Oak Woodlands and Savannas

Habitat Description

Oak woodlands and savannas are habitats that are shaped by the presence of the keystone species, the Oregon White Oak tree. These trees alone provide habitat for hundreds of species of wildlife, creating a interconnected network of ecosystem services in a variety of systems. Oak woodlands are characterized by the presence of oak trees creating 30-70% canopy cover that is dominated by the oak tree species, with little competition from other conifers. Oak savannahs are sprawling grasslands with a few mature, old growth oak trees dispersed throughout the range.

These habitats have historically been adapted to frequent low severity disturbances of fires. Now they can be managed in ways to replicate the effects of low severity burns through prescribed fires, grazing, or mowing. This helps to manage the understory for invasive weed species and fast-growing conifers that will quickly grow to overtop the oak trees. Listen to learn about Growing Oaks at Willamette University (a Conservation Spotlight episode).

Vegetation

Oak trees need full sunlight to grow to their fullest potential. They cannot thrive with surrounding conifers that create constant shade. Typically found in lower elevations below 3800 ft, these habitats are found in the foothills of the Coast and Cascade ranges within the Willamette Valley, as well as from all the way -down to California up to Canada.

Associated plant species include Pacific madrone, Willamette Valley Ponderosa Pine, Oceanspray, Poison Oak, Western Serviceberry, Tall Oregon Grape, Beaked Hazelnut, snowberry , and more.

Ecosystem Services

Oak trees are able to provide habitat for wildlife in areas where habitat is otherwise sparse. The leaves, acorns, deep root systems, bark, branches and understory plants provide food and shelter for mammals, amphibians, insects, birds, and more.

This tree’s ability to tolerate both hot dry summers and wet cold winters, makes it the perfect species to resist drought and extreme weather events in the face of changing climate.

These habitats have been managed by humans far before European settlers found their way to the Oregon Coast. The Kalapuya Peoples have had a symbiotic relationship with these habitats for over ten thousand years, and continue to steward these ecosystems today. Tribes have subsisted on the food resources harvested from the understory plant species such as Common Camas, as well as the acorns themselves. They also regularly practice controlled fires to manage the understory and competing vegetation. Due to this human interaction, these habitats have historically been adapted to a frequent disturbance regime in order to thrive. Now that fire suppression has been imposed in the Valley for the last century, these habitats are in decline.

Threats

What were once the dominant habitats and landscapes found in the Willamette Valley, oak woodlands and savannas are now reduced down to less than 10 percent of what was here before development and increased human activity changed the landscape.

Fire suppression, land conversion, conifer conversion, and invasive plant species all contribute to the loss of these historic habitats in the Valley.

With 90% of existing oak woodlands and savanna communities in the private ownership in the Valley, the responsibility of restoring these crucial habitats falls on individual landowners in many cases.

Wildlife

Oak woodland and savannas provide habitat for over two hundred wildlife species in the Valley of all kinds. Some species that thrive in these systems include Acorn woodpecker, White-breasted nuthatch, Red-tailed hawk, Black bear, Deer, Long-eared bat, Gopher snake, Red-legged frog, and more.

In some cases, the white oak ecosystem provides habitat for specialist species, such as the Fender’s Blue Butterfly, that can only lay their eggs on Kincaid’s Lupine, found in Oak Savannas.

These habitats provide habitat for many plant, animal and insect species that are considered threatened and endangered, and in need of conservation to bring the species back to full populations.

How to Help Oak Woodlands and Savannas

• Control invasive species
• Enhance and restore native understory species
• Wildlife enhancement and creation of bird nesting opportunities
• Plant more oak in favorable conditions
• Release mature oaks from overcrowding conifers and undesirable vegetation
• Get in touch with someone from Our Team if you are interested in receiving assistance with your oak woodland or savanna.
• Listen to our episode of Conservation Spotlight to learn about current community engagement efforts to restore and save these habitats.

Where to Visit Oak Woodlands and Savannas

• Bush’s Pasture Park: located in the heart of Salem, this is a lovely park to visit to see the beauty of oak woodlands, especially during peak Great Purple Camas and Fawn Lily bloom periods in the spring.
• Baskett Slough National Wildlife Refuge: located ten miles West of Salem in Polk County, this is a special place to be able to view threatened and endangered plant species blooming in the spring.
• Champoeg State Heritage Area: Just North of Woodburn, this state park is scattered with oak groves and historically significant prairie and savannas that have been in the process of intensive management and restoration efforts in collaboration with various agencies including Institute for Applied Ecology and the Confederated Tribes of Grand Ronde.