In recent years, the plantations are expanding throughout Brazil, as in the southern Rio Grande do Sul, southern Bahia, Mato Grosso do Sul, Piauí, Tocantins, Maranhão, several sub-regions of Minas Gerais, Parana and Santa Catarina, and the state of Pará. Faced with this also comes the need for research aimed at the development of plantations in these new areas. In Pará, the expansion of forest plantations is occurring quite intense, is about just over 200,000 hectares already planted 148,000 hectares of eucalyptus, of 60,000 hectares planted in full Jari Project in the Amazon rainforest. In this context, the state appears as a major center of expansion of forest plantations in Brazil, and is still a relatively recent activity in Pará, industry research needs facing the region. Given this reality, the systems of decision-making forestry or forestry, which are input variables and climatic, are increasingly essential in the planning of forest activities. Among these stands out ecophysiological modeling development of planted forest, a useful tool for strategic planning for deployment and conduct of forest plantations. It is therefore essential improvement tools that can contribute to the planning and development of planted forest sector in some areas of the state of Pará. Therefore, this study aimed to study and develop the general knowledge of ecophysiological modeling as a strategic and an essential tool for responsible forestry management in the Amazon region. Specifically the objective was: a change the time scale of the sub-model calculation of the monthly water balance (original model) to daily (proposed model), as well as make changes in the treatment of evapotranspiration and its components vapor pressure deficit (VPD); b) parameterize, calibrate and validate the model 3-PG in some areas of the Amazon to plant eucalyptus trees. Changes made in the proposed model produced a small gain in efficiency of the estimated values (volume, DBH, height) in the original model, however the changes proposed in this work because they have improved the physical rigors of the treatment processes that involve the water balance (vapor pressure deficit and evapotranspiration) reduced the empiricism of the proposed model. The original model proposed and showed good ability to extrapolate and described with good accuracy the patterns of growth in terms of volume, height and DBH. There was also a best fit by the model proposed. In summary the highest levels of stomatal opening due to higher soil water availability linked to higher precipitation, higher rates and larger areas of radiation interception of radiant energy due to higher IAF gave the plantations in the region of more favorable conditions for Felipe achieving high rates of photosynthesis at the end of the process translate into higher productivity.
