%0 Research article
%T Performance of percentile based diameter distribution prediction and Weibull method in independent data sets
%A Kangas, Annika
%A Maltamo, Matti
%D 2000
%J Silva Fennica
%V 34
%N 4
%R doi:10.14214/sf.620
%U https://silvafennica.fi/article/620
%X Diameter distribution is used in most forest management planning  packages for predicting stand volume, timber volume and stand growth.  The prediction of diameter distribution can be based on parametric  distribution functions, distribution-free parametric prediction methods  or purely non-parametric methods. In the first case, the distribution is  obtained by predicting the parameters of some probability density  function. In a distribution-free percentile method, the diameters at  certain percentiles of the distribution are predicted with models. In  non-parametric methods, the predicted distribution is a linear  combination of similar measured stands. In this study, the percentile  based diameter distribution is compared to the results obtained with the  Weibull method in four independent data sets. In the case of Scots  pine, the other methods are also compared to k-nearest neighbour method.  The comparison was made with respect to the accuracy of predicted stand  volume, saw timber volume and number of stems. The predicted percentile  and Weibull distributions were calibrated using number of stems  measured from the stand. The information of minimum and maximum  diameters were also used, for re-scaling the percentile based  distribution or for parameter recovery of Weibull parameters. The  accuracy of the predicted stand characteristics were also compared for  calibrated distributions. The most reliable results were obtained using  the percentile method with the model set including number of stems as a  predictor. Calibration improved the results in most cases. However,  using the minimum and maximum diameters for parameter recovery proved to  be inefficient.