...like on and off HWY 395 in the eastern Sierra.
Will it come earlier this year because of the drought?:confused:
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...like on and off HWY 395 in the eastern Sierra.
Will it come earlier this year because of the drought?:confused:
Speaking generically, droughts don't tend to change the timing of autumn color. They do cause trees that are stressed to give up for the year and either change color or just drop their leaves prematurely. That is already happening here in NY to some degree. The trees that are not stressed will change color at whatever time they normally would for the year. The net effect being that when true autumn color does happen, there are fewer trees left with foliage to change. Which generally means a less impressive autumn color season.
I imagine the dwarf willows and highest stands of aspen will kick in early. Anything visible from 395 per se usually occurs in Oct. But up in McGee Can or up around Lk Sabrina, Rock Creek etc there should be color soon. I'll know in a few days. But Greg - the pattern can be different here. Last year we also had a drought, and it was combined with both early onset of color and phenomenal color. I could hardly believe the "fall color" I was getting three weeks ago around 9 and 10,000 ft in the Great Basin, exp since it was combined with wildflower season still in its peak. Ironically, I've seen the same kind of thing happen on excess snowfall years
too. Our key indicator here is quaking aspen, with only dwarf willows transitioning earlier. The color starts at high altitude and slowly moves down. Often our best
"fall" color here on the coast is in January!
OK Drew - I don;t doubt that last year there was a drought and early onset of color. But explain the cause and effect for how the drought triggered the early onset of color (which is direct tot he OP's question).Quote:
Originally Posted by Drew Wiley
Fall color is primarily triggered by the length of the night. Once the night-time reaches a certain duration, then leaves create an abscission layer that blocks the flow of carbohydrates and minerals to the rest of the leaf. That in turn causes chlorophyl to stop being produced. Chlorphyl is the green color we see most of the year. So the absence of the chlorophyll is what allows the autumn color to be revealed. No abscission layer, no fall color. This does not change for east coast vs/ west coast.
Other less relevant factors are amount of sunlight and air temperature during the day and night. This is what accounts for slight variations in the onset of autumn color each year. But since the length of the night does not change by date from year to year, there is an earlisest possible onset date for fall color. Drought will not change that.
So there may have been a drought and early onset last year, but that is just a coincidence. Drought can impact the quality oft he autumn color (for better or for worse) but will not significantly impact the date autumn color begins since drought does not change length of night, amount of sunlight, daytime temps, or night-time temps. This is ignoring the effect of drought on stressed that change color early simply as a defense mechanism. Every year there are trees that change color very early because they are stressed, and inevitably there are people whoa re convinced that fall has started in August.
Sorry, Greg. There was a time when I had to memorize the entire Kreb's cycle. I fell one class short of a formal Botany degree and opted for a general field biology degree instead, since that was where my career was supposedly headed (wildlife, outdoorsy, etc). Or at least that was the idea, at least until all hell broke loose on the other side of the world and affected everything here too for my generation. Therefore I've since had the luxury of forgetting all that. And that is something I am expert at (forgetting). So I go with years and years of direct observation. Drought stresses trees. But light and temperature can be an extremely complicated subject. Drought years can have early onsets of snow. And quaking aspen are technically interconnected "organisms" based on common root systems, with certain clusters changing color at different times than others (even adjacent), and even different colors. They DON"T all change at the same
time, even on the same plot. A since aspen grows over an altitude differential on the east side of the Sierra from around 10,000 ft clear down to almost 6,000 in
spots, there is quite a variation in timing. But read my previous post. "Fall" did start in August where I just was, and the surroundings were lush. That was above the aspen belt, where hail and snow can fall anytime of year.