Current Research

My current work is exploring several research emphases: overstory and understory relationships in managed Douglas-fir forests; longer-term effects of vegetation control and logging debris manipulation on Douglas-fir plantation productivity; regeneration biology of Scotch broom; herbicide treatments for controlling invasive, nonnative plant species; and effects of logging debris and associated light quality on understory plants.

Research Interests

Biology and management of invasive, nonnative plant species; conifer seedling growth and physiology responses to microenvironment; restoration of understory plant communities in managed conifer forests; comparative growth and yield of Douglas-fir stands; and long-term effects of forest vegetation management and thinning on stand structure.

Past Research

My past work has explored the physiology of Douglas-fir under different levels of competition from woody and herbaceous vegetation; bud production and shoot growth of Douglas-fir; shoot growth of southern pines; and restoration of longleaf pine communities in the southern United States.

Why This Research is Important

Invasive, nonnative plants threaten the biodiversity and many ecological functions of Pacific Northwest forests. Methods are needed to prevent or mitigate plant invasions to protect native plant and animal communities. Research on conifer regeneration is critical to appropriate management of public and private forest land to ensure steady production of the ecological services that society demands.

Education

• Oregon State University, Ph.D. Silviculture 1989
• Oregon State University, M.S. Forest Ecology 1982
• Louisiana State University, B.S. Botany 1980

Featured Publications & Products

• Harrington, Timothy B., Ph.D..; Slesak, Robert A.; Schoenholtz, Stephen H. 2013. Variation in logging debris cover influences competitor abundance, resource availability, and early growth of planted Douglas-fir.
• Harrington, Timothy B., Ph.D..; Tappeiner , John C., II. 2009. Long-term effects of tanoak competition on Douglas-fir stand development.
• Harrington, Timothy B., Ph.D. 2011. Overstory and understory relationships in longleaf pine plantations 14 years after thinning and woody control.
• Harrington, Timothy B., Ph.D. 2009. Seed germination and seedling emergence of Scotch broom (Cytisus scoparius).
• Harrington, Timothy B., Ph.D. 2014. Synthetic auxin herbicides control germinating scotch broom (Cytisus scoparius).
• Harrington, Timothy B.; Peter, David H.; Devine, Warren D. 2014. Two-year effects of aminopyralid on an invaded meadow in the Washington Cascades.
• Wilk, Randall J.; Harrington, Timothy B.; Gitzen, Robert A.; Maguire, Chris C. 2015. Forest-floor disturbance reduces chipmunk (Tamias spp.) abundance two years after variable-retention harvest of Pacific Northwestern forests.
• Devine, Warren D.; Harrington, Timothy B., Ph.D..; Terry, Thomas A.; Harrison, Robert B.; Slesak, Robert A.; Peter, David H.; Harrington, Constance A.; Shilling, Carol J.; Schoenholtz, Stephen H. 2011. Five-year vegetation control effects on aboveground biomass and nitrogen content and allocation in Douglas-fir plantations on three contrasting sites.
• Harrington, Tim, Ph.D..; Miller, Karl; Parks, Noreen. 2013. Restoring a disappearing ecosystem: the longleaf pine savanna.

Publications

• Watts, Andrea ; Harrington, Tim ; Peter, Dave ; Slesak, Robert . 2019. Managing competing vegetation in Douglas-Fir plantations: The benefits of forest floor complexity.
• Carter, David R.; Slesak, Robert A.; Harrington, Timothy B.; Peter, David H.; D’Amato, Anthony W. 2019. Scotch broom (Cytisus scoparius) modifies microenvironment to promote nonnative plant communities.
• DeBruler, Daniel G.; Schoenholtz, Stephen H.; Slesak, Robert A.; Strahm, Brian D.; Harrington, Timothy B. 2019. Soil phosphorus fractions vary with harvest intensity and vegetation control at two contrasting Douglas-fir sites in the Pacific northwest.
• Peter, David H.; Harrington, Timothy B. 2018. Effects of forest harvesting, logging debris, and herbicides on the composition, diversity and assembly of a western Washington, USA plant community.
• Harrington, Timothy B.; Peter, David H.; Slesak, Robert A. 2018. Logging debris and herbicide treatments improve growing conditions for planted Douglas-fir on a droughty forest site invaded by Scotch broom.
• Harrington, Timothy B.; Devine, Warren D. 2018. Performance of four planted conifer species within artificial canopy gaps in a Western Washington Douglas-fir forest.
• Murphy, Michael S.; Schimleck, Laurence R.; Harrington, Timothy B.; Daniels, Richard F. 2018. Two-year stem curvature and growth responses of three full-sibling families of loblolly pine to five root/stem form treatments.
• Peter, David H.; Harrington, Timothy B.; Thompson, Mark. 2017. Effects of the light environment and stand history on beargrass (Xerophyllum tenax) morphology and demography.
• Harrington, Timothy B.; Harrington, Thaddeus A. 2016. Early density management of longleaf pine reduces susceptibility to ice storm damage.
• Slesak, Robert A.; Harrington, Timothy B.; Peter, Dave; DeBruler, Daniel G.; Schoenholtz, Stephen H.; Strahm, Brian D. 2016. Effects of intensive management practices on 10-year Douglas-fir growth, soil nutrient pools, and vegetation communities in the Pacific Northwest, USA.
• Slesak, Robert A.; Harrington, Timothy B.; D′Amato, Anthony W. 2016. Invasive scotch broom alters soil chemical properties in Douglas-fir forests of the Pacific Northwest, USA.
• Miller, Richard E.; Harrington, Timothy B.; Anderson, Harry W. 2016. Stand dynamics of Douglas-fir 20 years after precommercial thinning and nitrogen fertilization on a poor-quality site.
• Lane, Vanessa R.; Simmons, Robert P.; Brunjes, Kristina J.; Kilgo, John C.; Harrington, Timothy B., Ph.D..; Daniels, Richard F.; Ford, W. Mark; Miller, Karl V. 2015. Effects of precommercial thinning and midstory control on avian and small mammal communities during longleaf pine Savanna restoration.
• Devine, Warren D.; Harrington, Timothy B. 2015. Seedfall and seed viability within artificial canopy gaps in a western Washington douglas-fir forest.
• Devine, Warren D.; Footen, Paul W.; Strahm, Brian D.; Harrison, Robert B.; Terry, Thomas A.; Harrington, Timothy B., Ph.D. 2012. Nitrogen leaching following whole-tree and bole-only harvests on two contrasting Pacific Northwest sites.
• Peter, David H.; Harrington, Timothy B., Ph.D. 2012. Relations of native and exotic species 5 years after clearcutting with and without herbicide and logging debris treatments.
• Devine, Warren D.; Harrington, Timothy B. 2011. Aboveground growth interactions of paired conifer seedlings in close proximity.
• Slesak, Robert A.; Schoenholtz, Stephen H.; Harrington, Timothy B.; Meehan, Nathan A. 2011. Initial response of soil carbon and nitrogen to harvest intensity and competing vegetation control in douglas-fir (Pseudotsuga menziesii) plantations of the Pacific Northwest.
• Slesak, Robert A.; Schoenholtz, Stephen H.; Harrington, Timothy B., Ph.D. 2011. Soil carbon and nutrient pools in Douglas-fir plantations 5 years after manipulating biomass and competing vegetation in the Pacific Nortwest.
• Harrington, Timothy B., Ph.D. 2010. Manipulating stand structure of Douglas-fir plantations for wildlife habitat and wood production.
• Slesak, Robert A.; Schoenholtz, Stephen H.; Harrington, Timothy B., Ph.D. 2010. Soil respiration and carbon responses to logging debris and competing vegetation.
• Parks, Noreen; Harrington, Timothy; Devine, Warren. 2010. Toward more diverse forests: helping trees "get along" in a new organization.
• Strahm, Brian D.; Harrison, Robert B.; Terry, Thomas A.; Harrington, Timothy B., Ph.D..; Adams, A.B.; Footen, Paul W. 2009. Changes in dissolved organic matter with depth suggest the potential for postharvest organic matter retention to increase subsurface soil carbon pools..
• Slesak, Robert A.; Schoenholtz, Stephen H.; Harrington, Timothy B., Ph.D..; Strahm, Brian D. 2009. Dissolved carbon and nitrogen leaching following variable logging-debris retention and competing-vegetation control in Douglas-fir plantations of western Oregon and Washington.
• Harrington, Timothy B., Ph.D..; Harrington, Constance A.; DeBell, Dean S. 2009. Effects of planting spacing and site quality on 25-year growth and mortality relationships of Douglas-fir (Pseudotsuga menziesii var menziesii)..
• Devine, Warren D.; Harrington, Timothy B., Ph.D. 2008. Belowground competition influences growth of natural regeneration in thinned Douglas-fir stands.

Research Highlights

Highlight	Title	Year
PNW-2011-11	More Scotch broom found where logging debris was removed Scotch broom, a nonnative, invasive species, is a severe competitor of young Douglas-fir.	2011
PNW-2014-200	New Herbicides Developed to Fight Scotch Broom Scotch broom is a large, nonnative shrub that has invaded forest sites throughout the Pacific Northwest. Three recently developed herbicides pro ...	2014
PNW-2011-12	Presence of tanoak reduces Douglas-fir mortality from black-stain root disease Black-stain root disease is a native pathogen of conifers in the Pacific Northwest. The disease reduces growth and ultimately kills the infected ...	2011
PNW-2013-018	Some Logging Debris Cover Boosts Growth of Douglas-fir Seedlings on Low-nutrient Site Stem growth of Douglas-fir seedlings with 40 percent debris cover and competing vegetation was greater than that of seedlings with zero or 80 pe ...	2013