Boron and its effect on Tree Quality.
Some Canterbury forests have been treated with Boron for over 20 years, and as a result, these trees have shown some remarkable improvements, as compared with untreated trees.
Over the last 20 years, there has been a definite change in tree profile, health, and stability within the plantation, when trees have been treated with boron. Our first indication of how Boron effects tree growth, and formation, started in the Nursery.
Any nurseryman will tell you, that for them to control apical growth in their tree stocks, they undercut (cut the taproots), and for them to bulk up the root system, they can top the seedlings.
This told us, that tree shoots are "mirror" image of the root system. Initially we applied Boron to our plantation for only one reason, and that was to stop the die-back of the terminal leaders. The question was eventually asked, " if terminal growth is increased when Boron is applied, will root growth also be stimulated?" Well the answer was yes. Not only had tree topple been significantly reduced, but tree nutrient levels are improved. Obviously if a trees root system is increased, this tree has the ability to not only scavenge water better than before, but also increase its ability to obtain nutrients.
As a result we have found that nutrient levels appear to become more in balance by just adding boron. This seems logical if boron increases root growth as well as shoot growth. This increase in root growth will allow the trees to scavenge moisture and nutrients more effectively from the site.
In August 1992, when we experienced an unusually high snow fall, we had found significant compartments of trees severely effected by snow damage. This took the form in some cases, of trees being bent over to touch the ground. That may not seem strange, but the trees I'm talking about had, DBH (diameter at breast height) greater than 32 centimeters.
Samples were taken from these trees, and sent for analysis. Results showed that tracheid lengths, (fibre lengths), on average decreased by 38 %, while cell wall thickness was up to 51% thinner, in trees not treated with boron. This has lead me to the conclusion that board stiffness, and strength, will be significantly improved from trees treated with boron.
Timber sawn from boron deficient trees, has a tendency to warp during seasoning, regardless where the timber was taken from the tree. In some severe cases, outer wood warped just as much as core wood in radiata pine. This inferior wood quality, in my opinion, is indirectly responsible for the resin pockets we get in our Canterbury timber.
In the NZ forest service days, prior to 1987, I had the good fortune to work with many experienced scientists. One of the most intriguing experiences was their study of the cause of resin pockets. Some argue, that resin pockets are caused by the wind, others suggest its the drought conditions in Canterbury. It is my opinion, that both of these factors are responsible for resin pockets, in radiata pine, grown in Canterbury with one added factor, namely, boron deficiency.
As we all know, drought induces boron deficiency, and as previously stated, boron deficiency produces weak, walled fibres. This, combined with strong, continually blowing north west winds, rupture a weak point in the trees cell structure, and resin then floods into this cavity, thus forming resin pockets. Therefore, if you were planning to grow a clearwood regime, it is essential that boron is applied at a young age. Why prune, if your going to have resin pocket blemishes anyway.