Influence of branch architectures on gap fraction and clumping index of canopies

Abstract

Gap fraction (GF) and clumping index (CI) play key roles in plant light interception, and therefore they have strong impacts on plant growth and canopy radiative transfer processes. On the one hand, in the field of remote sensing, leaves were often assumed to be randomly distributed in tree crowns in previous researches. While this assumption is not correct for many forest canopies, especially for coniferous forests because trees have obvious hierarchical characteristics in an individual crown; one the other hand, reconstruction of detailed canopy architecture in a computer using methods of three-dimensional (3-D) architectural simulations is very labor-intensive and time-consuming at present. In this paper, structures within crown were described using simple probability models based on plant growing rules instead of 3-D simulations. Gap fraction (GF) and clumping index (CI) of foliage were calculated at branch level within crown. The results show that: (1) GF and CI are closely related to the number of nwb (the number of branches in a branch whorl): GF decrease and CI increase with increasing of nwb; (2) the assumption that branches or leaves are randomly distributed within crowns is not true, especially for larger value of nwb.