria (Rubiaceae) apresentou o maior número de espécies em todas as áreas (21 spp.), destacando-se também Miconia (20 spp.), Solanum (20 spp.), Piper (19 spp.), Ocotea (16 spp.), Leandra (16 spp.), Peperomia (15 spp.) e Myrcia (14 spp.). Os resultados confirmam a elevada riqueza de angiospermas no sul da Bahia e evidenciam, pela primeira vez, a ocorrência de espécies características de regiões montanhosas da Mata Atlântica do Sudeste do Brasil nessa região.

Tree species composition and structure of a 40-year chronosequence of secondary forests was compared with old-growth forests in southern Bahia, Brazil. Twelve stands were randomly selected that represented three age classes: 10, 25, and 40 year old with four replications in each class. All stands selected had been established after abandonment from swidden cultivation and were surrounded by old-growth forests. In every stand, ten 0.01-ha transects were established and all stems (C5 cm diameter at breast height) were measured and identified. Results were compared with the dataset of two neighboring old-growth sites. Mean diameter, total height, and stand basal area increased with age. Number of trees/ha peaked in 40 year old stands. The results showed that secondary forests in this region take much more than 40 years to recover the structure of old-growth forests. In contrast, species richness recovery was rapid with a continuous accumulation of species with age in secondary forests.Species richness and diversity increased with age as did similarity between secondary stands and oldgrowth stands. More than half of the species found in the 40 year old stands were shared with the neighboring old-growth forests. However, species richness and diversity were higher in old growth sites.

Floristic analyses (Principal Component Analysis and Analysis of Group Indicators) at the genus level were employed to characterize and compare seasonal forest formations in northeastern Brazil. The presence -absence of 248 genera of woody plants occurring in 24 floristic surveys was correlated with geomorphology and climatic variables. The analyses were consistent and point to the existence of two floristic groups of seasonal forests in the region, one more closely related to the Atlantic Coastal Forest (mata atlântica) and the other to the xerophytic formations (caatinga) of the region. The driest seasonal forest group experiences more than 8 dry months per year and/or a total annual rainfall of <1000 mm, and is found on the ancient eroded peaks in the semi-arid core and on the western slopes of the Borborema Plateau.Keywords: diversity, tropical dry forest, caatinga, Atlantic coastal forest. As florestas estacionais do nordeste brasileiro representam uma única unidade florística? ResumoAnálises florísticas no nível genérico (análise de componentes principais e análise de grupos indicadores) foram realizadas com o objetivo de caracterizar e comparar as formações florestais estacionais do Nordeste oriental brasileiro. A presença -ausência de 248 gêneros de plantas lenhosas presentes em 24 levantamentos florísticos foi correlacionada com a geomorfologia e variáveis climáticas. As análises foram consistentes e apontaram a existência de dois grupos florísticos de florestas estacionais, um mais relacionado às florestas litorâneas (mata atlântica) e outro às formações xerofíticas (caatinga). O grupo das florestas estacionais mais secas sofre pelo menos oito meses de seca por ano e recebe no máximo 1000 mm per year de precipitação, sendo estas encontradas sobre os picos elevados da região semiárida e na encosta ocidental do planalto da Borborema.Palavras-chave: diversidade, floresta tropical seca, caatinga, Floresta Atlântica costeira.

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-(Floristic composition and structure of the arboreal component of a transitional area of Atlantic forest in southern Bahia, Brazil). The purpose of this study was to attempt to detect a floristic transition in forest along an altitudinal gradient on a mountain side in southern Bahia, Brazil. The study site is located at the east-west transition from tropical moist to semideciduous forests. A belt transect of one hectare (10 × 1000 m) was established running up the slope (from ca. 350 m to 750 m elevation). All included trees and lianas ≥ 5 cm in diameter at breast height were numbered, collected, and measured. Density, dominance, frequency, and importance values (IV) were calculated for each species. We encountered 1400 individuals and 264 species of woody plants in 56 families. Cariniana legalis (Mart.) Kuntze had the highest IV, based on the dominance of a small number of trees. Discocarpus pedicellatus Fiaschi & Cordeiro and Ampelocera glabra Kuhlm. were the most frequent trees, with 90 and 86 individuals respectively. Ninety-six species were represented by a single individual. The Fabaceae and Myrtaceae were the most diverse families with 37 and 31 species respectively. Cluster analysis and correspondence analysis (DCA) revealed that the composition of the forest along the uppermost 30 percent of the transect was distinct from the rest. The lower and upper forests can be considered respectively as semideciduous and moist forests. Although there are some well-marked floristic differences between these forests, both clearly belong to the southern Bahian sector of the Atlantic coastal forests.Key words -altitudinal gradient, Atlantic coastal forest, Bahia, tropical semi-deciduous forest RESUMO -(Composição florística e estrutura do componente arbóreo de uma área transicional de Floresta Atlântica no sul da Bahia, Brasil). O objetivo deste estudo foi averiguar a existência de uma possível transição florística ao longo de um gradiente altitudinal numa floresta serrana do sul da Bahia, Brasil. A área amostrada situa-se em uma zona de transição (leste-oeste) entre florestas ombrófilas e estacionais. Um transecto linear abrangendo um hectare (10 × 1.000 m) foi situado na encosta da serra (de ca. 350 a 750 m.s.m.). Todas as árvores e lianas com DAP ≥ 5 foram numeradas, coletadas e medidas. Foram calculados valores de densidade, dominância, frequência e valor de importância (VI) para cada espécie amostrada. Foram amostrados 1.400 indivíduos agrupados em 264 espécies e 56 famílias de angiospermas. Cariniana legalis (Mart.) Kuntze teve o maior VI, devido à elevada dominância de poucos indivíduos. Discocarpus pedicellatus Fiaschi & Cordeiro e Ampelocera glabra Kuhlm. foram as espécies mais frequentes, com 90 e 86 indivíduos respectivamente. Noventa e seis espécies foram representadas por apenas um indivíduo. As famílias mais diversas foram Fabaceae e Myrtaceae com 37 e 31 espécies respectivamente. Análises de agrupamento e correspondência (DCA) revelaram que a composição florística da floresta situada na porção...

Despite having one of the world's highest deforestation rates, the tropical forest of RondBnia state in the southwest Amazon is virtually unknown in terms of nutrient dynamics. To fill this knowledge gap, the distribution of nutrients in a humid tropical forest located in the Ecological Reserve of Samuel, RondBnia state, was addressed. A total of 474 trees with diameter at breast height (DBH) > 10 cm were mapped at the Ecological Reserve of Samuel, a 20,000-ha area bordering the Samuel Hydroelectric Reservoir, which is located 50 km south of Porto Velho, RondBnia state, Amazon region, Brazil. These individuals belonged to ca 220 species distributed in 41 families. From this total, leaves of 354 trees were collected for chemical compositional analysis; boles of 96 trees and fine branches of 75 trees also were collected. Soil samples were gathered for fertility analysis at two soil depth intervals: 0-50 and 50-100 cm. In general, soils were acidic and very poor in terms of elemental contents. For plants, the highest concentrations of K, and Mg were found in leaves and fine branches, and the highest concentration of Ca was in the litter. The lowest nutrient concentration was observed in boles. The nutrient concentrations of leaves collected at Samuel were similar to that found in other terra jirme forests of the Amazon region and other tropical forests growing on poor soils. Comparisons of nutrient concentrations among families, genera, and species revealed that only N concentrations were distinct among botanical taxa; the variability found in concentrations of other nutrients were larger and did not reveal any significant differences. Like aboveground biomass, the total nutrient stocks of trees was concentrated in a few large individuals. This fact reveals important implications about the impacts caused by selective logging. Although few trees are cut per hectare in this activity, the effects on the ecosystem structure, due tn the loss of nutrients, may be underestimated.