In collaboration with Chuo University and Kyoto University, Assistant Professor Kohei Koyama of the Environmental Agriculture Research Division of Obihiro University of Agriculture and Veterinary Medicine demonstrated by morphological measurement that the branch size of the tree becomes a lognormal distribution from the branch structure of the tree.This is the world's first study to show that a lognormal distribution is generated from a branched structure in the morphology of multicellular organisms.The results were published in the British scientific journal "Proceedings of the Royal Society B: Biological Sciences".
The process in which the final size of an object whose size doubles (or decreases) has a lognormal distribution (Note) is called the "multiplication process (Zeebra process)".Various phenomena have been reported in fields other than biology, such as the process of widening the gap between rich and poor in economics, and the process of creating a bias in the geographical distribution of mineral content.
This time, the research group of Assistant Professor Koyama et al. Demonstrated by morphological measurement that the branch size at the end of the tree (Harnile that grows naturally in the forest of Tokachi Obihiro) has a lognormal distribution from the branched structure.In previous tree physiology and ecology, between the "scaling theory" and "allometry theory", which deal with the size and function of the entire tree, and the theory of physiology and ecology, which deals with the plasticity (change) of individual leaves and branches. There were no contacts.
By developing the results of this research, it is expected that the growth and function of complex and difficult-to-calculate forest foliage populations can be treated as a relatively simple stochastic model.
Note: The normal distribution is a typical example of a continuous probability distribution (the graph is usually a symmetrical bell).When the logarithmic value of a random variable has this normal distribution, it is called a lognormal distribution.
Paper information:[Proceedings of the Royal Society B: Biological Sciences]: A lognormal distribution of the lengths of terminal twigs on self-similar branches of elm trees
