The study of solar radiation is important to understand the several physical, chemical and biological processes that occur in the biosphere, particularly in the forest. The objective of this study has been to evaluate the temporal evolution of incident and reflected Photosynthetic Active Radiation (PAR) above and below the canopy of the Mata Atlantica forest. The study has been conducted in a Private Reserve Natural Heritage, located in the Coruripe city, Alagoas, during the period from October 2009 to September 2010, based on the PAR (2, 13, 26 m) observations obtained at the micrometeorological station, installed on a 24 meters high tower (10º 17' 36"S, 36º 17' 24"W, 160 m asl). According to the results the incident and reflected PAR outside (PAR↓_Ext and PAR↑_Ext) and inside (PAR↑_Spf) forest follow the seasonality imposed by the apparent motion of the Sun. The higher PAR values occur during the dry season, exceeding 600 and 12 W m-2, and during the wet season these averages was less than 300 and 8.0 W m-2, influenced by cloudiness. At the beginning and ending of sunlight time PAR↑_Spf values near zero were measured. The opposite measurements of about 14 W m-2, around 12 h (November and December) were observed.
tropical forest; solar radiation; seasonality; zenith angle; PAR
