In the grand scheme of things, this is a small set of quibbles, but some of what was conveyed in the recent Summer Wrap-Up lecture was, at best, misleading. I’m not an expert but have been in contact with a horticulture expert and have read enough to know that:
The narrative of vascular growth being correlated with autumn is overstated. Vascular growth happens all during the growing season (which, granted, is acknowledged in the stream). But it is not even necessarily dominant in the fall in terms of, for example, added girth.
The blanket statement that dark (fall) rings tend to be thicker than light (spring+summer) growth rings seems to be a gross mischaracterization. See attached photos grabbed from the web. My conclusion from quick googling is that it’s closer to 50-50 or perhaps slightly more girth added in lighter wood (spring+summer growth). Some examples show, in the same tree, certain time periods (or certain areas around the rings themselves) where light growth is thicker and others dark rings are thicker. Sometimes even within the same year but on one side of the tree vs the other.
Wood from dark rings is denser and there may in fact be more vascular cells per unit time produced in the fall compared to earlier. I cannot find definitive information on this.
All metabolic activity during the growing season is important and there for a reason. Various things, all important and timely, happen in the vascular system all season long. What happens in fall is different and no less or more “important” than at other times in the season.
It is more accurate to state that most temperate trees slow down foliar growth in the fall, but that does not translate into minimizing vascular growth in the spring.
I’m really puzzled about why this particular narrative is useful to Mirai. It doesn’t really hold up to scrutiny. It’s like saying that development of liver cells is more important than development of lung cells: no, they both happen for an evolutionary and biological reason.