The bucking, an optimal process, is a key procedure of timber production in China. Since 1949, the bucking has been considered one of the three major policies in timber production. However, the tree-stem bucking was only based on the cutter experiences in the past, so the benefits obtained were limited. Since 1960's, the optimal theories related to the tree-stem bucking have been studied around the world, which were mainly derived from operation research. Now, the popular optimal theories for tree-stem bucking are the dynamic programming and the network analysis. The optimal theories for tree-stem bucking were introduced in China at the end of 1980's. With the development of the computation technology, it is possible to decide what log lengths will yield the maximum value from the tree by using the optimal theories.
The method of directed diagram of network analysis for optimal tree-stem bucking is presented in the paper based on the Chinese special forest conditions. The potential cutting points along the tree are identified as nodes (Xn), the interval between two cutting points as the arc (Ya), and the value of each arc (Wij > 0) is determined by the price of the log. Therefore, the directed diagram of network of tree-stem bucking can be expressed by the point set (X), the arc set (Y), and the arc weight set (Wij), i.e. T = (X, Y, Wij), which can determine the longest path of tree's value. The possible paths among the nodes are determined by the adjacent matrix, and the longest path of tree's value can be found with the longest path labelling algorithm.
The algorithm is programmed, stored in the PC-1500 microcomputer, and tested practically in the Northeast forest region of China. The optimal bucking patterns will be obtained, if the lengths, diameters of the butt and top as well as the defect requirements are entered into the computer. The results show that the value of log per cubic meter can be increased 12.56% by using the optimal bucking system.
Key words: network analysis, directed diagram, bucking, tree-stem, logging operations.
Correspondence: Jingxin Wang, Forest Engineering Department, Northeast Forestry University, Harbin, China