Spectral Characterization of Difusse Par Irradiance under Tipuana Tipu Shading

Abstract

Tipa (Tipuana tipu) is a common tree in gardens and carparks, although the shading effect of its canopy must be still characterised to assess the decrease of temperature and quality of irradiance. This work is a preliminary study aimed to assess the effect of shading of tree canopies on the diffuse irradiance pattern received at the soil level in comparison to other conditions. The shade provided by a group of Tipa trees, located at the Universitat Politècnica de València (Valencia, Spain), was evaluated in this experiment and compared to cloudy days and direct sun. Photosynthetic Photon Flux Density (PPFD) and red/near infrared ratios were recorded with a portable spectrometer. Measurements were recorded in January and February 2017, at 10h, 13h and 16h. Depending on the region of the spectrum and time of the day, PPFD values ranged from 0.05 to 0.42, 0.40 to 1.14, and 0.94 to 3.90 μmol·m-2·s-1, for Tipa shade, cloudy days and direct sun, respectively. The spectral analysis of PPFD in cloudy days revealed maximum values in the green region and minimum at near infrared region, while maximum PPFD for tipa shade was mostly found at near infrared, revealing higher importance of this spectral region compared to cloudy days.

Keywords

• trees shading, infrared irradiance, photosynthetic photon flux