Age Reversion of the Rank Distribution of Aboveground Biomass Fractions in the Genus Salix L.

Abstract

Plant organs perform many different functions. The leaves provide the supply of assimilates, the stem and branches provide photosynthesis, transportation of water and nutrients, and the roots supply water and nutrients and contribute to physical stability. To achieve optimal performance at the plant level as a whole, there is a certain proportionality between these functions, which is mediated by the amount of biomass in the plant organs. The ratio of the biomass of one organ to that of another is known as the “biomass partitioning”, which is the cumulative result of the dynamic distribution of assimilates over time. Some implementations of the distribution of plant biomass fractions are non-Gaussian distributions, in particular, the Zipf-Pareto distribution. Using 6 coniferous genera of Eurasia as an example, it has been established that the regression coefficient of the Zipf-Pareto equation is not constant throughout the entire period of plant growth, but changes its sign at a certain age. The aim of this study has been to create a database on the biomass of the genus Salix L. and to determine the age of reversion of aboveground biomass fractions. The authors’ and attracted source materials have been used in the amount of 94 measurements of the aboveground biomass of willows aged from 1 to 79 years in the territory of the European part of Russia. The initial data on the biomass fractions have been ranked in descending order: stem, branches, foliage (respectively, i is equal to 1, 2 and 3) and approximated by a model in double logarithmic coordinates, including as independent variables not only the rank i, but also the age of the tree, its height and a combined variable in the form of the product of age by rank i. The latter has turned out to be statistically significant at the probability level of P < 0.0001, and its negative value reflects that at a certain age the sequence of fractions of aboveground biomass in descending order: leaves, branches, stem – changes to the opposite descending sequence: stem, branches, leaves – and the age of the reverse is about 2 years. The established fact of age-related reversal of fractions of the aboveground willow biomass and the determination of the age of the tree in which the reversal occurs are a contribution to the development of the theory of assimilate distribution in plants. © Andrey А. Paramonov, Аleksey А. Karaban, Vladimir A. Usoltsev, Ilya V. Tsvetkov, Sergey V. Tretyakov, Ivan S. Tsepordey 2025.