ИСТИНА

Effects of spatial heterogeneity of vegetation cover on transmission, reflection and absorption of photosynthetically active solar radiation were described using three-dimensional (3D) and one-dimensional (1D) modeling approaches. The widely used 1D models in respect of 3D approaches consider the vegetation cover as a horizontally homogeneous turbid medium that is obviously can result in some uncertainties in radiation flux estimates. For our numerical experiments a uniform ground surface area with regularly planted spruce trees of different density was taken. Two main model experiments were provided. In the first experiment the solar radiation transfer was simulated for actual 3D plant canopy structure. The second experiment imitated 1D plant canopy structure. The plant canopy in this experiment was considered as a horizontally uniform turbid medium. It was also assumed that the Leaf area index (LAI) of the trees in the experiment is dependent on vertical coordinate only. The values of LAI averaged for entire experimental plot for both modeling experiments were identical. The solar radiation transmission, reflection and absorption within each model experiment were calculated under different sun heights and a range of LAI of the forest stand (from 1 to 5).