Glenn Ahrens, OSU Forestry and Natural Resources Extension Agent – Clackamas, Marion, and Hood River Counties

At Hopkins Demonstration Forest we have an area of maturing forest – 80 or more years old – that we would like to manage with continued thinning or selective cutting rather than clearcutting. As I discussed in Part 1 of this story, this is a common situation for family forest owners. Many are interested in periodic selective harvesting of trees or small patches and keeping options open for the future. There are many challenges and tradeoffs to consider, but now we have to choose an option for our Hillside Forest stand at Hopkins.

Like many woodland owners, we have to balance the need for revenue with our other goals for aesthetics, recreation, and wildlife. In our case, goals for education and demonstration are also a high priority. This year in particular, we have major financial challenges to sustaining our woodland enterprise due to the COVID-19 pandemic. We have accumulated valuable timber inventory over the years since we don’t cut all of our annual growth. So, we are considering how much to draw upon our timber account to get us through hard times. And what kind of silvicultural options do we want to demonstrate in the process?

Forest Stand Conditions – The forest stands in question are two units of similar size, collectively called the Hillside Forest, occupying about 25 acres on the slope from hilltop (700 foot elevation) to stream bottom (400 foot elevation). The stands are composed of second-growth western redcedar and Douglas-fir regenerated after logging in the late 1930’s. The stands have been thinned three times over the last 30 years, maintaining many well-spaced trees with good crowns. They should be relatively stable when they are retained after thinning. There are also clumps of intermediate canopy trees and scattered gaps with brush and bigleaf maples. Current stand density is approaching the upper end of the “optimal management zone” based on average DBH (22 inches) and trees per acre (100). Read more about competition levels and on this approach to density management here.

80-year-old stand of Douglas-fir on upper slope of Hillside Forest at Hopkins.

The forest type changes from a drier Douglas-fir/cedar stand on the upper slope to a more moist cedar dominated stand on the lower slope. While cedar grows a little slower than Douglas-fir, it is now a major co-dominant component of our forest because of the residual cedar left after logging in the 1930’s (many of the cedars are over 100 years old now). Shade tolerant cedar provides the opportunity to manage for regeneration and multiple aged cohorts with thinning and smaller gaps, while Douglas-fir requires larger openings for good regeneration.

Denser patches of western redcedar targeted for thinning in Hillside Forest.

Goals and Objectives – Hopkins is managed to provide an “accessible example of sustainable forestry” and to support “science-based education to enhance understanding of, and appreciation for the complexities and benefits of woodland management.”  It is a working forest managed for multiple objectives including:

  • hands-on woodlands education for diverse audiences,
  • timber resources and revenue from timber harvests to help support the organization,
  • wildlife and fish habitat to accommodate a diverse natural fauna,
  • soil and water resources to maintain or enhance soil productivity and water quality,
  • and recreation opportunities, in conjunction with project development and educational activities.

For the Hillside Forest stands, we are focused on demonstrating the “complexities and benefits” of trying to meet all objectives in one stand with thinning and selective management of a mature forest. On the majority of the Hillside Forest, we are planning a relatively light thinning, removing about 25% of the trees and a similar portion of the standing volume, to reduce stand density to the lower end of the “optimal density management zone”. Such that the trees we leave should be able to refill the growing space. While we are at it, extra work to clear some of the brushy gaps and provide new regeneration of cedar is also planned. In one area of about 5 acres, where trees are widely spaced and there are more brush-filled gaps, we will cut most trees and regenerate a mix of Douglas-fir and cedar. The target for timber volume removal is about 4,000-5,000 board feet per acre in thinned areas and 15,000-20,000 board feet per acre in the larger clearing.

A key question for the longer-term is how long to continue thinning the large overstory trees and whether or not to do more regeneration harvesting to start new stands of Douglas-fir. Theoretically, we could just keep thinning the overstory and grow the stand from the current 22 inch average diameter to 30 inches (~30-35 years out) or 40 inches (~70-80 years out), at which point about 30 to 35 trees per acre would fully occupy the site. Another option is to convert some areas to uneven-aged management, with individual tree selection to regenerate cedar, along with larger patches (>3 acres) of regeneration harvest to provide new cohorts of Douglas-fir. For now, the plan for most of the Hillside Forest is to maintain individual tree crown vigor with thinning and keep options open for continued thinning or uneven-aged management in the future.

Scattered clumps of younger trees along with brushy gaps in Hillside Forest.

Tradeoffs and Costs – Felling and yarding tall timber (100-140 feet tall) while protecting residual trees  requires careful and skillful operations. That and the relatively low volume removed per acre will increase logging costs compared to clearcutting. But the larger, older Douglas-fir and especially the cedar have potential to be higher value. In terms of timber value, cedar logs are even more valuable than Douglas-fir ($1,000-1,500/mbf vs. $500-800/mbf delivered log prices over the last ten years). We also hope to produce higher value Douglas-fir sawlogs and transmission poles with this mature-forest management system.

While the planned thinning is relatively light, there is still a risk of loss or damage to residual trees from sudden exposure to sun and wind. The cedar may be particularly vulnerable to sun and heat exposure, which seems to be an increasing challenge for cedar at low-elevations in the Willamette Valley margins. There is also the potential for damage to soils, roots, stems, and crowns during thinning, especially with the large size of some trees being felled and yarded.

Help is needed to measure and mark trees for the thinning at Hopkins Demonstration Forest.

Educational opportunity – In keeping with our objective for hands-on woodland education and “learning while doing”, we would like to involve people in preparation and execution of the thinning project. Tasks include meeting with foresters, log buyers, and loggers to develop the operational plan for access, skid trails, and tree selection. We need help conducting pre-harvest inventory, marking stand boundaries, and selecting and marking which trees to leave or cut to meet our thinning target. Given the challenges of in-person events during the COVID-19 pandemic, we anticipate limited opportunities for a few people at a time in the woods. We also would like to capture some of the work on video to share with others online. If you are interested in participating, please contact me at To follow our progress, stay tuned for the next installment of this story.

We are pursuing this more challenging and costly style of management to see if we can “have it all” in one beautiful 25-acre hillside forest – timber revenue, species diversity, mature forest habitat, recreation value, and public education. Whatever happens, we will learn from the process.

Brad Withrow-Robinson, OSU Forestry & Natural Resources Extension for Benton, Linn and Polk Counties.

I talked to my friend Philipp in Portland the other night. We were checking in on family, comparing notes on how each are doing under the Stay Home order.  The big beneficiary at their house is the dog, Coffee, who has his four people at home and who seem unusually willing to take him for a walk.  Phil was also laughing that his yard had never been so free of weeds. 

Weeds had never been one of Philipp’s priorities.  Until now.

I have noticed that many rural landowners look at Fire Preparedness much like Phil looks at weeds.  In fact, many rural landowners are much more aggressive about clearing their home place of weeds, than they are about clearing their home place of fire hazards. 

Left: Three Zones of Defensible Space.  Image from:

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Brad Withrow-Robinson, OSU Forestry & Natural Resources Extension for Benton, Linn and Polk Counties.

Family woodland owners (like farmers, ranchers, beekeepers and others) typically have busy spring schedules with lots to do in the woods.  Many of those activities come with acres of physical distancing  from others outside their families, so life remains busy.

Although our offices are closed, OSU Extension remains an available and useful source of information for doing many spring woodland activities such as weed control, fire preparedness and prevention, developing wildlife habitat.  We remain available by phone or email to answer questions and direct you to the information you need.  

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Brad Withrow-Robinson, Forestry & Natural Resources Extension, Benton, Linn and Polk Counties. Photos Jody Einerson, Benton County Extension.

Backpack sprayers are often used to apply herbicides to control weeds in forestry and conservation work.   It is often helpful to apply two or more chemicals at a time in a “tank mix”.  For example, it is common to apply a foliar herbicide to kill actively growing weeds, along with a soil active herbicide to prevent new weeds from emerging over the following growing season.  Or it may be useful to apply two different herbicides with similar action, but that target different types of weeds (grasses v broadleaf plants).  Be sure to review the post on calibrating a backpack sprayer.

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Brad Withrow-Robinson, Forestry & Natural Resources Extension, Benton, Linn and Polk Counties. Photos by Jody Einerson, Benton County Extension.

In many of our herbicide application situations, the objective is to treat an area, such as a plantation of young trees, at a specific application rate.  By rate, we mean applying a specific amount of a material over a given area (e.g. ounces of product per treated acre).  This is essential when applying soil active herbicides, and also for area treatments (as opposed to targeted spot treatments) with foliar herbicides, particularly if the spray mix will be contacting the seedlings, such as in “over the top” applications. Applying too little material will not give you effective weed control, wasting time and money.  Too much material risks killing seedlings and other desirable plants, or causing other environmental damage.  Figuring out how much spray you are applying so that you can calculate how much herbicide to mix into the spray tank is called calibration.

Once you have calibrated your backpack sprayer, you can apply spray in any number of patterns, and still be putting out an accurate amount of material on a per acre basis.  That means you can accurately treat the entire plantation (broadcast), or discreet parts of that plantation such as row strips or patches around trees with confidence. 

Calibration requires a few simple activities and calculations, in two steps.  Here is a simplified refresher:

Step 1: Find the Application Rate (Gallons/Acre, gpa) you apply

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Brad Withrow-Robinson, Extension & Natural Resources Extension agent for Benton, Linn and Polk Counties.

Spring is the key time to tackle many non-woody weeds.  These non-woody (also called “herbaceous”) plants  include grasses and many common flowering plants including clovers, thistles, oxeye daisy, tansy ragwort and groundsel.  There are many native and also non-native herbaceous plants in the fields and forests of Oregon.

Taking care of unwanted plants/weeds in often an important part of taking care of your land.  Herbaceous weed control if often part of these common objectives:

  • Successfully planting tree and shrub seedlings
  • Reducing fine fuels defending against wildfire
  • Enhancing forest diversity/improving wildlife habitat
  • Easy access and enjoyment of your property
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UPDATE (May 6)

Due to COVID , Amy’s family has Postponed the Celebration of her life event that was scheduled for June 2020.  We will continue to update information about this and other activities at the bottom of this blog post.

As many readers in the north Valley are aware, our friend and colleague Amy Grotta passed away in late December in Portland.  Amy had been living with cancer for a number of years and her fighting spirit had been an inspiration for all of us.  She was an incredible human being, deeply respected and loved by all who knew her.  We will carry her memory with us always.

Amy was the OSU Forestry & Natural Resources (FNR) Extension agent in Columbia, Washington and Yamhill Counties.  I had the pleasure and good fortune of working with Amy for ten years since she joined FNR Extension.  Since we worked in adjacent Counties with many similarities in climate, forest types, and audiences, I guess it was natural for us to collaborate on projects.  We shared writing for the Tree Topics Blog and our individual newsletters, designed and taught many classes and events together. She was very talented and such a pleasure to work with.  Amy was an inspiration to me.

Amy had a strong passion for her work that came from a deep love of the natural world, and a commitment to helping people better understand and care for it. Amy was compassionate, unflappable, inclusive, and organized.  She liked to involve people, build community and get things done.  

Amy leaves a void in the lives of her family, colleagues and communities of which she was such a part.  There will be a celebration of life this summer, and other events in her memory will be organized in the future, such as work parties at the Matteson Demonstration Forest.  A memorial fund has been established to help continue her work there. I have included more information about that and about Amy’s life below. 

Brad W-R

Amy Grotta Obituary

Amy Grotta, 49, died December 24, 2019, in Portland, Oregon, after a four-year battle with chondrosarcoma. 

Amy was the wife of David Dreher, mother of Anna (17) and Eben (13), daughter of Emily Grotta and James Grotta, step-daughter of John Boudreaux and Kathy Dreyfus, and sister of Jacob, Andrew and Ben Grotta.

Amy was born in Charlottesville, Virginia, and moved around quite a bit as a child, living in Israel, New York, Mississippi, Colorado and Massachusetts. Eventually her family settled in Houston,Texas, where she graduated from Bellaire High School in 1988. Amy was an honor student, a talented gymnast, editor of her high school yearbook, and active in many high school clubs and youth organizations. 

Amy attended the University of California, Berkeley and graduated in 1992 with a bachelor’s degree in Conservation and Resource Studies. After graduation, she moved to Vermont where she worked as a wilderness trail crew leader, farm hand, gymnastics coach and high school teacher. In 1996, Amy left Vermont for the Peace Corps and spent two years working in rural Paraguay as an agroforestry technician and travelling with friends and family to Chile, Bolivia, Argentina and Brazil. 

After completing her Peace Corps service, Amy returned to Vermont and married David Dreher. Shortly thereafter, they moved to Corvallis, Oregon and Amy began graduate school at Oregon State University. After receiving her master’s degree in Forest Science in 2002, Amy was hired by Washington State University Extension as the forestry agent for King County. In 2008, Amy and her family returned to Oregon when she joined the Oregon State University Forestry & Natural Resources Extension as an assistant professor in the Department of Forest Ecosystems and Society. She became a tenured associate professor in 2015. 

Amy was a passionate educator who engaged effectively with the family forest landowner community as the Forestry and Natural Resources Extension agent for Columbia, Washington, and Yamhill Counties. She actively supported a group of Master Woodland Managers, members of the Women Owning Woodlands Network, three local chapters of the Oregon Small Woodlands Association, and the Oregon Woodlands Cooperative. Amy succeeded as an educator largely because she was not only knowledgeable but also very approachable. She embraced the challenges of working in a very diverse area and was equally at ease working with rural forest landowners, discussing rural/urban interface issues, or helping Portland neighborhoods maintain a healthy urban forest. These skills made her an effective, well-respected, and welcome leader among her colleagues.

In her work Amy sought to include and empower the people she worked on behalf of through her involvement in a number of citizen science initiatives. She was the driving force for the Oregon Forest Pest Detector program, a collaboration with several state agencies that trains volunteers to monitor for the arrival of invasive insect species. She was given the Vice Provost Award for Excellence, OSU Outreach & Engagement for her work on the program in May 2019. Her efforts with the Oregon Season Tracker program, which involves community members in climate science research through observations of precipitation and phenology, were recognized in September 2019 with the OSU Extension Association Search for Excellence award. Most recently she had been very involved with the Oregon Bee Atlas in their efforts to involve family forest owners in studying and understanding the role of wild pollinators in Oregon. Every project Amy was involved in benefited greatly from her participation. 

Amy’s neighbors and friends knew her as an avid gardener, a strong parent, and a lifelong lover of nature and wilderness who was always looking forward to the next adventure. She will be greatly missed by friends, neighbors, family, and colleagues. 

Celebrating Amy’s Life & Work

Amy’s family will reschedule Amy’s celebration of life the event from June 2020 to some future date, still to be determined.  We will do our best to update her friends and colleagues in the woodland and forestry communities as details emerge.  If you would like additional details for the celebration, please email Details will also be shared on Facebook through the In Memory of Amy Grotta group.

Amy’s passionate work at the Matteson Demonstration Forest will be carried on.  The local woodland owner community and the OSU College of Forestry are making plans for building an educational trail dedicated to Amy’s memory.  Volunteer crews will be organized when COVID restrictions allow.  In the meantime, folks in the Columbia and Washington County OSWA Chapters are busy in their home workshops building benches that will eventually be placed on the trail.

One of several benches being made for Amy’s trail.

Donations in memory of Amy may be made through the OSU Foundation. In alignment with Amy’s values and life’s work, all donations will be used to support the research, outreach and education activities of the OSU College of Forestry. Please send donations to: OSU Foundation, 4238 SW Research Way, Corvallis, OR 97333-1068. Please include this form with your donation and state that it is “in memory of Amy Grotta” and for the College of Forestry. If you are including a check, please write “College of Forestry, in memory of Amy Grotta” on the memo line of your check.  

For online donations, please visit the OSU Foundation’s Giving page. To ensure your donation is tracked correctly, 1) choose the ‘College of Forestry’ on the “Direct my gift to a specific OSU College or Campus” AND 2) put “In memory of Amy Grotta” in the comment box.   

By Amy Grotta, OSU Forestry & Natural Resources Extension – Columbia, Washington & Yamhill Counties

Slash is the term used to describe the treetops, limbs and other woody material left behind after a timber harvest. The amount of slash left behind will depend on several factors, including the size and quality of the harvested trees. Universally, how the slash is dealt with is an important consideration in the logging process. Heavy amounts of slash left on the ground can be a fire hazard and it makes tree planting more difficult and more costly.

Piling and burning is the most common method of slash treatment nowadays. However, some landowners are looking for alternatives to burning for various reasons. Pile burning can be challenging due to weather conditions or smoke restrictions. When logging contractors are busy, they may be reluctant to include pile burning in their contract due to the time involved, leaving it up to the landowner. And, there are greenhouse gas considerations with burning slash. For all of these reasons, it is worth looking at the pros and cons of other methods of slash treatment.

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By Amy Grotta, OSU Forestry & Natural Resources Extension – Columbia, Washington & Yamhill Counties

Back in February I introduced readers to a new initiative that OSU Extension has begun to learn more about how native bees use managed forests. Our first season of data collection is now in the books. I’d like to explain a bit more about how we designed this project and some early takeaways.

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Glenn Ahrens, OSU Forestry and Natural Resources Extension Agent – Clackamas, Marion, and Hood River Counties

Many family forest owners I meet have older trees and forests – 60 to 80 or more years old – and they would like to retain mature forest conditions. They are interested in periodic thinning, selective harvesting of trees or small patches, and keeping options open for the future. But landowners with larger older timber often hear that they are better off, from an economic and operational standpoint, to clearcut a patch and regenerate it all at once.

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