The bush northwest of Wingan Inlet in Croajingolong National Park now consists mostly of spindly Silvertop Ash (E. sieberi) stems, some dead, others struggling to recover from the massive 2019-20 fire.
These areas were logged for hardwood in the 1970s using a clear-fell technique that involved falling the majority of trees and leaving a few large trees to provide seed for regeneration. In the following autumn the logged areas, or coupes, were burnt to reduce the logging residue and encourage the release of seed from the few remaining trees.
The resulting Silvertop Ash revegetation was prolific. Foresters at the time believed that a healthy forest would regrow and that timber would be ready for harvest in fifty to eighty years. What eventuated was a dense forest dominated by Silvertop Ash saplings competing for space, light and nutrients. These conditions provided little opportunity for trees to form a canopy. Other tree species that were common in the area prior to logging, such as Yellow Stringybark (E. muelleriana) were mostly out-competed by the Silvertop Ash and the potential for the development of an understorey of shrubs and ground plants was limited.
In 1979 logged areas were included in the Croajingolong National Park, along with the country immediately surrounding Wingan Inlet that had been protected as a national park since 1909.
In January 1983 the Cann River Fire was ignited by lightning in the Bondi Forest area in NSW and by late March had burnt through to Mallacoota. The quantity and arrangement of fire fuel within the logged areas, along with extraordinarily dry conditions, resulted in extreme fire behaviour, killing and damaging the young Silvertop Ash saplings.
There was discussion at the time that the fire may have assisted in thinning out the dense regeneration, but there was sufficient seed available to germinate more regrowth.
Over the following decades, other than some planned burns, the logged areas experienced little or no fire activity. The Silvertop Ash saplings grew, but at a rate far less than was expected by the foresters back in the 1970s. With each sapling competing for space there was minimal canopy establishment.
The logged areas needed many decades without significant impacts to develop into mature forest. The massive fires that raged through eastern Australia in 2019-20 ensured that this was not going to happen and the landscape was again reduced to kilometre after kilometre of blackened, dead stems. After almost 50 years since the original logging, the regeneration process commenced once again.
It is fortunate that the former Wingan Inlet National Park surrounding the inlet was protected from logging, although in the 1970s the foresters were keen to log up to the park boundary where possible. Most of this area was also burnt in the 2019-20 fire and it now provides the opportunity to compare fire impacts between the logged and undisturbed areas.
Within these unlogged areas much of the mature canopy was also burnt. While some of the canopy appears to have been killed, new epicormic growth indicates that much of the canopy is regrowing and will be re-established. The new canopy will, in turn, reduce light reaching the ground, slowing the regrowth at this level. Less light and cooler conditions under the canopy will increase humidity and ground moisture, encouraging plants requiring these conditions.
Further from the logged areas and closer to the inlet, fire impacts in the mature forests are varied. Here the bush is more diverse with a greater occurrence of Mountain Grey Gum (E. cypellocarpa). Much of the canopy along the ridge tops was damaged, but is showing signs of recovery. In the gullies and rainforests, which also burnt in the extremely dry conditions, there has been damage to the canopy. Kanookas (Tristaniopsis laurina) are producing epicormic shoots, treeferns are resprouting fronds and liane vines are re-establishing over the canopy.
There are rare patches of mature forest near the damper gullies that show little evidence of fire. These may be a result of fire behaviour at the time and need closer investigation to understand how they could have escaped the inferno.
In the sandy soils closer to the coast and on the west side of the inlet a magnificent forest of mature Red Bloodwood (Corymbia gummifera) provides valuable habitat for a range of fauna including the Yellow-bellied Glider and Greater Glider. The fire in this area burnt hot enough to kill the understory of Blue Olive Berry (Elaeocarpus reticulatus) and damage the Bloodwood canopy, but recovery is well underway.
Unlike the logged Silvertop Ash forests, the post fire regeneration of the understorey in the mature Red Bloodwood forest has produced a diversity of species. There are other comparisons with the logged areas, such as the presence of wildlife, including Lyrebirds scratching through the leaf litter and Yellow-bellied Gliders screeching as they glide from tree to tree. In the burnt, logged areas there is only an eerie silence.
The Wingan Inlet area, where logged areas adjoin undisturbed national park, offers the opportunity to better understand the relationship between logged coupes and fire behaviour and why clear felling has failed to regenerate a healthy, diverse forest.
The complete loss of canopy cover and the increase in light and heat at the forest floor are the most obvious impacts of the clear felling process. The removal of vegetation and subsequent coup burn is a dramatic contrast to the natural process that occurs in the mature Silvertop Ash forest, which involves the germination of new vegetation from the death of a single tree created from an opening in the canopy, allowing regeneration in the immediate area below.
The massive fires in 1982-83 and 2019-20 demonstrated that the arrangement and structure of fire fuels in the logged areas contributed to extreme fire behaviour. The dense forest of young saplings readily carried crown fire through the landscape.
There was the opportunity in the 1970’s to employ selective logging practices that imitated the natural forest processes. However, this approach could not produce the quantity of logs required to satisfy the demands of the timber industry. Consequently the supply of logs ran out and sawmilling in the district collapsed.
The foresters who managed the clear felling process in the 1970s would be disappointed with spindly and dead Silvertop Ash stems that now dominate the landscape in the clear felled areas. The promise of a thriving, new forest has not been realised.