DIFFERENCES IN IRRADIANCE CHARACTERSTICS BETWEEN SYZYGIUM MALACCENSE AND MANGIFERA INDICA CAUSED BY THEIR TREE FORMS

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Spectral irradiance in the tree canopies of Syzygium malaccense and Mangifera indica was measured 10 years after planting on the campus of the Center for Superior Studies of Novo Aripuanã, Amazonas State University, Brazil. S. malaccense had a cylindrical tree form, with dense foliage and no gaps, whereas M. indica had a more rounded shape with some gaps between the leaves. The parameters of light quantity in terms of photosynthetic active radiation (PAR), photosynthetic photon flux density, and illuminance were larger in S. malaccense than M. indica according to absorption/transmittance in the PAR wavelength. A similar difference was also found in the ratios between red and far red and between PAR and near infrared, suggesting that areas immediately under S. malaccense received a larger amount of infrared light. Moreover, the fraction of sky that is visible also showed a similar difference between the species, suggesting that light quantity is dependent on this variable, whereas quality is dependent on how the leaves overlap. Both phenomena were traced back to the differences in tree form between the two species. These results offer a foundation for agroforestry aimed at cultivation of vines, shrubs, and low-rise fruit trees under canopy layers with different tree forms.