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Home , Fir, Oak, Quercus garryana

PNW Research Station

I n s i d e Invasion ...... 2 Answers About ...... 3 Regeneration ...... 4 Predicting Oak’s Future ...... 5 FINDINGS issue ninety eight / december 2007 “Science affects the way we think together.” Lewis Thomas

MOVE OVER, DOUGLAS-: WHITE NEED ROOM TO GROW

i n S UMMA R Y Oregon white oak and woodland habitat in the Pacific Northwest has declined to less than 10 percent of its former range, and much of what remains is of poor quality. In addition to and agricultural development, habitat is being lost to that have invaded oak areas, which were once maintained through frequent burning by Native Americans. The conifers eventually overtop and kill the shade-intolerant oaks. Many landowners, conservation groups, and public agencies are interested in restoring the cultural legacy and biodiversity associated with oak habitat. Until recently, however, there has been little specific information available on the effects of management practices to guide their actions. D. PeterD. Many landowners, conservation groups, and public agencies are interested in retaining the cultural The Oak Studies Group at the PNW Research legacy and biodiversity associated with Oregon white oak habitat. Station laboratory in Olympia, , has been building a body of research to aid the “Our route has been through reverse a long-standing trend. And not a restoration of oak habitat. They have shown that the complete removal of overtopping conifers— what might be called a hilly moment too soon. Oregon white oak, also called Garry oak, now exists on only a as opposed to partial removal previously country, the grass mostly fraction of its former range in many areas, suggested—is the best way to increase stem burned off by recent fires, and and the woodlands and that growth, promote new , and bolster the whole country sprinkled remain are largely in poor condition. production. An updated growth model with oaks, so regularly dispersed Oregon white oak habitats have been in predicts that many oaks will die unless released as to have the appearance of a trouble since the mid 1800s. The moist, from overtopping conifers. By recruiting continued orchard of oak .” well-drained soils that are found in val- volunteers from to —Henry Eld, Wilkes Expedition, ley bottoms and support the best oak for an annual acorn count, the researchers 1841, near Independence, Oregon habitat also create the most valuable have found that the best acorn producing trees farmland. So, not surprisingly, agri- have wide crowns, few competitors, and grow t’s beginning to look like Oregon white cultural development and urbanization in moist, well-drained soils. When planting oak th oak will get an 11 hour reprieve. have supplanted most of the prime oak seedlings, the group stresses the importance of I Throughout the Pacific Northwest, a habitat. What’s more, ever since Native initial seedling size and post-planting treatments fledgling campaign of oak research and Americans stopped regular burning to control weeds and prevent animal browsing. restoration is taking and beginning to through the valleys and foothills, conifer trees—primarily Douglas-fir—have been steadily encroaching on the oak’s territory. K EY FINDINGS Without frequent fires to keep them in check, fast-growing conifers eventually overtop and • The effect of releasing oaks from overtopping Douglas-fir was greatest when all nearby ultimately kill the sun-loving oaks. conifers were removed. During the 5 years after release, oak stem growth and acorn production increased, and the formation of new branches increased the size of the Oak habitat is now a rare sight in a landscape crowns. Oak trees with relatively large crowns prior to release responded most rapidly. replete with conifers. Connie Harrington, There were no symptoms of shock or other negative effects of release on oak trees. a research forester with the PNW Research Station in Olympia, Washington, believes • Oaks are found in many habitats, but the best acorn producers have wide crowns, few that their scarcity helps explain why so many competitors, and grow in moist, well-drained soils. High variation in acorn production people have rallied around the oak restora- across years is related to winter temperature and spring and summer precipitation. tion cause. “I also think people are attracted to the open spaces and the special and • Whether Oregon white oak seedlings are grown in nursery beds and planted bare- wildlife that are associated with oaks,” says root, or grown in containers, it is important to promote a vigorous root system that Harrington. will allow seedlings to establish quickly after planting, before soils become dry during “Oregon white oak savannas and woodlands summertime. Early growth is strongly affected by initial seedling size, and beneficial represent a biological and cultural legacy in post planting treatments include weed control and tree shelters. the Pacific Northwest. Many of the plants and animals associated with oaks are not found in • The widely used ORGANON growth model has been updated for Oregon white oak. conifer ,” says Harrington. “Therefore, It predicts mortality of oak trees will be high unless overtopping conifers are removed if we allow the oak legacies to disappear we’ll but that growth in response to treatment is better than previously predicted. lose critical ecological diversity and wildlife habitat.”

Harrington leads the station’s Oak Studies Indeed, Oregon white oak woodlands and and information for oak restoration- Group. Their work spans from Vancouver savannas are among the most endangered ists on the ground. Other researchers and Island to northern California and is focused ecological communities in the Pacific restorationists are also working with Oregon on practical strategies for restoring and man- Northwest, and their future is dependent on white oak and associated prairie systems, but aging Oregon white oak habitat. the active participation of thousands of private as Harrington explains “I think our group’s landowners. Over the past 7 years, the Oak work is different in that we have emphasized “Most of the oak resource is on private land, Studies Group has partnered with conserva- studies specifically designed to learn more so it’s important for us to find ways to get tion organizations, state and federal agencies, about managing the tree component of these the information packaged for landowners and universities, and landowner groups to develop ecosystems.” those who work with landowners, not just for a research program that readily translates into other scientists,” she explains.

Conifer Invasion Purpose of PNW Science Findings regon white oak is shade intolerant, or never in terms of management actions To provide scientific information to people meaning its cannot efficient- having an impact,” says Harrington. “I’ve who make and influence decisions about ly photosynthesize unless they never worked on a project where I thought the managing land. O receive full sunlight. Oak branches that are topic was so time critical.” PNW Science Findings is published in heavy shade will die. If most of the crown monthly by: Recognizing this, many landowners and con- becomes shaded, the tree might persist servation groups have elevated oak habitat Pacific Northwest Research Station for several decades, but eventually it will restoration to a priority. One such example USDA Service succumb. Prior to widespread agricultural P.O. Box 3890 is Military Reservation, near settlement, Native Americans favored the Portland, Oregon 97208 Tacoma, Washington, which is home to the oaks by frequently burning the savannas. (503) 808-2137 largest oak stands west of the Cascades in After regular burning by Native Americans Washington, and contains many examples Send new subscriptions and change of address ceased, the invasion of other — of woodlands and savannas that have been information to [email protected] especially Douglas-fir—began. Due to invaded by conifers. Harrington and her col- Sherri Richardson Dodge, editor their faster growth and a greater maximum leagues teamed with Fort Lewis’ [email protected] height, the conifers quickly overtopped oaks Program and initiated a study to examine the Keith Routman, layout throughout the Pacific Northwest. effects of releasing Oregon white oak from [email protected] Most of the overtopped oaks have long overtopping conifers. since died. But there are still many places “We evaluated three levels of release from Forest where oaks are hanging on despite the siege Department Service Douglas-fir competition: a full release where of Agriculture of conifers. These are the high-priority all Douglas-fir within one tree-height were restoration sites. “For many stands, it’s now

Science Findings is online at: http://www.fs.fed.us/pnw/ The site includes Science Update—scientific knowledge for pressing decisions about controversial natural resource and environmental issues.

2 removed, a half-release where all Douglas-fir “Overall, our findings suggest that release that feed upon and will promote natu- within one-half of a tree height were removed, will result in positive changes for overtopped ral oak regeneration. And the formation of and a control where only a few trees were oaks,” says Devine. “Increased acorn pro- new branches indicates that the release has removed,” explains Warren Devine, a research duction will benefit many wildlife species increased the oak’s vigor.” forester at the PNW Research Station labora- tory in Olympia, who was a lead investiga- tor on the experiment. “We found that the response of oak trees was greatest in the full release. During the first 5 years after the treat- ment, oak stem growth and acorn production increased and new branches formed, which increased the size of the tree crowns. Oak trees that had relatively large crowns prior to release responded most rapidly.” Harrington was pleased to see that the full release was so effective. “First of all, we found out that it was possible to remove the large overtopping conifers with very little damage to the smaller oaks,” she says. “Also, prior to our research, it was unknown whether these oak trees could recover after decades of suppression, or if an abrupt and total release from conifers would adversely affect the oaks. Many people had recommend- ed only doing a partial release as a first step, but our research demonstrated that a staged release was not necessary. Managers can now choose the type of release activity that best fits their management objectives and financial C. Harrington resources.” Because of the prolonged absence of wildfire, conifers such as Douglas-fir have encroached into thousands of acres of oak habitat, where they eventually overtop and kill the oaks.

Answers About Acorns corns are oaks of the future. They tree,” explains Peter. “We did several surveys Based on these surveys, Peter estimates that are also a rich source of food for from the ground and even rented a lift truck an oak with a healthy mushroom-shaped Amany mammals, birds, and insects. for some trees to ensure we were counting the crown can produce from zero to 1,000 acorns For example, the western grey squirrel, a acorns high in the canopy.” in an average year. Factors that affect the size species listed as threatened in the state of of the crown, such as age and crowd- Washington, relies heavily on acorns for food ing by other trees, influence acorn during the fall and winter. Unfortunately, production by individual trees, while the loss of oak habitat has resulted in fewer winter temperature and spring or oak trees, and the small-crowned oaks that summer precipitation seem to control remain produce few acorns. As part of devel- year-to-year variability. oping a comprehensive restoration strategy, Peter summed up his experience Harrington and her colleagues set out to doing whole-tree acorn surveys in address some fundamental questions about three words: difficult, tedious, and acorns. time-consuming. Fortunately, by For example, how many acorns do Oregon comparing the whole-tree count white oaks produce? At what age does an data with a previously developed oak first produce acorns? What is the age of code system, he found that he could maximum acorn production? What controls still make useful estimates of acorn the variation—from tree to tree and year to production by simply categorizing year—in acorn production? a tree’s acorn production into four codes. The codes ranged from Code According to David Peter, no one really knew 1: No acorns, to Code 4: Clusters of the answers to these basic questions. Peter acorns all over the tree with limbs is an ecologist at the Olympia Lab and coor- potentially bending under the weight dinates the investigation into acorn produc- PeterD. of the . This simple protocol can tion. “We started our research by completing Researchers conducted several whole-tree acorn counts be followed by anyone interested several whole-tree acorn counts, where we to establish accurate estimates of acorn production before in oaks, which turned out to be a used binoculars to count every acorn on the switching to a simpler protocol, which was followed by volunteers from throughout the Pacific Northwest. tremendous asset.

3 For several years now the group has col- Some of the volunteers are interested Thanks to the new acorn data, the researchers laborated with dozens of volunteers for an landowners with no specific training of any now estimate that acorn production begins annual acorn count. “Acorns are best counted kind, while others work for land management when an oak is 10 to 20 years old, and that during the end of August and beginning of agencies or conservation organizations. production levels-off around age 80. Open- September, before they begin dropping off “At least 70 people in California, Oregon, grown, mushroom-shaped crowns produce the tree and while their yellowish color pro- Washington, and British Columbia have more acorns than vase-shaped crowns, which vides contrast against the green leaves,” says collected acorn production data since 1999, are typical of dense woodlands. Oaks growing Harrington. “Without the help of the volun- and 18 government agencies or private in wetlands or on steep, south-facing slopes teers, it would be impossible to gather data institutions have contributed personnel or produce the fewest acorns, while open-grown throughout the range of Oregon white oak access to facilitate the study,” says Peter. trees on moist, well-drained soil produce the during such a short time-span.” most. D. PeterD. Oregon white oak acorns are an important wildlife food but acorn production is quite variable. The For several years, scientists have been collaborating with volunteers to monitor acorn production across best acorn producers have wide crowns and few a range of site conditions. High variation across years is related to winter temperature and to spring and competitors, and grow in moist, well drained soils. summer precipitation.

Oak Regeneration he Oak Studies Group parlayed their limited information to start from, we needed success using volunteers for acorn to explore a wide range of sites and practices.” T counts into another component of oak Fortunately, by recruiting volunteers, they restoration: planting oak seedlings. “When were able to do just that. we started studying regeneration, there were “People involved with oak habitat restoration very few publications with information on tend to be very enthusiastic about their work,” establishing Oregon white oak, and most says Devine. “They have been quite helpful previous plantings could only be considered to us.” a modest success,” says Devine. “With such

L A n d M A N AG E M e n t I M pl i cAt i o n s

• Overtopped Oregon white oaks can be restored by removing all the competing trees. Previously, many people had recommended only a partial release as a first step, but new research demonstrates that this is not necessary. Managers can choose the type of release activity that best fits their management objectives and financial resources. Choosing not to release oaks from overtopping competition will result in oak mortality and thus, fewer restoration options for the future.

• Oregon white oak has been eliminated from many of its original locations in the Pacific Northwest, and thus, planting oak seedlings is often the most effective way to reestablish the species. Using high-quality planting stock and post-planting treatments that suppress weed competition and reduce animal damage are the best ways to ensure success.

• Identification of stand and habitat characteristics associated with varying levels of acorn The researchers evaluated three levels of release production allows managers to determine which trees and stands are likely to have the from Douglas-fir competition (A = no release; B greatest acorn production potential, and if desired, to apply treatments that will increase = half release; C = full release) and found that the acorn production. response of oak trees was greatest when all nearby Douglas-fir were removed.

4 With the help of more than a dozen volunteers spread throughout the region, Devine has been monitoring oak planting success for the past 4 years. He’s found that the quality of - ing stock is very important; stout, 2-year-old seedlings have proven to be the best choice. After that, it is a matter of irrigating, prevent- ing animal browsing, and controlling compet- ing vegetation. In a series of trials, he and Harrington found that oak seedlings planted within 4-foot-wide weed-mats had increased growth because otherwise weeds consume most of what little water is available during the summer months. Protecting seedlings from browsing by deer, elk, or is also important, and the researchers have found tall tree shelters to be very effective in getting the seedlings off to a good start.

ORGANON is a free, publicly available tree growth simulator, which can be used to predict the survival and growth of oaks under different management strategies.

Predicting Oak’s Future o help landowners anticipate the may now find oak restoration easier to FOR FURTHER READING effects of different restoration strate- justify,” says Gould. Gould and Harrington gies, the researchers have combined used the new model to predict the effects Devine, W.D.; Harrington, C.A. 2006. T Changes in Oregon white oak (Quercus their own data with all the other oak growth of several alternative scenarios in a 50-year data they could find throughout the region, landscape planning exercise that was based garryana Dougl. ex Hook.) following including field data from Oregon State on data from real stands. About 60 percent of release from overtopping conifers. Trees— University (OSU) and the PNW Research the oaks in stands with overtopping conifers Structure and Function. 20: 747–756. Station’s Forest Inventory and Analysis were predicted to die and many of those Devine, W.D.; Harrington, C.A.; Leonard, L.P. Program. that would survive would be in poor vigor. 2007. Post-planting treatments increase Gould commented “Losing the existing oaks Peter Gould, who is also a research forester growth of Dougl. ex would greatly limit future options for oak at the Olympia Lab, Harrington, and David Hook. (Oregon white oak) seedlings. restoration.” Marshall, a former research forester at the Restoration Ecology. 15(2): 212–222 lab, have synthesized these data into a suite Previously, the response of oaks to manage- Gould, P.J.; Marshall, D.D.; Harrington, of growth equations that can be used to ment within the model was based on just 10 to C.A. [In press]. Prediction of growth predict growth and survival of oak under 15 trees—now it incorporates more than 800. and mortality of Oregon white oak in the different stand conditions and management This is the same pattern we see for oak infor- Pacific Northwest. Western Journal of strategies. “The new equations predict long- mation generally. Until recently, there was Applied Forestry. term survival under a conifer overstory to relatively little known about the biology and be much poorer, and growth after release or management of oaks, but now, thanks to the Harrington, C.A.; Devine, W.D. 2006. A thinning to be much better, than predicted Oak Studies Group and the enthusiasm of vol- practical guide to oak release. Gen. Tech. by previous equations,” explains Gould. The unteers, landowners, and conservation groups, Rep. PNW-GTR-666. Portland, OR: U.S. team collaborated with Professor David Hann Oregon white oak restoration is becoming a Department of Agriculture, Forest Service, at OSU to incorporate these equations into the well-developed science. Hopefully it will be Pacific Northwest Research Station. 24 p. newest edition of ORGANON, a widely used, enough to save this important ecosystem from Peter, D.; Harrington, C.A. 2002. Site and tree publicly available tree growth model (the the brink of extinction. factors in Oregon white oak acorn produc- model can be downloaded at: http://www.cof. “The creation of a thousand tion in western Washington and Oregon. orst.edu/cof/fr/research/organon/downld.htm). Northwest Science. 76: 189–201. forests is in one acorn.” “Since the new model predicts substantial —Ralph Waldo Emerson benefits of treatments such as removing conifers or spacing out the oaks, managers

WRITER’S PROFILE Jonathan Thompson is an ecologist and science writer living in Corvallis, Oregon.

5 PRSRT STD US POSTAGE PAID PORTLAND OR FINDINGS PERMIT N0 G-40 U.S. Department of Agriculture Pacific Northwest Research Station 333 SW First Avenue P.O. Box 3890 Portland, OR 97208-3890 Official Business Penalty for Private Use, $300

scientist profile S The Oak Studies Group may be reached at: PNW Research Station/USDA Forest Service 3625 93rd Avenue SW Olympia, WA 98512 Harrington: phone: (360) 753-7670; e-mail: [email protected] Devine: phone: (360) 753-7675; e-mail: [email protected] Gould: phone: (360) 753-7677; e-mail: [email protected] Peter: phone: (360) 753-7654; Members of the Oak Studies Group (from left): Dave Peter, Peter Gould, Connie Harrington, and e-mail: [email protected] Warren Devine, Resource Management and Productivity Program, PNW Research Station.

CONNIE HARRINGTON is a research PETER GOULD, also a research forester, is For more information, visit: http://www.fs. forester interested in , tree currently working on several projects focusing fed.us/pnw/olympia/silv/oak-studies/acorn_ physiology, and plant productivity (and has on the growth of northwestern species; he survey/survey-background.shtml. a special fondness for neglected species). received a Ph.D. from Pennsylvania State She received her Ph.D. from the University University in 2005. COOPERATORS of Washington in 1984. DAVE PETER is an ecologist who studies Gary McCausland (retired), Jeff Foster, WARREN DEVINE is a research forester Pacific Northwest plant communities, Jim Rohde (retired), Joe Reasoner, U.S. who, in addition to his research on including community structure, composition, Army, Fort Lewis Military Reservation Oregon white oak, also studies conifer and fire history. He received his Ph.D. from Patrick Dunn, Eric Delvin, and Peter regeneration in even- and uneven-age the University of Washington in 2005. Dunwiddie, The Nature Conservancy systems. He received his Ph.D. from the University of Tennessee in 2002. Hugh Snook, Bureau of Land Management

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