Features

The narrow-leaf ironbark-white cypress pine Callitris glaucophylla association has undergone perhaps the most systematic and far-reaching exploitation of any in NSW (see also June NPJ). Ironbark was the favoured species for railway sleepers and huge volumes have been removed. There was a phase in forestry history from the late 1960s to the mid-1980s where a culling program was viewed as the most efficient way to deal with the species, seen then as an uneconomic and declining resource. About 10,000 hectares were culled out in the Pilliga alone, though this practice was carried out throughout the north-west woodland belt. The thinking was to create a plantation-type environment for white cypress pine, an approach still canvassed by State Forests.

On top of this, a commercial use was found in the form of an export industry of ironbarks as droppers for electric fences (or "insultimber"). This has prospered since the mid-eighties and is still continuing. At no time has the forestry industry in the west been compliant with any harvesting prescriptions, except for those devised by themselves. According to recent estimates undertaken for the Brigalow Belt Regional Assessment, across the whole State Forest estate in the Pilliga the average density of E. crebra is now two mature trees (trunk diameter equal to or greater than 50 cm) per hectare.

Typically this species grows tall and straight with few lateral branches below the canopy of the tree. This is typical of a forest growth form and gives an idea of how the pre-European community may haveappeared. I recently assessed 20 plots in the Pilliga West and conducted a stump-count analysis. The results indicate that the average density of mature trees was in the range of 14-31 stems per hectare (average 24.45). Large cypress stems were found to be on average 4.4 per hectare in the same habitats, indicating that this species is a sub-dominant to the ironbark.

Ironbark forest,
Pilliga West
Photo: David Paull

This community must have been an impressive one before Europeans came, with a tall dry forest structure and character. It probably had a foliage cover of 10-30% and a canopy about 30m high, excluding emergent individuals. The understorey was probably relatively open, with patches of tall shrubs and a groundcover storey dominated by grasses and forbs.

If this tree density is compared to today, it suggests that there has been a decline in mature stems of ironbark by over 90% on average in the Pilliga West; the decline of large cypress stems has been equally disastrous. It is obvious that this community has been highly impacted by human usage in the last 100 years. Some areas have a higher than current average density, perhaps up to 10 mature trees per hectare, while others have a lower density – some compartments have been virtually cleared of their large ironbarks. The impact on the function of this community must be enormous. The impact on the fauna has been equally enormous.

It is thought that a recent population crash of brushtail and ringtail possums has occurred in the Pilliga West, facilitated by a declining tree-hollow resource, in combination with a disproportionate effect by feral predators. Such a pattern has been documented elsewhere for these species.

It is clear from a conservation management point of view that this ironbark community is in dire need of protection from future hardwood removal. NPA is dedicated to getting parts of the Pilliga declared as national park, so that it may be free from future charcoal schemes.