Stand,harvest,and Equipment Interactions in Simulated Harvesting Prescriptions

We evaluated potential interactions ofstand type, harvest ing method, and equipment inan experiment using interactive simulation. We examined three fel l ing methods (chain saw, feller-buncher, harvester) and two extraction methods (grapple skidder and forwarder) performing clearcuts, sheltenvood cuts, and single-tree selection cuts in both an uneven-aged natural stind and zn even-aged planted stand. Elementai t ime, distance traveled, travel intensity, and hourly productivity were est imated for each combination of stand type, harvesting method, and equipment. This technique provides a useful tool for comparing al ternat ive systems in a range of harvest ing si tuat ions. Forest managers must consider the interactions of stand, harvest, and machine factors when selecting effective harvesting systems. These decisions are often difficult given the range of equipment available and the desire to use new harvest ing schemes without f ield data on such interactions. Factors such as the tree size removed, initial and residual stand density, harvesting prescription, equipment dimensions, and operat ion methods can each affect the production and cost of a sys tem. Many researchers (20,2 1,25,32-34) have reported on the productivity and profi tabi l i ty of individual harvest ing machines. The majority of these works addressed a single harvest method. Fewer reports are available that examined comparisons and interactions of harvesting systems (23,24,26,27). Such side-byside field comparisons identify differences in harvesting systems. However, field studies are handicapped by the difficulty and/or cost of replicat ing experiments over a variety of conditions. In addit ion, some influencing factors such as bunch size are more difficult to control in the woods. Computer s imulat ion combined with a l imited amount of f ie ld data overcomes many ofthese shor tcomings . Many harvest ing s imulat ion programs have been developed since 1960. Goulet et al. (15 17) summarized the models available through 1980. Most of the models developed up to that time were deterministic, numerical simulation programs (1,5,29,36). The Harvesting Analysis Technique (3 1) was perhaps the most widely used of the programs in this category. None of the programs developed during this t ime per iod displayed resul ts in graphical form or obtained user input in graphical form due to the computer hardware widely available at the t ime. Since 1980, harvest ing s imulat ion programs have largely been developed on personal computer platforms and increasingly use graphical modes for both real rime user input and renorting of results. Garbini et al. (14) used numeticai slrnulation with graphical annmation to illustrate material movement and machine act ivi t ies in cont inuous s imulat ion of a log merchandiser. In another decision s imulator appl icat ion, graphical animation and numerical data were used to make log bucking decisions (28). Fridley et al . (I I , 13) and Fridley and Jorgensen (10) reported the use of graphical interactive simulation for studying the design of swing-to-tree feller-bunchers used for thinning. Their program was used to identify the effect of various design parameters on feller-buncher performance during thinning (12). An interactive simulation program for modeling fellerbunchers was developed by Greene and Lanford (IS: 19) to examine the effects of stand and operating factors on the productivity of a small feller-buncher in second thinning operat ions. They also found variabi l i ty between simulat ion operators but it did not appear to affect the utility of interactive simulation (22). Block and Fridley (3) described a three-dimenThe authors are, respectively, Former Graduate Research Assistant, and Professor, Center for Forest Business, Daniel B. Wamell School of Forest Res., The Univ. of Georgia, Athens, GA 30602-2152; and Former Project Leader, USDA Forest Serv., Southern Res. Sta.. Engineering Res. Unit, Auburn Univ., AL 34849. Funding for this research was provided in part by the USDA Forest Serv. Southern Res. Sta. RWU-4702, Auburn, AL. This paper was received for publication in July 1997. Reprint No. 8696. OForest Products Society 1998. i Forest Products Society Member. Forest Prod. J. 48(9):81-86. FOREST PRODUCTS SOCIETY VOL. 48, NO. 9 81 3 -; . Lt.‘..:. :.i;.: : .; :. ..L.. .-. puter graphics simulation of a fellerbuncher. The program allowed the user to s vary physical parameters of the fellerbuncher that would affect its performance in the woods. Baumgras et al. (2) presented a s imulat ion model to es t imate stump-to-truck production rates and multiproduct yields for conventional groundbased t imber harvest ing systems in Appalachian hardwood stands. A method of estimating tree damage was also addressed in conjunction with an interactive machine simulation program that could model harvest ing performance in a variety of si lvicultural operations (6).