PG Bison: Mule power for low impact thinnings
PG Bison uses specially bred mules to extract thinnings in their southern Cape forests, thus minimising environmental impacts and providing opportunities for small contractor operations. PG Bison owns some 8 500 ha of plantations around Sedgefield and George, with 6 000 ha planted to timber, mainly Pinus radiata. The plantations, known as Ruigtevlei and Brackenhill, are managed as a single unit.
|Mules skid thinnings to roadside at PG Bison's Ruigtevlei plantation.||
PG Bison's southern Cape harvesting forester, Jan Stander (left) with Jaap Steenkamp of NMMU.
Harvesting forester in charge of these plantations is Jan Stander who took the SA Forestry magazine team around to show us a thinnings and clearfelling operation on Ruigtevlei in Sedgefield.
The total harvest off these plantations is 85 000 m3 per annum, which provides around 50% of the raw material needs of the new PG Bison sawmill at George. The balance of timber required for the mill, which was built in 2004, is purchased from MTO and other timber growers in the southern Cape. The Mean Annual Increment (MAI) on these plantations average 16.5 m3, according to Jan.
When the SA Forestry magazine team visited Ruigtevlei on a hot February day, five contractor teams of eight people were busy doing the second thinning in a 15-year-old P. radiata compartment. The thinnings teams were felling and de-limbing in-field with chainsaws and using mules to skid the tree lengths to roadside down some fairly steep slopes, where they are cross-cut and stacked by hand.
The thinnings operation produces sawlogs for the George sawmill, industrial timber which is sold to a private client and building and fencing poles destined for PG Bison's woodline plant at Groot Brak Rivier.
Mules are bred by PG Bison on the estate from Percheron mares crossed with Spanish donkeys, and are loaned to the contractors for low impact skidding. There is no soil compaction within the compartments and minimal damage to standing trees during the extraction operation.
Jan says the mules are tough and work steadily for eight hours a day, skidding two to three stems to roadside at a time.
The mules are kept in grazing camps overnight with plenty of lucerne available to supplement the natural grazing. They're also fed a special high protein lunch of lucerne and cubes to ensure they're in tiptop condition, and water is readily available to keep them hydrated. Jan said that the local horse rescue unit has made routine visits and they were impressed with the condition of the animals. A PG Bison team also does regular inspections of the breeding programme and contractor operations to make sure standards are maintained.
I asked Jan why they go to all the trouble of breeding mules when they could just use the pure bred Percherons. He told me that although the pure bred horses are bigger and stronger than the mules, they are too eager and would tire themselves out in a few hours.
"By introducing donkey blood, the animal calms down and works steadily all day," he said. "The mules are much better suited to this job."
The advantages of using mules over more conventional equipment, like high leads or mechanical skidders, is reduced environmental impacts in the plantation and improved safety. Another important benefit is that it provides small start-up harvesting contractors, who may not have the resources to purchase expensive capital equipment, with an opportunity to get into the forestry harvesting business.
The clearfell harvesting is also done manually with chainsaws, using a Franklin grapple skidder to bring the tree lengths from in-field to the landing where they are cross-cut and stacked by a Bell three-wheeler for the various product lines, including saw timber, industrial timber and poles.
Clearfelling is done at 27/28 years at roughly 35 cm DBH by two 14-man contracting teams.
Small 'bostrokke' bring the timber from the edge of the compartment to a roadside depot, from where they are loaded onto the long haul transport vehicles.
After clearfelling, the slash is spread evenly across the compartment and the bigger pieces sawn up by hand. Ideally, the clearfelled compartments are re-planted in the next planting season which is 1st April to mid-September.
Published in February 2010