Curbing tree mortality in Sonoma
“The issue is quite serious,” said Jessica Misuraca, chair of the Sonoma Overlook Trail Stewards and a member of the City of Sonoma Parks, Recreation & Open Space (PROS) Commission, regarding the rise in tree mortality. “When you combine the dehydration effects that our local trees suffer due to our particular climate with additional factors — such as insect predation, high wind, extreme sun, disease, sudden flooding and pollution — tree survival rate can plunge.”|
Richard Dale, executive director of Sonoma Ecology Center.
Jessica Misuraca — chair of the Sonoma Overlook Trail Stewards and a member of the city of Sonoma Parks, Recreation & Open Space Commission — stands under a dead tree that straddles a footpath on Sonoma Overlook Trail on Tuesday, Oct. 3, 2023. (Robbi Pengelly/Index-Tribune)
Jessica Misuraca — chair of the Sonoma Overlook Trail Stewards and a member of the City of Sonoma Parks, Recreation & Open Space Commission — walks past a fallen ree on a Sonoma Overlook Trail footpath off First Street West on Tuesday, Oct. 3, 2023. (Robbi Pengelly/Index-Tribune)
Unless fallen trees are very large and could be hazardous to hikers, the dead ones are left, as they would be in nature, to provide sustenance for the young trees and the many creatures that make the forest their home. Photo taken on Sonoma Overlook Trail on Tuesday, Oct. 3, 2023. (Robbi Pengelly/Index-Tribune)
Staff members from the Sonoma Ecology Center’s Restoration Program move wood from diseased and dead trees to a staging area at Montini Open Space Preserve in Sonoma on Tuesday, Oct. 3, 2023, for a future burn. This will convert the material to biochar, a material that locks up carbon for centuries, and increases the soil’s capacity to hold water. (Courtesy of Richard Dale/Sonoma Ecology Center)
Sonoma Sunrise Rotary Club members help Sonoma Ecology Center’s Restoration Program staff move wood to a staging area on the Montini Open Space Preserve in Sonoma on Tuesay, Oct. 3, 2023. (Courtesy of Richard Dale/Sonoma Ecology Center)
Landscape designer Bob Schneider, left, and arborist Manuel Hernandez from Sonoma Ecology Center’s Restoration Program observe a damaged ginkgo — most likely due to drought and changes in landscape maintenance — on the grounds of Sonoma Developmental Center on Tuesday, Oct. 3, 2023. (Courtesy of Richard Dale/Sonoma Ecology Center)
An oak tree on the Montini Open Space Preserve in Sonoma with a fungal infection after succumbing to the sudden oak death pathogen. Photo taken on Tuesday, Oct. 3, 2023. (Courtesy of Richard Dale/Sonoma Ecology Center)
These redwoods at Sonoma Developmental Center were planted in a location where they needed irrigation. They appear to have died from lack of water after the irrigation pattern was changed. Photo taken on Tuesday, Oct. 3, 2023. (Courtesy of Richard Dale/Sonoma Ecology Center)
A blue oak tree on the Montini Open Space Preserve in Sonoma that died after years of drought. Photo take on Tuesday, Oct. 3, 2023. (Courtesy of Richard Dale/Sonoma Ecology Center)
Dead and stressed bay trees on Montini Open Space Preserve in Sonoma on Tuesday, Oct. 3, 2023, after suffering from years of drought. (Courtesy of Richard Dale/Sonoma Ecology Center)
Richard Dale, executive director of Sonoma Ecology Center.
Jessica Misuraca — chair of the Sonoma Overlook Trail Stewards and a member of the city of Sonoma Parks, Recreation & Open Space Commission — stands under a dead tree that straddles a footpath on Sonoma Overlook Trail on Tuesday, Oct. 3, 2023. (Robbi Pengelly/Index-Tribune)
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Jessica Misuraca — chair of the Sonoma Overlook Trail Stewards and a member of the city of Sonoma Parks, Recreation & Open Space Commission — stands under a dead tree that straddles a footpath on Sonoma Overlook Trail on Tuesday, Oct. 3, 2023. (Robbi Pengelly/Index-Tribune)
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DANIEL JOHNSON
INDEX-TRIBUNE STAF WRITER
October 3, 2023, 7:42PM Updated 5 hours ago
7 tree care tips
Janet Hartin, area environmental horticulture adviser for U.C. Cooperative Extension in Los Angeles County, offers these tree care tips.
• Select trees that perform well in your climate.
• When planting a new tree, make sure it has a space 2.5 times larger than the container.
• Remove any tree ties that are cutting into the trunk or branches of your trees.
• Keep all plants and mulch several inches away from tree trunks.
• Keep tree trunks dry. They should not come into contact with water from sprinklers and hoses.
• Regularly water newly planted trees, but water mature trees infrequently and deeply.
• Prune trees only as needed and avoid topping them.
Trees can endure many stressors in their environment — even for decades — but due to changing climate conditions, inappropriate planting and management, and other factors, many are dying in Sonoma Valley.
“The issue is quite serious,” said Jessica Misuraca, char of the Sonoma Overlook Trail Stewards and a member of the Sonoma’s Parks, Recreation & Open Space (PROS) Commission. “When you combine the dehydration effects that our local trees suffer due to our particular climate with additional factors — such as insect predation, high wind, extreme sun, disease, sudden flooding and pollution — tree survival rate can plunge.”
In open spaces and parklands, where forests are mainly native, the threats are almost entirely climate based. But in residential areas, poorly planted and non-native trees are often deprived of the essential elements — space, water, sun — needed to survive, Misuraca said.
Richard Dale, executive director of Sonoma Ecology Center, said that he isn’t aware of any systematic study of tree mortality in Sonoma Valley. The California Office of Environment estimated that 170 million trees died in the state from 2010 to 2021, about 4% of the country’s 4 billion trees.
“So, if Sonoma Valley is representative, with .1% of Californi’s area, you could speculate that 170,000 trees died from drought-related stress here,” Dale said.
PROS and the city’s Climate Action Commission have been working together to address the problem, and plan for a future that considers the needs of trees.
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“There are some very knowledgeable people on and working with these commissions,” he said.
He said that the ecology center’s Restoration Program is specifically dedicated to supporting healthy and resilient landscapes in Sonoma Valley.
“In this work, we spend a lot of time working with trees,” Dale said. “We have an arborist on staff and grow, plant and maintain hundreds of native trees annually.”
At the Montini Open Space Preserve, Restoration Program staff are implementing a grant-funded effort to reduce wildfire fuel along the lower trails by removing dead and diseased trees. They use the debris to ceate habitat and make biochar, which collects harmful carbon from the environment and increases the soil’s capacity to hold water.
Dale is intrigued by the Miyawaki Method, which restores native forests on very degraded soils.
“It’s an exciting concept that seems appropriate for disturbed areas and other situations,” Dale said. “It creates diverse and dense forest patches while looking carefully at local soil, climate and other characteristics.”
These patches, planted in pockets of circles approximately 12 feet in diameter, use drought-tolerant plants and have been found to have a 95% survival rate, and compared with traditional methods, grow 10 times faster and generate up to 100 times more biodiversity as well as enhance soil biology.
“It’s similar to permaculture and no doubt other systems of horticulture that look at growing things in a relational system,” Dale said. “There’s no question we need to reduce the net loss of trees worldwide, and this is a carefully thought-out methd to do that.”
Why trees are dying
Tree species throughout Sonoma Valley are stressed for different reasons, Dale said. In wildland landscapes, tan oaks as well as coast live and black oaks are vulnerable to sudden oak death, which has spread throughout the Valley.
Dale said that the Glass and Nuns fires also damaged trees, to varying amounts depending on the species and how hot the fire was when the tree was impacted. Conifers — including Douglas fir, gray pine and knobcone pine — are susceptible to bark beetle infestations, which are intensified by drought when these host trees are still stressed.
Even blue oaks that typically handle heat and dryness well are dying in numbers that suggest significant stress, Dale said.
“If you walk along Sonoma’s hillside backdrop, on Overlook or Montini Open Space Preserve trails, you can see several of these tree species in varied stages of stress or lying on the ground,” he said. “Along roads and landscaping, you can see similar stress, as droght and pathogens affect the same wildland species, along with eucalyptus, acacia, coast redwood and others. Our recent wet season helped relieve a lot of stress for trees, though many are still compromised and likely won’t survive.”
Dale said that many factors contribute to trees’ stress and mortality.
“Climate change is a large factor,” he said. “As temperatures rise, in a Mediterranean climate like ours where it doesn’t rain for months each year — even if there’s plentiful rain in winter — soils will dry out from increased evaporation, and plants will require more water, adding to the loss of soil moisture. As a result, the last decade, with its many dry years, caused significant stress for trees throughou
