Archive for category: Special Report

Leaves on deciduous trees change color in autumn from green to various hues of lime, yellow, gold, orange, red and brown because of a combination of shorter days and colder temperatures.

Throughout spring and summer, green chlorophyll (which allows trees to absorb sunlight and produce nutrients) is made and replaced constantly.

However, as days grow shorter, “cells near the juncture of the leaf and stem divide rapidly but do not expand,” reports Accuweather.com. “This action of the cells form a layer called the abscission layer.

“The abscission layer blocks the transportation of materials from the leaf to the branch and from the roots to the leaves. As Chlorophyll is blocked from the leaves, it disappears completely from them.”

That’s when vivid yellow xanthophylls, orange carotenoids and, due to a different process, red and purple anthocyanins emerge.

Orange is found in leaves with lots of beta-carotene, a compound that absorbs blue and green light and reflects yellow and red light, giving the leaves their orange color.

Yellow comes from Xanthophylls and Flavonols that reflect yellow light. Xanthophylls are compounds and Flavonols are proteins.  They’re what give egg yolks their color.

Though always present in the leaves, Carotenoids and Xanthophylls are not visible until Chlorophyll production slows.

Red comes from the Anthocyanin compound. It protects the leaf in autumn, prolonging its life. Anthocyanins are pigments manufactured from the sugars trapped in the leaf, giving term to the vernacular expression, “the leaves are sugaring up.”

The best fall color occurs when days are warm and nights are clear and cold. California’s cloudless skies and extreme range of elevations (sea level to 14,000′) provide ideal conditions for the development of consistently vivid fall color, as seen in these reports. 

Environmental changes affect fall color. California is experiencing a prolonged spate of hot, dry and smoky air. That dehydrates the soil and reduces photosynthesis, which affects fall color.

CaliforniaFallColor.com has been monitoring news reports of whether this autumn is predicted to be more colorful or less than in previous years. Sources in New Hampshire, Minnesota and Southwest Colorado predict dull color due to drought. North Carolina is getting mixed reviews. Wisconsin is estimated to have a normal autumn, and Maryland is optimistic for a vibrant Autumn due to moisture and hot days.

As for California, we conclude that the beauty of our show will depend upon conditions at specific locations and that no overall prediction for a given region with the state or California as a whole can be made with any reliability. Nevertheless, late summer hot, dry days and smoky air will dull fall color in many places.

“Soil moisture is essential to tree health, obviously, so if there has not been enough moisture at fall color time, color could be delayed, just plain dull, or leaves can die early without changing color,’’ Val Cervenka, forest health program coordinator for the Minnesota Department of Natural Resources was reported in the Duluth News Tribune, this week, as saying. “Trees that are under stress usually show it first in their leaves. Since so much of a tree’s energy goes into producing leaves, the tree can conserve energy by simply dropping the leaves, like it does before it goes dormant in the winter,” he continued.

Marissa Y. Thompson, Ph.D. of New Mexico State University wrote on the university’s website in 2001 that, “Plants can be affected in both a positive and negative manner by smoke.” She continued that “Smoke, produced by combustion of some material, means that there is increased carbon dioxide over a limited area. This is good for the plants and can increase their growth if there is sufficient light.

“The smoke particles that we see, however, are particulate pollution which can coat the leaf surface, reducing photosynthesis. These particulates can also clog stomatal pores, reducing gas exchange in the leaf. These effects are bad for plants,” Thompson concluded.

Science is often torn between two conclusions, i.e., more CO2 resulting from combustion is good for plants, however smoke particles can reduce photosynthesis which is not good for plants.

Our conclusion is that the smoke caused by this autumn’s earlier-than-usual wildfire season will, on the whole, not be good for fall color. Combined with hot, dry days it has desiccated the leaves on many trees – particularly those that were stressed from disease or localized drought. That means, less dramatic fall color.

Further, smoke particulates – should they remain soiling our air – will reduce the beauty of whatever fall color appears, because fewer light waves will make it through the smoky atmosphere to illuminate the leaves.

That’s a dismal prediction for this early in the year. So, we should note that it’s still two weeks from the Autumnal equinox and a lot can happen that could change this within the next month.

1. It could rain. Some long-range forecasts predict rain at the end of September. Where moisture falls, forests will thrive, leaves will remain fresh and fall color will appear in dazzling displays.
2. The air could clear. The number and ferocity of California’s wildfires have exceeded normality. They’ve been fed by lightning strikes, high temperatures and wind. A drop in any of these influences could return the state to a more normal fire season.

So, be informed, but don’t lose your enthusiasm. Despite the disappointing present, there will be bright spots of gorgeous fall color to find along the backroads and byways of California. And, when they can be seen, we will report them.