Paleo-ecophysiology of forests : reconstructing structure and function of tree populations.

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The purpose of the present project is to reconstruct structure and functional quantities of tree populations for over several decades by developing methods for such estimation. Development of even-aged stands of coniferous species is of particular interest. The items to be reconstructed include stand density, biomass of tree parts, growth of individuals and its size distribution. Yearly changes of the variables are also estimated. We used hard data taken from the field observations for reconstruction. No attempts had been made for estimation of variables that had already disappeared from the scene for decomposition or mortality. One of the aims of this research is to show that such reconstruction is possible. We also intend to use the method for assessing the effect of the global warming on forest ecosystems by examining the reconstructed changes in forest structure and function.We showed that it is possible to estimate parameters of the size distribution function of individual trees in the past by assuming Hozumi, Shinozaki & Tadaki's (1968) -3/2 power distribution as the biomass distribution function of individuals in even-aged stands, and by the use of tree ring data at breast height of about 15 largest trees in the stand. The reconstruction could be done even for the size and frequency of individuals that have already disappeared from the forest. In addition, a method was developed to estimate stand density, biomass of tree parts, total stem volume of the stand, growth of individual trees and their size distribution in the past, by applying the parameter value of the so called "stem slenderness index" for a given time in the past. This parameter is calculated from the stem analysis data of several trees. Assessment of accuracy of the present method is necessary in the future studies through the analysis of reconstructed population structure for stands of which structural data exist for a time in the past.