An example of tree manifold element along with the grass covering present in the same earth surface volume that is given in this photo might depict the reality of objects to model and simulate while pursuing more or less fundamental procedure for mathematical simulation of many Agricultural problems as well as of Urban Atmospheric Boundary Layer air quality.
The complexity and many physical features that need to be simulated in the ordinary tree and grass structures still are not easy to include rigorously in the strict mathematical model. It is believed, that up to now (2000-th) the difficulty is overwhelming and all the physical effects not yet to be included into models simultaneously. Nevertheless, there are developed models and mathematics in agro-sciences to simulate many features of agriculture and phytocenosis elements.
We used few of them while providing the VAT two scale modeling and simulation.
Few plots below are taken from publications by Shcherban et al. (1986a,b) -
Shcherban, A.N., Primak, A.V., and Travkin, V.S., "Mathematical models of flow and mass transfer in urban roughness layer," Problemy Kontrolya i Zaschita Atmosfery ot Zagryazneniya," No.12. pp.3-10, (1986a), (in Russian).
Shcherban, A.N., Primak, A.V., and Travkin, V.S., "Turbulent Transfer in Urban Agglomerations on the Basis of Experimental Statistical Models of Roughness Layer Morphological Properties", Trans. World Meteorol. Org. Conf. Air Pollution Mod. & Applic., WMO, Geneva, V.2, pp.259-266, (1986b).