Mathematical and ecological traits of above and belowground biomass production of beech (Fagus silvatica L.) trees growing in pure even-aged stands in north-east France

Abstract

AbstractTree biomass and biomass increment equations were specially developed in 1996–1997 to study the ecophysiological functioning of an experimental European beech stand, aged about 30 year-old, in the Hesse forest (NE France). In order to extend such a study to beech stands of different age classes, it was necessary to build biomass and biomass increment equations that could be used for any age; we call them generalized biomass equations.To build such generalized equations, trees were sampled in different forest plots covering the whole age range. Moreover, in each plot, several trees were chosen to represent the different crown classes (from dominant to suppressed). Sampled trees were felled down and the root system excavated for a sub-sample of trees, for biomass analysis by separating the main compartments of the above and belowground tree parts. When it was not possible to measure the total biomass of a given tree compartment (large trees), wood samples were taken in the concerned compartment. Moreover, equations were built to estimate the biomass of the missing parts of the root system and branch compartments that were likely to have suffered losses during root excavation and tree felling, respectively. Multivariate linear and non-linear models including possible random effects were tested to represent the biomass and biomass increment variations of each tree compartment and of their aggregation in the above and belowground parts of the tree.Compatible biomass and biomass increment equations for the different tree compartments and their combination in above and belowground tree parts were developed and fitted, allowing the analysis of the variations of the biomass distribution and allocation with tree age. Stem growth efficiency was also calculated and appeared dependent on tree age and tree social status.The biomass and biomass increment equations established for beech in this study allow the estimation of the biomass and carbon stocks and fluxes (NPP) for the even-aged beech stands of the Hesse forest, whatever the age of the stand; they could also be used to analyze the effects of different silvicultural treatments on the biomass and carbon stocks and fluxes of beech stands, using the available stand growth and yield models developed for beech in France.