Uma das vegetações que tem sido utilizada pelas populações tradicionais ao longo do tempo, e investigada por especialistas é a do semiárido. Muitos estudos realizados nessa região são direcionados para espécies de usos madeireiro e medicinal. Nesta pesquisa, realizou-se uma análise pontual da distribuição local de Myracrodruon urundeuva Allemão, com base em informações coletadas em comunidades rurais de seis municípios do estado da Paraíba. Foram registrados 1.559 indivíduos de M. urundeuva em 144 horas de turnê guiada. Percebeu-se que que as populações desta espécie tendem a formar aglomerados, estando alguns localizados próximos as residências, o que pode ser explicado pela utilização medicinal das cascas para diversas enfermidades. Os dados abordados neste estudo refletem as características ambientais de cada área estudada, indicando para cada região a melhor forma de manejo para as populações locais desta espécie. A B S T R A C TThe objective of this study was to analyze the daily and seasonal variations of the components of the radiation balance -and photosynthetically active radiation for the Caatinga during a dry year in Pernambuco Semi-Arid. The experiment was conducted during the year 2012 in Petrolina, PE, located in the Brazilian semiarid region. To determine the components of the radiation balance we used a balance radiometer CNR1 model installed the 13.3 meters of surface. Additionally, we analyzed the interaction between vegetation and radiation using sensors to monitor the photosynthetically active radiation above and in different positions under the canopy of scrub. These data were used to calculate the fraction of intercepted photosynthetically active radiation (fRFAi) and absorbed (fRFAa). A wide seasonal variation of solar radiation and net radiation was observed that reached daily averages around 23 MJ m-2 d-1 and 15 MJ m-2 d-1, respectively. In this case, it was observed that the magnitude of the component values of the radiation balance was mainly affected due to the cloudiness and changes in vegetation which mainly affected the levels of emittance and reflection surface. With regard to fractions of intercepted and absorbed photosynthetic active radiation, it was observed that they had daily average values over the next years, which were equal to 0.69 and 0.64 in order. This data can be extremely useful for a better understanding of the interaction between the savanna and the atmosphere under natural climatic conditions.Keywords: radiation, net radiation, photosynthetically active radiation, Caatinga, dry.