Comparação entre o fator de reflectância bidirecional de um dossel de mudas de Eucalyptus grandis e o fator de reflectância direcional hemisférico de suas folhas isoladas

Abstract

Radimetric measurements were performed on an Eucalyptus grandis seedling canopy and in detached leaves from that canopy, considering three growing stages: old, intermediate and young leaves. From the canopy it was determined the Bidirectional Reflectance Factors (FRB) in different times of the day (from 08:00 am to 3:00 pm, in 1 by 1 hour) and from the up size of the leaves it was determined the Hemispherical Directional Reflectance Factors (FRDH). ANOVAs statistical procedure was applied in order to compare FRB and FRDH in all collecting times to evaluate the illumination geometry influence in both parameters relationship in specific spectral regions: Band (450 a 520 nm), Band 2 (520 a 600 nm), Band 3 (630 a 690 nm) and Band 4 (760 a 900 nm). The results showed that for that specific canopy (structural characteristics) the illumination geometry did not influence the relationship between FRB and FRDH in all bands and different time of day. The FRDH from the younger leaves were frequentely similar to the FRB in the visible region, independently of the time of the day, which indicated that the superior portion of the canopy was better illuminated. In the near infrared, due the multiple scattering, it was not identified any similarity between FRB and FRDH along the time.