Tricking Mother Nature

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Status: Finished  |  Genre: Memoir  |  House: Footsteps, yarns and little fibs

Growing trees for the production of timber,

Tricking Mother Nature

The bread and butter tree species grown by the plantation forestry industry in New Zealand is Pinus radiata. In the recesses of history it used to be called Pinus insignus and over the years the species has had a few common names, among them Monterey Pine. Monterey Pine in its natural habitat, is a coastal tree of California and its form (shape), doesn’t make it a suitable tree to mill on a commercial scale. However some farsighted and clever individual convinced our government to establish forests of the species to supplement our dwindling indigenous timber resource.

The tree grew much straighter and taller than it did in coastal California, and the New Zealand foresters became visionaries much like their forebears, they had the vison to investigate the possibility of genetically manipulating the species through selective breeding. It had already been done with horses, dogs, cattle, sheep, pigs, wheat, barley… you name it. There was a wide variability in tree quality, amongst the progeny of the Californian seed and foresters began to pick out certain traits. Vigour was one of the qualities they decided was most valuable. There’s an accounting method called compound interest which is applied to the cost of producing a forest crop for harvesting, and it was quickly realised that the earlier the crop can be harvested, the better the bottom-line profit for the crop. There are other advantages of vigour, not least being the tree’s ability to grow clear of weed competition faster so further crop maintenance wasn’t required. Those early costs have compound interest applied to them for the rest of the crop’s life.

So we looked for the largest trees in our stands of Radiata, and every now and then we found wolf trees. These trees have vigour to burn, but they also have huge, ugly branches, and it’s branches that cause knots and other defects in timber; the trunk grows around a branch, so when a log is cut longitudinally, the branch will appear as a knot in the timber. Small knots don’t affect the strength of timber but big ones do, but as for aesthetics, it’s in the eye of the beholder if knots are beautiful or not. Wolf trees are usually covered with stem cones, another defect in timber. Not that the stem (trunk) occludes the cone, although I have seen it do so. As the stem fattens, it pushes the cone out together with the bark, when the trunk pushes the cone, the cone stem attached to it, breaks at the pith, but stays attached to the cone, so it leaves a neat, round hole in the timber as it’s pushed out. Although it isn’t a strength defect, when selecting trees for seed, stem cones were a negative factor. So wolf trees were avoided as parents and we didn’t want their pollen either.

With vigour sorted, branching was considered. The smaller the diameter of the branches, the better the timber, if a knot is over one third of the cross-section of a board, it was prone to breakage so we chose trees with branches no bigger than an inch in diameter. Steep-angled branches were no good, because bark becomes caught in the occlusion and as the timber ages the bark rots, causing the knot to fall out leaving a gaping hole. So trees with small, horizontal branches were selected. Depending on the end use of the timber, different labour intensive silvicultural techniques are used on the crop. Which is a pig and a poke really, because you’re planning for the use of a log thirty years in advance! Silviculture, is the pruning of branches, and thinning aimed at keeping the branches green (alive), becoming tight knots (with no bark around them), and thinning to foster growth, which can also cause branches to grow fatter, so careful management is required. And at all times, you have to remember the bottom line.

Gradually we found elite trees, which we marked with three white bands painted around the trunk to identify them and their progeny was recognised as a clone. Progeny from the clones we planted into seed orchards. We climbed the trees to harvest the cones, and of course, the older the tree, the taller it became, and yes, I’ve had my share of falls! A better method was devised. Rootstock was planted and a scion (a small growing tip) from an elite tree was grafted onto it. These trees produced mature cones at an early age and the trees were kept shorter. Female flowers on most dicotyledon plants require pollen from a male flower to fertilize them and because conifers are wind pollinated the seed orchard trees could only be guaranteed to be 50% elite, so it didn’t take long until somebody figured out that if cattle could be artificially inseminated, why not trees? Pollen was collected from elite trees and introduced to the seed orchard trees’ female flowers, which was a pretty easy technique.

There was another factor to consider as it turned out… long internodes. Mostly the branches on Radiata Pine grow in whorls, and hopefully one whorl per annum. A node is where the branches spring from. So as the climate spring progresses, the terminal bud sends up a straight shoot which extends to a metre or more. Come autumn, growth slows and the terminal bud sets with the buds of the next seasons’ branches (whorl). The year’s growth, which is between nodes is called the internode, and the timber within the internode is free of knots and other timber defects. A board would have groups of knots (the whorl), a metre of so of clear wood and then another group of knots. In a factory, the knots are cut out, and the clear pieces are finger jointed together, ending with defect-free pieces of timber that can be as long the customer needs.

Gradually different clones were produced by careful cross-pollination and trees with measured growth factors could be guaranteed. So… if you collect seed from any old Radiata tree, it’s called bulk seed and it will have a growth factor of one. The cloned trees may have any number from 17 to 26 attached to them, which means on the same site as the bulk seed tree was planted, the cloned tree will produce 17 to 26 percent more wood volume. An obvious financial win.

While the seed of the cloned trees was expensive to produce, it was also in short supply and couldn’t meet the demand. So we nurserymen became creative. After the NZFS was disbanded, I took on the role of nurseryman and we bought our first batch of GF19 seed. Sure, we could’ve simply handed the seed price onto the forest grower by selling seedlings, but if we used the seed to establish stools (trees to take yearly cuttings from), we could gradually build up enough cuttings to supply the demand with cutting-grown plants. In our climate getting Radiata cuttings to put out satisfactory roots was no walk in the park but we gradually made progress. It meant that trees had to be grown in cells (small containers), which increased handling and transport costs, and the planters had a heavier load to carry, but the system worked.

It may be said, we tricked Mother Nature into allowing us to produce better and bigger timber trees, but now we’re selling a lot of the logs for export. What those countries do with the wood is their business, but I suspect like us they’re laminating and finger jointing to make small pieces of timber into large pieces that are stable and free from defect. We’re also making ply and particle board, all of which are easier to work with, and so, only a small percentage of the trees need to produce clear timber.

The important thing to remember about plantation forestry is, while being a monoculture for which there has been widespread criticism, plantation forestry is a resource that is renewable and there aren’t many resources on the planet that can be… Anyway, the one truth is that there will always be change, but you know… I’ve witnessed a few changes and found them to be quite fascinating.

 

 

 

 


Submitted: December 06, 2020

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Comments

Serge Wlodarski

Good article. I get to do some amateur lumberjacking, whenever wind knocks down one of the eastern white pines in my yard. They are huge.

Sun, December 6th, 2020 12:46pm

Author
Reply

I didn't think too many would be interested Serge. I've always like P. strobus, but they are only planted here as a member in an arboretum. Watch that chainsaw, they bite! Usianguke

Sun, December 6th, 2020 12:08pm

ratwood2

Very interesting article. Thanks for taking the time to do the research.

Sun, December 6th, 2020 4:00pm

Author
Reply

I'm pleased you found it interesting Mr 'wood. Actually no resarch required, I know about this like the back of my hand. Usianguke

Sun, December 6th, 2020 12:02pm

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