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HJ Andrews Experimental Forest

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Long-Term Ecological Research at the H.J. Andrews Experimental Forest (LTER6)  (Oregon State University)

Research Focus

The Andrews Forest is situated in the rugged mountainous landscape of the Pacific Northwest. It contains excellent examples of the region's conifer forests, its wildlife and its stream ecosystems. 

When established in 1948, the site was covered by a mix of old-growth forest, 400-500 years old, and mature tree stands, 100-150 years old, born after wildfires. Beginning in the 1950's, a series of small watershed manipulations laid the foundation for research involving ecosystem function, vegetation succession, nutrient dynamics and forest-stream interactions. This research continues today. The old-growth forests were the subject of intensive basic research beginning in the 1970s, including the original work on northern spotted owl. In the 1980s, these basic studies were augmented with applied research in forest cultivation, wildlife, landscape ecology, carbon dynamics and other topics.

Since the 1990s the key research question has been: How do land use, natural disturbances, and climate affect three key ecosystem properties:

  • carbon and nutrient dynamics
  • biodiversity
  • and hydrology

Research Outcomes

Monitoring bird songs: Andrews Forest LTER researchers created computer technology that allows them to listen to multiple bird sounds at one time, to analyze how avian diversity may be changing as a result of habitat loss or climate change. The ecological monitoring system, one of the first of its type, is in many ways more practical than having a researcher sit in the field for hours on end.

Stream temperatures: An analysis of long-term data related to streams in the western United States found that, despite a general increase in air temperatures over the past several decades, streams are not necessarily warming at the same rate. The study points out the value of long-term data about streams that have experienced minimal human impacts, such as the streams being monitored at the Andrews Forest.

Old growth: Decades of research showed Andrews' scientists that old-growth forests, with their large, old trees and specialized plants and animals, are vital, unique components of a healthy landscape. This understanding has transformed the way we conserve and manage old-growth forests.

Ecosystem value of dead wood: Andrews' scientists revealed the importance of dead trees to diversity of animal habitat and the flow of vital nutrients in forests and streams. These studies profoundly influenced forest management.

Temperature patterns: Andrews' scientists discovered how cold air in mountainous terrain can sink into valleys and become trapped in the forest canopy. This creates a complex microclimate that is often disconnected from surrounding weather patterns and has important implications for how mountain forests will respond to climate change.

Education & Outreach

The Andrews Forest Education program provides an opportunity for undergraduate and graduate classes from regional and international schools to visit the forest for field courses, study tours and research experiences. K-12 programs give teachers the experience and skills to lead research projects with their students, and middle school students the unique opportunity to study the forest on the ground and in the canopy. 

Scientists at Andrews also created innovative programs that bring together scientists and writers, artists, philosophers and others, leading to new programs such as Long-Term Ecological Reflections, emulated widely.

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Images (1 of )

  • Close-up shot of Rosalia beetle (black with white bands) on a branch.
  • Tree stand, snow, two researchers working amid trees in mid-ground
  • Scientist releasing spotted owl in woods; owl is a blur in motion
  • One woman scientist waist-deep in stream, the other looking at a machine readout on the rocky bank
  • Old growth forest shot with blue-green hues
  • Small red cabin on a snow day, two snowmobiles in front
Rosalia funebris, the Rosalia beetle. Its larva bore into soft woods.
Jeff Miller
Fred Bierlmaier and Hazel Hammond surveying the instrumentation at a stand of Pacific silver fir and mountain hemlock with common beargrass.
Al Levno
Releasing a spotted owl.
Ken Hammond
Kathy Motter and Hazel Hammond doing flow retention measurements in Lookout Creek, Andrews Forest LTER.
Al Levno
Old growth cedar on McRae Creek, H.J. Andrews Experimental Forest
Al Levno
Vanilla Leaf Climate Station Winter service check by snowmobile, Andrews Forest LTER.
Al Levno