Posts Tagged: bark beetles
Chris Fettig: How Bark Beetles Are Transforming Forests with a Little Help from Climate Change
USDA forest research entomologist Chris Fettig of the USDA's Pacific...
USDA forest research entomologist Chris Fettig will discuss bark beetle damage (shown) when he delivers a UC Davis Department of Entomology and Nematology seminar at 4:10 p.m., Wednesday, Feb. 1. (Photo courtesy of Chris Fettig)
Beetles from Belize at the Bohart Museum Open House
Beetles from Belize at the Bohart! The Bohart Museum of Entomology open house on...
Professor Fran Keller of Folsom Lake College and a Bohart Museum of Entomology scientist, is shown here wearing her Bohart Museum rhinoceros beetle shirt at Kensington Palace. Keller taught science to community college students in London during the fall semester. She designed this beetle, which is available in the Bohart Museum gift shop.
Some of the insects collected during a Bio Blitz in Belize for the Bohart Museum of Entomology. (Photo by Fran Keller)
UC Davis ENT Seminars: From Bark Beetles to Meat-Eating Bees
From bark beetles to meat-eating bees! And from UC Davis to France... Seminar...
This is a gallery of bark beetles. A seminar on forest beetles will be among the seminars hosted by the UC Davis Department of Entomology and Nematology. (Photo by Kathy Keatley Garvey)
Wild bees will be among the UC Davis Department of Entomology and Nematology's seminar topics. This is a yellow-faced bumble bee, Bombus vosnesenskii, sipping nectar from amethyst sea holly, Eryngium amethstinum, in Sonoma. (Photo by Kathy Keatley Garvey)
How Do Monarchs Know When to Migrate? Bohart Museum Open House Jan. 18
How do monarch butterflies know when to migrate? Take the case of a male monarch reared, released...
Eight microscopes will be available at the Bohart Museum of Entomology open house on Jan. 18. Visitors can view the research projects of doctoral students. (Photo by Kathy Keatley Garvey)
Ants will be the topic of Zachary Griebenow of the Phil Ward lab, UC Davis Department of Entomology and Nematology. This image shows emeritus professor Jerry Powell of UC Berkeley identifying insects at the Bohart Museum of Entomology. (Photo by Kathy Keatley Garvey)
Multiyear Drought Caused Massive Forest Die-off in Sierra Nevada
The most extreme drought event in hundreds of years caused a catastrophic die-off of the Sierra Nevada's mature trees in 2015-2016.
A study published today in Nature Geoscience details how UC Merced Professor Roger Bales and his colleague Professor Michael Goulden from UC Irvine tracked the progress of the devastation caused by years of dry conditions combined with abnormally warm temperatures.
The researchers warn that matters are expected to get worse as global mean temperatures increase.
“Parts of the Sierra Nevada reached a ‘tipping point' in 2015, where annual precipitation plus stored subsurface water were not enough to meet the water demand of the forest,” Bales said.
The trees in California's mixed-conifer mountain forests have roots that can draw water from as deep as 5 to 15 meters down, which has historically protected the trees against even the worst multi-year droughts.
But the severity of California's 2012-2015 dry-spell “exceeded this safety margin,” the researchers said. When forest stands exhausted the subsurface moisture, they became vulnerable to attack by pests, leading to widespread tree death.
From 2012 to 2015, the entire state experienced a crippling drought, but it was especially severe in the southern Sierra Nevada. The four-year period was the driest in the past century, combined with below-average precipitation and above-average warmth extending year after year.
“This forest die-off can be viewed as a ‘perfect storm' — the intersection of four years of low precipitation, hotter temperatures than in past droughts, and a heavily overstocked forest from centuries of fire suppression,” Bales said.
The research was supported by National Science Foundation and the U.S. Department of Agriculture. Observations by the U.S. Forest Service Aerial Detection Survey showed that many tree stands suffered complete loss of mature conifers. Pines were especially hard hit by an infestation of bark beetles.
Sierra Nevada Research Institute Director Bales, Distinguished Professor of Engineering with the Department of Civil and Environmental Engineering in the School of Engineering, and Earth System Science Professor Goulden examined tree communities at a variety of elevations and latitudes in the sprawling mountain range using field and remote-sensing observations.
A post-drought survey found that tree mortality was greatest near 3,800 feet of elevation, with nearly 80 percent loss in 2016.
The study outlines a key factor in the die-off: A period of unusually dense vegetation coinciding with a prolonged drought and warmer-than-usual temperatures. The heat and proximity of trees and plants to one another caused accelerated evapotranspiration — moisture evaporating from leaves and rising up in the sky as water vapor. This caused the trees to draw even more water from the ground.
“We expect climate change to further amplify evapotranspiration and ground moisture overdraft (when more water is taken out of the soil than is replaced by precipitation) during drought,” Goulden said. “This effect could result in a 15 percent to 20 percent increase in tree death for each additional degree of warming.”
With their improved understanding of the contributions of factors such as elevation, vegetation density, heat, precipitation and soil water amounts, the researchers said they now have a framework to diagnose and predict forest die-offs brought on by drought.
“Using readily available data, we can now predict where in mountain forests multi-year droughts are likely to have the greatest impact, and the threshold at which those impacts are expected to occur,” Bales said.