O índice de área foliar (LAI) é um parâmetro essencial para a caracterização da estrutura das copas e consequentemente para a avaliação da vitalidade das plantas. Neste estudo compararam-se valores de LAI obtidos através de métodos directos destrutivos e através da análise de fotografia hemisférica, em oliveiras jovens das cultivares ‘Galega’ e ‘Cordovil de Serpa’, num olival da região de Moura. Os valores determinados por fotografia hemisférica subestimaram significativamente (P<0,05) os obtidos pelas medições directas. Assumindo que os métodos directos estimam o LAI com maior precisão, os valores obtidos destrutivamente foram utilizados como referência para o cálculo de equações de regressão entre os resultados dos métodos indirecto e directo. A partir destas ajustaram-se os valores determinados através da fotografia hemisférica, de forma a permitir a sua aplicação futura para avaliação do LAI em oliveiras jovens. Os resultados obtidos indicam que o método e o equipamento utilizados podem ser adequados para a determinação do LAI em oliveiras jovens desde que devidamente calibrados.

The determination of leaf area index (LAI) is essential in the characterization of the canopy structure and plants vitality evaluation. In this study destructive measurements of LAI were compared with values obtained by hemispherical photography analysis, of young olive trees cv. Galega and cv. Cordovil de Serpa, in an olive orchard of Moura region. As the direct method is assumed to be the most correct for estimating LAI, this method served as reference for the performance of the indirect methods. In order to be able to use the indirect methods to determine the LAI in the future, regression equations have been calculated taking into consideration the results of the indirect and the direct methods. Our results suggest that this procedure is an alternative method suitable to LAI determination in young olive trees after specific calibration.

Automatic Differentiation is a relatively recent technique developed for the differentiation of functions applicable directly to the source code to compute the function written in standard programming languages. That technique permits the automatization of the differentiation step, crucial for dynamic simulation and optimization of processes. The values for the derivatives obtained with AD are exact (to roundoff). The theoretical exactness of the AD comes from the fact that it uses the same rules of differentiation as in differential calculus, but these rules are applied to an algorithmic specification of the function rather than to a formula. The main purpose of this contribution is to discuss the impact of Automatic Differentiation in the field of dynamic simulation of chemical engineering processes. The influence of the differentiation technique on the behavior of the integration code, the performance of the generated code and the incorporation of AD tools in consistent initialization tools are discussed from the viewpoint of dynamic simulation of typical models in chemical engineering.