Influence of shade trees on radiation and wind regimes in agroforestry

In agroforestry systems the crops are growing under the canopy of so called "shade trees". The growth rates and yield of crops depend strongly on energy and water fluxes between agroforestry system and atmosphere. The radiation and turbulent regimes in agroforestry systems are controlled by number (canopy density) and structural parameters of shade trees (see e.g. de Almeide and Valle, 2007 on the review of abiotic factors influence on cacao agroforestry). To quantify the influence of shading trees during different seasons as well as cumulative annual effect, the radiation and turbulent transports in agroforestry canopies were modelled on examples of cacao agroforestry system in Indonesia and karite-sorghum agroforestry in Burkina Faso. Because of high heterogeneity of vegetation structure typical for agroforestry system a 3D approach has to be applied to describe the canopy transport adequately. In present study the high resolution small scale 3D model of radiative transfer (SPM-3D) (Bioclimatology Group, Goettingen University) was implemented. The wind regime was modelled by means of 3D Boundary layer Model SCADIS (DTU Wind Energy). The 3D structure of different shade trees and its variations were measured directly and retrieved from hemispherical photos.