Side-Branching Statistics of Plant Root Networks

Many studies exist that characterise plant root architecture by calculating the fractal dimension of the root network, but few studies quantify the branching characteristics of the root network. This paper examines the Tokunaga side-branching statistics for the root systems of four plants--Sugar Beet (Beta vulgaris), Lucern (Medicago sativa), Common Wheat (Triticum aestivum) and White Clover (Trifolium michelianum)--and compares the resulting statistics to those calculated by similar means (by other authors) for the Kentucky and Powder River drainage basins and several Diffusion Limited Aggregation (DLA) models. The plant root networks studied all contained similar numbers of different order roots, but the side-branching statistics differed, offering one explanation for the differing visual appearance of the branching root networks. The White Clover plant had similar Tokunaga branching statistics to the drainage networks and DLA models. This may be due to the dichotomous root structure of the White Clover plant, which produces a network that is much more similar in appearance to the two drainage networks and DLA models than the other three plants, which had herringbone root. All of the root networks, drainage basins, and DLA models had branching networks that could be quantified well to very well by Tokunaga side-branching statistics. For many years, engineers have avoided implementation of stabilisation schemes involving vegetation, due to the inherent problems involved in the quantification of their dynamic and complex root structures. The use of Tokunaga statistics as a simplifying measure of root branching characteristics, may aid in this aspect, as well as others, such as the modelling of nutrient or water uptake.