The need

Australian softwood plantations (mostly pine) take around 25–30 years to grow before they are harvested for timber. Until recently, growers had to wait until harvest to know whether the wood would be strong and suitable for building.

This project, supported by Forest & Wood Products Australia (FWPA), set out to explore whether wood-quality measurements taken during the middle of a plantation’s growth cycle (mid-rotation) could reliably predict the quality of the wood when trees are harvested years later, to help forest managers predict future timber quality years before harvest.

Mid-rotation refers to the middle stage of a plantation’s growth cycle, roughly halfway between when the trees are planted and when they are harvested. It’s a useful stage for assessment because the trees are developed enough to show meaningful wood properties, but still young enough that growers can adjust management decisions before harvest.

The research

Our research, led by chief investigators Associate Professor David Lee, Dr Geoff Downes and Dr Vilius Gendvilas from UniSC’s Forest Research Institute, tested a technique called ‘Resi,’ which stands for ‘resistance drilling.’

Resi involves drilling into a standing tree and measuring how much resistance the drill bit encounters. That resistance correlates with how dense and stiff the wood is. Density correlates with how strong the wood is, while stiffness (often measured as “modulus of elasticity,” or “MoE”) signifies how well the timber will perform structurally (how it resists bending under load). These wood properties influence how good the timber will be for structural uses such as building or framing.  

Our researchers then compared these mid-rotation Resi measurements with results from sawmills, including how timber boards produced from harvested trees performed in terms of stiffness (green and dry mill wood). 

Resi is much faster than older methods (roughly three times faster than some acoustic-based methods), which makes it suitable to use on a routine basis across plantations. 

They also created computer models that use the Resi data to predict how much usable wood a plantation will produce, and what the overall economic value of that timber may be. These predictions were then built into the software tools the industry already uses (such as YTGen), making the information easy for growers and processors to access.

The findings

• Mid-rotation Resi measurements can successfully predict “harvest-age” wood properties (density and stiffness). In practice, Resi data from young or mid-rotation plantations mapped well to subsequent mill-site board stiffness after harvest.
• Sources of measurement error — for example, differences between different Resi instruments, operators, or drill bits — were found to be negligible at commercial scale. In other words, the method is reliable and robust enough for routine use across different sites and operators.
• As a result of this validity, more than 30 Resi instruments have already been adopted across Australia by growers and processors — used routinely in forest inventory and log-supply planning.
• Incorporating Resi-based predictions into industry tools (like YTGen) means that plantation managers can estimate future timber yield and quality early — helping in decisions about how long to grow (rotation length), when to harvest, and which plantations will deliver the best value.

The impact

For growers:

• They can predict future wood quality early and make better decisions about how long to grow the trees, how to manage them, or which areas of the plantation have the highest value.
• Resi technology reduces risk and improves planning, especially when timber markets demand consistent quality.

For sawmills and processors:

• They get better information about what quality of wood they will receive years ahead of time. This helps with planning production, reducing waste, and ensuring strong, reliable timber for construction.

For the wider community, and our planet: 

• Reduce waste by predicting wood quality early, which means fewer trees need to be harvested to meet building demands.
• Better use of plantations supports a more stable and sustainable timber supply.
• Better planning means we get more high-quality timber from the same amount of land, which eases pressure on native forests and supports long-term forest conservation.
• Healthy, well-managed plantations store carbon as they grow, and producing strong, durable timber for construction keeps that carbon locked away for decades.
• Smarter forest management leads to better use of resources, lower environmental impact, and a more reliable supply of renewable, climate-friendly building materials.

The future 

This revolutionary tool should continue to be expanded, especially to strengthen communication between growers and processors so that wood flow and supply chains are optimised.

There is potential to combine Resi data with other technologies, such as remote sensing, Lidar and photogrammetry, to further enhance predictions of yield and quality.

The project also recommends building large, estate-wide datasets to better understand how different factors — like site conditions, climate, management practices, and even the genetics of the trees — influence wood quality. Having this broader information would help improve the prediction models and lead to better decision-making and higher-quality outcomes across the industry.