Two-Story Equations of Transmission of Solar Energy (TSETSE) in open boreal conifer tree stands

Abstract

This paper presents the two-story equations of transmission of solar energy (TSETSE) model aimed to mimic the directional signature of the transmittance measured beneath conifer tree stands which form a highly clumped and discontinuous medium. The architecture of such tree species affect the radiation distribution at the forest floor in providing interesting problems for radiation process modeling. A tree is sketched by a conic-shaped crown laying above a very thin trunk. The model contains a geometrical component to account for the between-crown gap probability and a volume component to describe the radiative transfer within a single crown which is here assimilated to a turbid phytomedium. The diurnal pattern of the simulated transmittance at a local point between trees yields peaks of the radiation loading at the understory as a function of tree arrangement and whorl structure. The practical aspect of the inversion method is achieved in several steps and rests on the location of these radiation peaks, standing for the originality of this work. Once calibrated upon oblique measurements of the radiation penetration, TSETSE allows for a retrieval of the tree distance, dimensions of the crown, and leaf area index. Copyright 1999 by the American Geophysical Union.