Distribuição local e regional de Myracrodruon urundeuva Allemão (Anacardiaceae) no semiárido do nordeste do Brasil (Local and regional distribution of Myracrodruon urundeuva Allemão (Anacardiaceae) in the semi-arid region of northeastern Brazil)

Uma das vegetacoes que tem sido utilizada pelas populacoes tradicionais ao longo do tempo, e investigada por especialistas e a do semiarido. Muitos estudos realizados nessa regiao sao direcionados para especies de usos madeireiro e medicinal. Nesta pesquisa, realizou-se uma analise pontual da distribuicao local de Myracrodruon urundeuva Allemao, com base em informacoes coletadas em comunidades rurais de seis municipios do estado da Paraiba. Foram registrados 1.559 individuos de M. urundeuva em 144 horas de turne guiada. Percebeu-se que que as populacoes desta especie tendem a formar aglomerados, estando alguns localizados proximos as residencias, o que pode ser explicado pela utilizacao medicinal das cascas para diversas enfermidades. Os dados abordados neste estudo refletem as caracteristicas ambientais de cada area estudada, indicando para cada regiao a melhor forma de manejo para as populacoes locais desta especie. A B S T R A C T The 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.