SignificanceIdentifying and explaining regional differences in tropical forest dynamics, structure, diversity, and composition are critical for anticipating region-specific responses to global environmental change. Floristic classifications are of fundamental importance for these efforts. Here we provide a global tropical forest classification that is explicitly based on community evolutionary similarity, resulting in identification of five major tropical forest regions and their relationships: (i) Indo-Pacific, (ii) Subtropical, (iii) African, (iv) American, and (v) Dry forests. African and American forests are grouped, reflecting their former western Gondwanan connection, while Indo-Pacific forests range from eastern Africa and Madagascar to Australia and the Pacific. The connection between northern-hemisphere Asian and American forests is confirmed, while Dry forests are identified as a single tropical biome.

The scaling of stem and crown was studied in eight Cecropia species in Amazonian and southeastern forests of Brazil. The Amazonian species, C. concolor, C. palmata, C. purpurascens, C. sciadophylla, and C. ulei were studied in Manaus, Amazonas, Brazil. The southeastern species, C. glaziovii, C. hololeuca, and C. pachystachya were studied in Linhares, Espírito Santo, Brazil. Measures of diameter, height, number of branches, number of leaves, and total leaf area were log transformed and regressed on height. Three models of mechanical designs of trees, elastic, constant stress, and geometric similarity, were tested for Cecropia. None of the models can totally describe Cecropia, but geometric similarity was a close approximation. Most of the species did not vary in diameter-height relationships between unbranched and branched individuals. Safety factors diminished with height in most species studied. The crown-height relationships were similar for all species. Numbers of branches and leaves showed some variation among species and are related to height of first branching. Total leaf area had a constant allometric relationship among species, although regression intercepts differed according to species leaf areas. The scaling relationships of stem and crown in Cecropia varied with adult size of the studied species.

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). A APA Sul-RMBH foi criada para compatibilizar a atividade econômica e a conservação do seu patrimônio natural, que abrange áreas de Floresta Estacional Semidecidual, Cerrado e Campo. O objetivo deste estudo foi caracterizar as comunidades arbóreas de alguns remanescentes florestais da APA quanto à estrutura, composição e similaridade florística. Foram estudadas oito áreas florestais distantes até 60 km entre si. Em cada área, foram amostrados 30 pontos quadrantes, tomando-se as medidas de circunferência e altura das árvores (≥ 15 cm de circunferência). No total, foram identificados 55 famílias, 121 gêneros e 221 espécies. O número de famílias variou de 24 a 36 e o de espécies de 40 a 68. A altura média foi de 9,1 a 11,5 m e o diâmetro médio foi de 10,8 a 17 cm. A similaridade florística (Jaccard) variou de 5,8 a 23,4%, mostrando serem as matas bastante distintas. Não houve correlação significativa entre distância geográfica e a similaridade. Os índices de diversidade de Shannon (H') variaram de 3,11 a 4,04 nats/indivíduo. A manutenção da diversidade na APA Sul-RMBH dependerá do estabelecimento de estratégias de preservação do maior número possível de remanescentes e das matas ciliares que mantêm a conectividade entre áreas já preservadas. Palavras-chave:Biodiversidade, conservação, floresta semidecídua ABSTRACT -(Floristic and structural heterogeneity of forest remnants in the Área de Proteção Ambiental ao Sul da Região Metropolitana de Belo Horizonte (APA Sul-RMBH), Minas Gerais State, Brazil). The APA Sul was created to conciliate economic activities and natural resource conservation of forest, savanna, and grasslands of the metropolitan area of Belo Horizonte, SE Brazil. The aim of this study was to characterize the floristic composition and structure of the tree community of some forest remnants from APA Sul. We studied eight sites with distances among them up to 60 km, using the point-centered quarter method. In each area, we sampled 30 points, and measured circumference (≥ 15 cm) and height of trees. We found 55 families, 121 genera and 221 species. The number of families varied from 24 to 36 and, the number of species from 40 to 68. Mean height ranged from 9.1 to 11.5 m and, mean diameter from 10.8 to 17 cm. Floristic similarity indexes (Jaccard) among areas ranged from 5.8 to 23.4%, showing that the areas were very different. There was no significant relationship between geographic distance and similarity index. Shannon Diversity Indexes varied from 3.11 to 4.04 nats/individual. Biodiversity conservation in APA-Sul will depend on the public policies that guarantee the conservation of the largest possible number of forests and of the riparian forests that maintain the connectivity among preserved areas. Key words: Biodiversity, conservation, semideciduous forest IntroduçãoO Estado de Minas Gerais ainda apresenta remanescentes do que foi uma extensa faixa de florestas pertencentes ao domínio da Mata Atlântica, atualmente reduzida à cerca de 4% de sua cobertura original (Costa et al. 1998). Estas áreas f...

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