When in doubt, play chromatic
Joe Pass
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Early selection: how early is early enough? Part 4
In the previous post we were able to screen trees for wood properties at 2 years of age, separating normal and compression wood by leaning the trees. We obtained genetic parameters, breeding values, etc. However, we also discovered that planting the trees directly in the ground was still subject to too much environmental variability. So, take a guess… we planted another trial.
This time we had 90 families and 10 clones, for a total of 3,000 trees growing in 75 litre bags, leaning, with slow-release fertiliser, an irrigation system. Not only that, but we tested 3 different populations: clonal (derived from trees selected at ‘traditional’ 8 years of age for growth and stiffness), seed orchard (derived from trees selected at ‘traditional’ 8 years of age for growth and basic density), and new selections (selected for a combination of traits).
As a start, heritabilities increased substantially (sometimes doubling it), which is not surprising considering that the trees were in bags. One cool thing was that we could observe differences between populations at 2 years of age; so selecting at ‘traditional’ 1/4-1/3 of rotation does actually pick up trees on different wood properties trajectories. This was 1- confirmation of something we hinted some years ago (coming post) and 2- guiding other work I am writing up at the moment.
This “bagged trial” was published Open Access as: Apiolaza LA and Sharma M. 2023. Selection history affects very early expression of wood properties in Pinus radiata. New Forests DOI: 10.1007/s11056-023-09997-3.
Early selection: how early is early enough? Part 3
In my previous post we were able to detect extremes of wood density and stiffness with leaning trees at 8 months of age, vertically splitting the sample to separate normal and compression wood. This was doable, but the size of the wood samples was a tad small to screen large numbers of trees, so we proposed screening parents of a seed orchard with a trial including 49 controlled-pollinated families at ages 2, 3, 4 and 5 (harvesting one quarter of the trees per year).
After 2 years, we processed the first quarter of the trial (492 trees) extracting a 200 mm long stem bolt from the leaning trees (see photo below) and found that:
- Wood properties were under moderate genetic control at 2 years of age, so we felt we could, at least, screen out the worst families.
- There was more environmental variation than desired (particularly soil) and lots of wind, which altered the leaning angle of the trees.
- This variability left us feeling that there was no point on continuing with the experiment in that site (sometimes you win, sometimes you lose) and that we needed to setup an alternative experiment. TO BE CONTINUED. YES, OF COURSE THERE IS ANOTHER EXPERIMENT.
More details in: Apiolaza, L.A., Chauhan, S. and Walker, J.C.F. 2011. Genetic
control of very early compression and opposite wood in Pinus radiata and its implications for selection. Tree Genetics & Genomes 7(3): 563-571. PDF available at https://luis.apiolaza.net/publications/
Early selection: how early is early enough? Part 2
In the previous post I mentioned that we wanted to screen trees for wood properties as early as possible, BUT there is a lot of “noise” with the mix of normal and reaction wood (compression in softwoods or tension in hardwoods). The main problems for running a glasshouse experiment were:
- How to separate normal and reaction wood? Here the good-old-leaning-trees approach was handy.
- Trees move a lot in real life, what’s the effect of thigmomorphogenesis (fancy name for response to movement)? How can we move them? Build a rocking machine: having good technicians help.
- How good are the screening methods? Before embarking in a big experiment, better look first in a few clones with contrasting wood properties (4 Arborgen varieties). If that doesn’t work, pull the plug.
So we got a glasshouse with four clones, some ramets standing, some leaning and some rocking for eight months. Standing trees and rocking trees had random arcs of compression wood, but rocking reduced wood stiffness by 20%, which is similar to what happens to mature trees on the edge of stands. Leaning trees nicely separated normal and compression wood, which now could be analyzed separately; not only that, but they magnified the differences between the clones. TO BE CONTINUED.
Read more details here https://rdcu.be/donFJ
Luis A. Apiolaza, Brian Butterfield, Shakti S. Chauhan & John C. F. Walker. 2011. Characterization of mechanically perturbed young stems: can it be used for wood quality screening? Annals of Forest Science 68: 407–414.
Early selection: how early is early enough? Part 1
Different people write for different reasons. In my case, I write to remember how and why I did research with colleagues; and to share the results, of course. After working for a while in a topic, it is easy to forget how the whole project started, which is why I will write a few notes on early selection for wood properties. This is part 1.
Fifteen years ago, Prof Walker and I were chatting about reducing rotation age for radiata pine, which involved “fixing” corewood quality. Corewood—the first 10 rings or so in a tree—has high microfibril angle that leads to low stiffness and poor dimensional stability. But how early could we assess it?
Trees are large, heterogeneous and crazy expensive to measure. Could we instead measure small trees or, let’s be heroic, seedlings? One problem is that small trees generate random arcs of reaction wood (compression in softwoods, tension in hardwoods), creating a lot of “noise” in the assessments. Can we separate these types of wood to reduce or eliminate the noise? We set up a glasshouse experiment where we wanted to assess wood properties differences at 1 year of age. TO BE CONTINUED
Read more details here https://rdcu.be/donFJ
Luis A. Apiolaza, Brian Butterfield, Shakti S. Chauhan & John C. F. Walker. 2011. Characterization of mechanically perturbed young stems: can it be used for wood quality screening? Annals of Forest Science 68: 407–414.