Effect of Tractor Logging Upon Hardwood Stands

The study was designed to compare the amount and kind of damage to the residual stand resulting from the use of 12 different combinations of skidding equipment and two skidding methods. Log length and tree length skidding of mixed hardwoods by diesel-powered, crawler-type tractors equipped with various conventional logging attachments were included. Tests were conducted on a stand improvement cut in unevened aged, upland hardwood timber located in the Ozark Uplift region of Southern Illinois. The stand consisted of 20 to 40 sawtimber-sized and 35 to 45 pole-sized trees per acre with generally heavy understory of saplings. The log-length stand averaged 71 sq. ft. of basal area and 6500 board feet of volume per acre. The tree-length stand had 63 sq. ft. of basal area and 3900 board feet of volume. Approximately 3300 board feet were cut from the log length and 1600 from the tree length stands. On the log-length area, an average of 4.8 trees exceeding 1.5 inches in diameter were struck per thousand sq. ft. of bunching area with 2.7 of these seriously injured. On the tree length area, about 5.9 trees were struck and 4.5 seriously injured. In both instances about 85 percent of the trees struck and approximately 95 percent of those severely damaged were saplings. On the log-length area, regardless of tractor size, the area disturbed per thousand board feet of logs bunched was significantly and consistently smaller when sulky or arch was used. The basal area of trees struck increased with tractor size from 0.19 sq. ft. per 100 lineal feet of skid trail for the 32 h.p. tractor to 0.76 sq. ft. for the 66 h.p. tractor. Before logging, the original stocking on the log-length area was 57 percent and on the tree-length area 55 percent. After logging, the percentages were 48 and 49 percent, respectively. With reasonable precautions, less than 10 percent of the residual trees should be damaged as a result of the logging operation.

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