PRODUCTIVITY OF A TREE LENGTH HARVESTING SYSTEM THINNING PONDEROSA PINE IN NORTHERN ARIZONA

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1 PRODUCTIVITY OF A TREE LENGTH HARVESTING SYSTEM THINNING PONDEROSA PINE IN NORTHERN ARIZONA Jason D. Thompson USDA Forest Service Auburn, AL jasonthompson@fs.fed.us ABSTRACT - In the fall of 2 a productivity study was performed on a tree length harvesting system thinning a Ponderosa pine stand in Flagstaff, Arizona. This study was a component of a Joint Fire Sciences Program project investigating opportunities to lower the costs of fire hazard reduction treatments in over stocked stands. The harvesting system consisted of a Hydro-Ax 421 E rubber tired feller-buncher with a shear head, a Caterpillar 528 grapple skidder and a Denharco 44 stroke delimber mounted on a Caterpillar 3C base. Detailed time study was used to gather productivity data for all machines in the harvesting system. This paper presents the results of the study including a description of the stand, study methods and productivity equations for each machine. INTRODUCTION The Joint Fire Science Program (JFSP) is a partnership among six federal agencies to address wildland fire and fuels issues confronting land managers. Some estimates suggest that there are over 4 million acres of forest in the United States with high fuel loads making them vulnerable to wildfire. The spate of catastrophic wildfires over the last several years has confirmed the need for research into the causes of wildland fire and management options to control it. The JFSP focuses on four main areas: fuels inventory and mapping, evaluation of fuels treatments, scheduling of fuels treatments, and monitoring and evaluation (National Interagency Fire Center, 2). This paper documents a component in a JFSP project to look at ways of lowering costs of fire hazard reduction treatments in overstocked stands. The overall objectives of the project are to assess the economic costs and benefits of different harvesting practices and regionally based utilization opportunities in fuel reduction treatments (Lowell et al, 2). The component of the project being reported here is the productivity study of a tree length harvesting system thinning a Ponderosa pine (pinus ponderosa) stand. The study was conducted in the Coconino National Forest on the outskirts of Flagstaff, Arizona during October 2. Detailed time study techniques were employed as the harvesting system thinned two -acre units. The data was used to determine productivity of the individual machines and to allow the development of regression equations to predict performance under varying stand conditions. DATA COLLECTION A video camera was used to record the feller-buncher working. The machine cycle was broken down into four elements: Move-to-tree, Fell, Move-to-dump and Pile. Tree data consisted of dbh and height. Video was also used to record the stroke delimber working. The following elements were used to describe the machine cycle: Reach, Process, Stack and Clear. Butt

2 diameter and number of pieces processed per tree was recorded. DBH was calculated using a regression equation developed from the relationship of butt diameter to dbh obtained from the skidding data. A digital stopwatch was used to record elemental times for the skidder. The machine cycle was broken down into Travel-empty, Load, Travel-loaded and Deck. Data collected included skid distance and bundle data. Bundle data consisted of the number of trees, butt diameter, and dbh and height where possible. Data for all machines was analyzed to extract elemental cycle times, calculate productivity and develop regression equations. HARVESTING SYSTEM AND STAND DESCRIPTION The harvesting system represented the most common system working in Northern Arizona. The tree length system consisted of three machines; a Hydro-ax 421E rubber tired feller-buncher with an 18 shear felling head, a Caterpillar 528 rubber tired grapple skidder and a Denharco 44 stroke delimber mounted on a Caterpillar 3 excavator base. * After scouting the harvest unit the contractor flagged the unit into smaller areas to limit skidding distance and volume of wood to each landing. The feller-buncher began felling by clearing the landing area and then felling a path to the rear of the harvest area and working towards the landing. This method allowed the operator to be better oriented as to the location of the landing. Bundles were placed with the butts facing the landing to facilitate easier skidding. The skidder was moved on site a day after the feller-buncher in order to avoid machine interaction. The skidder skidded bundles from the landing outwards until the area was completed. The stroke delimber was the last machine moved onto the site. The machine processed all trees at the roadside landing. Two lengths of saw logs (16 ft and 12 ft) and firewood logs were processed from the trees. The firewood logs were left tree length. The harvest units consisted of natural stands of ponderosa pine (pinus ponderosa). Age and size ranged from younger blackjack trees to large yellow bellies. The terrain was flat with occasional rock outcrops. The average number of trees per acre was 196 and average basal area was 119 ft 2. Both harvest units were classified as Class III fuel hazard. RESULTS Hydro-ax 421E A total of 49 cycles (935 trees) were videoed during the detailed time study of the fellerbuncher. Tree data was recorded for 157 of the 49 cycles. Data analysis was performed on these 157 cycles (385 trees). The average number of trees per cycle was 2.45 with an average dbh of 8.58 inches. The average total cycle time per tree was seconds, which equates to 2 trees per hour. Table 1 reports the summary of cycle elements and tree data for the feller-buncher. The regression analysis indicated that the number of trees per cycle and the basal area per cycle best modeled time per tree. Figure 1 illustrates how time per tree varies with the number of trees per cycle. * The use of trade, firm, or corporation names in this publication is for the information and convenience of the reader. Such use does not constitute an official endorsement or approval by the U.S. Department of Agriculture of any product or service to the exclusion of others that may be suitable.

3 Time / tree (sec) Table 1: Summary of time study data for Hydro-Ax 421E. Move-to-tree (sec) Fell (sec) Move-to-Dump (sec) Pile (sec) Total Cycle Time (sec) Trees per cycle DBH per cycle (inches) Basal Area per cycle (sq. ft.) Volume per cycle (cubic ft.) Time/tree (sec) = (# trees)-4.788(ba)+28.2 R 2 =.34, P= Number of Trees Figure 1: Time per tree vs. number of trees per cycle for Hydro-Ax 421E (BA=.89ft 3 ) Caterpillar 528 The detailed time study of the grapple skidder resulted in 1 cycles (525 trees). Table 2 contains a summary of the time study data. The average skid distance was 98 yards and the average number of trees per turn was With an average time per tree of 36.5 seconds productivity was calculated to be 18 trees/hr. From the results of the regression analysis the log of the number of trees per cycle and the distance were found to best model time per tree (Fig. 2). Table 2: Summary of Time Study Data for Caterpillar 528. Travel-empty (sec) Loading (sec) Travel-loaded (sec) Decking (sec) Total Cycle (sec) Trees per cycle Distance (yards)

4 Time/tree (sec) 1 Time/tree (sec) = 15.49(log(trees)) +.138(dist) R 2 =.69, P= # Trees/cycle Figure 2: Time per tree vs. number of trees per cycle for Caterpillar 528 (@1 yards). Denharco 44 The stroke delimber was videoed processing 218 trees. See Table 3 for a summary of the time study data. The average dbh was 1.5 inches with a maximum of 19.6 inches. The number of pieces processed from each tree ranged from 1 to 4 with an average of The average total time per tree (per cycle) was 4.83 seconds, which yields a productivity of 88 trees/hr. The results of the regression analysis to model time per tree indicated that the number of pieces per tree and the square of dbh accounted for most of the variability in the data (Fig. 3). Table 3: Summary of time study data for Denharco 44. Reach (sec) Process (sec) Stack (sec) Clear (sec) Move (sec) Total cycle (sec) DBH (inches) Number of pieces per tree

5 Time/tree (sec) 1 Time/tree=.19437(# pieces)+.1112(dbh 2 ) R 2 =.68, P= DBH (inches) Figure 3: Time per tree vs. DBH 2 for Denharco 44 (2 pieces). DISCUSSSION The feller-buncher handled the range in timber size (6 16 dbh) well. The low R 2 value for the regression equation is attributed to a couple of factors. First, the marked trees that were videoed for the time study were marked for the product recovery component of the JFSP project and were handled separately from the other trees harvested. We did not anticipate that the fellerbuncher operator would treat the trees differently. Second, it is possible that another factor not measured during the study accounted for a significant amount of the variability in the data. Distance between trees (tree density) is the most probable factor. The skidder performed well in the study conditions. The layout of the landings kept the skid distance short with a range of 26 to yards. The time study revealed that the machine spent almost half (47%) of each cycle on the landing. A majority of this time was spent pushing up logs and building the height of the log pile. The stroke delimber proved to be the limiting machine of the system with a production rate of just 88 trees/hr. Observations showed that the delimber double handled 1% of the trees. This occurred because the operator cut saw logs starting from the butt end. If there was a second log in the tree or the remainder of the firewood bolt needed additional processing the operator had to re-handle the tree to cut the second piece. REFERENCES National Interagency Fire Center, United States Government. 2. Science & technology: joint fire sciences program. Lowell, E., R. Rummer, and D. Larson. 2. In-woods decision making of utilization opportunities to lower costs of fire hazard reduction treatments. Project proposal. 24.