A Forest Inventory Method Based on Density-adapted Circular Plot Size

A method using sample plots with "fixed number of stems, random circular plot size" in the stand-description phase was studied both theoretically and empirically in several regards; it was also developed for practical purposes. We call this inventory method "the density-adapted method".The advantage of this method, compared with the currently employed method, is that the work per sample plot is proportional to the amount of useful information gathered per sample plot. In simulation studies, "forests" are simulated, and the density-adapted method is then used in these "forests". Generally speaking, the bias amounts to a few percent in the realistic forests that are simulated. The bias is sometimes positive and sometimes negative. Positive bias results from a high degree of clustering, negative from high evenness.In actual stand structures, the density-adapted method has been proven to produce an insignificant amount of bias.Long-term prognoses in conjunction with timber assessment calculations have proven to be of high quality when based on inventory data from the density-adapted method. This type of data can also be used when analyzing optimal treatment programs by means of the optimization procedure of the Forest Management Planning Package, which is a Swedish management planning system.A number of electronic instruments for forest inventory that help to streamline the job is described. Transfer of data from the electronic measuring devices is done automatically in the field. The data collector is programmed especially for this purpose and features procedures for immediate data-quality control.