Oak Decline

Research Issue

Management solutions are urgently needed to cope with the large number of oak trees that are declining and dying in oak-dominated forests.  This problem is referred to as oak decline and has become a chronic problem for the region’s aging oak forests. Oaks most susceptible to decline are red oak group species such as black oak (Quercus velutina) and scarlet oak (Q. coccinea); relatively old (>70 years) or large trees; growing on dry sites with shallow or rocky soils, especially on broad ridges or south-facing slopes. 

Periodic large-scale episodes of oak decline are often associated with drought. Other events that can incite decline include repeated defoliation by insects or injury from frost, ice, or wind.  Once oaks begin to decline, they become susceptible to many other kinds of diseases and insect pests that cause further stress or damage. These include armillaria root rots, which girdle tree root; hypoxylon cankers, which kill stems; red oak borer larvae and carpenter worms, which damage wood; and two-lined chestnut borers, which kill branches and whole trees by girdling them with their tunnels. 

Even though oak decline and associated diseases and insect infestations have occurred in the past, the extent of these problems today is unprecedented because red oaks are now the most common tree species on poor-quality sites. These red oaks largely established after the extensive timber harvesting and grazing practices of the late 1800s and early 1900s. Now thousands of acres of forest land containing red oaks are reaching or surpassing maturity and are thus increasingly susceptible to oak decline. Moreover, research conducted in the Missouri Ozarks suggests that populations of the fungal agents of armillaria root rot are increasing because of the increased availability of dead or dying root tissue from stressed oak tress. 

This combination of forest age, species composition, and accumulated diseases and stresses has caused oak decline to change from an episodic problem to a chronic one that has greatly affected not just the oak forests themselves but also the animals and people who live in or near them. These effects include decreased timber value; decreased acorn production, which affects both oak reproduction and wildlife food amounts; increased fire danger; and reduced recreation opportunities. 

Our Research

NRS scientists in this unit are investigating oak decline and identifying management solutions specific for the Ozarks Highlands. Research currently underway or in development has two aspects: 

Forest Restoration—Developing methods for restoring and managing pine-oak woodlands with a more diverse mixture of  site-adapted species. In this work,we examine methods for reestablishing and growing shortleaf pine reproduction along with oaks in forests and woodlands at vulnerable sites for oak decline. We are developing prescribed fire techniques and other disturbances that will create compositions and structures thought to exist prior to extensive European settlement in the Ozark Highlands. We are cooperating with the University of Missouri and the Missouri Department of Conservation. 

Silviculture—Developing silvicultural methods for mitigating oak decline and maintaining healthy oak forests and woodlands. In this work, we are developing methods to identify at-risk trees and methods for thinning and stand improvement harvesting that can reduce oak mortality. We are cooperating with the University of Missouri and the Missouri Department of Conservation.

Expected Outcomes

Expected outcomes include management guides and recommendations to be used by professional foresters and forest landowners for restoring and managing shortleaf pine and oak mixtures and methods for maintaining healthy oak forests and woodlands.

Research Results

Kabrick, J.M.; Dey, D.C.; Shifley, S.R.; Villwock, J.L.  2011.  Early survival and growth of planted shortleaf pine seedlings as a function of initial size and overstory stocking.   In: Fei, S.; Lhotka, J.M.; Stringer, J.W.; Gottschalk, K.W.; Miller, G.W. (eds.) Proceedings: 17th Central Hardwood Forest Conference; 2010 April 5-7; Lexington, KY. NRS-GTR-P-78. Newtown Square, PA: USDA Forest Service, Northern Research Station: 277-286.

Fan, Z.; Xiuli, F.; Spetich, M.A.; Shifley, S.R.; Moser, W.K.; Jensen, R.G.; Kabrick, J.M. 2011. Developing a stand hazard index for oak decline in upland Oak forests of the Ozark Highlands, Missouri. Northern Journal of Applied Forestry 28(1): 19-28. 

Fan, Z.; Kabrick, J.M.; Spetich, M.A.; Shifley, S.R.; Jensen, R.G.  2008.  Oak mortality associated with crown dieback and oak borer attack in the Ozark Highlands.   Forest Ecology and Management 255: 2297-2305

Jensen, R.G.; Kabrick, J.M.  2008.  Comparing single-tree selection, group selection, and clearcutting for regenerating oaks and pines in the Missouri Ozarks.   In: Jacobs, D.F.; Michler, C.H. (eds.) 2008. Proceedings: 16th Central Hardwood Forest Conference; 2008 April 8-9; West Lafayette, IN. NRS-GTR-P-24. Newtown Square, PA: USDA, Forest Service, Northern Research Station: 38-49.

Kabrick, J.M.; Dey, D.C.; Jensen, R.G.; Wallendorf, M.l  2008.  The role of environmental factors in oak decline and mortality in the Ozark Highlands.   Forest Ecology and Management. 255: 1409-1417.

Kabrick, J.M. Fan, Z.; Shifley, S.R.  2007.  Red oak decline and mortality by ecological land type in the Missouri ozarks.   SRS-GTR-101. Asheville, NC USDA Forest Service, Southern Research Station: 181-186 [CD-ROM].

Dwyer, J.P.; Kabrick, J.M.; Wetteroff, J. 2007. Do improvement harvests mitigate oak decline in Missouri Ozark forests?. Northern Journal of Applied Forestry. 24(2): 123-128.

Kabrick, J.M.; Dey, D.C.; Gwaze, D.  2007.  Shortleaf pine restoration and ecology in the Ozarks: Proceedings of a symposium.   NRS-GTR-P-15. Newtown Square, PA: USDA Forest Service, Northern Research Station. 215 p.

Shifley, S.R.; Fan, Z.; Kabrick, J.M.; Jensen, R.G. 2006. Oak mortality risk factors and mortality estimation. Forest Ecology and Management 229:16-26

Heitzman, E.; Muzika, R.M.; Kabrick, J.; Guldin, J.M.  2004.  Assessment of Oak Decline in Missouri, Arkansas, and Oklahoma.   In: Yaussy, D.A.; Hix, D.M.; Long, R.P.; Goebel, P.C. (eds.) Proceedings: 14th Central Hardwood Forest Conference; 2004 March 16-19; Wooster, OH. NE-GTR-316. Newtown Square, PA: USDA Forest Service, Northeastern Research Station: 510.

Research Participants

Principal Investigator

• John M. Kabrick, Research Forester, US Forest Service, Northern Research Station 
• Stephen R. Shifley, Research Forester, US Forest Service, Northern Research Station 
• Dan C. Dey, Research Forester and Project Leader, US Forest Service, Northern Research Station 

Research Partners

• W. Keith Moser, Research Forester, US Forest Service, Northern Research Station 
• Marty Spetich, Research Forest Ecologist; and Jim Guldin, Project Leader; US Forest Service, Southern Research Station
• John Dwyer and Rose-Marie Muzika, University of Missouri, Columbia
• Zhaofei Fan, Mississippi State University
• Cary Steen and Randy Jensen, Missouri Department of Conservation
• Charlie Studyvin, Forest Silviculturist, USDA Forest Service, Mark Twain National Forest

For further information log on website :
http://www.nrs.fs.fed.us/sustaining_forests/conserve_enhance/timber/herbicides/