Towards Commercialising Cypress as a High-Value Plantation Forest Species

Report Date: March 2017

Author: Dean Satchell, Sustainable Forest Solutions, R.D. 1 Kerikeri, Northland 0294
+64 21 2357554

dsatch@gmail.com

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Conclusions

The FRI historical clonal cypress trials

Lessons learned

Very few if any of the clones evaluated from these historical trials are suitable for deployment as the "silver bullet" for growers. The clones evaluated in these historical trials were mostly selected on early growth and form (P. Milne, pers. com) and some were selected from single trees based on their performance on one site. These strategies have provided insight into selection processes, the conclusion being that early selection is not recommended, although selections could still be made from single trees provided the propagules were thoroughly tested (and for some time) on a range of sites before being considered for deployment. The BHYB clones showed promise in these trials by growing into very good trees across a range of sites (i.e. showing resilience), whereas other clones such as PS1 performed well in some sites but not others (not resilient).

Importantly, what these trials do offer are lessons for applying to future selection and trial work and questions that could form the hypotheses for future research. Mediocre clones offer insight as relative performance across a range of challenging sites. The hostile sites prove more challenging for mediocre clones than good clones and so the data reveals those variables that are challenging for cypress.

Regional variation

In this study clones have been found to respond differently to site climatic and soil conditions. Understanding how each clone responds across a full spectrum of sites is not possible because the original experimental design was not intended for this. Most of the clones are not available in all the sites, a shortcoming not anticipated when initiating this research project. There is, however, some insight into relative performance of clones across a range of sites available in the data collected in this study. 

Generalisations include:

• Rainfall is good for growth, but if excessive becomes detrimental.
• Warmth is good for growth but carries with it the risk of disease.
• Cool, high elevation conditions can induce good growth rates, provided soil fertility is sufficient.
• Sufficient soil fertility is defined differently for different clones. 

Immediate Deployment

Growers do not currently have confidence that available cypress seedlines and clones are sufficiently well improved for a profitable outcome. Confidence in the industry is at an all time low, yet confidence is an essential precurser to developing an industry. Deployment of improved clonal cypress offers the greatest potential for regenerating confidence in the industry, primarily because genetic gains are high and rapidly achieved. 

In the longer term, breeding programmes could offer improved seedlines with larger gains than current clonal selections and these breeding programmes should be continued. However, in the current industry setting, identifying superior clonal selections and deploying these is the clear priority for industry. Cost of clonal production has reduced significantly in recent years (P. Milne pers. comm.) and deploying these to growers willing to demonstrate their productivity would provide a showcase for future investors.

Issues that growers need to consider include:

• Clonal (cutting grown) cypress is generally more costly to produce than seedling stock;
• Clonal forestry may hold a higher biological risk than growing seedlings because of the narrower genetic base;
• Clonal forestry offers consistently good growth, form and wood properties if propagules are well selected;
• Clones can be selected for local and regional conditions;
• Once seedlines are sufficiently improved these could offer faster initial growth and therefore shorter rotations or greater volume within the same rotation than clonal forests;
• Thorough evaluation is required before deployment of improved clonal stock selected from young trees.

In weighing these issues up it is the author's opinion that clonal forestry has the greatest potential for producing an economic return to growers in the short and medium term, while also renewing grower confidence in the species. Currently available clones, although rated in some cases as satisfactory and suitable for deployment (e.g. Ovensii), could undoubtedly be improved on with new selections propagated from mature elite trees. These would need to be tested for rejuvination and cutting strikeability, followed by mass deployment only after a period of assessing establishment issues. 

A number of undesireable log and wood properties that reduce log value and grade recoveries have not yet been selected against in cypress breeding programmes. Propensity for fluting, ingrown bark, pale colour, low wood density and low heartwood content all contribute to reduced value to the grower. However, with clonal selection the time period from selection to deployment could be dramatically reduced by testing and screening mature trees before selecting candidates for mass propagation. Because clonal selections can be made from mature trees, once a selection is proven to be easy to propagate, this opportunity, should be pursued by industry.

Elite cutting-grown trees should be made available to growers as soon as possible as an alternative to the unproven seedling stock and less than adequate leyland clones currently available in the market. Economic evaluations of productivity and grade recoveries could accompany the availability of improved clones to provide a rationale for industry buy in. 

Correct Siting

Different cypress species, hybrids and clones offer a range of specific resiliences that could be tailored to site and used to advantage in breeding programmes. Some cypress clones and species are not plastic in their siting requirements and require specific conditions to thrive. Each species and clone has strengths and weaknesses including suitability or unsuitability to cold, warmth, rain, wind, snow and soil nutrient status. Observations and results from this historical FRI trial series offer some insight into these but further studies would be prudent to confirm such insights. In particular, inter-species hybrids could be bred and selected for adaptability to certain sites or regions, using the parents' strengths to advantage. However this strategy would need to be verified with regional trials of each new hybrid selection. Scion have hybrid clonal material about to be deployed to nationwide trials, which offers growers hope, provided these are planted and trialed in locations representing future deployment opportunities, such as the South Island high country.

Economic Value Study

An economic case for growing cypress is required for industry to have confidence in producing commercial returns from cypress. Selecting the regime with greatest potential to produce good returns from improved tree stock would require work into potential returns for a range of rotation lengths and stockings. Quantifying log yields, product values and grade recoveries would make this possible. Estimating future product values might need to take into account forecasted future availability of appearance timbers and current directions being taken in wood processing. Because cypress is slower growing than radiata pine and Douglas fir in New Zealand, if cypress timber is not likely to achieve a future price premium over radiata pine then growers should not expect to achieve greater (or even equivalent) returns. Key qualities influencing profitability might include wood properties such as colour, hardness, heartwood content and even stiffness and density for the appearance structural market.

Growing an industry

Research continues at Scion into producing improved germplasm for deployment, because historically industry have perceived cypress to have commercial potential as a plantation forest crop. However, interest in planting the species has waned, especially in the last decade, primarily because of health issues with the current crop and fear of a poor commercial return from the species. This report identifies pathways to commercialising the species, and in particular the need for deploying high quality clones in order to give industry some confidence in the species and to begin planting trees again, which would then justify an ongoing breeding and research programme. Selection criteria identified in this study in addition to selecting for growth, form and disease resistence, includes resistence to toppling, resilience to low soil nutrient status, wind and cold resistence, resilience across a wide range of climatic influences, desireable wood properties, and long term resistence to crown breakages.