Easter Wreath

Easter!, photo by Staci DeVries

Happy Easter, if that’s something you celebrate.

View the photo background bigilicious and see more in Staci’s slideshow.

The science behind the magic: Fall color explained

yellow-glory-by-scottie

Untitled, photo by Scottie

The Science of Color in Autumn Leaves from the United States National Arboretum is such an excellent explanation of the science behind the magic of Michigan’s fall color show that I try and share it every year:

The process that starts the cascade of events that result in fall color is actually a growth process. In late summer or early autumn, the days begin to get shorter, and nights are longer. Like most plants, deciduous trees and shrubs are rather sensitive to length of the dark period each day. When nights reach a threshold value and are long enough, the cells near the juncture of the leaf and the stem divide rapidly, but they do not expand. This abscission layer is a corky layer of cells that slowly begins to block transport of materials such as carbohydrates from the leaf to the branch. It also blocks the flow of minerals from the roots into the leaves. Because the starting time of the whole process is dependent on night length, fall colors appear at about the same time each year in a given location, whether temperatures are cooler or warmer than normal.

During the growing season, chlorophyll is replaced constantly in the leaves. Chlorophyll breaks down with exposure to light in the same way that colored paper fades in sunlight. The leaves must manufacture new chlorophyll to replace chlorophyll that is lost in this way. In autumn, when the connection between the leaf and the rest of the plant begins to be blocked off, the production of chlorophyll slows and then stops. In a relatively short time period, the chlorophyll disappears completely.

This is when autumn colors are revealed. Chlorophyll normally masks the yellow pigments known as xanthophylls and the orange pigments called carotenoids — both then become visible when the green chlorophyll is gone. These colors are present in the leaf throughout the growing season. Red and purple pigments come from anthocyanins. In the fall anthocyanins are manufactured from the sugars that are trapped in the leaf. In most plants anthocyanins are typically not present during the growing season.

As autumn progresses, the cells in the abscission layer become more dry and corky. The connections between cells become weakened, and the leaves break off with time. Many trees and shrubs lose their leaves when they are still very colorful. Some plants retain a great deal of their foliage through much of the winter, but the leaves do not retain their color for long. Like chlorophyll, the other pigments eventually break down in light or when they are frozen. The only pigments that remain are tannins, which are brown.

The explain that because the starting time of the whole process is dependent on night length, fall colors appear at more or less the same time every year and are not overly dependent on temperature, rainfall or other factors, other than the fact that weather can shorten or prolong the show by stripping leaves from trees.

Click through to the US Arboretum for more and also see Fall & Fuit from the Science of Color!

View Scotties’ photo bigger and see more in his Infrared slideshow.

Tons more fall photos on Michigan in Pictures!

Wild & Scenic Rivers: September color along the Carp River

big-carp-river-in-september-fall-color

West from the Lake of the Clouds, photo by Jim Sorbie

Glints of yellow, orange and red are starting to pop up around the state, so it’s probably time to get some fall wallpaper for your computer! Check that link for a ton and get fall color reports and color touring ideas from the Pure Michigan Fall Color page!

It’s also been a while since I added a Michigan Wild & Scenic River to the blog, so here’s the somewhat brief entry for the Carp River from the National Wild & Scenic Rivers:

The Carp River, in Michigan’s Upper Peninsula, flows through predominantly forested lands with little development along its way. Spring’s high water provides for canoeing and offers steelhead fishing and dipping for smelt near the river’s mouth. Summer is the time for brook or brown trout, and fall brings salmon fishing. The Carp is known for its outstanding recreation, wildlife, geologic, ecological, fisheries and heritage resource values. The river flows through the Mackinac Wilderness Area.

Michigan has 16 nationally designated Wild & Scenic Rivers – get them all at that link!

View Jim’s photo background bigtacular and see more in his Color Tour 2014 – UP & Canada slideshow.

Why is Ice Blue or Green?

The Blue Ice

The Blue Ice, photo by Charles Bonham

The Causes of Color answers the question: What causes the blue color that sometimes appears in snow and ice?

As with water, this color is caused by the absorption of both red and yellow light (leaving light at the blue end of the visible light spectrum). The absorption spectrum of ice is similar to that of water, except that hydrogen bonding causes all peaks to shift to lower energy – making the color greener. This effect is augmented by scattering within snow, which causes the light to travel an indirect path, providing more opportunity for absorption. From the surface, snow and ice present a uniformly white face. This is because almost all of the visible light striking the snow or ice surface is reflected back, without any preference for a single color within the visible spectrum.

The situation is different for light that is not reflected, but penetrates or is transmitted into the snow. As this light travels into the snow or ice, the ice grains scatter a large amount of light. If the light is to travel over any distance it must survive many such scattering events. In other words, it must keep scattering and not be absorbed. We usually see the light coming back from the near surface layers (less than 1 cm) after it has been scattered or bounced off other snow grains only a few times, and it still appears white.

In simplest of terms, think of the ice or snow layer as a filter. If it is only a centimeter thick, all the light makes it through; if it is a meter thick, mostly blue light makes it through. This is similar to the way coffee often appears light when poured, but much darker when it is in a cup.

Click through for lots more about light & color!

Charles took this photo last March off Gills Pier on the Leelanau Peninsula when there was a whole lot more ice than there is this winter. View it background bigilicious and see more in his Leelanau Peninsula slideshow.

More winter wallpaper and more amazing ice on Michigan in Pictures.