(22º30' e 22º33'S; 42º15' e 42º19'W) foram identificados, descritos e mapeados. Foram identificadas seis unidades fisionômicas, sendo duas florestais (floresta aluvial e floresta submontana) e quatro não florestais (formação pioneira com influência fluvial, capoeira aluvial, capoeira submontana e campo antrópico). As características fisionômicas e florísticas mais relevantes de cada unidade foram descritas e discutidas com base na análise comparativa entre as seis unidades fisionômicas e com outros trechos de mata atlântica. O mapeamento foi realizado com emprego de fotointerpretação analógica, em escala de 1:20.000. Na avaliação da cobertura vegetal atual foram estimados 2.608 hectares de remanescentes florestais em variados estados de preservação (floresta aluvial -17,9% e floresta submontana -34,3%), indicando a expressiva representatividade de formações não florestais com influência fluvial (20,0%) ou antrópica (27,9%). Palavras-chave: mapa de vegetação, mata atlântica, composição florística, fito-fisionomia ABSTRACT (Physiognomic-floristic characteristics and vegetation map of the Poço das Antas Biological Reserve, Silva Jardim, Rio de Janeiro, Brazil) Six vegetation types are described for Poço das Antas Biological Reserve, Rio de Janeiro State, Brazil (22º30' e 22º33'S; 42º15' e 42º19'W). Two forest formations (alluvial forest and submontane forest) and four non-forest formations (fluvial pioneer, alluvial scrub, submontane scrub and manmade grasslands) were identified. Relevant floristic and physiognomic characteristics of each unit are described and compared to analogous Atlantic Rain Forest formations. The vegetation was mapped using analog photo interpretation on a scale of 1:20,000. An estimated 2,608 ha of forest remnants in various states of preservation were detected (alluvial forest -17.9%; submontane forest-34.3%), plus a significant representation of non-forest formations with fluvial influence (20.0%) and manmade interference (27.9%).
RESUMO Investigou-se aspectos do efeito da fragmentação e isolamento de habitats sobre a estrutura dos elementos arbóreos encontrados em três fragmentos florestais de diferentes tamanhos e formas, situados na Reserva Biológica de Poço das Antas, Silva Jardim, RJ. Foram demarcados transectos de 10 m de largura e comprimento variado de acordo com a extensão do fragmento, com orientações norte-sul e leste-oeste, subdivididos em parcelas contíguas de 10 x 25 m, sendo todos os indivíduos arbóreos com DAP $ 5 cm marcados e coletados dados de altura e diâmetro. Registraram-se 1.771 indivíduos, distribuídos em 43 famílias, 107 gêneros e 207 espécies. As áreas apresentam alta diversidade, onde as famílias Euphorbiaceae, Sapotaceae, Annonaceae, Moraceae e Nyctaginaceae configuram-se como as de maior valor de importância. A proporção elevada de espécies (70%) em baixa densidade representa risco potencial de extinção para muitas populações locais, por outro lado a presença de espécies comuns em diferentes estágios de desenvolvimento, aliado ao arranjo espacial e a distância entre as áreas, permitindo a ação de polinizadores e dispersores atuam no sentido de minimizar este efeito.
RESUMO A Reserva Biológica de Poço das Antas, situada no município de Silva Jardim, Rio de Janeiro apresenta cobertura vegetal formada por áreas de campos, capoeiras, capoeirões e fragmentos florestais. Este trabalho realizou o levantamento florístico e a análise da estrutura do componente herbáceo/subarbustivo de área de pasto abandonado, visando obter informações que auxiliem o estudo do processo de regeneração natural da área. A área de estudo apresenta indivíduos lenhosos, distribuídos esparsamente ou em moitas, tendo sido utilizada como pasto em tempos anteriores a criação da Reserva. O levantamento da vegetação foi efetuado através do método de pontos e revelou o predomínio de espécies de gramíneas e ervas ruderais, como Imperata brasiliensis, Lygodium volubile e Blechnum serrulatum.
In order to assess long-term community dynamics in tree populations, we investigated trees with a diameter at breast height (DBH) ≥ 5 cm in an 11-ha fragment of submontane tropical forest in southeastern Brazil, at the beginning and end of a seven-year period. We observed a general tendency toward decreasing numbers of trees and toward stability in basal area. The stability in basal area was associated with an equilibrium between the loss of trees and the basal area gain from the horizontal growth of surviving trees, as well as from recruits The abundance of dead trees was significantly higher than was that of recruits. Changes in tree abundance occurred mainly in the lower DBH classes, whereas changes in basal area occurred mainly in the intermediate DBH classes. Among trees with a DBH ≥ 10 cm, the observed rates of mortality and recruitment (2.4% yr −1 and 1.8% yr −1 , respectively) were similar to those reported for other tropical forests. When we examined only trees with a DBH ≥ 10 cm, we found the half-life to be 29.5 years, which places the forest fragment studied among the most dynamic of tropical forests. Over the seven-year period evaluated, the tree community lost ten species, with no new records. The most abundant species showed the highest rates of mortality and recruitment. Climax species, whether shade-tolerant or light-demanding, accounted for more species and individuals than did pioneer species, suggesting that the former group has a greater influence on forest dynamics. The results suggest that the tree community studied is in or is approaching a state of dynamic equilibrium, the changes in community structure and composition being attributed to periodic fluctuations.Tree community dynamics in a submontane forest in southeastern Brazil: growth, recruitment, mortality and changes in species composition over a seven-year period Acta bot. bras. 28 (2): 190-197. 2014. Solange de Vasconcellos Albuquerque Pessoa and Dorothy Sue Dunn de Araujo Acta bot. bras. 28(2): 190-197. 2014.
Tropical forests are one of the most important ecosystems and loss of biological diversity in these is a major concern. We studied seven forest remnants on the coast of Rio de Janeiro, southeastern Brazil, three medium-sized (24-63 ha) and four small (5-11 ha), to assess the influence of size, degree of disturbance and isolation on composition and diversity of the tree layer. A total of 443 species in 60 families and 185 genera were recorded, with Myrtaceae, Lauraceae and Fabaceae being the most species-rich families. The results showed areas of high α-diversity (α= 34.86-75.69) and a slightly greater decline of similarity with distance between the study areas. Remnant size not explained the variation in the species composition and we found correlation between the level of disturbance and the floristic composition. The remnants had low floristic similarity, strongly influenced by the degree of disturbance. Results suggest that disturbance influences composition and diversity and confirm the importance of including both medium-sized and small remnants in the conservation of tropical forest diversity.
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