I was with him yesterday. The only trees dead were the ones that had been tapped. In one case a tree had a split trunk. The untapped side was still healthy. Tapped side dead. I'll text him to get a picture as he is there now.
Addendum....Our climate. We live on the north Atlantic islands, but our climate is temperate.
Our birch trees rarely grow thick barks; it's just generally not cold enough. In Northern America, and in Northern Europe, they have a continental climate. It gets very cold, a deep cold that lasts, during Winter. We can have a Winter that never actually freezes. Maybe that's why there is an issue. Our mild weather allows the survival of pathogens and rot, while the deep hard cold not only encourages thicker bark, but kills off a lot of the disease vectors.
Interesting article.
https://pbsociety.org.pl/journals/index.php/asbp/article/viewFile/asbp.2012.036/998
atb,
M
But tapping through to the cambium in one spot does not destroy the entire network of xylem and phloem any more than a broken or sawn branch does. I think Mary may be on to something with wondering why Sugar maples don't die.
I don't for a minute dispute what John and Emma found - but I'm interested in the underlying science
The other thing to note is jd's observations lack a control sample. Photos of trees that weren't tapped. If the Birch forest had any sign of Birch polypore then the chances are they will die off anyway. Not saying he's wrong, just that correlation is not always causation.
What would your definition of a control sample be?
There are at least 300 -350 silver birch that would be considered canopy adults in those woods. Apart from four that were wind blown and one that fell due to a hollow trunk that it had for near on 15 years, then the correlation is pretty concise. For example, If you had 350 rats and you fed them all the same diet apart from 15, then after time all 15 died and the others thrived. The conclusion would be pretty straightforward. And the living trees are perfect controld samples as they haven't been tapped.
Remember I've been away from the woods for quite a while and these trees died in the last 3 years and the results now are rotten trees that have collapsed and are well advanced in terms of rot and death occurred at least two years ago.
I can give you a load of photo's of the other trees. Polypore isn't widespread in these woods, and is found on the stumps of a few of the dead trunks.
The results are so slow (7 years), that a detailed study of this method would be a long way off. But I strongly urge people to drop this method of tapping.
Easy now. All I said was that in the results you presented there was no control sample.
I know (went into factual reporting mode, so my posts are blunt, but don't tale that personally. It's what I'm used too).
But what would you consider a control sample MM? Wouldn't that be the untapped trees?
I'm feeling pretty sucky (not in a Southey way) about these trees. They were healthy and not due for the chop. The only comfort I can take is from the woodpeckers that are using one to nest in.
A statistically significant sample of trees of a similar age and location to the ones tapped.
From what you initially told us we had no way of knowing if all Birch trees over a certain age died. If you wanted to prove causation then you would need a statistically significant sample that died and a control sample that proves the rule.
I'm guessing you picked certain trees to tap, maybe based on age or even accessibility, but I emphasise "guessing". Not saying you're wrong by any means, just that it warrants further investigation.
Birch seems to play the numbers game, germinate well grow fast and form big stands, then die young. It is far more common to find rotting birch. Birch only seems to get to any age in other countries that are drier and have proper winters.