Background to Plantation Establishment in Victoria

As noted by Turner et al. (2004), the lack of a native softwood species in Victoria led to the establishment of small test plantations of softwood species potentially suited for timber production under Victorian soil and climatic conditions. This work commenced as early as 1880. It involved testing of a range of ‘best-bet’ conifer species based on expectations of their performance and productivity in other states like NSW, SA and WA as well as in New Zealand and also in their native habitat in the USA and southern Europe. It was soon discovered that Pinus radiata (Radiata Pine) was most suited to the environmental conditions commonly encountered in southern Australia and this became the dominant species for the rapid expansion of a softwood plantation resource in Victoria and other southern states.

Plantation development in Australia expanded in the early 1960’s when the Australian Forestry Council sought Commonwealth funds to support State and Territory funding for a Plantation Extension (PX) program to make Australia self-sufficient in softwood timber in the shortest possible time frame. The PX initiative presented a broad range of research challenges to ensure plantations did not fail but instead were highly productive consistent with the limitations of the range of site types encountered across the country. Soils and nutrition R&D played a major role in the ultimate success of this ambitious PX program.

Initial plantations were established almost exclusively on land that had been cleared of native forest for intensive gold mining activity. Many of these denuded sites failed to adequately regenerate naturally on the highly eroded soils in areas around Ballarat, Creswick, Beechworth and Castlemaine. Likewise areas of remnant native forest and scrub were often encountered on land harvested of highly productive Eucalyptus regnans (Mountain Ash) forest to meet the continuing post-war demand for hardwood timber. Many of these denuded areas were then converted to agriculture. In many instances these agricultural pursuits failed and the land was abandoned and reverted back to scrub, particularly in the Otway Ranges and the Strzelecki Ranges. Some of these abandoned farms were reforested with Mountain Ash whilst others were converted to Radiata Pine plantations. The Forests Commission Victoria (FCV) had set ambitious targets for plantation expansion under the PX program, and large areas of native forests on crown land in many parts of the state including north-eastern Victoria, south Gippsland and south-western Victoria were converted to Radiata Pine.

Extensive site appreciation surveys were conducted by skilled and experienced foresters from the Commission to identify areas (mainly in coastal and foothill forests) in targeted regions likely to be suitable for conversion to softwood plantations. The focus of the surveys was on soils (fertility as judged by indicator species, propensity for erosion when cleared), vegetation (forest type), topography and rainfall (total and seasonal distribution). The surveys were constrained by soil classification maps for the native forest estate. Following the surveys, native forests on the foothills around Benalla, Myrtleford, Bright and Shelley in north-eastern Victoria and elsewhere as guided by the surveys were converted to pine plantations. As the PX program progressed, there was increasing public concern however about the loss of native forest ecosystems, especially those with high biodiversity values, to a monoculture of introduced Radiata Pine. Conversion of native forests to pine plantations began to be phased out in the late 1970’s, and the practice was immediately halted following the release of the 1986 Victorian Timber Industry Strategy. Future plantation establishment was confined to cleared land. Cleared farmland judged suitable for Radiata Pine plantations was progressively purchased by Government. The selection of suitable land and the establishment of plantations on such land led to a number of research challenges. In 1988 the Flora and Fauna Guarantee Act was introduced to conserve the biodiversity of native forest ecosystems, reinforcing the directions of the Timber Industry Strategy in relation to plantation development.

Early Stages of Softwood Plantation R&D

The land available for plantations (mainly coastal and foothill forests) was generally on the poorer soils considered to be unsuitable for agriculture. Growth of Radiata Pine on cleared native forest land was often poor, especially on soils disturbed by gold mining in the past, and plantation failure was not uncommon. The FCV had established a Research and Education Branch in the 1950s as a multidisciplinary group of forestry scientists with an initial focus on investigating problems related to the silvicultural management of native forests, particularly regeneration processes following clear felling. The organisation recognised the importance of R&D in support of forest management and the same approach was taken as part of the plantation expansion (PX) program that commenced in 1961. The initial focus of this research was on tree improvement, nursery practices to produce quality planting stock, site preparation, planting techniques, pests and diseases, and disorders associated with tree nutrition. Research staff were called upon to solve problems related to plant propagation at the various nurseries (e.g. Flinn et al. 1980) and the establishment, growth and management (including pruning regimes) of Radiata Pine plantations.

Survival and early growth of Radiata Pine on the wide range of forest soils encountered was highly variable resulting in a gradient in site productivity and merchantable yields within and between compartments. Failure was often associated with poor soil conditions (compaction, poor drainage, low organic matter) indicating the need for soil cultivation to prepare sites for planting. However early growth was often poor even on the better structured soils indicating that other issues related to soil fertility were most likely limiting tree growth. The rather mixed success of Radiata Pine plantations was not unique to Victoria; similar problems of poor establishment and growth on forest soils were encountered in regions selected for the establishment of softwood plantations in New South Wales, Tasmania, South Australia and Western Australia. It became quite obvious to the Australian Forestry Council that there was a lot to be gained from collaboration between the various State forestry organisations, the CSIRO (Division of Forestry and Forest Products) as well as the forestry schools at the University of Melbourne and the Australian National University.

Research Working Groups covering a range of disciplines, including a Soils & Tree Nutrition Group, were established by the Australian Forestry Council to provide a forum for forestry scientists of the various state organisations, CSIRO and universities to meet, share experiences, and collaborate in finding solutions for problems related to soils and tree nutrition. This Working Group system proved to be highly successful, not only for collaborating scientists but also for timely feedback to the Council on matters of national or regional importance.

Some of the early investigations in NSW and ACT plantations identified low availability of phosphate in native forest soils as one of the likely reasons for poor growth of Radiata Pine. This did not come as a surprise as the paucity of plant available phosphate in the highly weathered soils of Australia was known to be a major limitation for agricultural crops and pastures.

Soils and Tree Nutrition R&D for Plantation Establishment

The first experimental fertiliser trial of the Forests Commission was established in 1950 at Anglesea on a site where the original 1920’s plantation of Radiata Pine had failed. The trial was designed to compare the growth of P. radiata, P. pinaster (Maritime Pine) and P. caribaea (Carribbean Pine) in response to soil cultivation and phosphate fertiliser and was implemented by Max Raupach and colleagues of CSIRO (Division of Soils) and Brian Gibson (FCV, Research Branch). Soil cultivation increased height growth of Radiata Pine by 20% to age 5 years and there was a strong growth response to phosphate fertiliser (superphosphate at 1 t/ha) increasing volume at age 17 from 30 m3/ha to 215 m3/ha (Raupach et al. 1975). This study also showed that volume growth of Radiata Pine was well correlated with levels of phosphorus in foliage indicating the potential of foliage analysis as a diagnostic tool for identifying phosphorus deficiency in pine plantations. Responses of Maritime Pine and Carribbean Pine to cultivation and phosphate fertiliser were more variable and smaller compared with Radiata Pine.

The trial at Anglesea served as an experimental model for further field trials established in the early 1960’s in poorly growing plantations on former mining sites at Scarsdale and Happy Valley to determine growth responses to phosphate fertilisers (Flinn et al. 1979a).

These early trials showed that poor growth of Radiata Pine due to low soil fertility could be diagnosed by foliage analysis and soil testing to identify specific nutrients limiting tree growth. Research in Australia and New Zealand progressively identified levels of key nutrients associated with either satisfactory growth or retarded growth due to one or more nutrient deficiencies. Foliage diagnostic features were also developed to support foliar analysis results. The head of the Research Branch (Ron Grose then followed by John Jack and Fred Craig) recognised the importance of developing such diagnostic tools to determine the nutrient status of pine plantations in need of remedial treatment with fertilisers to improve their productivity. The Research Branch, located in offices at LaTrobe St at the time, commenced work instigated by Fred Craig on the development of analytical procedures for chemical analysis of soils and pine foliage using shared laboratory facilities at the old School of Forestry on Tin Alley at the University of Melbourne. In the meantime new offices and research facilities were built at 1 MacArthur Place (next to the FCV head office at Treasury Place) and the laboratory was equipped with state-of-the-art instruments for physical and chemical analysis of soils, plant tissue and water. This increased the capacity for sample analysis and enabled the development of sampling protocols for the annual monitoring of tree nutrition in research trials and diagnostic testing of pine plantations with suspected nutrient deficiencies based on visual symptoms in the various forest districts in Victoria.

It is noteworthy that in preparation for a possible new plantation estate in Victoria, the FCV established an extensive series of test plots scattered across a wide range of coastal and lowland native forest sites including east Gippsland, south-western Victoria and north-eastern Victoria. These test plots proved exceedingly valuable as foliar samples could be collected and analysed to give advanced notice of possible nutrient deficiencies in each region and soil type.

The research of forest soils and tree nutrition expanded under David Flinn with the installation of a number of trials testing the effects of soil cultivation, weed control and fertiliser on survival and early growth of Radiata Pine on low productivity sites at a number of locations including Scarsdale, Narbethong, Neerim East, Heywood and Rennick.

This work showed strong and often synergistic growth responses to the combination of soil cultivation, chemical weed control and fertiliser and often showed the requirement for follow-up treatment with mostly phosphate fertiliser after 3 to 4 years to maintain the supply of phosphorus to thinning age.

The gains in volume production in response to phosphorus fertiliser applied at planting and age 4 were substantial increasing productivity of Radiata Pine up to five-fold on forest soils low in plant-available phosphate in trials at Narbethong and Neerim East (see graph).

This provided a benchmark for the productive capacity of plantations on similar soil types and was subsequently extended to include other soil types following the change in ownership to Hancock Victorian Plantations Pty Limited (HVP) in 1998. Results for these phosphate fertiliser trials in 1st and 2nd rotation plantations formed the basis for the phosphate response model currently used for the nutrient management of plantations in Victoria.

Nursery Soils and Seedling Nutrition

Production of healthy bare-rooted seedlings free of any nutrient deficiencies and disease is fundamental to the successful establishment of new plantations. To this end, routine surveys of the nutrient status of seedlings and of soil properties commenced in 1971 for the Benalla, Koetong and Rennick nurseries in (Craig 1971) and later for the Trentham nursery. This intensive monitoring continued on a regular basis from 1972 to 1981. Results for all of these individual surveys were reported in the Forest Research series.

A detailed analysis of the surveys conducted between 1971 and 1975 was undertaken in 1980 for the Benalla, Trentham and Rennick nurseries (Flinn et al. 1980). These three nurseries have contrasting soils and climates. Samples of seedling tops from these crops were analysed for essential plant nutrients including N, P, K, Ca, Mg, sulphate S, Al, Fe, Mn, Zn, Cu and B. Soils were analysed for pH, C, N, and water-stable aggregates as an indicator of soil structure. The results of the analysis underlined the importance of applying a balanced fertiliser regime. Such a regime should take account of both the unique chemical properties of each nursery soil and the nutrient requirements of the seedlings. Careful soil management is critical in preventing deterioration in soil structure, which was a particular problem in the Benalla nursery.

Derivation of fertilizer regimes for Radiata Pine nurseries with highly contrasting soils ranging from deep sands to shallow flood plain soils with a high silt content and a heavy clay subsoil to a basalt derived soil with high phosphate retention is a challenging task. Hopmans and Flinn (1983) found that multi-element fertiliser applications including pre-sowing additions were in some instances resulting in salinity problems at Benalla, and that fertilizer uptake was low at all three nurseries. They developed modified regimes which not only took account of soil nutrient status prior to sowing but also estimated nutrient requirements of the seedlings based on fertiliser efficiency and nutrient uptake by seedlings. The regimes involved a range of pre-sowing and post-sowing fertilisers at varying rates according to the individual soil properties at each nursery. This regime, which was a major departure from earlier fertiliser programs, was expected to increase fertiliser efficiency. They also recommended a greater emphasis on green cropping to maintain soil structure.

As noted by Flinn et al. (1980), soil structure in the 40-ha Benalla nursery established in 1967 was deteriorating, manifested by pronounced slaking and poor infiltration, so much so that it was standard practice for drill holes to be covered with sand to ensure satisfactory emergence of Radiata Pine germinates. The soil also lacked aggregation due to a low clay content in the surface horizon. Flinn and Waugh (1983) undertook a study to determine whether soil conditions and hence seedling performance could be improved by adding organic matter and gypsum/dolomite. The immediate aim was to reduce slaking and increase infiltration of irrigation water and aggregation. A randomised block design was used to inter alia evaluate the addition of 170 t/ha of sunflower hulls. The treatment was found to reduce bulk density and surface crusting and markedly increase infiltration capacity. Flinn and Waugh (1983) concluded that soil conditions can be improved for seedling growth by adding large quantities of organic matter, reducing cultivation and maintaining an intensive green cropping regime.

Second Rotation Decline

In the late 1960s studies in South Australia showed a significant decline in the productivity of second rotation (2R) plantations established mainly on coastal sands. This called into question the long-term sustainability of Radiata Pine plantations on soils of low fertility and the silvicultural regime of burning harvesting residues and intensive soil cultivation to prepare sites for planting the second rotation. Plantations were being established under the FCV’s PX program on similar soils in south-western Victoria and there was concern about the long-term viability of the Radiata Pine resource beyond the first rotation (1R). A research project was established by Fred Craig, David Flinn and Ross Squire (who co-ordinated the study) to determine any 2R decline and investigate an alternative silvicultural regime for coastal sands. Growth of 1R and 2R Radiata Pine was compared on the same sites and on matched sites comparing the original cultural practices (burning and soil cultivation) with an alternative regime of retention of harvesting residues and pit planting aimed at conserving organic matter and nutrients (Squire et al. 1979). This showed better growth of 2R pine with retention of harvesting residues due mainly to higher uptake of nitrogen and lower water stress. It was also shown that burning of harvesting residues resulted in significant losses of organic matter and nutrients, especially nitrogen, from the plantation ecosystem (Flinn et al. 1979b). In due course this work led to the adoption of retention of harvesting residues as standard operational practice for successive rotations of Radiata Pine. The original 2R trials continued to final harvest at age 30 years and showed increased productivity over two rotations (MAI: 21 to 27 m3/ha/yr) largely attributed to the retention of litter and harvesting residues (Hopmans and Elms 2009)

A common assertion by a number of stakeholders has consistently been that pines “ruin” soils and cause soil acidity. This issue has been intensively studied in southern Australia (see Turner et al. 2004). Hopmans et al. 1979 undertook a detailed investigation of chemical properties of sandy soils under pine and native eucalypt forest in south-western Victoria. They found no evidence of pines being associated with soil acidity. Although soils under both ecosystems were very low in organic matter, nitrogen, total phosphorus and exchangeable cations except for calcium (as would be expected on such sandy soils derived from limestone). Soils under pine were found to be higher in some nutrients, although there was some evidence of a decline in phosphorus, calcium and magnesium from the surface horizon. They concluded that there was only a slight overall effect of pine on the nutrient status of the coastal sands after one rotation.

Boron Deficiency of Radiata Pine

Young plantations established on cleared native forest sites in north-eastern Victoria as part of the FCV’s PX program showed a high incidence of ‘die-back’ in the early 1970s, especially during drought years. The symptoms were consistent with boron deficiency observed in other pine species and foliage analysis of Radiata Pine with ‘die-back’ in cleared bays and healthy trees in heaped windrows confirmed that the symptoms were associated with boron deficiency. Subsequent trials in 2-year-old pine showed that trees treated with a broadcast application of borax recovered and remained free of ‘die-back’ to canopy closure when within stand recycling of nutrients commences and the net demand on soil boron decreases (Hopmans and Clerehan 1991). Early treatment with boron fertiliser was adopted as standard practice for the silvicultural management of Radiata Pine in north-eastern Victoria.

Stem Deformity in Plantations on Farmland

From the late 1970s onwards farm properties, mostly grazed pastures in close proximity of existing plantations and processing facilities, were purchased to establish pine plantations using the same practices as developed for cleared forest land. Plantations on improved pastures were fast-growing providing effective weed control and appropriate site preparation practices were followed, but of very poor form with trees showing lack of apical dominance, numerous thick branches and twisted stems. The visual symptoms resembled copper deficiency; however treatment with copper did not alleviate these symptoms. Furthermore there was strong genotypic variation in the expression of stem deformity as shown in a Radiata Pine progeny trial on improved pasture (Pederick et al. 1984). A joint investigation of possible causes of stem deformity of pine on pastures with the University of Melbourne showed significant differences in soil fertility and in particular availability of soil nitrogen compared with native forest sites; however there was little difference in nutritional physiology of straight and deformed trees (Turvey et al. 1993). Subsequent trials showed that stem deformity could be induced in straight trees on a former native forest site by nitrogen fertiliser applied at high rates (Hopmans et al. 1995). New progeny trials on pastures confirmed consistent genotypic variation in the expression of stem deformity (Bail and Pederick 1989). This enabled the selection of a ‘High-Fertility’ breed of Radiata Pine for cutting propagation to raise planting stock for pasture sites and therefore provided a practical solution to the problem; however the actual physiological cause of stem deformity remains unknown.

Privatisation of Radiata Pine Plantations

In 1993 the Government established the Victorian Plantations Corporation (VPC), a state-owned enterprise responsible for the management of plantations on a commercial basis in preparation for the privatisation of the plantation resource. In 1998 the state-owned Radiata Pine plantations (including the IP) were sold to Hancock Natural Resources of Boston, USA and the new company (Hancock Victorian Plantations, HVP) engaged CFTT (and later FSC) as the R&D provider based on annual Service Agreements. Plantation R&D became more closely aligned with HVP’s management objectives for the softwood resource with emphasis on the impact of R&D on stand productivity, merchantable yields and financial returns. The primary aim was to optimise the productivity of existing plantations through improved genetics and silvicultural management including site preparation, weed control and fertilisers as well as the management of pests and diseases. Soils and nutrition R&D was a major focus for HVP.

Optimising Plantation Productivity

Past soils and tree nutrition R&D was largely focused on the diagnosis and remedial treatment of nutrient deficiencies at an early age to improve growth to first thinning. Thinning changes the stand dynamics, it reduces inter-tree competition for nutrients and water and opens up the canopy for crown expansion of the retained trees. Earlier studies in Victoria, New South Wales and South Australia showed that application of nitrogen immediately after thinning stimulates the production of foliage biomass and promotes stem growth provided the availability of water and other nutrients are not limiting. This provides an opportunity to enhance the growth and productivity of older plantations and further R&D on this topic was given high priority. A number of trials were established across the HVP estate to determine growth response to fertilisers applied after first and second thinnings (T1 and T2). This showed that post-thinning responses to nitrogen fertiliser were well correlated with the pre-treatment nutrient status. Therefore levels of nitrogen in foliage were a good indicator of the responsiveness of stands and could be used for the selection of thinned stands for treatment. This work also showed that responses on some sites were adversely affected by deficiencies of other nutrients such as sulphur and copper. Furthermore growth and responses to fertiliser were also affected by foliage losses caused by infestations of the Monterey pine aphid (Hopmans and Elms 2013). Infestations of this pine aphid are now common in plantations in south-eastern Australia and therefore stand selection for post-thinning promotion of growth with fertiliser should take into account the nutrient status as well as crown health of trees in order to optimise responses.

The research on soils and tree nutrition started by FCV in the 1960s and continued during the 1980s marked a decade of institutional changes before ownership of the plantations was transferred to HVP who built onto the existing knowledge base. This has transformed the nutrient management of plantations using foliage diagnostic testing at an early age and after thinning to determine tree nutrient status and the requirement for fertiliser. Soils and tree nutrition research by FCV and its successors and continued by HVP has made a significant contribution to the recent development of fertiliser response models for Radiata Pine plantations (May et al. 2017) to predict growth responses, merchantable yields and financial returns for the optimisation of wood production.

In more recent times, there has been a trend towards site-specific management in Australia and beyond. Essentially, this involves having good information on soils and local geology so that a regime of site preparation, weed management and fertilisers can be prescribed to optimise productivity on each site type.

Plantation Certification

There has been widespread and consistent criticism by a broad range of stakeholders that pine plantations were inter alia ‘ruining’ soils, reducing long term stream flow, impairing water quality and having significant impacts on fauna. Whilst Radiata Pine growers used the best available science to debate these issues, there were no standards upon which stakeholders and growers could refer to. In the early 2000s, Standards Australia established a Steering Committee and appointed a Technical Reference Committee to guide the development of an Australian Forestry Standard. The Technical Committee had wide representation of all stakeholders covering social, cultural, economic, environmental, industry and other relevant groups. David Flinn was the Independent Forest Scientist on this broad ranging Committee. The Committee worked tirelessly to draft Australian Standard – Forest Management-Economic, social, environmental and cultural requirements for wood production. This became known as The Australian Forestry Standard. The objective of the Standard was to provide forest managers and owners with economic, social, environmental and cultural criteria and requirements that support the sustainable management of forests for wood production. It was the first time in the history of forestry in Australian where all stakeholders had a common base upon which to objectively judge whether plantations and natural forests were being well managed.

To be certified under the Standard, forest management must meet all requirements grouped under nine Criteria. In the development of the Standard, particularly for Criterion 4 relating to maintaining productive capacity of plantations and Criterion 6 relating to protection of soil and water resources, the soils and nutrition R&D undertaken in Victoria played a key role in formulating requirements to be met under these two Criteria and associated Criteria. In particular, the 1R/2R study, the extensive field experiments investigating the interaction between site preparation, weed management and fertilisation provided guidance on the efficient and responsible use of chemicals (including fertilisers) in the environment.

Requirements that must be met to be certified relating to soils and nutrition include:

• Management actions must not compromise the productive capacity of the plantation area.
• Establishment (regeneration) of plantations must be effective and timely.
• Identify and assess the inherent soil and water values that can be adversely affected by plantation operations.
• Maintain the protective and productive functions of the plantations through good management of factors such as erosion, chemical pollutants and contaminants that effect a range of important soil and water properties including soil biology, soil structure and fertility, and water quality and steam flows.
• Minimize any nutrient loss.

The first plantations to be certified in Australia was the HVP estate in 2003. Smartwood undertook the certification assessment. A broad based audit team including David Flinn undertook the assessment. Smartwood developed its own Standard which drew heavily on the Draft Australian Forestry Standard which in turn drew heavily on Victorian Plantation R&D over a lengthy period. During the audit process, many stakeholders were critical of HVP management practices associated with chemical weed control, fertilisation practices, site preparation procedures and impacts of plantation activities on stream flow and water quality. But for the R&D undertaken by FCV on these and related issues, it is doubtful if HVP would have been certified. However, HVP was able to demonstrate that it met most of the Criteria under its nine Principles (AFS used Criteria and Requirements as opposed to Principles and Criteria of Smartwood, but as would be expected they both had similar requirements to be met for certification).

Certification is now widely used to satisfy stakeholder needs and confirm that wood is being sourced from “sustainably“ managed forests. A more appropriate description however is that the certification process demonstrates that certified forests and plantations are being “well managed” and are going down the path of continuous improvement, also known as adaptive management. (Raison et al. 2001)

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