Glenn Ahrens

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he/him/his

Forestry

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503-655-8631
[email protected]

Expertise: Cutting and selling trees , Forest health and management , Riparian areas , Water management and conservation

Locations: Clackamas County , Hood River County , Marion County

Links: Clackamas Extension Forestry

Biography

Glenn Ahrens is Extension Forester, Oregon State University Extension Service, Clackamas, Marion, and Hood River Counties, and Director, OSU Hardwood Silviculture Cooperative. His general mission for OSU Extension is to improve our knowledge of forest resources and options for sustaining and expanding benefits from forests. Glenn has a B.S. in Forestry from Humboldt State University (1982) and an M.S. in Forest Science from Oregon State University (1990). He has over 30 years of experience in research, Extension, and private consulting. Glenn’s areas of specialty include forest ecology, silviculture, vegetation management, and hardwood management.

Content by Glenn Ahrens

Postfire follow-up: Using the LEAF assessment template

The days following a wildfire are a critical time for recovery outreach. Learn how to help landowners set priorities, outline goals and connect with needed resources.

Kara Baylog, Glenn Ahrens, Stephen Fitzgerald, Lauren Grand, Alicia Christiansen, Kidane Giday, Aaron Groth, Ariel Cowan | Sep 2025 | OSU Extension Catalog

Steps to reforestation success after wildfire

After a wildfire hits a property, owners can opt for natural regeneration or decide to plant seedlings. Learn the factors that drive reforestoration decisions.

Glenn Ahrens, Max Bennett | Jul 2025 | OSU Extension Catalog

Will my tree live? Assessing postfire survivability

Trees can survive wildfire, but much depends on the tree species and the amount of damage to the crown, bark and root system. Sometimes, trees can die years later.

Glenn Ahrens | Jul 2025 | OSU Extension Catalog

Forests in a changing climate: A framework for management

Two potential strategies for addressing climate change can help forest managers prepare for a future with less water and warmer temperatures.

Stephen Fitzgerald, Glenn Howe, Glenn Ahrens | Jun 2025 | OSU Extension Catalog

Not all flame's the same: Willamette Valley & Western Cascades

Fire once shaped the Willamette Valley and Western Cascades through frequent Indigenous burning and occasional lightning fires, creating diverse habitats. Today, changes in land use, invasive species and climate have ...

Kayla Bordelon, Glenn Ahrens, Carrie Berger, Emily Jane Davis | May 2025 | OSU Extension Catalog

Tree School Online expands access to forest education for Oregon’s landowners

Tree School events were provided online in a series of 35 webinars hosted by OSU Extension in Clackamas County in collaboration with the Oregon Forest Resources Institute and the Oregon Partnership for Forestry Education.

Sarah Cameron, Glenn Ahrens | Mar 2025 | Impact story

Managing Oregon's westside landscapes with fire in mind

As wildfires become more frequent and intense, managing landscapes in Oregon's westside regions is crucial for both beauty and safety. The Oregon State University Extension provides key strategies for balancing fire risk reduction ...

Glenn Ahrens, Carrie Berger, Kayla Bordelon, Stephen Fitzgerald, Lauren Grand, Aaron Groth, John Punches | Aug 2024 | Collection

Managing Willamette Valley margin forests with fire in mind

Explore strategies to enhance fire resilience in the drier, mixed-severity fire-prone forests of Oregon's Willamette Valley margin. The brief emphasizes the importance of reducing fuel loads, creating defensible spaces ...

Glenn Ahrens, Carrie Berger | Aug 2024 | OSU Extension Catalog

Episode 46: Storm Damage (in English)

In this episode, Lauren Grand is joined by Glenn Ahrens and Scott Altenhoff to discuss the impact of storms on Oregon's forests and preventative measures that can be taken to mitigate tree damage caused by storms.

Lauren Grand, Glenn Ahrens, Scott Altenhoff | Mar 2024 | Podcast episode

The intriguing life of coho salmon and a conservation opportunity for landowners

Coho salmon rely on cool, connected streams, and private forest owners play a key role in their recovery. Learn how your simple restoration efforts can make a lasting impact on this threatened species.

Sarah Cameron, David Bugni, Glenn Ahrens | Dec 2023 | OSU Extension Catalog

Tree Health Webinar Series: Alder and Broadleaf Trees (in English)

As part of the Tree Health Webinar Series, Glenn Ahrens discusses the forest health outlook for alder and broadleaf trees, future projections in Oregon, and actions that landowners and managers can take for their trees.

Glenn Ahrens | Aug 2023 | Video

Tree Health Webinar Series: Douglas-fir (in English)

As part of the Tree Health Webinar Series, Dave Shaw discusses the forest health outlook for Douglas-fir, future projections in Oregon, and actions that landowners and managers can take for their trees.

Glenn Ahrens, David C. Shaw | Aug 2023 | Video

Tree Health Webinar Series: Why Are My Trees Dying?

As more trees die each year, these 30-minute webinars address current health issues impacting some of our common species, what it means for the trees, and what you can do.

Glenn Ahrens, Sarah Cameron, David C. Shaw, Christine Buhl, Laura Lowrey | Aug 2023 | Collection

Tree Health Webinar Series: True Firs (in English)

As part of the Tree Health Webinar Series, Laura Lowrey discusses the forest health outlook for true fir trees, future projections in Oregon, and actions that landowners and managers can take for their trees.

Glenn Ahrens, Laura Lowrey | Aug 2023 | Video

Tree Health Webinar Series: Western Redcedar (in English)

As part of the Tree Health Webinar Series, Christine Buhl discusses the forest health outlook for western redcedar, future projections in Oregon, and actions that landowners and managers can take for their trees.

Glenn Ahrens, Christine Buhl | Aug 2023 | Video

Treatments for bronze birch borer?

P: I had an arborist out because one of my birch trees had died and needed removal. He said it was the bronze birch beetle and that it was beginning to affect a second birch. He said it could be treated with a ...

R: View answer | View all featured questions

Episode 32: Tree School (in English)

In this episode, Scott Leavengood visits the 33rd annual Clackamas Tree School to interview Sarah Cameron and Glenn Ahrens about what the event is and why it's so beneficial.

Scott Leavengood, Sarah Cameron, Glenn Ahrens | Apr 2023 | Podcast episode

Episode 13: Woodland Management (in English)

In this episode, Jacob Putney discusses the importance of managing forests with Glenn Ahrens. Ahrens is an assistant professor for Oregon State University's College of Forestry and extension agent for Clackamas, Marion, and Hood River Counties.

Jacob Putney, Glenn Ahrens | Mar 2022 | Podcast episode

June 2021 heat impacts on trees explained

The June 2021 heat wave caused significant damage to trees in Oregon. Learn some key findings on causes, types of damage, physiological "thermotolerance" of trees, and possible forest management implications.

Glenn Ahrens | Dec 2025 | OSU Extension Catalog

Treatment options for young forest stands damaged by fire or ice

Fires and ice storms in recent years have done serious damage to young forest stands in the Willamette Valley. Without much salvageable timber, landowners must decide how to restore the stands. Here are some options.

Glenn Ahrens | Dec 2025 | OSU Extension Catalog

Why some trees can stand up to ice storms

The ice storm in 2021 in Clackamas and Marion counties provided lots of lessons about the kinds of trees that are vulnerable to weather damage. It also showed that well-spaced trees are stronger in the face of adversity.

Glenn Ahrens | Dec 2025 | OSU Extension Catalog

Oregon State University Extension Service

EC 1196  |  Revised June 2019, Reviewed 2023
View online: https://extension.oregonstate.edu/catalog/pub/ec1196

Selecting and buying quality tree seedlings

Amy Grotta, Glenn Ahrens and Max Bennett
Man planting forest seedling
EC 1196
Learn how to choose trees adapted for long-term growth under your local conditions.
Seedling health is crucial to reforestation. Timber producers want to choose trees adapted to local conditions and primed for long-term growth. Learn what qualities to look for.
Seedling health is crucial to reforestation. Timber producers want to choose trees adapted to local conditions and primed for long-term growth. Learn what qualities to look for.
View now

© 2019 Oregon State University. Extension work is a cooperative program of Oregon State University, the U.S. Department of Agriculture, and Oregon counties. Oregon State University Extension Service offers educational programs, activities, and materials without discrimination on the basis of race, color, national origin, religion, sex, gender identity (including gender expression), sexual orientation, disability, age, marital status, familial/parental status, income derived from a public assistance program, political beliefs, genetic information, veteran’s status, reprisal or retaliation for prior civil rights activity. (Not all prohibited bases apply to all programs.)

Accessibility: This publication will be made available in an accessible alternative format upon request. Please contact [email protected] or 541-737-3311.

Balancing tree growth and wildlife habitat

While it can be challenging to find the balance, there is much that we can do to meet our objectives for wildlife while controlling weeds and reducing fuels. Recent research at OSU can help us make informed decisions about some of the tradeoffs.

Glenn Ahrens | Jul 2024 | OSU Extension Catalog

How to Manage Your Forest - Module 1: Silviculture (in English)

Our first online training module covers Silviculture, or the art and science of managing forests to achieve your objectives, with nine sections to view.

Glenn Ahrens, Bob Parker, Paul Oester, Stephen Fitzgerald | May 2024 | Video

Identifying and Managing Mountain Beaver Damage to Forest Resources

The mountain beaver is a medium-sized rodent of the western Pacific Northwest. Mountain beavers cause damage to forest regeneration by clipping or girdling seedlings or saplings or both, and undermining roots. Methods...

Jimmy Taylor, Donivan Sphar, Glenn Ahrens | Jun 2021 | OSU Extension Catalog

A guide to riparian tree and shrub planting in the Willamette Valley: Steps to success

This guide to riparian tree and shrub planting in the Willamette Valley provides information on planning, materials, preparation, techniques, site maintenance and monitoring and evaluation.

Brad Withrow-Robinson, Max Bennett, Glenn Ahrens | Aug 2024 | OSU Extension Catalog

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