But geography doesn’t automatically describe vibrant colors – the weather often plays a more important role. So where was the weather favorable for a good foliage picking this year?
Ideal foliage conditions depend on a good combination of temperatures (neither too hot nor too cold) and humidity (not too wet or too dry). The problem is that some areas Owns I encountered these harsh conditions, particularly in the West and New England.
More than 75% of the West is under drought conditions. More than 80% of the areas of Massachusetts, Maine, Rhode Island and New Hampshire suffer from severe drought.
But some of the same New England areas experiencing drought conditions also happen to show more pronounced fall colors.
“This year we’re seeing exceptionally vibrant foliage fall in Vermont,” said Dr. William Keaton, professor of forest and forest ecology at the University of Vermont. “This is due to a combination of factors, including good tree growth last year, mild droughts, warm days and cold nights over the past month.”
While the dryness may lead to more vibrant colors, the timing may be premature.
“Colors this year are coming two weeks earlier than usual and will likely disappear quickly and aggressively,” Keaton said. “This is largely because droughts cause stress on trees – physiological stress. In this sense, while droughts may enhance some color, stress is not a good thing and may be a harbinger of things to come, climate change.”
In addition to starting early, the duration of the leaf color is also likely to be affected.
“In terms of leaf fall, droughts can cause leaves to change color early, but they may die and fall early,” said Caitlin Weber, data analyst at Climate Central. “Prolonged and more severe droughts can cause physical damage to trees such as loss of roots, slow growth, and make it difficult for trees to protect themselves from pests and diseases.”
This is why the level of dehydration matters, too.
Vermont, for example, has predominantly moderate drought (Level 1 out of 4), versus New Hampshire, Massachusetts and Maine, which predominantly suffers from severe drought (Level 2 out of 4). Almost all of Rhode Island suffers from severe drought (Level 3 out of 4).
“Mild to moderate drought may actually enhance leaf fall to some extent, as long as it does not lead to much ‘browning’ or early leaf fall,” Keaton said. “Then again, a drought in one year may result in less robust leaf production the following year.”
So it is not always an instant effect. Often, the effects of dehydration are delayed. Currently, 76% of Vermont experiences mild or worse drought conditions. But at the same time last year, 0% of the state was under drought conditions.
“Good tree growth in the past year has allowed trees to store energy and nutrient reserves during the winter, which has resulted in robust leaf growth in the spring and summer,” Keaton said. “But that works the other way as well … a bad drought one year can lead to weak foliage the following year.”
Extreme heat and climate change
Ideal conditions for vibrant foliage include warm days and cold nights. This encourages the production of a chemical called anthocyanin, which adds red and purple colors in some species, such as maple.
“The contrast of temperatures between night and day accelerates the loss of chlorophyll from the leaves, leaving behind the secondary photosynthetic pigments (carotenoids) that give us the yellow and orange colors,” Keaton said.
However, just like drought, intense heat can stress trees enough to cause premature browning or leaf loss. And moderate heat, or prolonged heat – when the fall looks more like an expanse of summer – can delay the change to fall colors, because trees don’t get a signal that the fall has arrived.
“It’s also possible for plants to completely miss a signal and lose their leaves faster,” said Weber.
Western states like Colorado and New Mexico often see an increase in tourism as travelers look for the vibrant leaves of aspen and oak trees. Both states, along with Nevada and Utah, recorded their hottest August this year. New Mexico experienced its second dry summer (June through August) on record.
“The causes of leaf fall are complex and actually not fully understood,” Keaton said. “Drought is only one of many factors, the other being the period of light and the contrast between daytime and night temperatures in the fall. It all just shows just how wonderful our forest ecosystems are!”
Forest fires add another obstacle / dilemma
Wildfires will also complicate leaf grabbing in Colorado and California this year. Several states are still dealing with poor air quality and a foggy sky of smoke. This fog will impede your ability to see the vibrant colors.
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