So Autumn

The fall glow in the Range of Light is especially remarkable in Yosemite Valley these days. We are at that point in the sun's apparent migration in the sky when it sets very low in the west, in the skyline notch that is the Merced River Canyon. It's the analog sunset point to that which produces the 'firefall effect' at Horsetail Fall. That photogenic phenomenon happens about 7-8 weeks after Winter Solstice; we are now 7-8 weeks before solstice. The low sunset lets a more colorful sunlight into the Valley at the end of the day. (Horsetail Fall is just trickling now so won't produce the volume of mist/water that catches the light in February.)
In mid-summer the sun sets well to the north of the Merced's exit point, so is high over the canyon rim; in winter it sets high over the canyon wall to the south - in both cases setting when the sunlight is still whiter.
During the day, the sun is traversing a lower angle than in summer, too, but still reaches more of the Valley floor than it does in mid-winter. The Valley's deciduous plants are ending their growing season with the decay of chorophyll that allows other leaf pigments to shine before leaves drop to the ground. Big-leaf maples put on the biggest color display now, and these bands of yellow highlight their preferred wetter, shady habitat in ways that may not have been apparent all summer. The one sugar maple in Old Yosemite Village turned more yellow than red this year, and the afternoon up-canyon breezes have this tree already about 20% bare now. Black oaks are going brown-yellow but many leaves have dropped from some. Dogwoods are still largely green, but showing their startling pink in places. Black cottonwoods are mostly bare now. The brightest plant in the Valley now is dogbane or Indian hemp (Apocynum) - their radiant gold almost hurts one's eyes.
The meadows are a light brown, the fallen pale leaves cover darker ground, more sunshine reaches the ground through branches that are baring. Even ponderosas participate in this season, browning and shedding some of their needles after the dry summer. It all adds up to a lighter albedo. Though the days are shorter and the sun is lower, Yosemite Valley is reflecting more light and is brighter than it is all summer. Only the winter snow will raise the Valley's albedo beyond this dreamy, pale glow of autumn.
Incense cedars are raining their helicopter seeds now. Gray squirrels have been shredding pine cones for a few weeks and their litter of cone scales is everywhere. Been seeing more chickarees than usual in the Valley, also working over the ponderosa cones. Down canyon a bit, Torreya has been dropping its strange green fruits.
The Merced is running at about 80 cfs at Pohono Bridge and dropping since our last storm on 5 October (average for this date is around 33 cfs). Last evening the Valley rim was entirely mantled in a cloud layer that built just at sunset.

Foliage change

Rain ten days ago really swelled the Merced River. The historical average flow for last week was below 30 cfs. It had been running closer to 100 cfs, then leapt to over 600 after the rain. That the high country got snow showed in the nice 24-hour cycle of melt ebb and flow shortly after the storm. Our waterfalls are again looking exceptional for this time of year.
Ladybird beetles are on the move in this warm (moist) weather, with many swarming in El Portal the past couple of days.
A red-shouldered hawk, and a pair of great horned owls were heard in the volunteer campground in Yosemite Valley. A Say's phoebe was seen in Rancheria Flat.
Orion and Canis Major dominate the morning skies if you're out early and have a view to the south.
The sugar maple in old Yosemite Village has just started to show a tiny touch of color. At the Valley elevation, other than dogbane and some bracken, most color has not yet appeared. Alders skip the show and just start dropping their green leaves into the river when they're done, which is now.
Higher up you'll find aspen and bilberry being more colorful now. It should be a good weekend for getting out in the park.
Half Dome cables are down for the winter, Backpackers, Yosemite Creek and Crane Flat Campgrounds are closed for the season now.

Autumn Out

Walked up northwest from Foresta to Little Nellie Falls on Saturday - very crowded - with foliage color, blue sky, deer and bear tracks, a few birds (including a surprise solo horned lark!), and millions of springtails. There were some puddles in ruts on the Coulterville Road from the prior weekend's rain. On the surface of the sunlit puddles were rafts of millions and millions of the tiny gray insects, too small to break the surface tension, even when massed this way. They were hopping continuously, there were dispersed individuals on the muddy road surface, but the party was all afloat. Hard to comprehend but wonderful to observe.
Sunday's saunter took us from Chinquapin out the old logging rail grade southeast to the Alder Creek watershed. It is unusual to be able to stroll on the horizontal for mile after mile above 6000' in the Sierra, but here's a pleasant legacy of commercial forestry. From the 1907 railroad that came to El Portal, steep (up to 78%!) inclines were built up the south side canyon wall in 1912 and the north side canyon wall by 1924. It's hard to imagine the costly labor of hundreds of people creating this access for extracting sugar pine from what is now peaceful forest. There's a bit of patchy snow, which held tracks of coyote, deer, bear and squirrel. Aspens in Bishop Meadow are bare now, the black oaks and dogwoods still have a bit of color hanging on.
Glacier Point and Tioga Roads are still closed, though the weather will determine whether this is a closure for the whole season or not. A La Nina season is expected, which could go either way for wet/dry.
A new speed record for ascending the Nose Route on El Capitan was established over the weekend: just under two hours, 37 minutes. Human springtails?

Into Merced Grove

After weeks of nice foliage color, it's STILL really colorful in Yosemite. Black oaks in the Valley have come into their own, dogwoods, bracken, azalea, dogbane and maples are still so bright. Adding to the glow, now the forest floor is lightened by fallen leaves, too. I was with a group in Merced Grove over the weekend and we enjoyed the quiet of the big trees enhanced by the startling albedo change brought on by yellow dogwood, azalea and hazel. What a colorful look for this deep shady valley.
It was mighty pleasant to walk on the old Coulterville Road to the old ranger cabin, in the middle of Yosemite's smallest sequoia stand. I'll be snowshoeing in for a night in the ranger cabin with another group the first weekend of February.
Sunday night brought snow down to about 6000' in Yosemite. Glacier Point Road and Tioga Road are closed, perhaps for the whole winter now. The Valley's great fall colors now include a good amount of white, from snow extending down from the south rim, and ice that builds on Yosemite and Sentinel Falls.

Indian Summer

Another storm Friday night. Tioga Road is closed for now. Glacier Point Road closed then reopened. Exceptionally warm weather is forecast for this week, up into the mid-70's for Yosemite Valley. The river is still above average from the 24 October rains, but is much closer to normal volume than when it filled meadows and covered trails early last week. Foliage is quite colorful in spots still - many of the maples add color with leaves on the ground. Cottonwoods are lighting up now.
Yes, Oprah camped here a few weeks ago, but even better news: biologists at Texas Tech published the formal description of a new species of pseudoscorpion that lives in some of the talus caves along the north wall of the Valley: Parobisium yosemite. There are about 3300 species of these tiny arachnids worldwide, part of a vast, hidden world of scavengers and predators in the leaf litter, under rocks, and in the soil. Pseudoscorpions lack the stinger/tail of a scorpion and are too tiny to harm us. Oprah has 30 million viewers a day but she doesn't get to live in Yosemite like this little critter does.
Once again, Yosemite claims the world championship for the wintertime population of the white-headed woodpecker. My copy of Audubon's 2009 Christmas Bird Count summaries came last week, and there we are: there were more white-headed woodpeckers in Yosemite on last winter's count day than anywhere else. The Yosemite CBC has been the kingdom of Picoides albolarvatus three times in the past 20 years or so. Check the NPS site and consider joining us for this winter's count, 19 December.

Anthocyanin

Fall foliage is looking good in Yosemite Valley now. The sugar maple (pictured) is like one very small glimpse of Vermont; an exotic species we especially cherish for 2-3 weeks a year. The native maples are bright yellow for the most part now. While it's been warm for the past couple of weeks, there was a tiny bit of frost on the lowest parts of Valley meadows a while back, so we could say that we're in Indian Summer. Black oaks are shelling Yosemite Village with a healthy acorn crop - a good time to be an Indian. Deer, pigeons, bears, woodpeckers, etc. are eating and/or storing lots of that mast now. Mule deer bucks have lost their velvet; a time for visitors to be cautious about approaching too closely with their eager photography.

Illilouette Gorge

The sugar maple is peaking now, its bright blaze of surreal orange dominating that part of the old village like a column of flame. The native maples are getting brighter, too (the Fern Spring corner has a new, pale light now), though many are still entirely green. Oaks aren't yet very colorful; some are just browning. Cottonwoods are mostly still green along the river; even up higher, the aspen are just begining to color. Dogbane is one of the brightest natives in the Valley now.
I made a trip up Illilouette Gorge to the base of the waterfall yesterday; a bouldery scramble. Don't try this unless you're up for considerable steep clambering. Some light rain slicked the rocks a bit, but it was nice to be out where no one else was, across the canyon from the busy Mist/Muir Trail. Sagebrush, Brickellia, and plenty of Douglas-fir. Band-tailed pigeons overhead, a canyon wren in the rocks. One primate looking at a waterfall.

Geo Notes

Last week's heavy rains brought a small debris flow down the Cathedral Spires gully, covering Southside Drive with several inches of sand and gravel. A rockfall at Church Bowl seriously injured a local girl last week; thankfully she appears to be recovering well. Another good-sized rockfall occured yesterday, from beneath Horsetail Fall on El Capitan, sending up a big cloud of dust from the ledge below the East Buttress.
The famous sugar maple is just starting to turn. Native big-leafed maples vary in their color now from bright yellow, to leaf margins starting to brown, to altogether green. Willows and cottonwoods will start to color soon, but haven't yet. The meadows in Yosemite Valley are the most yellow places at the moment. Torreya 'drupes' are mature and dropping in the isolated pockets where they grow. Invasive black locust trees are finally being removed from Old Yosemite Village by Resource Management.