Green Horizons

In the Winter 2005 issue of Green Horizons, we included a story about a mechanized forest thinning trial sponsored by the Eastern Ozarks Forestry Council (EOFC) and the Missouri Department of Conservation. The trial was designed to help determine the best methods for thinning Ozark hardwood stands. Due to space constraints, only the key findings are presented here. A complete description of the results "Productivity, Economics and Environmental Impact of Conventional and Mechanized Equipment of Thinning Ozark Forests," is available online at www.eofc.org. Authors are Peter Becker, research coordinator, Eastern Ozarks Forestry Council; Jason Jensen, resource forester, Missouri Department of Conservation; and Dennis Meinert, soil scientist, Missouri Department of Natural Resources. (Manuscript condensed for Green Horizons by Hank Stelzer, Extension Forester)

Study Overview
To refresh our readers’ memory, the study site was a 70-year old, overstocked upland oak forest in northern Wayne County near Greenville, Mo. The dominant trees were black oak, white oak, post oak, hickory, and shortleaf pine. The mature black oaks had been stressed by a three-year drought and mortality was readily apparent. The slopes of the study site ranged from 3 to 60%, with an average slope of 30%. The topsoil was 3-6 inches deep, and soils were moderately to well-drained.

A crop tree management system was applied by marking trees selected to be left in the forest on the basis of expected longevity, quality, overall health and potential for growth response. Due to the declining condition of the black oak, shortleaf pine and white oak species were favored. The initial intent was to remove sufficient timber to open at least two sides of the crown of leave trees. Due to the presence of red oak borer and the general poor health of the red oaks, the availability of suitable leave trees was quite low, and substantially larger amounts of timber were removed. The crowns of nearly all leave trees were opened on four sides, and the resulting stand resembled a shelterwood cut.

The three thinning technologies evaluated were:

1. chainsaw felling and extraction by skidder
2. mini-crawler with hotsaw
3. harvester felling and forwarder extraction

General Results
The attitude, skill and performance of the personnel operating the logging equipment -- and not the equipment itself -- are the primary determinants of "good" versus "bad" logging. In the hands of exceptionally skilled operators, all of the logging technologies tested proved capable of thinning Ozark forests satisfactorily. The selection of an appropriate system boils down to issues of productivity (including economics), damage to crop trees, and environmental impact.

This special "Bobcat-like" harvester grabs the small tree and cuts it off close to the ground with chainsaw.

Productivity
The crawler/hotsaw was the only logging technology for which production cost exceeded revenue. The operators in this system were very experienced and motivated so its relatively low productivity likely reflects real limitations of the equipment operating in sawlog-sized hardwood stands.

Average total machine production costs per unit volume did not differ significantly between chainsaw/skidder and harvester/forwarder. However, as technical problems were resolved and the out-state operators became accustomed to Ozark conditions, the production cost of the harvester/ forwarder technology was 14% less than that for chainsaw/ skidder.

Industry observers readily acknowledged the high productivity of the harvester/forwarder, but presumed that its high capital cost would make it cost ineffective, even for commercial logging operations not involving small-diameter tree removal. Ownership costs for the harvester and forwarder are relatively high, but several factors could moderate the total machine costs.

Conventional felling and skidding is not practical for removing small-diameter trees from the forest.

Scheduled hours should account for bad weather days, and tracked equipment (such as the harvester/forwarder) can operate in weather and ground conditions unsuitable for wheeled equipment (such as a conventional cable- or grapple-skidder). During the study, the conventional equipment was unable to operate due to rain, whereas the mechanized equipment operated efficiently and without rutting. Also, the utilization rate (percentage of scheduled hours that are productive) of mechanized equipment is higher than that of conventional equipment. However, the durability and reliability of the harvester head processing tough hardwoods is yet to be fully tested in the Ozark woods. There was no replication of operators or equipment within technologies, and the areas logged were small and fragmented by normal operating standards. In addition, no account was taken of mobilization, overhead, or profit in production costs. Further, revenues were inflated by the relatively high proportion of sawlogs in these thinnings, and by high sales prices for sawlogs due to shortages caused by wet weather. All of these factors prohibit further generalization of these conclusions.

Damage to Crop Trees

This harvester not only cuts the tree, but removes limbs and "bucks" the main stem into logs

Damage to the bole (main stem) of the crop trees was low and comparable among technologies. The frequency of all residual trees with any amount of bole damage in all harvested plots was 3% in chainsaw/skidder, 13% in crawler/hotsaw, and 11% in harvester/forwarder. The exceptionally low incidence of damage in chainsaw/skidder reflects the loggers’ expertise. Crown damage was significantly greater for the harvester/forwarder, but still acceptable. Thus, crop tree management is feasible at acceptable levels of environmental impact for all three technologies.

Environmental Impact
Relative to other soils nationwide, the stony soils of the Ozarks resist compaction and permit multiple entries by heavy equipment. Therefore, there was no real difference in soil disturbance and compaction among the logging technologies. But the crawler/ hotsaw did appear to expose relatively more soil than the other technologies. Soil compaction sufficient to impede rooting was rare because the heavy equipment traveled over felled tree tops.

Operator Impressions

• Harvesting (thinning) small-diameter trees with conventional equipment is inefficient and costly.
• Directional felling with chainsaws in hardwood stand is challenging, but worked well here because of the wide spacing between crop trees.
• Cutting went better than expected with the crawler/hotsaw. This equipment and one chainsaw feller would work well producing grade logs.
• Hills were not too steep for safe, productive operation of the harvester/forwarder.
• Branch removal was sometimes difficult for the harvester.
• When teamed with a cut-to-length machine, it is important to have a steady and reliable fkow of trailers on which to offload timber.

Observer Impressions

• Handling times by the forwarder could have been reduced if a color marking system had been employed on the harvester head to distinguish log grades.
• Excessive harvester/forwarder down time would be fatal to a business because of high ownership and operating costs so proper daily maintenance, an assured timber supply, and reliable haulage are all essential.

Techniques used by harvester operators to minimize impacts to leave trees and soils include:

• Place harvester slash onto the path of the machine and having the forwarder follow this same path
• Reach up with the harvester to remove forks from trees before felling the main stem to reduce damage to tops of leave trees
• Plan a path through the stand that brings the harvester within reach of the maximum number of cut-trees with the minimum amount of machine movement
• Minimize the amount of forwarder travel by creating as few piles of pieces as possible

Editor’s Note: Missouri’s forest have been thrown out of balance by indiscriminate over-cutting, over-grazing and lack of proper management. The results from this study suggest that mechanized harvesting is a viable option to help bring Missouri’s forests back into balance by removing the small-diameter trees that are currently choking the State’s woodlands. The EOFC is actively seeking additional funding to replicate the study in order to obtain more comprehensive data for detailed economic analyses.