Background
The forestry industry has long used thinning to increase yields of desirable timber. More recently, thinning has been applied to forest ecosystems to restore the complex habitats required by animals and to reinstate the ecological processes that have been disrupted by human-induced land use changes. This type of thinning is commonly referred to as restoration thinning.
Previous scientific research shows that thinning can increase the diversity and abundance of animals in forest ecosystems, while simultaneously accelerating carbon sequestration and reducing the threat of catastrophic fire.
In addition to thinning the forest, leaving the fallen timber behind may also improve habitat quality by providing more shelter and complexity than animals can use. Therefore, to establish best-practices for Hidden Vale—and other Eucalyptus restoration initiatives across Australia—our work will test whether the combination of thinning and augmenting ground structures (e.g., leaves and logs) could benefit animal biodiversity more than either of those initiatives alone.
Ultimately, by focusing our work in a small (lower-cost) area, we will be able to inform TFF management which are the best-value practices to use across the property.
Aims
Our preliminary thinning prescription is to reduce the total density of canopy species (>3 cm DBH) down to 280 trees / ha, focussing first on the smallest spotted gums (we aim to thin this species down to 200 trees / ha). We will also moderately thin other canopy species including Corymbia tessellaris (Moreton Bay ash), Angophora leiocarpa (Rusty gum), Lophostemon confertus (Brush box) and Eucalyptus crebra (Ironbark).
The overarching aim of our proposed thinning experiment is to restore structure, floristics, habitat and ecological processes. Key to this is reducing competition among stems to accelerate the recovery of retained stems.
Methodology
The QLD Herbarium has kindly provided benchmarking data for four sites of RE12.9-10.2 (courtesy of Dr Teresa Eyre and Annie Kelly). These are considered by experts to be the best available examples of the structure and composition of this RE in this part of the SEQ bioregion. For comparison, we have undertaken preliminary surveys in one of the proposed thinning areas. The area was chosen as a conservative comparison to clearly demonstrate the potential benefit of restoration thinning.
Expected Outcomes
Our experiment will provide data of enormous benefit to any individuals to groups wishing to accelerate the rewilding of degraded landscape. We expect to observe rapid changes in the growth of the trees within a few years of treatment. But the addition of habitat complexity—provided directly by the thinning activities—may be a game changer for restoration projects and could lead to much cheaper and faster restoration programs. The selection and the mapping of the sites has been an enormous undertaking, but this has placed us in an excellent position to now review the path forward for the economics and scale of the thinning trials.
Logistics for undertaking the thinning have not yet been finalised. These could present both regulatory and economic challenges to the success of the project, so these will need to be assessed carefully before any thinning activities can be signed off.
This is an exciting long-term study that will meet Hidden Vale’s central aims of restoration and allow us to both show what practices improve restoration outcomes and measure those improvements. We will be able to determine how rapidly different kinds of animals respond to thinning and/or the addition of structural complexity over time, using surveys and also camera traps that offer exciting public-engagement potential.