A new way of moving sawn logs promises to minimise damage to forest soils and water.

The environmentally friendly system, which uses modified excavators to move logs from the stump to the roadside landing, was demonstrated this week at CSIRO field days in Daylesford (Victoria) and Smithton (Tasmania).

"Using excavators reduces machinery travel, compared to the normal system of dragging logs behind a skidder," says Chris Dare, a post-graduate student working with CSIRO Forestry and Forest Products, who has examined the productivity and impact on the soil of excavators and skidders working in clear-felled eucalypt forest. Mr Dare presented his results at the field days.

Mr Dare says the use of excavators for logging - with the digging 'bucket' at the front replaced with a grappling device - began in the United States. Excavator logging uses the slewing action of the machine to move logs from the stump to the roadside landing in a series of steps.

"The excavator can move more than two dozen logs in one trip to the landing whilst a skidder needs up to seven trips to move the same amount of wood. So soil disturbance, erosion and compaction is much lower for excavator logging," he says.

First trials in Australia started in the early 1990s, but 18 months ago only two operators were using excavators. "Since then it has started to expand - operators are using them in Victoria and Tasmania, and people are looking at using them in Queensland and Western Australia,." he says.

Overall, skidders do produce better productivity figures, says Mr Dare, moving about 38 cubic metres of timber per hour compared with 25 for excavator logging. But analysis of the results show that the distance excavators have to travel is crucial.

"Where landings are in the best positions, excavator logging is more productive," Dare says. "The key is to keep the distance between the landing and the furthest collection point down to 200 metres, which means ideally you want a landing every 400 metres or so."

Conditions during the excavator trial provided a severe test of soil impact as the study was performed in the middle of the wettest winter in the area for 85 years. By contrast, the skidder trial took place in dry weather in mid-summer.

"Skidding was locked out of the forest in the winter because of the damage it would cause," Dare says. "However, where conditions are the same, disturbance to the soil is significantly reduced by using excavators."

The study was conducted at Daylesford, Victoria, as part of the Forestry Technology Program, a partnership between the Australian Logging Council, CSIRO and the University of Melbourne. Collaborators were Pritchard Logging and the Victorian Department of Natural Resources and the Environment. The Forest and Wood Products R&D Corporation provided funding.

For further information contact:

Chris Dare (02) 6281 8212
Mick Crowe (02) 6281 8357