No abstract

The woody plants in an edge area formed approximately 35 years ago in an Atlantic Forest fragment in northeastern Brazil were examined, and three environments defined: edge, intermediate, and interior. Canopy tree densities and basal areas were found to be similar in all three environments, and also similar to previous published studies in the same region; species richness was greatest at the forest edge. The understory showed greater species richness in the forest interior, but greater diversity and equitability in the intermediate environment. Understory environments close to the forest edge demonstrated larger stem diameters than in the forest interior, although at lesser densities and with smaller total basal areas. Our results indicated the existence of distinct patterns in canopy and understory that most likely reflect differences in the response times of these two vegetation layers, with the understory being more sensitive to alterations in environmental structure. Keywords

RESUMO Foram identificados padrões florísticos e estruturais relacionados à degradação pelo uso antrópico da caatinga a partir da seleção de comunidades vegetais em três ambientes: degradado, medianamente degradado e conservado. As plantas foram amostradas em três estratos verticais: lenhosas altas (altura ≥ 3 m), lenhosas baixas (50 cm ≤ alt. < 3 m) e regeneração (alt. < 50 cm). Foram estimadas riqueza, densidade e diversidade, e analisadas as curvas densidade-espécie e espécies-área. Como efeito da degradação, a vegetação apresentou menor número de espécies no estrato das lenhosas baixas: foram três espécies no ambiente degradado e 10 no conservado. Diversidade e densidade também foram menores no ambiente degradado (0,56 e 2.328 ind/ha), do que no conservado (1,32 e 26.557 ind/ha). Dominaram o estrato das lenhosas baixas Malvastrum coromandellianum no ambiente degradado, e Cordia leucocephala e Croton mucronifolius no conservado. Não se detectou influência da degradação no estrato da regeneração, exceto pelo menor número de espécies no ambiente degradado, estimado pelo modelo espécie-área. São condições favoráveis ao desenvolvimento desse estrato: maior densidade dos estratos superiores e maior espessura do horizonte A do solo.

Questions Which types of land use adjacent to Atlantic Tropical Forests induce the strongest edge effects in terms of the functional responses of arboreal and understorey plants? Which functional traits respond to stress imposed by each land‐use type in the two forest layers? Location Full‐protection conservation areas in the metropolitan region of Recife, Pernambuco State, Brazil. Methods We calculated the proportions of species and individuals of woody plants in terms of their functional traits (seed size, maximum height, dispersal syndrome and regeneration strategy) along the edge and in the interior of tropical Atlantic Forest remnants exposed to different degrees of adjacent urbanization along their borders (urban, suburban and rural) by establishing 120 sampling points (60 plots considering the arboreal components and 60 subplots considering woody understorey plants).The degree of urbanization adjacent to the edges of the remnant forests were determined by mapping the sites based on satellite images. The intensities of the edge effects on functional composition, and the differences in the functional traits were assessed using multivariate analysis. Results Functional composition along the edges and within the forest interiors of remnants with the highest densities of urban areas around them demonstrated the greatest variability of both the arboreal and understorey components. The arboreal component of the forest sites adjacent to rural areas (intense agricultural activities) tended to demonstrate intermediate intensity edge effects. Species showing shade intolerance, with smaller maximum heights, producing small seeds and with abiotic dispersion were present in high proportions in forests bordering heavily urbanized areas. Biotic dispersal predominated in the arboreal component of the rural remnant. Conclusions From a functional point of view, the forest with the most highly urbanized border is more impacted by edge effects than forests bordering on suburban or rural areas. Nonetheless, in an urban–rural gradient, intense agricultural activity was observed to create intermediate pressure in terms of the intensities of its edge effects. These edge effects differentially impact the functional traits of the arboreal and understorey components, influencing different traits, depending on the type of border.

Edge effects on the structure and dynamics of the canopy and understory of a forest fragment were examined in Igarassu, PE, Brazil. Two 10 × 100 m transects perpendicular to the forest edge (and divided into 10 × 10 m plots) were separated into outer (0-50 m) and inner edges (50-100 m) and their vegetations compared to those of 10 plots in a 20 × 50 m transect in the forest interior (280 m from the edge). The plots were the sampling units. All woody plants with stem perimeters at breast height (PBH) > 15 cm (canopy) were identified and measured within each plot. Plants with PBH < 15 cm and perimeter at soil level > 3 cm (understory) were also identified and measured in the 5 × 5 m subplots. The results indicated that canopy and undergrowth at the edge of the forest fragment studied were not totally recovered in structural terms, for most of the parameters analyzed.Key words: canopy, mortality, plant, recruitment, understory Efeito de borda na estrutura de dinâmica de um fragmento de Floresta Atlântica no nordeste do Brasil RESUMOOs efeitos de borda foram determinados no dossel e no sub-bosque de um fragmento florestal em Igarassu, PE, Brasil. Dois transectos de 10 × 100 m, perpendiculares à borda da floresta e divididos em parcelas de 10 × 10 m foram separados em borda externa (0-50 m) e borda interna (50-100 m) e a vegetação foi comparada com as parcelas de um transecto de 20 × 50 m no interior da floresta (280 m de distância da borda). Dentro de cada parcela, todas as plantas lenhosas com diâmetro do caule à altura do peito (DAP) > 4,77 cm (dossel) foram identificadas e medidas. Em sub-parcelas de 5 × 5 m, plantas com DAP < 4,77 cm e diâmetro ao nível do solo > 0,96 cm (sub-bosque) também foram identificadas e medidas. As amostras de solo foram coletadas em cada parcela e analisadas textura e propriedades químicas. As medições foram feitas em 2005 e repetidas em 2008. O dossel teve maior número de espécies e densidade de plantas na borda, enquanto o sub-bosque apresentou maior número de espécies, densidade de plantas e área basal no interior. Recrutamento e aumento em diâmetro ao longo dos três anos foram maiores no interior, tanto no dossel quanto no sub-bosque. A análise de correspondência canônica mostrou que as características do solo não afetaram a distribuição das espécies. Considerando que alguns resultados encontrados para o dossel pode ser dito que a borda do fragmento é selada, mas o sub-bosque está ainda na fase de recuperação.