Efeitos da fragmentação florestal sobre o estabelecimento de quatro espécies arbóreas em florestas de terra-firme na amazônia central

The Amazon basin maintains the largest proportion of tropical forests in the world. However, this region has been suffering with high rates of deforestation and habitat fragmentation. Forest fragmentation can affect either positively or negatively the persistence of tropical tree species some species can increase their densities whereas other species can diminish or even to be locally extinct. Here we tested for the effects of forest fragmentation on the establishment of two canopy species (Eschweilera coriacea and Scleronema micranthum) and two understory species (Helianthostylis sprucei and Rinorea racemosa). The study area is the Biological Dynamics of Forest Fragments Project, in central Amazon, Brazil (2°30 S, 60°O). We compared mortality and recruitment rates of individuals ≥ 10 cm DBH between forest edge and interior sites and among different forest fragment sizes and the density of smaller individuals 1.0-9.9 DBH between edge and interior. While R. racemosa showed high recruitment rate and greater density of smaller individuals in fragmented areas, H. sprucei showed high mortality rate and lower density of small individuals. The canopy species E. coriacea apparently does not respond to the changes occurred from the fragmentation processes. In contrast, demography and population structure of S. micranthum was changed in fragmented areas. For this species, both mortality and recruitment rates were higher in fragmented areas, while the density of small trees was similar between fragmented and continuous areas. The results of this study show that forest fragmentation can lead to differentiated effects in the establishment and demography of tree species and that all tree species life stages should be considered to effectively assess the effects of fragmentation on plant populations. Moreover, these findings suggest that life history and demographic traits of each species, rather than the position that a species occupies in the canopy, determine the susceptibility of a species to forest fragmentationA bacia amazônica sustenta a maior área de florestas tropicais úmidas no mundo. Contudo, nesta região vem ocorrendo elevadas taxas de desmatamento que resulta na perda e fragmentação dos habitats. O processo da fragmentação pode afetar tanto positivamente quanto negativamente o estabelecimento de espécies arbóreas em fragmentos - algumas espécies podem aumentar suas densidades enquanto outras diminuírem ou mesmo se extinguirem localmente. Este trabalho testou os efeitos da fragmentação florestal sobre o estabelecimento de quatro espécies arbóreas, sendo duas espécies de dossel (Eschweilera coriacea e Scleronema micranthum) e duas de sub-bosque (Helianthostylis sprucei e Rinorea racemosa). O trabalho foi realizado na área experimental do Projeto Dinâmica Biológica de Fragmentos Florestais, Amazônia central (2°30 S, 60°O). Foi feita comparação da mortalidade e recrutamento de indivíduos com DAP ≥ 10 cm de cada espécie entre áreas de borda e interior de floresta e diferentes tamanhos de fragmentos e comparação da densidade de indivíduos com DAP de 1 a 9,9 cm entre borda e interior. Enquanto R. racemosa apresentou alta taxa de recrutamento e maior densidade de indivíduos jovens em áreas fragmentadas, H. sprucei apresentou alta taxa de mortalidade e menor densidade de indivíduos jovens. As espécies de dossel apresentaram também respostas distintas à fragmentação. E. coriacea aparentemente não responde às alterações decorrentes do processo de fragmentação. Contrariamente, a demografia e a estrutura populacional de S. micranthum foi alterada em áreas fragmentadas. Para esta espécie, tanto as taxas de recrutamento e mortalidade foram maiores em áreas fragmentadas, porém não houve diferença na densidade média de juvenis entre áreas fragmentadas e contínuas. Os resultados deste estudo mostram que a fragmentação florestal pode levar a efeitos diferenciados no estabelecimento e demografia das espécies arbóreas e que se devem considerar todos os estágios de vida da planta para avaliar apropriadamente os efeitos da fragmentação. Além disso, os resultados deste estudo sugerem que particularidades de história de vida e demográficas, em vez da posição que as espécies ocupam no estrato, determinam a maior ou menor susceptibilidade à fragmentação florestal de cada espécie individualmente

Biochemical and behavioral responses of the Amazonian fish Colossoma macropomum to crude oil: The effect of oil layer on water surface

The largest Brazilian terrestrial province of petroleum mining is located at the margins of Urucu River, Amazonas. Mined crude oil is transported along 400km across Solimões River to be refined in Manaus. Thus, the main goal of this study was to evaluate the effects of crude oil exposure on biochemical, physiological and behavioral parameters of juveniles of the Amazonian fish tambaqui (Colossoma macropomum). The toxicity of water-soluble and insoluble oil fractions and the influence of a layer formed by the oil on the water surface from low and high concentrations of crude oil were analyzed. The results showed a strong physical effect of oil at the water surface and a significant effect on fish behavior. Swimming time and response to alarm substance decreased when fish was exposed for just one day to water insoluble fraction, and remain lower after 30 days of exposure, compared to control. Chronic exposure to water insoluble fraction of the inert oil also affected these two parameters. Critical swimming velocity decreased in fish exposed to both crude and inert oil water insoluble fraction. These reductions are possibly related to a decrease in aerobic capacity. Only exposure to high concentrations of petroleum water-soluble fractions induced transient alterations of the analyzed parameters. The exposure of fish to low and high concentrations of water insoluble fraction of Urucu oil caused a reduction of responses to alarm substance, spontaneous swimming activity and swimming capacity (Ucrit), decreased activity of acetylcholinesterase, and increased activity of alkaline phosphatase. Severe hypertrophy of lamellar epithelium and extensive lamellar fusion of the gills were also observed. Overall, these results show significant behavioral and physiological changes caused by the oil layer on the water surface, which means that toxicity of petroleum produced by its chemical components is, in fact, in this fish species, enhanced by the presence of an oil phase as a physical barrier. •Effects of crude oil on the Amazonian fish tambaqui were analyzed.•Behavioral and physiological parameters were affected by the oil layer.•Oil layer at water surface causes stronger effects than dissolved PAHs.•Amazonian fish species that use air-water interface are vulnerable to oil layer during an oil spill. © 2014 Elsevier Inc