Understanding the mechanism of photosynthetic seasonality in Amazonian evergreen forests is critical for its formulation in global climate and carbon cycle models. However, the control of the unexpected photosynthetic seasonality is highly uncertain. Here we use eddy-covariance data across a network of Amazonian research sites and a novel evapotranspiration (E) and two-leaf-photosynthesis-coupled model to investigate links between photosynthetic seasonality and climate factors on monthly scales. It reproduces the GPP seasonality (R-2=0.45-0.69) with a root-mean-square error (RMSE) of 0.67-1.25gCm(-2)d(-1) and a Bias of -0.03-1.04gCm(-2)d(-1) for four evergreen forest sites. We find that the proportion of diffuse and direct sunlight governs the photosynthetic seasonality via their interaction with sunlit and shaded leaves, supported by a proof that canopy light use efficiency (LUE) has a strong linear relationship with the fraction of diffuse sunlight for Amazonian evergreen forests. In the transition from dry season to rainy season, incident total radiation (Q) decreased while LUE and diffuse fraction increased, which produced the large seasonal increase (similar to 34%) in GPP of evergreen forests. We conclude that diffuse radiation is an important environmental driver of the photosynthetic seasonality in tropical Amazon forests yet depending on light utilization by sunlit and shaded leaves. Besides, the GPP model simulates the precipitation-dominated GPP seasonality (R-2=0.40-0.69) at pasture and savanna sites. These findings present an improved physiological method to relate light components with GPP in tropical Amazon. Plain Language Summary Understanding the mechanism of photosynthetic seasonality in Amazonian evergreen forests is critical for its formulation in global climate and carbon cycle models. However, the control of the unexpected photosynthetic seasonality is highly uncertain. Here we use eddy-covariance data across a network of Amazonian research sites and a novel evapotranspiration (E) and two-leaf-photosynthesis-coupled model to investigate links between photosynthetic seasonality and climate factors on monthly scales. It reproduces the GPP seasonality (R2= 0.45-0.69) for four evergreen forest sites. We find that the proportion of diffuse and direct sunlight governs the photosynthetic seasonality via their interaction with sunlit and shaded leaves, supported by a proof that canopy light-use efficiency (LUE) has a strong linear relationship with the fraction of diffuse sunlight for Amazonian evergreen forests. We conclude that diffuse radiation is an important environmental driver of the photosynthetic seasonality in tropical Amazon forests yet depending on light utilization by sunlit and shaded leaves. Besides, the GPP model simulates the precipitation-dominated GPP seasonality (R2= 0.40 similar to 0.69) at pasture and savanna sites. These findings present an improved physiological method to relate light components with GPP in Amazon.

Using wood produced under forest management in the Amazon has been proposed as a way of preserving the ecosystem, generating jobs and to aid in climate change mitigation by using wood products as carbon stock and through CO2 uptake from the atmosphere during forest regrowth. However, the scarcity of research based on primary data of Amazonian lumber incorporated into construction can unknowingly lead to incorrect forest management and consequently forest destruction. Besides, it is necessary to verify the real environmental impacts. Two approaches were applied in this research to evaluate the wood product chain: material flow analysis and CO2 footprint calculation of managed Amazonian lumber. The research quantified the resource efficiency and CO2 footprint based on residue generation during the raw extraction in 5 forest plots in State of Pará, followed by the lumber production and the end-of-life phases, giving the CO2 balance between the emissions from residue decomposition and the CO2 uptake during forest regrowth, disregarding the energy consumption. Results indicated that the large quantities of logging residues are the main source of CO2 emissions in the material flow from selective logging, ranging from 9% to 36% of the initial forest biomass, while timber logs represented between 4% and 11%. Logging residues ranged from 2.9 t t-1 to 3.1 t t-1 per tonne of log. Combined with an average sawmill lumber yield of 54%, wastage rate values increased to between 5.7 t t-1 and 6.6 t t-1, resulting in a CO2 footprint of managed Amazonian lumber ranging between -6.6 tCO2 t-1 for reduced impact logging as carbon stock, to emissions of 6.1 tCO2 t-1 from cradle-to-gate for conventional logging. From cradle-to-grave the total CO2 footprint of lumber is estimated to range from neutral to 7.5 tCO2 t-1. Resource efficiency ranged from 13% to 15%. In this study, only the forest under reduced impact logging was able to fully recover its initial aboveground biomass, showing that in most cases regulations in the New Forest Code for Amazon forest management may not ensure sustainable logging, leading to forest destruction. Policies need to be improved and integrated with results from empirical research based on primary data to achieve sustainable exploitation of the Amazon forest. / O processo seletivo de utilização da madeira de manejo florestal na Amazônia tem sido proposto como forma de conservação e preservação do ecossistema, associada a geração de empregos e à mitigação de mudanças climáticas, pelo estoque de carbono dada a absorção de CO2 da atmosfera durante o crescimento da floresta. No entanto, a limitação de pesquisas baseadas em dados primários sobre madeiras amazônicas incorporadas na construção civil pode levar, inconscientemente, ao manejo florestal incorreto e, consequentemente, à destruição da floresta no contexto original e de reais impactos ambientais provocadas por ações inadequadas. Duas abordagens foram aplicadas nesta pesquisa para avaliar a cadeia de produtos de madeira: análise de fluxo de material e cálculo da pegada de CO2 da madeira manejada na Amazônia. A pesquisa analisou a eficiência dos recursos e a pegada de CO2 com base na geração de resíduos durante a extração em 5 florestas no Estado do Pará, produção madeireira e o fim de vida, proporcionando o balanço de CO2 entre as emissões da decomposição de resíduos e a absorção do CO2 durante a recomposição florestal, desconsiderando a energia consumida. Os resultados indicaram que o expressivo volume de resíduos florestais é a principal fonte de emissões de CO2 no fluxo de material proveniente da extração seletiva, variando de 9% a 36% da biomassa florestal inicial, enquanto os troncos de madeira representam entre 4% e 11%. Os resíduos de exploração florestal variaram de 2,9 a 3,1 t de resíduos por tonelada de tora. Combinado com um rendimento médio de madeira de serraria de 54%, os valores da taxa de desperdício aumentaram para entre 5,7 t e 6,6 t de resíduos por tonelada de tora e madeira serrada, resultando em uma pegada de CO2 variando entre -6,6 tCO2 t-1 (exploração de impacto reduzido) considerado estoque de carbono e as emissões de 6,1 tCO2 t-1 do berço à porta. No final da vida útil, estima-se que a pegada total de CO2 da madeira entre o berço e o túmulo é de neutra (exploração de impacto reduzido) a 7,5 tCO2 t-1, com uma eficiência de recursos variando de 13% a 15%. Neste estudo, apenas a floresta sob prática de extração de impacto reduzido foi capaz de recuperar totalmente sua biomassa inicial acima do solo, mostrando que as regulamentações do Novo Código Florestal para o manejo da florestal amazônica pode não garantir a sustentabilidade de uso do recurso florestal para aquela exploração que não esteja alicerçada dentro desse contexto de conservação da floresta original. As políticas precisam ser melhoradas, integradas e dinâmicas com base em resultados derivados de pesquisas empíricas baseadas em dados primários garantindo a exploração sustentável na Amazônia.

Made available in DSpace on 2015-04-13T12:17:38Z (GMT). No. of bitstreams: 1 DISSERTACAO MARCOS.pdf: 2310482 bytes, checksum: 08bbc133d41c52da12f2d2c336476c94 (MD5) Previous issue date: 2011-12-12 / FAPEAM - Fundação de Amparo à Pesquisa do Estado do Amazonas / In Brazil the production in little amount and the absence of quality of the forest seeds of produced native species are considered a problem in the productive chain of production of forest seeds. The lack of knowledge on the process of production of forest seeds is one of the pass for the sector. The theoretical referential of this research had the pretension to all offer to basement for the understanding of the process of production of forest seeds and of the conceptualization of quality and its some aspects related with the process. This research analyzes the quality of process of production of native forest seeds of the Center of Native Seeds of Amazon (CSNAM), in the direction to consider, instructions of work for the production process, observing and organizing the information concerning the current process of production, for this, it was needed to mapper the processes, to know the available data of each stage of production and the congruence with the legal Law 10711 and its devices; To identify the requirements essential of the quality of each stage of the process and to define the instructions of work of all the stages of the production process. The employed method was the same that it is used for systematization considered for NBR ISO 9000:2000. How much to the results it could be observed by means of analyzes of the data generated during the production of sixty and two lots, that much lacks to structuralize and to accomplish the production of native forest seeds in CSNAM with the quality the one that if considers. / No Brasil a produção em pouca quantidade e a ausência de qualidade das sementes florestais de espécies nativas produzidas é considerada um problema na cadeia produtiva de produção de sementes florestais. A falta de conhecimento sobre o processo de produção de sementes florestais é um dos gargalos para o setor. O referencial teórico desta pesquisa teve a pretensão de oferecer embasamento para a compreensão de todo o processo de produção de sementes florestais e da conceituação de qualidade e seus vários aspectos relacionados com o processo. Esta pesquisa analisa a qualidade do processo de produção de sementes florestais nativas do Centro de Sementes Nativas do Amazonas (CSNAM), no sentido de propor, instruções de trabalho para o seu processo de produção, observando e organizando as informações acerca do atual processo de produção, para isso, necessitou-se mapear os processos, conhecer os dados disponíveis de cada etapa de produção e a congruência com a Lei 10711 e seus dispositivos legais; Identificar os requisitos essenciais da qualidade de cada etapa do processo e definir as instruções de trabalho de todas as etapas do processo de produção. O método empregado foi o mesmo que é utilizado para padronização de processos e implementação proposto pela NBR ISO 9000:2000. Quanto aos resultados pôde-se observar por meio da analise dos dados gerados durante a produção de sessenta e dois lotes, que muito falta para se estruturar e efetivar a produção de sementes florestais nativas no CSNAM com a qualidade a que se propõe.