Tremer, Von N.Von N.TremerHansen, JanJanHansenGadow, Klaus vonKlaus vonGadow2018-11-072018-11-072007https://resolver.sub.uni-goettingen.de/purl?gro-2/49591Forest models which are used to simulate alternative rnanagement options require components for estimating regeneration dynamics. Such model components are a pre-requisite for medium and long-term evaluations of alternative silvicultural treatments, based on real observed initial state variables. The case study presented in this paper shows the results of a particular approach of modelling the diameter growth of natural Beech regeneration. In Lower Saxony regeneration saplings are defined as mature trees when they reach a breast height diameter of 7 cm. It seems logical, because of the particular definition of a threshold diameter, to model the diameter growth of regeneration saplings rather than their height growth, and to use the information for estimating periodic ingrowth of saplings into the main stand. The empirical data base includes 189 plots of the Lower Saxony forest district Grunenplan. These plots had been assessed in 1999 and were remeasured in 2004. Sample trees were selected at the time of remeasurement to evaluate the diameter increment at the root collar. Based on these data, a multiple log-linear model could be derived. The model estimates the mean annual root collar diameter increment within a 5-year interval for individual beech saplings (Gl. 2, Tab. 7), The model predictors (initial diameter, competition, expected change of competition) are comparable with single tree growth models for mature trees (Tab. 11). Only such variables were considered in the model which are either easily obtained in the field or already available from routine inventories, or which can be derived from existing inventory data. For this reason it was necessary to parameterise a specific model component for estimating the initial root collar diameter of a Beech sapling (Gl. 3, Tab. 9). The initial root collar diameter is an important input variable for the growth model. The initial diameter was found to be an essential predictor. Knowledge of the initial diameter is indispensable because, when adding the estimated increment of a 5-year growth period, we need to be able to verify which sapling reaches or exceeds the threshold diameter (DBH 7 cm). A linear model was parameterised to estimate the breast height diameter from the root collar diameter (Eq. 4). The approach presented in this study is suitable for estimating the change of a given regeneration structure and the ingrowth, based in available inventory data.journal_article000251900600002