The fuelwood processing set-up in operation on coupe TO010C.

Part of coupe TO010C after harvest of timber but before fuelwood harvest.

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An adjacent part of coupe TO010C after fuelwood harvest.

Several years of research on coarse woody debris (CWD) and its biodiversity have crystallised down to a set of provisional prescriptions, developed by Forestry Tasmania (FT) conservation biologist Simon Grove and colleagues,  that could be applied in the event that integrated harvesting of fuelwood from native forests proceeds in Tasmania.  The prescriptions – aimed at ensuring sufficient CWD is left on-site to cater for its dependent biodiversity - are currently undergoing evaluation by FT, but an early opportunity to test their implementation came late last year, when Gunns was given the go-ahead by FT to trial fuelwood harvesting in some State forest coupes near Triabunna.  Forestry Tasmania staff, including native forest silvicultural research staff Mark Neyland, Mitchell Raspin and Leigh Edwards, monitored the operation and its outcomes.  

While the implications are still a matter of internal discussion, it is clear that the operation was rather different from that envisaged to prevail under ‘mainstream’ integrated industrial fuelwood harvesting, such as would occur if the proposed wood-fired power-stations were operating in the state’s southern and north-western forests.   Nevertheless, the provisional prescriptions are largely area-based, specifying that a percentage of the harvest area should remain unavailable for fuelwood harvest (based on similar ecological principles to aggregated retention silviculture).  This seems likely to present no greater challenge for the style of fuelwood harvesting practised in this trial than for ‘mainstream’ integrated industrial fuelwood harvesting.  

The first point of difference in this trial is that the fuelwood harvest was carried out after the main timber harvest, not concurrent with it as envisaged.  The second is that the fuelwood was processed on-site, using a chipper/hogger that converted it into a mulch-like material that was conveyed directly into the back of a truck for carting off.  This choice of machinery dictated the nature of the material harvested, leading to a third point of difference.  Whereas the prescriptions had been developed for scenarios under which the largest-diameter, longest and least-decayed logs would be the most sought-after, this machinery was able to take shorter and smaller-diameter and more highly-decayed material too.  In fact, the set-up was probably operating most efficiently when processing shorter, smaller-diameter branchwood, offcuts and split logs, as these required less pre-treatment before being fed into the chipper.  This material comprises the main components of logging waste, and much of it was easily raked up by excavators without the need to venture far from existing snig-tracks.  It also happens to be the material most likely to be combusted in subsequent regeneration burning (due this autumn) had it not been harvested – so its loss to fuelwood harvesting may have lesser consequences for biodiversity than would the loss of larger-diameter, more combustion-resilient ‘downers’.  On the other hand, the tendency to harvest split logs implies a greater tendency to deliberately split them in the first place – a practice that is discouraged by the prescriptions because it grossly reduces their ecological integrity (assuming such logs remain unharvested).

Simon Grove is due to meet shortly with the contractors involved in this operation, to discuss their impressions of the trial and the impact of the prescriptions on their operations.  His findings will feed back into the overall prescription development process.