Exploring the use of herbicide in forest management

How much should be used? Does it help production or hurt it? Is it good for the economy or not? And with global demand for wood resources expected to increase by up to 40% in the next 15 years, answers are needed.

Matt Betts, an associate professor of forest, wildlife and landscape ecology at the Oregon State University College of Forestry, is working to provide those answers through a project funded by landowners, the USDA, the National Council for Air and Stream improvement and the Institute for Working Forest Landscapes (IWFL).

The IWFL was launched in 2013 by the OSU College of Forestry to focus research programs on innovative approaches for managing landscapes that will enhance people’s lives and improve the health of our lands, businesses and vital ecosystems. The IWFL develops adaptive forest management techniques that integrate social, ecological and economic objectives at the landscape level.

Betts says the money contributed by the IWFL allows the team to spend about a year putting together the results of the research.

“Without this funding, we wouldn’t have been able to continue for so long and put the data together to get results,” Betts says. “Herbicide use and early seral forests are two of the most important topics in forest management right now, and we’re hopeful our results will help inform those controversies.”

He says this research looks into what levels of intensive forest management are best to optimize timber production and other ecosystem services such as wildlife conservation, pollinators and other aspects of biodiversity.

“By collecting data on all these different attributes in young forests, we can look at the relationship between timber production and different services of the forest,” Betts says.

While this particular study began in 2015, Betts already had six years of data on tree growth through a well-designed experiment. He says that by 2018, the team will be able to model future tree growth and will have extensive data on other services as well.

The Betts’ study, entitled “Quantifying Trade-offs and Synergies Between Ecosystem Services in Intensively Managed Forests,” is the first of its kind to apply a true experimental approach to addressing pressing research questions in young, managed forests. The project also is unique in its ambitious sample size (32 full-size forest stands distributed across Oregon’s northern Coast Range).

PhD student Thomas Stokely has been assisting the project for six years. He focuses on food-web dynamics.

“We want to know how herbicides influence tree growth and other factors,” Stokely says.

Stokely and Betts hypothesize that while deer and elk don’t eat much Douglas Fir, they do enjoy munching on plants, weeds and other growth that herbicides kill. When managers use herbicides, sometimes deer and elk resort to munching on young Douglas firs. However, if managers cut back on herbicide use, the animals might have more to eat besides the small limbs of highly-valued trees.

“So far, we have evidence of an ecosystem service where the hardwoods are retained when you spray less herbicide,” Stokely says.