The use of herbicides in forests is a controversial topic in Oregon, throughout the country and the world. For the past eight years, Oregon State professor of landscape and wildlife ecology Matthew Betts and his research team have studied them closely, in a study partially funded by the college’s Institute for Working Forest Landscapes. The research team paid close attention to the effects on wildlife and timber production.

“This study is relevant locally because herbicide use is commonly-used on Oregon Department of Forestry and industrial lands,” Betts says. “In the Pacific Northwest, it’s the primary silvicultural method that follows clearcutting.”

Betts says the topic is becoming relevant globally as herbicides become more popular in plantation forests worldwide. Currently, about 35 percent of timber comes from plantations, and in the next 50 years, experts project that most timber will come from this source. Betts believes now is the time for forest managers to have adequate scientific information to inform decisions about whether or not to use herbicides.

His study on intensive forest management is the largest of its kind in the world. The research team worked together with industry and the State of Oregon to study 32 stands of 15 acres or more with four different levels of herbicide treatments ranging from no treatment at all in the control group through more heavily treated stands similar to those in a commercial setting, and an extreme treatment that exceeds current spray practices.

Stands that have or haven’t been treated with herbicides can usually be recognized based on the amount of vegetation growing at the foot of young forests whose canopies haven’t yet closed. Untreated forests tend to have green floors, whereas heavily treated forest floors are initially quite bare.

Eight years into the experiment, Betts says the saplings they started with are huge in relative terms. The research team has also learned how herbicides affect various species of plants and animals within the forest.

“There’s little doubt that on the timber side, trees grow faster when herbicides are sprayed,” Betts says. “Our study shows that the most heavily sprayed stands produce up to 30 percent more volume, but there is an effect on biodiversity.”

The study measured herbaceous plants, birds, pollinators such as bees, deer, elk, moths and other insects.

“There were more bird species in areas where we didn’t spray herbicides,” Betts says. “Wilson’s Warbler was one of the most affected species. We also saw depressed numbers of pollinators. Surprisingly, we did not detect much of a change in populations of deer, elk and moths.”

Betts says that around year five of the study, for the most part, the number of species began to equalize and recover.

“Even the heavily-sprayed stands began to turn green,” he says. “In the end, some species responded negatively, some species have been resilient and some responded negatively and then recovered.”

Land managers pay up to $200- 250 per acre for herbicide spray. Money is spent up front and not returned until stands are harvested at age 40-50.

On the economic side of the study, the research team concluded that herbicide isn’t cheap, and that spraying does not always generate additional financial value.

“You could spend $250 per acre now, or invest that money in a bank somewhere. If your expectation is a financial yield of seven percent or greater, we’ve found that it doesn’t make economic sense to spray, all other things being equal,” says Betts.

He emphasizes the study saw no failed stands or plantations, and valuable biodiversity tended to increase without herbicide use. The research team will continue to monitor the stands up to the 15-year mark when the canopy will start to close, limiting sunlight to shrub species. They also plan to survey the general public about aspects of the study and perceptions about herbicide use.

That’s where Mark Needham, Oregon State professor of social science, policy and natural resources, comes in.

“We began surveying in early 2019,” Needham says. “We’re focusing on a number of small, rural communities in the coast range near the stands in the study. We plan to ask residents about their knowledge, attitudes and perceptions associated with the herbicide issue. We hope to survey at least 400 people.”

Instead of asking one-off questions, Needham says that in this context, it’s important for survey respondents to make tradeoffs and prioritize their interests.

“This study spans so many different areas including wildlife, soil, water, pollinators and economic impacts, so it’s important to make sure we look at the tradeoffs people are willing to make within the context of herbicide use,” Needham says.

Betts agrees land managers and the general public need to decide if they want forests with more biodiversity but less timber growth per acre, or less biodiversity and high rates of timber production.

“Without spray,” he offers, “you need to spread out forestry operations to get the same amount of lumber. With spray, you have more tightly-packed and intensely managed stands, which can potentially free up land for conservation.”

Betts realizes these are hard decisions. “The results of this study are just not as straightforward as we expected them to be,” Betts says. “We hope this science will help managers and the public make educated decisions about herbicide use amid the controversy.”

Oregon State University is one of two sites for the Wood-Based Composites Center (WBC), an industry and university cooperative research center funded by the National Science Foundation. The other is Virginia Tech University. The two institutions work with academic and industry partners to advance the science and technology of wood-based composite materials. The center completed a number of research projects in FY 2017 and FY 2018 that will lead to wood product innovations and improved performance.

Micron level 3D visualization of adhesive bonds in wood products

For the first time, researchers achieved a true characterization of the micro-structure of adhesive bonds in wood.

Laminated wood products, like glulam beams and plywood, rely on the integrity of adhesive bonds that are only a few microns thick. Adhesives penetrate the porous structure of wood. This project asked the question, ‘does the extent of penetration affect mechanical performance of the final product?’

Fred Kamke, director of WBC and JELD-WEN Chair of Wood-Based Composites Science, says the goal of the project was to observe how adhesive bonds perform when subjected to mechanical loads and moisture, focusing on the analysis on the adhesive bond.

Richardson Chair in Wood Science and Forest Products, John Nairn, created a mathematical model to predict mechanical performance of an adhesive bond based on its microstructure. Kamke and his graduate students collected the 3D microstructure data and used micro and nano x-ray-computed tomography to create 3D digital models of adhesive bonds. While wood is an extremely porous structure that readily absorbs adhesives, the researchers found that as much as 50 percent of the adhesive that penetrates the cell lumens may not contribute to bond strength. However, penetration of adhesive into the cell wall helps to stabilize the bond against the effects of moisture.

“Cell wall penetration improves the moisture durability,” Kamke says. “With this information, adhesive companies can improve their formulations and create adhesives to be engineered for a particular application, saving money for the manufacturers and improving performance of the products.”

Natural formaldehyde emissions from wood

Some adhesives, such as ureaformaldehyde, emit low levels of formaldehyde over their lifetime as they slowly decompose. Modern adhesive formulations and test protocols ensure these levels fall within the acceptable federal guidelines. However, as formaldehyde detection technology improves, the adhesive industry faces pressure to reduce formaldehyde emission levels.

Kamke says there are still many unanswered questions about formaldehyde.

“People wonder if formaldehyde is in their house,” he says. “Can it cause us harm? How much formaldehyde is OK? How low should emissions be? Although we don’t know have all of the answers to these questions, government regulations still need to be met.”

What researchers do know is that many substances, including human bodies, other animals and natural materials like wood, emit low levels of formaldehyde naturally.

Chip Frazier, Virginia Tech professor of sustainable biomaterials, wanted to learn exactly how much formaldehyde pure, natural, virgin wood does emit. The tests showed how formaldehyde levels in different wood species are affected by temperature change, and what formaldehyde levels are derived from wood itself.

“This data establishes a baseline level of source formaldehyde from wood, and will likely have a significant impact on future federal indoor air quality policy and the future of wood-based composite products, because just particleboard and fiberboard production alone is a $1.6 billion industry in the United States,” Kamke says. “This study and the resulting policy changes will have impacts on everyone involved in bonding wood with adhesives, and will have a positive impact on future indoor air quality across America.”

Outreach work continues

The WBC continues to educate the public through traditional classroom and online short courses. Seven online courses were added in 2016.

Kamke says the most popular is a basic course on wood adhesives that’s been running for 15 years.

“Our plan is to add more online courses,” Kamke says. “Enrollment is growing, and we are proud to continue to educate the producers and the public about the wonderful world of wood-based composites.”