THE MARKING FOR BUCKING UNDER UNCERTAIN IN AUTOMATIC HARVESTING OF FORESTS

The marking for bucking is the problem of converting a single tree ste m into logs in such a way that the total stem value according to a giv en price list for logs is maximized. Proper marking for bucking is of crucial importance in harvesting of forests. The annual production of saw timber in Scandinavia is tens of millions m(3). Since, furthermore , sawn timber is by far the most valuable forest product in Scandinavi a, any improvement in the marking for bucking procedure Will yield a l arge profit. To solve the marking for bucking problem optimally one ha s to know the whole tree stem. However, it is not economically feasibl e to run the whole stem through the measuring device before cutting. T herefore, it is a normal situation under computer-based marking for bu cking that the first cutting decisions are made before the whole stem is known. In this paper the forest harvesting process will be consider ed under a general growth curve model useful especially for repeated-m easures data. The main objective is to predict the unknown portion y(n (2)) of the current stem, which will be estimated from the stem data y (1), y(2), ... , y(n-1) on the previously processed n - 1 stems and fr om the known diameter values y(n(1)) on the current stem. Then a predi ctor of y(n(2)), say (y) over cap(n(2)), jointly with the known party y(n(1)) is used in marking for bucking. It turns out that this techniq ue can improve radically the efficiency of harvesting, so that our res ults provide important knowledge for developing automatic bucking syst ems of modern harvesters.