Tag Archives: Forestry

Keeping Oregon Forests Green: What Swiss Needle Cast Disease is Teaching Us About Forestry

I’ll never forget driving through the steep and windy I5 corridor of the Klamath Mountains when I moved to Oregon. Wet roads bordered by thick fog with protruding trees that were lusciously green. Very, very green. This concept of ‘Keeping Oregon Green’ started as a fire prevention act, and Oregon’s color is a quality that visitors and residents adore. Unfortunately there is sleeping giant that is gaining momentum, slowly turning Oregon’s forests from green to yellow with an eventual needle fall of the iconic state tree. This color change is from a microscopic fungus that all Douglas-fir trees have around the world, but for some reason it’s only harming the trees along the Oregon coast range. Our guest, a 4th year PhD student Patrick Bennett, is peeling away the layers of complexity to reveal why Oregon’s green forests are dwindling.

Aerial view of Douglas-fir stand with Swiss needle cast near Tillamook, Oregon. Chlorotic (yellow) foliage is a major symptom of the disease.

Douglas-fir needles with pseudothecia (fruiting bodies) of the fungus (Phaeocryptopus gaeumannii) emerging from the stomata.

It is estimated that Swiss Needle Cast disease is affecting nearly 1,000,000 acres in Oregon and Washington alone leading to economic losses estimated at $128 million per year. The fungus covers the stomata, openings in the needles, used to exchange air and water essential for plant metabolism. As more of these stomata become clogged the tree cannot make enough glucose so the needle dies, turns yellow, and eventually the needle falls off entirely. Douglas-fir trees typically keep needles for five years, but in heavily affected areas the needles last one year before falling off leaving the tree extremely thin and frail. Even though the fungus does not directly cause death, it leaves our iconic state tree highly susceptible to drought, beetles, nutrient limitations, and wildfires.

This disease was first discovered in Switzerland, hence the name Swiss Needle Cast, in the 1920’s. At that time it was only negatively affecting Douglas-fir trees planted outside their native habitat. But since the 1980’s the natively planted Douglas-fir trees, within a narrow band parallel to the coast range, are showing annual growth decreases by as much as 50%. Recently there have been advancements in molecular biology and computing power that allow researchers to identify the genetic heritage of pathogens. Using these tools scientists can focus on population genetics to figure out why there is such a discrete area affected along the Oregon coast range. Some evidence points to  warming winters and fungal-subspecies expansion as reasons for the spread of this fungal disease. But Patrick has indications to suggest it’s death by a thousand cuts and begs the question of whether the future of forestry is in danger.

Growing up in southern California Patrick wasn’t exposed to the forests he studies today. It wasn’t until he attended Humboldt State University where he got his first exposure to towering canopies and ecology. His first research experience was in the Lassen Volcanic National Park in California where his advisor, Dr. Patricia Siering, pushed him to develop his own scientific study. Needless to say he was hooked on science and after taking a mycology class he also knew he was jazzed on studying mushrooms so he continued his passions that lead him to Oregon State University.

Dr. Patricia Siering (Humboldt State University – Biology Department) collecting boiling hot sulfuric acid from Boiling Springs Lake in Lassen Volcanic National Park in Northern California with the help of undergraduates and graduate students.

Patrick Bennett is a 4th year PhD student in Dr. Jeff Stone’s lab in the department of Botany and Plant Pathology housed in the College of Agricultural Sciences where he is investigating how population genetics can be used to better understand the factors contributing to the recent emergence of Swiss Needle Cast as a damaging forest pathogen in the native range of Douglas-fir. Be sure to tune in Sunday April 30th at 7PM on KBVR Corvallis 88.7FM or by listening live.

Horse Farms to Tree Farms: Studying the Relationship Between Land Management and Biodiversity

If you wander forests of the Oregon Coast Range you might encounter a strange sight: exclosures made of timber and steel-braided wire, standing in a clear-cut forest. These exclosures, which stand 100-feet long, 50-feet wide and 8-feet high, are the research and work of Thomas Stokely, a PhD candidate in the department of Forest Ecosystems & Society in the College of Forestry. The exclosures were constructed to study the impact of deer and elk grazing on tree growth, and to address a larger research question in forestry management: What does intensive forest management mean for biodiversity?

Completion of exclosure construction in the Oregon Coast Range

Completion of exclosure construction in Oregon Coast Range

To study the impact of deer and elk on commercial tree growth, Thomas constructed constructed 28 stands in which a team of researchers manipulated the intensity of herbicide spray treatments in each area (non-sprayed, light, moderate and intensive herbicide treatments). For six years, under the direction of his adviser Matthew Betts, Thomas and has measured plant communities, arthropods, herbivory and plantation development inside these exclosures and in open plots where wildlife is allowed free access.

Thomas Stokely cutting fence rows through logging slash and large stumps to construct wildlife exclosures

PhD student, Thomas Stokely cutting fence rows through logging slash and large stumps to construct wildlife exclosures

The exclosure research in the Oregon Coast Range relates to Thomas’s goals as a scientist who’s invested in understanding how industry impacts biodiversity. “As the world population grows, we need more resources,” he said. “We want to value the product, but we also value biodiversity and wildlife habitat. Is there a way we can manage for both timber production and wildlife habitat? If so, what role do biodiversity and wildlife play in the management of natural resources? If management alters biodiversity or excludes wildlife, what are the implications for ecosystem functioning?” These are questions that continue to drive his research and his career path.

Mature Roosevelt elk bulls browsing through a plantation with exclosure in the background

Mature Roosevelt elk bulls browsing through a plantation with exclosure in the background

Thomas has been interested in plant-animal interactions and the environment since he was a child. Growing up on a horse farm in southwest Missouri, he watched horses grazing and wondered about their relationship with the habitat in and around the farm. He first considered studying the policy side of humanity’s relationship with the natural world, but political science wasn’t a good fit—he wanted to pursue a more hands-on approach to studying biodiversity. After reading about the reintroduction of wolves in Yellowstone, he knew he wanted to work directly with land and habitat management. He earned a BS in environmental science at University of Missouri before coming to Oregon State. Upon completing his PhD, Thomas plans to work in applied ecology where he hopes to use science to guide land management and conservancy practices.

Tune in to hear our conversation with Thomas Stokely on Sunday, November 13th at 7:00 pm on 88.7 FM KBVR Corvallis or listen live online