Résumé :
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The major results of a trial to determine the cost and productivity of an alternative method of performing PCTs (pre-commercial thinnings), are listed below. This method combines corridor mowing and a modified method of thinning leave-strips using brushsaws. 1. The average productivity of corridor mowing (mowed strips only) was 0.43 ha/PH. Average machine speed was 33 metres/minute or 2.0 km/hour. 2. Worker productivity in unmowed strips using brushsaws and modified pre-commercial thinning rules averaged 0.18 ha/PH and ranged from 0.11 to 0.33 ha/PH. 3. Worker productivity decreased curvilinearly with increasing softwood density. 4. Pretreatment softwood stocking was decreased 13% from 69 to 56%, following modified pre-commercial thinning (corridor mowing and PCT). 5. The cost of corridor mowing using a Hydro-Ax 721E averaged $186/ha. Since only 33% of each hectare was mowed, the cost of mowing corridors on a total area basis was estimated at $61/ha. 6. The cost of a manual pre-commercial thinning with brushsaws using modified rules averaged $129/ha of leave-strip, based on 20,000 stems/ha. If only 67% of the total area was covered (because of mowing), the leave-strip thinning cost would amount to $86/ha. 7. The total cost of this method, including mowing (l/3 of the area) and thinning leave-strips (213 of the area) is $147/ha for stands with 20,000 stems/ha. Costs of the modified methods are 25 - 55% less than costs using conventional methods with brushsaws at densities between 10,000 - 30,000 total stems/ha.
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