Dinâmica do carbono na conversão de floresta para pastagens em argissolos da formação geológica Solimões, no sudoeste da Amazônia.

O objetivo deste trabalho foi avaliar a dinâmica, o estoque e a razão isotópica do carbono nos três tipos de uso da terra do sudoeste da Amazônia, onde predominam Argissolos com argilas de alta atividade. Foram selecionados dois locais da região leste do Estado do Acre e, em cada local, abriram-se trincheiras nas quais foram coletadas amostras indeformadas nas profundidades de 0 a 5, 5 a 10, 20 a 25 e 50 a 55cm, sob cobertura de floresta primária, floresta secundária e pastagens. Nas amostras, determinou-se a densidade aparente, teor de carbono e a razão isotópica do carbono, além de características físicas (granulometria) e químicas (pH, teores de cátions trocáveis, acidez potencial). Os resultados mostraram que o uso do solo com pastagens foi responsável pela maior densidade aparente do solo, decorrente da compactação provocada pelo pisoteio do gado. Sob pastagens, os solos apresentaram ainda maiores estoques de carbono nas camadas superficiais, sendo que os resultados da diluição isotópica de ?13C indicaram que em torno de 40 a 50% deste carbono foi originado das próprias gramíneas, nas profundidades de 0 a 5 cm

SPECTRAL RESPONSE IN LASER SYNTHESIZED WxMo(1-x)S2 ALLOYS

We report the spectral response of 2D WxMo1-xS2 alloys based photoconductors fabricated by direct laser synthesis of single source precursors. A comparative study for the main figure of merits of these devices is presented

Educação, pesquisa, extensão e conservação na paisagem fragmentada, uma conciliação necessária.

A Fazenda Experimental Catuaba (FEC), o antigo seringal, é um sítio consolidado para ações de ensino, pesquisa e extensão da Universidade Federal do Acre (UFAC). Ela provê suporte para atividades de grupos de pesquisa, para estudantes do ensino médio e de cursos de graduação e de pós-graduação, e para treinamentos, oficinas e cursos de capacitação, todas alinhadas com um dos principais objetivos da Convenção da Diversidade Biológica, a conservação da biodiversidade e dos serviços ecossistêmicos. Este capítulo sintetiza os resultados principais dos 30 anos de pesquisas realizadas na FEC e alerta para a diminuição do número de fragmentos e para o aumento da extensão das bordas no seu entorno e para a perda de biomassa, de biodiversidade e de serviços ecossistêmicos, em função dos efeitos do fogo e do desmatamento. Ele destaca a importância da UFAC efetuar o Cadastro Ambiental Rural e o Plano de Recuperação Ambiental (PRA) da FEC, e aponta para a perspectiva de abertura de um caminho para a integração com os PRAs do entorno e a viabilização da tão necessária conectividade com fragmentos vizinhos. A conectividade dos remanescentes da paisagem fragmentada é possível, envolve a integração de propriedades e a restauração de área de preservação permanente dos igarapés da FEC, e pode integrar, de fato, pelo menos dois fragmentos de cerca de 900 hectares, dobrando a sua efetividade. The Fazenda Experimental Catuaba (FEC), the former rubber production forest, is a consolidated site for teaching, research and extension activities at the Federal University of Acre (UFAC). It provides support for activities of research groups, for high school students and for undergraduate and graduate courses, and for training, workshops and courses, all aligned with one of the main objectives of the Convention on Biological Diversity, the conservation of biodiversity and ecosystem services. This chapter summarizes the main results of the 30 years of research carried out at FEC and presents warnings and concerns of the decrease in the number of fragments and the increase in the extent of the edges in its surroundings and the loss of biomass, biodiversity and ecosystem services due to the effects of fire and deforestation. It also highlights the importance of UFAC making the Rural Environmental Registry and the Environmental Recovery Plan (PRA) of the FEC, and points to the prospect of opening a path for integration with the surrounding PRAs and enabling the much needed connectivity among neighboring fragments. The connectivity of the remnants of the fragmented landscape is possible and it involves the integration of properties and the restoration of the permanent preservation area of the FEC streams, and can in fact integrate at least two fragments of around 900 hectares, doubling their effectiveness.bitstream/item/219530/1/27084.pd

Drought-induced Amazonian wildfires instigate a decadal-scale disruption of forest carbon dynamics

Drought-induced wildfires have increased in frequency and extent over the tropics. Yet, the long-term (greater than 10 years) responses of Amazonian lowland forests to fire disturbance are poorly known. To understand post-fire forest biomass dynamics, and to assess the time required for fire-affected forests to recover to pre-disturbance levels, we combined 16 single with 182 multiple forest census into a unique large-scale and long-term dataset across the Brazilian Amazonia. We quantified biomass, mortality and wood productivity of burned plots along a chronosequence of up to 31 years post-fire and compared to surrounding unburned plots measured simultaneously. Stem mortality and growth were assessed among functional groups. At the plot level, we found that fire-affected forests have biomass levels 24.8 ± 6.9% below the biomass value of unburned control plots after 31 years. This lower biomass state results from the elevated levels of biomass loss through mortality, which is not sufficiently compensated for by wood productivity (incremental growth + recruitment). At the stem level, we found major changes in mortality and growth rates up to 11 years post-fire. The post-fire stem mortality rates exceeded unburned control plots by 680% (i.e. greater than 40 cm diameter at breast height (DBH); 5–8 years since last fire) and 315% (i.e. greater than 0.7 g cm−3 wood density; 0.75–4 years since last fire). Our findings indicate that wildfires in humid tropical forests can significantly reduce forest biomass for decades by enhancing mortality rates of all trees, including large and high wood density trees, which store the largest amount of biomass in old-growth forests. This assessment of stem dynamics, therefore, demonstrates that wildfires slow down or stall the post-fire recovery of Amazonian forests. This article is part of a discussion meeting issue ‘The impact of the 2015/2016 El Niño on the terrestrial tropical carbon cycle: patterns, mechanisms and implications’

Effects of molecular structure on the physical, chemical, and electrical properties of ester‐based transformer insulating liquids

This article presents the experimental studies carried out on the environmental friendly polyol ester insulating liquids to investigate the effect of molecular structure on the physical, chemical, and electrical properties. Six different polyol esters that can be produced from the transesterification of various methyl esters with neopentylglycol/trimethylolpropane alcohols were synthesized and compared with those of refined, bleached, and deodorized palm oil (RBDPO) and mineral transformer oil. The finding suggests that the physical properties like fire point, pour point, and viscosity are very much affected by the molecular weight and molecular composition of the polyol esters. The electrical properties are also highly influenced by the molecular structure‐related characteristics, such as the polarity, dipole polarization, carbon chain length, and degree of branching. The results confirm the findings of previous studies that the polyol esters and RBDPO have more polarity and dipole polarization compared to mineral oil. The experimental evidence showed that the newly synthesized insulating liquids have favorable thermal and electrical properties, thus suggesting that the insulating liquids have the potential to replace conventional insulating liquids to provide a more sustainable power system in the future