Three recently completed, FWPA-funded projects using data spanning 30 years in Australian forestry plantations have resulted in actionable recommendations and guidance for improving productivity, profitability and health of plantation forests.
Download the 3 reports
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A tool to predict fertiliser response & profitability in softwood plantations across Australia: Download here.
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Optimising Nutrition Management of Hardwood Plantations for Sustainable Productivity & Profitability: Download here
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Optimising productivity of hardwood plantations: yield gap analysis for Eucalyptus globulus plantations in southern Australia: Download here
Project findings
Findings have provided insight into nutrition and environmental factors that limit plantation productivity. Existing tools such as ProFert, a fertiliser decision support tool, have been updated and enhanced with this long-term data and are providing immediate value to the industry.
“Consultation with our grower members revealed a clear need and appetite for significantly increased investment in plantation nutrition – both through RD&E and capacity building”, said Jodie Mason, FWPA’s Head of Forest Research.
“Investing in better calibration of decision support tools such as ProFert goes some way to bridging the gap left as industry experts retire. Some of our new nutrition and physiological modelling projects also have a stronger focus on capacity building to strengthen expertise.”
The three projects presented here were developed to support increasing productivity from Australia’s plantation estate, which has remained static or in decline, in terms of area, for the past decade.
“There is a strong desire within the industry for increased output to keep in-line with increased demand,” said lead researcher and McGrath Forestry Services Principal, John McGrath.
“Land in Australia, especially high-quality land, is very expensive. That means the best option for foresters is to make sure they get the best out of the land they currently have.”
The three projects each investigated aspects of enhancing productivity:
1. The Softwood Nutrition Project looked to increase confidence in the use of fertiliser by providing reliable predictions of plantation response. To do so, it synthesised long-term data from south-west Western Australia to understand the environmental and management factors that influence fertiliser response. Both plantation productivity and the response to fertiliser in southern WA were strongly related to water supply. The distinct rainfall and evaporation gradients in this region allowed the interaction between fertiliser and water supply to be evaluated.
- There were strong relationships between concentrations of phosphorus and nitrogen in soil and response to fertiliser, with the response to additions of both nutrients decreasing as the concentrations of these nutrients in the soil increased. The strong relationships between soil nutrient concentrations and fertiliser response demonstrated that soil analysis can be used as a predictor of response. The Olsen bicarbonate extractable phosphorus provided a useful index of phosphorus status while total soil nitrogen provided a good estimate of nitrogen status.
- The interactions between water availability and nutrient supply were defined and used to create multi-dimensional relationships that were included in the ProFert model to predict the impact of water supply on the responses to phosphorus and nitrogen.
- The duration of the responses to both phosphorus and nitrogen were estimated from the time course of responses. The longer residual effectiveness of phosphorus contrasts with the relatively short-term responses to applied nitrogen, which only lasts between four to six years depending on the application rate.
As a result of this research, the ProFert tool was recalibrated and extended its regional coverage, to provide greater knowledge to the industry.
2. The Hardwood Nutrition Project encompassed a network of trials across southern Australia, similarly, looking to provide predictability and guidance around fertiliser response and usage to increase productivity. It also observed interactions with climate, such as temperature and water, and soil nutrition.
The study found warmer temperatures to be a key component in boosting response to fertiliser and tree growth. Additionally, a more targeted use of fertiliser found that nitrogen was the best option to achieve higher productivity, compared with phosphorous and potassium. This was in part due to historical agricultural use of these fertilisers on the land where hardwood plantations have been established, and continued access to remnant nutrients in the soil.
The ProFert tool was once again recalibrated with data regarding the higher recommended rate of nitrogen than has previously been used operationally.
3. The Optimising Productivity – Hardwood Yield Gap Project looked at the historic gaps between potential hardwood plantation yield and productivity in southern Australia, compared to actual yields. In assessing why there may be a gap, the project aimed to identify management actions to reduce it.
Researchers interrogated large data sets of operational and trial productivity data, along with management and environmental data, to provide an understanding of the impact of environment and forest management practices on productivity. This included empirical analyses, a forest modelling and prediction framework, and case study demonstrations, focusing on 10-year yields for planted Eucalyptus globulus.
Climate factors, in particular water availability and temperature, were the primary limitations to productivity. Soil water holding capacity, (largely defined by soil depth) was also found to be important, along with land use history and consequent fertility.
Modelling suggested yield gaps of 150-200 m³/ha at harvest in several regions. To address this shortfall, researchers set about supporting forest growers to predict how and where management interventions could provide the greatest benefits. The main mechanisms available to address the yield gaps are increased nitrogen fertilisation and the maintenance of stocking at adequate levels. The Agricultural Production Systems sIMulator (APSIM) was calibrated for hardwood productivity to effectively provide a prediction tool for the industry.
The importance of long-term data and insights
“One thing all three projects have done is to create new insights from pre-existing historical data,” John McGrath said.
“We’ve taken the results of nutrition and silvicultural trials conducted across Australia from as far back as 30 years. So, while our involvement in these three relatively short-term projects has been recent, in many ways the projects themselves have been in development for much longer.”
“Obviously, the climate has a massive influence on the growth rate of trees, but also the scale of their response to fertiliser and nutrition management. That interaction between the environment and the management of the plantations has been a core theme throughout all three projects.”
The research teams also recognised that climate change is an important consideration, particularly considering rotations in softwood plantations can be 30 or 40 years. So, response to fertiliser is likely to change over long rotations alongside the changing climate.
“There’s the longitudinal climate change the whole world is experiencing, but also the short to medium term climate variability we have long seen in Australia, such as its extended periods of drought, will influence how plantations need to be managed,” said McGrath.
“This variation has always existed, but data and statistics available from past work haven’t necessarily been applicable or appropriate when looking as far ahead as the life cycle of trees and plantations.”
Understanding these factors and their impact on fertiliser, silvicultural manipulations and thinning generally has not been considered or integrated into forest management practices in Australia to date.
Using geographical differences to deepen understanding
“One of the things we’ve managed to do is to use the vastness and diversity of Australia to our advantage,” said McGrath.
“If you look at, say, southern West Australia, variations in certain climatic conditions are quite narrow. So, when you look at the impact of factors like temperature on response to fertiliser across that region, you don’t get much of an indication because the temperature variations are small.”
“But when you pull together datasets from as far afield as Tasmania or southeast mainland Australia, you can compare much larger variations. This is when you really start to see the impact.”
The Hardwood Nutrition Project provided a great example of this. The team established around 40 trials across the whole of southern Australia, including Tasmania, the Green Triangle, and southern Western Australia. The temperature variation across these regions was around 8 or 9 °C. The team found the overall potential for tree growth was constrained by colder temperatures, particularly in Tasmania. Warmer temperatures and plenty of water, in some other regions, meant trees grew much more rapidly and, consequently, response to fertiliser was found to be much stronger in those areas.
“Originally these were three standalone projects,” McGrath said. “But when we saw common themes start to emerge it made more sense to look at them together.”
“The issue of climate and its impact on fertiliser response is inherent in all three projects. So, in many ways, the projects work together, while at the same time having their own nuances.”
Distinctions between hardwood and softwood findings
One significant variation observed was that, historically, softwood plantations tended to be established on areas with ex-forest soils that hadn’t benefitted from any improvement in nutrition from agriculture. These plantations responded well to phosphorus and nitrogen, and sometimes potassium.
Conversely, hardwood plantations have largely been established on ex-agricultural land. These don’t demonstrate a significant response to phosphorus because of its historic application through agricultural practices.
Knowledge into practice: improving industry guidance
John McGrath said all three projects were designed to result in practical outcomes for the forestry plantation industry.
“Making tools like ProFert available to industry is an important means of taking what we have learned and presenting it to forestry practitioners in a useful way,” McGrath said.
“Our next steps will involve a softwood version of the yield gap project, which is also being supported by FWPA.”
The recalibrated ProFert tool has already been adopted and implemented by the Forest Products Commission (FPC).
Dr Anjanette Chandler, Manager Forest Genetics at FPC said ProFert has allowed the organisation to bring together decades of forestry nutrition research into a single tool.
“This tool has the ability to optimise the nutrition response and profitability for softwood plantations in the southwest of Western Australia,” Dr Chandler said.
“ProFert is currently being used as part of FPC’s annual forest nutrition program to ensure plantation productivity is optimised throughout the rotation.”
Ben Bradshaw, R&D Manager at Australian Bluegum Plantations said the yield gap analysis project provides important support for hardwood plantation growers across Australia. “The findings clearly demonstrate that nutritional inputs and management are important for improving productivity and returns from the existing hardwood estate.” he said.
“The calibration of the ProFert tool has been a key goal for hardwood growers to optimise nutritional inputs to improve wood yield and financial returns. The broad distribution of the historic and new data provides confidence in the application of ProFert across the primary hardwood growing regions.”
“Profert also provides for exploration of returns from a range of fertiliser types, quantities and input timing offering flexibility to fertiliser regimes in response to seasonal and climatic variability. ”
Identifying the regions and plantations that are likely to respond to more intensive silvicultural inputs such a heavier fertilisation, optimising stocking and competition control and understanding the responses to these inputs has resulted in the potential to substantially improve plantation productivity.
The improved silvicultural systems have been underpinned by the further development and calibration of both the empirical fertiliser response prediction tool ProFert and the process-based yield prediction APSIM model.
FWPA invests in effective and relevant research and development to help drive outcomes for its members and the wider forest and wood products industry.
