The Zurich method for sapwood estimation

We present a new predictor for the estimation of the number of missing sapwood rings in oak. It circumvents a number of problems with predictors used in traditional sapwood estimation procedures such as mean ring width or tree age. Instead, we use the mean ring width of the last 9 heartwood rings and the first sapwood ring, which mirrors the growth level during sapwood formation. We present a model to produce a 95 % prediction interval for the felling year. Our method accounts for the skewed distribution of the number of sapwood rings towards higher values.