SALT LAKE CITY (ABC4) – Utah has faced a dry and hot summer. The Beehive State entered the summer months with limited snowpack and limited precipitation did not improve the situation. As we enter fall, those impacts may impact a favorite fall pastime – the changing of the leaves.
The months of September and October are often synonymous with seeing the leaves on our trees change from green to yellows, oranges, and even reds. This year, because of the dry conditions, those colors may not be as vibrant.
As the days starting getting shorter, trees like the aspens of the Manti-La Sal National Forest receive a signal to stop producing the chlorophyll, which makes the leaves green. This occurs in spite of the dry conditions, Andrew Orlemann with the U.S. Forest Service explains.
“On the other hand, it is my personal opinion that, during drought years, the colors tend to be dull and brownish instead of bright yellow and orange,” Orlemann explains.
Kuhns explains the drier weather can, in fact, impact the colors we see.
“One of the main things that happens to many tree species in a drought is the edges of the leaves will start to turn brown and die earlier in the growing season than they would have if the weather were cooler and wetter,” Dr. Mike Kuhns, a Utah State University Extension Forester and professor tells ABC4.com. “This decreases water use but the premature browning of the leaves results in less leaf area to turn color and more muted colors than if the leaves stayed healthy longer into the fall.”
Trees, like most plants, can suffer under drought conditions.
“Almost all native or ‘wild’ trees in Utah grow in the mountains at fairly high elevations,” Dr. Kuhns explains to ABC4.com. “This is because the climate is naturally cooler and wetter at higher elevations, and trees need more water than most other plants to survive and grow. Even during droughts, there is more water available at higher elevations and trees are able to survive.”
But as we know, most of us do not live in the mountains, instead, call the valleys home. These areas are naturally dry, warm, and treeless, Kuhns explains. You still see trees around, of course, many thanks to people watering them.
SLIDESHOW: Falls colors in Utah
For the aspen trees in the forests across central and southern Utah, Orlemann says drought conditions have two main impacts.
“First, under severe drought stress, hydraulic function can be impaired, reducing the tree’s ability to transport water and nutrients from roots to leaves,” Orlemann explains. This can cause the trees to die, he adds, but says research has shown there is a lag of three to five years until widespread die-off from drought is seen. “Second, in nursery studies, scientists have found that aspen trees under drought stress will produce fewer and smaller leaves. The tree can recover from this condition – producing larger leaves later – if the drought is short-lived.”
Orlemann, who works in the Manti-La Sal National Forest, says if you visit the forest this year, you may notice aspen clones showing signs of these stressors.
IMAGE: When Utah’s trees are predicted to hit peak fall colors
“Tree crowns may appear somewhat thin and ragged, rather than lush and full,” Orlemann says. “And, in some cases, overstory trees may be obviously dead or dying.”
If you are worried about the aspens of the Manti-La Sal National Forest, Orlemann offers a good note to put your fears at ease:
“The aspen is the most widely distributed tree species in North America. It can grow at elevations from 5,000 feet to 12,000 feet and is well adapted to disturbance. After a wildfire, for example, healthy clones will respond by sprouting from lateral roots. These sprouts can be as numerous as 10,000 to 20,000 stems per acre. Though there are many factors that can affect aspen health – from diseases to drought – it is a resilient species, genetically diverse and productive, and I expect that it will be improving the scenery of the Manti-La Sal for many decades to come.”