Abstract
ResumoDevido à importância de quantificar a radiação solar interceptada (K*) pela vegetação, determinou-se a interferência da área foliar da copa de uma laranjeira Pêra-Rio sobre a eficiência de interceptação (εint) e o coeficiente de extinção de radiação (k). Para a medida da radiação solar transmitida foi instalado um piranômetro abaixo da copa. O sensor, distante 0,65m do tronco, girava horizontalmente em torno do mesmo (3 rpm), realizando uma medida espaço-temporal. O mesmo modelo teórico usado para determinar o coeficiente de extinção ‘k’ (Teoria de Monsi & Saeki) foi usado também para a estimativa de K*. Os dados revelaram uma clara interferência dos ramos e galhos sobre a εint, com valor mínimo de 0,52 com ausência completa de folhas. Os resultados também foram distintos em relação à obtenção do coeficiente de extinção ‘k’, mais uma vez por influência das estruturas lenhosas. A simulação de K* a partir dos coeficientes de extinção (k), obtidos por ajuste linear e quadrático, resultou, respectivamente, em classificações boa e ótima de acordo com o cálculo do índice de desempenho ‘c’.
Highlights
Transpiration and photosynthesis of a plant, its yield and production quality, and its microclimate characteristics, essentially depend on the absorbed solar radiation, conditioned by leaf area and its efficiency of interception of radiant energy.The availability of solar radiation at the Earth’s surface is primarily related to the variables associated with the Earth-Sun relationships, while the magnitude of this radiation interception by a tree, for example, further depends on architecture and the density of canopy foliage as well as the optical properties of vegetation and the relationship between direct and diffuse radiation.The transmitted fraction that reaches the surface below the canopy is crucial for the establishment of biotic factors, their characteristics and disturbances (Endler, 1993)
As the measurements extended over approximately 2 months, starting with a solar declination (δ) of 16.68o N and ending with δ of 23.40° N, the reduction in solar radiation coincided with the decrease of leaf area of the tree canopy (Figure 1b), but the period of measurements without foliage showed values higher than days with leaf area index (LAI) = 1.40
Values measured of Qg, when the LAI of orange tree was 1.4, were 20% lower than those measured with maximum LAI
Summary
Transpiration and photosynthesis of a plant, its yield and production quality, and its microclimate characteristics, essentially depend on the absorbed solar radiation, conditioned by leaf area and its efficiency of interception of radiant energy.The availability of solar radiation at the Earth’s surface is primarily related to the variables associated with the Earth-Sun relationships, while the magnitude of this radiation interception by a tree, for example, further depends on architecture and the density of canopy foliage (associated with leaf area and porosity of the crown) as well as the optical properties of vegetation and the relationship between direct and diffuse radiation.The transmitted fraction that reaches the surface below the canopy is crucial for the establishment of biotic factors, their characteristics and disturbances (Endler, 1993). Transpiration and photosynthesis of a plant, its yield and production quality, and its microclimate characteristics, essentially depend on the absorbed solar radiation, conditioned by leaf area and its efficiency of interception of radiant energy. The availability of solar radiation at the Earth’s surface is primarily related to the variables associated with the Earth-Sun relationships, while the magnitude of this radiation interception by a tree, for example, further depends on architecture and the density of canopy foliage (associated with leaf area and porosity of the crown) as well as the optical properties of vegetation and the relationship between direct and diffuse radiation. The presence of foliage gaps in the crown plays important role in radiation transmittance, producing qualitative and quantitative changes of radiant energy available for the strata below the canopy or at soil surface, enabling or enhancing the natural occurrence of plants in those strata and even causing temporal morpho‐physiological changes (Buler & Mika, 2009; Cardoso et al, 2010; Machado et al, 2002; Pezzopane et al, 2002)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
