atomic_fungus (atomic_fungus) wrote,

#5849: Trees, WTF

Leaves on some of the trees are already turning.

Running a couple minor errands this morning I noticed that some trees are turning colors, not all over but in patchs. It seems to be confined to maples, though, so I don't know if that's a disease thing or if it's related to the biochemistry of the species.

The fact is, we had a rather cool August. There was one day--perhaps two--where we had swimming weather, and at that neither day was really hot, the way you'd expect of the midwest in August. September has been very cool, as well, and over the past few days nighttime temps have been below 50°.

Going back further, July was cooler than normal; though it started off hot enough the last week of the month was very moderate.

Now, here's how I figure deciduous trees know when to shed leaves: in the spring, when the leaves pop out, daylight is getting longer. Days get longer until the summer solstice, which is when they start to get shorter again. But because the solstice is a dwell point--a place near which the day-to-day change in daylight time is slight--it's at least another month or six weeks before the day-to-day change is significant, and it's not until the autumnal equinox (which is the point of most rapid change) that the tree really notices that the days are getting shorter.

Figure that there's some kind of chemical which begins to form when photosynthesis ceases for the day. Photosynthesis eliminates it, but at about the same rate it forms, so it takes an hour to get rid of an hour's worth of production. After the equinox, the nights (non-photosynthetic time) are longer than the days (photosynthetic time) and the chemical begins building up, because there's not enough daylight to get rid of it. It hits some threshold and the tree decides Winter is coming! and starts the process for shutting down the leaves and shedding them. This process cuts off the supply of sap to the leaves, and they turn colors and fall off.

Now: what if temperatures go too low during summer, or before the whatever-it-is can build up to trigger the shedding? Deciduous trees lose their leaves as a survival mechanism; they tend to break if snow and ice fall on them before the leaves are gone. So I'm wondering if there's another mechanism which says, "Hey, it's getting too cold! Shed the leaves!" even if the sunlight thing hasn't gone off yet. And some species would be more sensitive to it than others.

...a lot of stew to make from one oyster, I know. But as an intellectual exercise, relatively harmless.

* * *

Today's XKCD:

This is how computers treat files. That's what makes it funny.

* * *

Today's task is to finish paint prep in the front hall and then paint it. Hopefully I can get the new light fixtures in, too; that would be nice. We'll see.

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