Carrying on the theme of approaches to growing timber: should it be easy and
profitable; or should we bang our heads against a brick wall? Take the present enthusiasm for naturally durable Eucalypt timber in New Zealand: what are the trade-offs in growing such species, as against growing less durable or non-durable species?
There will be some generalisations here – and the the picture will be generally correct: useful enough for the purposes of entrepreneurial decision-making.
The more durable species are slower growing and/or require more resources than the less durable ones; they also have more limited or specific choice in siting. It may be easier to get better grades of sawn timber from a lot of the more durable eucalypts than from many of the non-durable ones.
The faster growing species that give a wider choice in siting, are less resource hungry; are less durable; and tend to have problems such as distortion, checking and other downgrade if processed by sawing. In some circumstances some of these faster species may also be more prone to pest attack.
One recent entusiasm has been to replace low strength CCA treated Pinus radiata pine vineyard posts with stronger and naturally durable eucalypt posts.Having looked at these radiata vineyard posts, I can understand why they are breaking. The closest immediate remedy is to use radiata from older denser stronger trees as quarter round posts. The next closest remedy is to use one of the less toxic preservative treatments instead of CCA, to minimise environmental effects. Suppose we do need to use an even stronger timber, then E nitens might be the best choice` – fast grown young trees totally sapwood easily treated. I’ll repeat this for emphasis: E nitens fast growing totally sapwood easily treated with low toxicity chemicals – could be the more profitable alternative to naturally durable eucalypt timber.
Another enthusiasm has been for fast grown short fat butt logs at wide spacings which more easily produced better timber than that from taller thinner trees. One could grow a whole lot more timber in a shorter time at closer spacing. In the past this has presented problems when sawing solid timber from the ash group of eucalypts and E nitens.with the latter seen as a chip, pulp, or peeler log species. Collapse, washboard surface, checking and distortion can be common with these species – especially when grown at close spacings which tend to give problems in sawing. New processing technology eliminates these problems.
The traditionally more easily processed naturally durable eucalypt species now have competition: new processing technology; new less toxic chemical treatments; along with totally sapwood short rotation eucalypts.