Carpotroche brasiliensis is a native tree of the Brazilian Atlantic Forest with potential economic value for cultivation in agroforestry systems. We conducted an experiment to determine the photosynthetic and survival responses of young C. brasiliensis plants to electrochemical changes in flooded soils as an indication of their flood tolerance and potential for cultivation in flood-prone areas. Soil flooding decreases the reduction–oxidation potential (redox) potential (Eh), pH, and electrical conductivity (Ec) of the soil, with subsequent recovery of the pH and Ec. Decreases in Eh negatively affect net photosynthesis (A). In flooded soil, decreased A was associated with decreased stomatal conductance (gs) and after 21 days was also associated with decreases in the instantaneous carboxylation efficiency (A/Ci) and potential quantum yield of photosystem II (Fv/Fm). Although flooded C. brasiliensis seedlings developed morphological structures known to increase flood tolerance, this was not enough to prevent severe signs of flooding stress. After 21 days of flooding, flooded plants were unflooded, and 17 days after plants were removed from flood, 90 percent of the unflooded plants died. Our results demonstrate that young plants of C. brasiliensis are suitable for planting in agroforestry systems only in areas with well-drained soils.
Landscape-scale habitat loss can change the floristic composition of forest fragments, affecting the survival of specific groups of plants, as shade-tolerant and emergent trees. This increasing in tree mortality creates forest canopy gaps of different sizes that ultimately determine the solar radiation available in the forest understorey. We conducted a study aiming to assess how the loss of forest cover at landscape level (i.e. deforestation) affects the sunfleck dynamics, a proxy of light regime in forest understorey. We expected that fragments located in landscapes with less forest cover have a high number of larger canopy gaps and, consequently, long-lasting sunflecks. In each forest fragment, a 100 per 50 m plot was established, and in each plot, we took 10 hemispherical photographs. The images were analysed using the Gap Light Analyzer software. The sunflecks were divided into six temporal classes. We evidenced that landscape-scale deforestation increased the frequency of all sunfleck intervals >8 min, particularly the long-lasting (> 32 min) sunflecks. We propose that the increasing frequency of long-lasting sunflecks reduces suitability of microhabitat to some shade-tolerant species in local fragments, a potential proximal mechanism contributing to compositional shifts of tree assemblages observed in forest fragments within deforested landscapes.
Forest loss is one of the most serious threats to biodiversity in the tropics and mainly occurs due to the conversion of native forests by the expansion of human activities. In addition, regional climate change is likely to adversely affect the remaining biota. These disturbances may have direct or indirect consequences on the demographic structure of plant species in human-modified landscapes. To test this hypothesis, and thus look for management practices aimed at enhancing the population viability, we used the palm species Euterpe edulis Mart. (Arecaceae) to assess the demographic structure of five ontogenetic stages prior (2014) and after (2017) a prolonged drought event (2015) that occurred in the northeastern Atlantic Forest of Brazil. We also investigated the influence of landscape forest cover on the ontogenetic demographic structure, given that forest remnants were embedded within landscapes ranging from 6 to 97% of forest amount. We revealed that forest cover was a key predictor explaining the abundance patterns of E. edulis, with all ontogenetic stages (except seedlings, immature, and adults) exhibiting lower abundance in forest remnants surrounded by lower amount of native forests. Conversely, the regional drought event unaffected the demographic structure of this palm species, which may suggest that populations of E. edulis were able to cope with an isolated, though severe, drought event. The impacts of forest loss on E. edulis demographic structure, particularly on juveniles, raises a concern about the future persistence of E. edulis populations, since the early stages represent the adult generation in the near future. Management measures, including species reintroduction, forest restoration, environmental education programmes and the enforcement of environmental laws must be encouraged to safeguard E. edulis populations in the Atlantic Forest.
Introdução: A perda de habitat e a fragmentação florestal são processos que levam a alterações na composição florística dos remanescentes florestais, afetando diretamente a sobrevivência das árvores de grande porte, ou emergentes. Este aumento na mortalidade de árvores cria clareiras no dossel da floresta de diferentes tamanhos que, em última análise, determinam a radiação solar disponível no sub-bosque da floresta. A dinâmica de sunflecks, que é um proxy do regime de luz no sub-bosque, tem influência no ganho de carbono da vegetação do sub-bosque e no processo de regeneração e recrutamento de plântulas. Objetivo: O presente estudo teve como objetivo avaliar como a perda de cobertura florestal em escala de paisagem afeta a ocorrência e a dimensão de clareiras no dossel florestal, usando a frequência e duração de sunflecks. Esperamos que paisagens com menor cobertura florestal tenham clareiras de maior tamanho e, consequentemente, apresentem mais sunflecks de longa duração. Por outro lado, paisagens mais florestadas, devem apresentar maior número de sunflecks de curta duração. Material e Métodos: Foram selecionados 18 fragmentos em um gradiente contínuo de perda de cobertura florestal, localizados nos municípios de Una e Belmonte no sul da Bahia. Foram estabelecidas parcelas de 100 x 50 m. Nessas parcelas foram obtidas 10 fotos hemisféricas. As fotografias hemisféricas foram obtidas utilizando uma câmera digital Nikon Coolpix 4300, equipada com uma lente (180º). As imagens foram analisadas utilizando-se o software Gap Light Analyzer (GLA). Os sunflecks foram divididos em 6 grupos de classes temporais diferentes: 2 > 4 min, 4 > 8 min, 8 > 16 min, 16 > 32 min, 32 > 64 min e = 64 min. Resultados: Evidenciamos que o desmatamento em escala de paisagem aumentou a frequência de todos os intervalos de sunflecks à partir de > 8 min, e particularmente os sunflecks de longa duração (> 32 min). Conclusão: Nós propomos que o aumento da frequência de sunflecks de tempos maiores reduz a adequação de habitats de algumas espécies vegetais tolerantes à sombra em fragmentos mais desmatados, sendo o sunfleck um mecanismo proximal potencial que contribui para mudanças na composição de árvores observadas em fragmentos florestais mais desmatados na paisagem.
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