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ŠUMARSKI LIST 1-2/1993 str. 34     <-- 34 -->        PDF



During tractor dragging of roundwood timber forest soil becomes compressed
by the tractor wheels (caterpillar mounting) and by the hauled timber.

Most damage is caused by the vehicle´s wheels in the form of wheel-traces of
compacted soil or cuts deep into the ground. The kind of wheel-traces depends on
the soil bearing capacity, while the soil bearing capacity is dependant on moisture
in the soil at the time.

The depth of the wheel-traces is determined by the soil condition, number of
journeys and by the measurements and weight of the load, and not the kind of
tractor. In the case of soil compaction deformations measured were from 2.1—3.2
cm in depth. The depth of the cuts into the ground by both tractors on average
ranged from 13.8—24.5 cm.

The width of the wheel-trace is bigger in articulated tractors than in adapted
aggricultural tractors, and furthermore the width in hilly country increases compared
to that in flat country. The same applies to the overall width of the compressed

The overall width of the compressed area for the adapted agricultural tractor
in hilly country (250 cm) approaches the width of the drag road for the articulated
tractor in flat country (254.2cm).

The total compressed area for the theoretic density of a drag road of 50 to
200 mm for the articulated tractor is likely to be 1.3% to 6.5% of the felling strip.
With regard to the drag road length an adapted agricultural tractor damages 1.0%
to 5.0´ „ of the

The greatest damage by a articulated tractor (by tractor wheels) amounts
to 0.7%—2.9% of the felling strip area in flat country and 1.2%—5.0% of the felling
strip area in hilly country. With regard to the adapted agricultural tractor the
maximum in flat country is 2.0% and in hilly country 2.5% of the felling strip

Damage to soil during timber dragging cannot be entirely eliminated, but can
be reduced to an ecologically and manageable amount by the application of the
most suitable technical and technological solutions, choice of the right time regarding
seil bearing capacity, and by comprehensive permanent education of staff,
including the introduction of lawe and regulations.

During the exploitation of plantationsit is possible to partially protect the
ground by layers of branches on the drag road. The earlier practiced technique of
laving roundwood is now abandoned except in sporadic cases.

Erosion of the drag roads and tractor tracks will be diminished by coordinating
their gradient to the erosivity of the surface and the expected amount of precipitation.