Current Research

My research focuses on understanding the drivers affecting forest growth and disturbance at multiple spatial and temporal scales, and how these affect carbon sequestration, forest structure, and species' distributions. I pursue these questions through the application of regionally-comprehensive forest monitoring datasets combined with satellite trend detection and modeled climate and physiographic variables. I am reconstructing changes in carbon through time as it moves between pools in forest ecosystems. Other ongoing studies include improving our ability to predict tree canopy cover using tree measurements,  estimating the extent of regional wildlife habitat, determining rates and patterns of land use change, and digitizing detailed county-level forest type maps from the 1930s.

Research Interests

• Effects of disturbance and management on forest composition and structure
• Accurate accounting of changes in forest sector carbon stores
• Conditions and trends of Washington's forest resources

Past Research

My past research has included investigations of long-term vegetation response to canopy gaps in mature conifer forests, applications of adaptive management studies in coastal Oregon, effects of fire and prescribed burning on regeneration and soil moisture in Sierran mixed conifer, and regional distribution and abundance of invasive species.

Why This Research is Important

My work is important because forest inventories provide an unbiased examination of forest conditions and trends across large regions and multiple ownerships. The proper collection, compilation, and analysis of inventory data provides a solid factual bedrock to inform policymakers and managers and supports additional modeling studies that evaluate the potential impacts of future changes in management and environment.

Education

• Oregon State University, Ph.D. Forest Ecology 1995
• University of Washington, M.S. Forest Ecology 1990
• University of Washington, B.S. Environmental Studies 1985

Professional Organizations

• Society of American Foresters (SAF), Member (2018 - Current)
• Ecological Society of America, Member (1990 - Current)
• International Union of Forestry Research Organizations, Deputy Coordinator (2014 - )
• International Association for Landscape Ecology, Member (1992 - )
• Northwest Scientific Association, Member (1990 - )

Featured Publications & Products

• Hessburg, Paul F.; Charnley, Susan ; Wendel, Kendra L.; White, Eric M.; Singleton, Peter H.; Peterson, David W.; Halofsky, Jessica E.; Gray, Andrew N.; Spies, Thomas A.; Flitcroft, Rebecca L.; White, Rachel . 2020. The 1994 Eastside Screens large-tree harvest limit: review of science relevant to forest planning 25 years later.
• Gray, Andrew N.; Cohen, Warren B.; Yang, Zhiqiang ; Pfaff, Eric . 2019. Integrating TimeSync disturbance detection and repeat forest inventory to predict carbon flux.
• Long, Jonathan ; Gray, Andrew ; Lake, Frank . 2018. Recent trends in large hardwoods in the Pacific Northwest, USA.
• Gray, Andrew N.; Whittier, Thomas R.; Harmon, Mark E. 2016. Carbon stocks and accumulation rates in Pacific Northwest forests: role of stand age, plant community, and productivity.
• Whittier, Thomas R.; Gray, Andrew N. 2016. Tree mortality based fire severity classification for forest inventories: A Pacific Northwest national forests example.
• Gray, Andrew N.; Azuma, David L.; Lettman, Gary J.; Thompson, Joel L.; McKay, Neil. 2013. Changes in land use and housing on resource lands in Washington state, 1976 2006.
• Gray, Andrew N.; Spies, Thomas A.; Pabst, Robert J. 2012. Canopy gaps affect long-term patterns of tree growth and mortality in mature and old-growth forests in the Pacific Northwest.
• McIntosh, Anne; Gray, Andrew; Garman, Steven. 2012. Estimating canopy cover from standard forest inventory measurements in western Oregon.
• Zielinski, William J.; Dunk, Jeffrey R.; Gray, Andrew N. 2012. Estimating habitat value using forest inventory data: the fisher (Martes pennanti) in northwestern California.
• Gray, Andrew N.; Barndt, Katie; Reichard, Sarah H. 2011. Nonnative invasive plants of Pacific coast forests: a field guide for identification.

Publications

• Kline, Jeffrey D.; Houston, Laurie L.; Gray, Andrew N.; Monleon, Vicente . 2021. Evaluating empirical evidence for housing development effects on the management of remaining private-owned forest in the U.S..
• Allensworth, Elijah ; Temesgen, Hailemariam ; Frank, Bryce ; Gray, Andrew . 2021. Imputation to predict height to crown base for trees with predicted heights.
• Smith, Robert J.; Gray, Andrew N.; Swanson, Mark E. 2020. Peak plant diversity during early forest development in the western United States.
• Turner, Sabrina B.; Turner, David P.; Gray, Andrew N.; Fellers, Will . 2019. An approach to estimating forest biomass change over a coniferous forest landscape based on tree-level analysis from repeated lidar surveys.
• Smith, Robert J.; Gray, Andrew N. 2019. Combining potentially incompatible community datasets when harmonizing forest inventories in subarctic Alaska, USA.
• Poudel, Krishna P.; Temesgen, Hailemariam ; Radtke, Philip J.; Gray, Andrew N. 2019. Estimating individual-tree aboveground biomass of tree species in the western U.S.A..
• Barker, Jason S.; Fried, Jeremy S.; Gray, Andrew N. 2019. Evaluating model predictions of fire induced tree mortality using wildfire-affected forest inventory measurements.
• Poudel, Krishna P.; Temesgen, Hailemariam ; Gray, Andrew N. 2018. Estimating upper stem diameters and volume of Douglas-fir and Western hemlock trees in the Pacific northwest.
• Pattison, Robert ; Andersen, Hans-Erik ; Gray, Andrew ; Schulz, Bethany ; Smith, Robert J.; Jovan, Sarah . 2018. Forests of the Tanana Valley State Forest and Tetlin National Wildlife Refuge, Alaska: results of the 2014 pilot inventory.
• Zielinski, William J.; Gray, Andrew N. 2018. Using routinely collected regional forest inventory data to conclude that resting habitat for the fisher (Pekania pennanti) in California is stable over 20 years.
• Gray, Andrew . 2017. Avances en el conocimiento de la din mica forestal: el papel del monitoreo regional.
• Bansal, Sheel; Brodie, Leslie; Stanton, Sharon; Waddell, Karen; Palmer, Marin; Christensen, Glenn; Kuegler, Olaf; Chase, John; Thompson, Joel; Jovan, Sarah; Gray, Andrew; Todd, Morgan. 2017. Oregon s forest resources, 2001 2010: ten-year Forest Inventory and Analysis report.
• Smith, Robert J.; Jovan, Sarah ; Gray, Andrew N.; McCune, Bruce . 2017. Sensitivity of carbon stores in boreal forest moss mats - effects of vegetation, topography and climate.
• Watts, Andrea; Gray, Andrew; Whittier, Thomas. 2017. There s carbon in them thar hills: But how much Could Pacific Northwest forests store more.
• Bell, David M.; Gray, Andrew N. 2016. Assessing intra- and inter-regional climate effects on Douglas-fir biomass dynamics in Oregon and Washington, USA.
• Stevens, Jens T.; Safford, Hugh D.; North, Malcolm P.; Fried, Jeremy S.; Gray, Andrew N.; Brown, Peter M.; Dolanc, Christopher R.; Dobrowski, Solomon Z.; Falk, Donald A.; Farris, Calvin A.; Franklin, Jerry F.; Fulé, Peter Z.; Hagmann, R. Keala; Knapp, Eric E.; Miller, Jay D.; Smith, Douglas F.; Swetnam, Thomas W.; Taylor, Alan H.; Jones, Julia A. 2016. Average stand age from forest inventory plots does not describe historical fire regimes in ponderosa pine and mixed-conifer forests of western North America.
• Lintz, Heather E; Gray, Andrew N.; Yost, Andrew; Sniezko, Richard; Woodall, Chris; Reilly, Matt; Hutten, Karen; Elliott, Mark. 2016. Quantifying density-independent mortality of temperate tree species.
• Turner, David P.; Ritts, William D.; Kennedy, Robert E.; Gray, Andrew N.; Yang, Zhiqiang. 2016. Regional carbon cycle responses to 25 years of variation in climate and disturbance in the US Pacific Northwest.
• Pattison, Robert R.; Gray, Andrew N.; Tango, Lori. 2015. A baseline assessment of forest composition, structure, and health in the Hawai i experimental tropical forests.
• Oliver, Marie; Gray, Andrew. 2015. A bird s-eye view: Land-use planning and assessments in Oregon and Washington.
• Temesgen, Hailemariam; Affleck, David; Poudel, Krishna; Gray, Andrew; Sessions, John. 2015. A review of the challenges and opportunities in estimating above ground forest biomass using tree-level models.
• Pattison, Robert R.; Gray, Andrew N.; Sullivan, Patrick F.; Manies, Kristen L. 2015. Down woody material, soil and tree core collection and analysis from the 2014 Tanana pilot plots.
• Turner, David P; Ritts, William D; Kennedy, Robert E; Gray, Andrew N; Yang, Zhiqiang. 2015. Effects of harvest, fire, and pest/pathogen disturbances on the West Cascades ecoregion carbon balance.
• Poudel, Krishna P; Temesgen, Hailemariam; Gray, Andrew N. 2015. Evaluation of sampling strategies to estimate crown biomass.
• Bell, David M.; Gray, Andrew N. 2015. Examining Pseudotsuga menziesii biomass change dynamics through succession using a regional forest inventory system.
• Gray, Andrew N.; Thompson, Joel L.; Lettman, Gary J. 2015. Land-use change and new houses on forestland: contrasting trends over 30 years in Oregon and Washington.
• Davis, Raymond J.; Ohmann, Janet L.; Kennedy, Robert E.; Cohen, Warren B.; Gregory, Matthew J.; Yang, Zhiqiang; Roberts, Heather M.; Gray, Andrew N.; Spies, Thomas A. 2015. Northwest Forest Plan the first 20 years (1994-2013): status and trends of late-successional and old-growth forests.
• Yatskov, Mikhaill A.; Harmon, Mark E.; Krankina, Olga N.; Barrett, Tara M.; Dobelbower, Kevin R.; Gray, Andrew N.; Fasth, Becky; Trummer, Lori; Hoyman, Toni L.; Dudoit, Chana M. 2015. Regional biomass stores and dynamics in forests of coastal Alaska.
• Meigs, Garrett W.; Kennedy, Robert E.; Gray, Andrew N.; Gregory, Matthew J. 2015. Spatiotemporal dynamics of recent mountain pine beetle and western spruce budworm outbreaks across the Pacific Northwest Region, USA.
• Woodall, C.W.; Domke, G.M.; Coulston, J.; Russell, M.B.; Smith, J.A.; Perry, C.H.; Healey, S.; Gray, A. 2015. The great carbon push-pull: where science is pushing and policy is pulling the official forest carbon inventory of the US.
• Gray, Andrew N. 2015. The role of old forests and big trees in forest carbon sequestration in the Pacific Northwest.
• Gray, Andrew N.; Whittier, Thomas R. 2014. Carbon stocks and changes on Pacific Northwest national forests and the role of disturbance, management, and growth.
• Azuma, David L.; Gray, Andrew. 2014. Effects of changing forest land definitions on forest inventory on the West Coast, USA.
• Gray, Andrew N.; Whittier, Thomas R.; Azuma, David L. 2014. Estimation of aboveground forest carbon flux in Oregon: adding components of change to stock-difference assessments.
• Woodall, C.W.; Walters, B.F.; Oswalt, S.N.; Domke, G.M.; Toney, C.; Gray, A.N. 2013. Biomass and carbon attributes of downed woody materials in forests of the United States.
• Gray, Andrew. 2013. Changes in fragmentation of western Washington forest land (Project WC-EM-08-01).
• Lintz, Heather E.; Gray, Andrew N.; McCune, Bruce. 2013. Effect of inventory method on niche models: random versus systematic error.
• Schulz, Bethany K.; Gray, Andrew N. 2013. The new flora of the northeastern USA: quantifying introduced plant species occupancy in forest ecosystems.
• Gray, Andrew N.; Brandeis, Thomas J.; Shaw, John D.; McWilliams, William H.; Miles, Patrick. 2012. Forest Inventory and Analysis Database of the United States of America (FIA).
• Woodall, Christopher W.; Smith, James E.; Domke, Grant M.; Healey, Sean P.; Coulston, John W.; Gray, Andrew N. 2012. Technical aspects of the forest carbon inventory of the United States: recent past and near future.
• Barrett, Tara M.; Gray, Andrew N. 2011. Potential of a national monitoring program for forests to assess change in high-latitude ecosystems.
• Lintz, Heather E.; McCune, Bruce; Gray, Andrew N.; McCulloh, Katherine A. 2011. Quantifying ecological thresholds from response surfaces.
• Brady, Timothy J.; Monleon, Vicente J.; Gray, Andrew N. 2010. Calibrating vascular plant abundance for detecting future climate changes in Oregon and Washington, USA.
• Griffiths, Robert P.; Gray, Andrew N.; Spies, Thomas A. 2010. Soil properties in old-growth Douglas-fir gaps in the western Cascade Mountains of Oregon.
• Zielinski, William J.; Gray, Andrew N.; Dunk, Jeffrey R.; Sherlock, Joseph W.; Dixon, Gary E. 2010. Using forest inventory and analysis data and the forest vegetation simulator to predict and monitor fisher (Martes pennanti) resting habitat suitability.
• Campbell, Sally; Waddell, Karen; Gray, Andrew. 2010. Washington s forest resources, 2002 2006: five-year Forest Inventory and Analysis report.
• McIntosh, Anne C.S.; Gray, Andrew N.; Garman, Steven L. 2009. Canopy structure on forest lands in western Oregon: differences among forest types and stand ages.
• Gray, Andrew N.; Monleon, Vicente J.; Spies, Thomas A. 2009. Characteristics of remnant old-growth forests in the northern Coast Range of Oregon and comparison to surrounding landscapes..
• Kline, Jeffrey D.; Moses, Alissa; Azuma, David L.; Gray, Andrew. 2009. Evaluating satellite imagery-based land use data for describing forestland development in western Washington.
• Moser, W. Keith; Barnard, Edward L.; Billings, Ronald F.; Crocker, Susan J.; Gray, Andrew N.; Ice, George G.; Kim, Mee-Sook; Reid, Richard; Rodman, Sue U.; McWilliams, William H. 2009. Impacts of nonnative invasive species on US forests and recommendations for policy and management.
• Azuma, David; Menlove, James; Gray, Andrew. 2009. Reserved and roadless forests.
• Zald, Harold S.J.; Gray, Andrew N.; North, Malcolm; Kern, Ruth A. 2008. Initial tree regeneration responses to fire and thinning treatments in a Sierra Nevada mixed-conifer forest, USA.
• Gray, Andrew. 2008. Monitoring and assessment of regional impacts from nonnative invasive plants in forests of the Pacific Coast, United States.
• Meyer, Marc D.; North, Malcolm P.; Gray, Andrew N.; Zald, Harold S. J. 2007. Influence of soil thickness on stand characteristics in a Sierra Nevada mixed-conifer forest.
• Fiala, Anne C.S.; Garman, Steven L.; Gray, Andrew N. 2006. Comparison of five canopy cover estimation techniques in the western Oregon Cascades..
• Gray, Andrew N.; Fried, Jeremy S.; Christensen, Glenn; Potts, Larry. 2006. Timber resource statistics for forest land in eastern Washington, January 2002..
• Gray, Andrew. 2005. Eight nonnative plants in western Oregon forests: associations with environment and management..
• North, Malcolm; Oakley, Brian; Fiegener, Rob; Gray, Andrew; Barbour, Michael. 2005. Influence of light and soil moisture on Sierran mixed-conifer understory communities..
• Gray, Andrew N. 2005. Nonnative Plants in the Inventory of Western Oregon Forests.
• Gray, Andrew N.; Azuma, David L. 2005. Repeatability and implementation of a forest vegetation indicator..
• Gray, Andrew N.; Zald, Harold S.J.; Kern, Ruth A.; North, Malcolm. 2005. Stand conditions associated with tree regeneration in sierran mixed-conifer forests..
• Gray, Andrew N.; Veneklase, Charles F.; Rhoads, Robert D. 2005. Timber resource statistics for nonnational forest land in western Washington, 2001..
• North, Malcolm; Chen, Jiquan; Oakley, Brian; Song, Bo; Rudnicki, Mark; Gray, Andrew; Innes, Jim. 2004. Forest stand structure and pattern of old-growth western hemlock/Douglas-fir and mixed-conifer forests.
• Gray, Andrew. 2003. Monitoring stand structure in mature coastal Douglas-fir forests: effect of plot size..
• Gray, Andrew N; Spies, Thomas A; Easter, Mark J. 2002. Microclimatic and soil moisture responses to gap formation in coastal Douglas-fir forests.
• North, Malcolm; Oakley, Brian; Chen, Jiquan; Erickson, Heather; Gray, Andrew; Izzo, Antonio; Johnson, Dale; Ma, Siyan; Marra, Jim; Meyer, Marc; Purcell, Kathryn; Rambo, Tom; Rizzo, Dave; Roath, Brent; Schowalter, Tim. 2002. Vegetation and Ecological Characteristics of Mixed-Conifer and Red Fir Forests at the Teakettle Experimental Forest.
• Gray, Andrew N.; Spies, Thomas A. 1997. Microsite controls on tree seedling establishment in conifer forest canopy gaps.
• Gray, Andrew; Spies, Thomas. 1995. Water content measurement in forest soils and decayed wood using time domain reflectometry.

Citations of non US Forest Service Publications

• Gray, A. N. and T. A. Spies. 1996. Gap size, within-gap position, and canopy structure effects on conifer seedling establishment. Journal of Ecology 84:635-645.

• Gray, A. N. and J. F. Franklin. 1997. Effects of multiple fires on the structure of southwestern Washington forests. Northwest Science 71:174-185.

• Gray, A. N. 2000. Adaptive ecosystem management in the Pacific Northwest: a case study from coastal Oregon. Conservation Ecology [online] 4:6.

• Monleon, V. J., A. I. Gitelman, and A. N. Gray. 2002. Multi-scale relationships between coarse woody debris and presence/absence of western hemlock in the Oregon Coast Range. Pages 311-318 in C. Gatsonis, A. Carriquiry, A. Gelman, D. Higdon, R. Kaas, D. Pauler, and I. Verdinelli, editors. Case Studies in Bayesian Statistics, Volume VI. Springer-Verlag, New York

• Vance, N., A. Gray, and R. Haberman. 2002. Congruent management of multiple resources: proceedings from the Wood Compatibility Initiative workshop. USDA Forest Service Pacific Northwest Research Station, Portland, OR. General Technical Report PNW-GTR-563

• Lindh, B. C., A. N. Gray, and T. A. Spies. 2003. Responses of herbs and shrubs to reduced root competition under canopies and in gaps: a trenching experiment in old-growth Douglas-fir forests. Canadian Journal of Forest Research 33:2052-2057.

• Gray, A. N. and C. Miller. 2006. Vegetation change in the Blue River Landscape Study: 1998-2005. Pacific Northwest Research Station, U.S. Department of Agriculture, Forest Service, Corvallis, OR. unpublished report on file at, http://andrewsforest.oregonstate.edu/pubs/pdf/pub4202.pdf

• Rudis, V. A., A. N. Gray, W. McWilliams, R. O'Brien, C. Olson, S. Oswalt, and B. K. Schulz. 2006. Regional monitoring of non-native plant invasions with the Forest Inventory and Analysis program. Pages 49-64 in R. E. McRoberts, G. A. Reams, P. C. Van Duesen, and W. H. McWilliams, editors. Proceedings of the 6th Annual Forest Inventory and Analysis Symposium. USDA Forest Service, Denver, CO. http://www.treesearch.fs.fed.us/pubs/14244

   

• Schroeder, T. A., A. Gray, M. E. Harmon, D. O. Wallin, and W. B. Cohen. 2008. Estimating live forest carbon dynamics with a Landsat-based curve-fitting approach. Journal of Applied Remote Sensing 2:023519.

• Azuma, D. L., J. Menlove, and A. N. Gray. 2009. Reserved and Roadless Forests. Pages 16-18 in W. B. Smith, P. D. Miles, C. H. Perry, and S. A. Pugh, editors. Forest Resources of the United States, 2007. US Deparment of Agriculture Forest Service, Washington D.C. http://www.treesearch.fs.fed.us/pubs/34056

• Christensen, G.A.; Gray, A.N.; Kuegler, O.; Yost, A. 2019. Oregon Forest Ecosystem Carbon Inventory: 2001-2016. Salem, OR: Oregon Department of Forestry. 343 p. https://www.oregon.gov/ODF/ForestBenefits/Pages/ForestCarbonStudy.aspx
• Christensen, G.A.; Gray, A.N.; Kuegler, O.; Tase, N.A.; Rosenberg, M.; Loeffler, D.; Anderson, N.; Stockmann, K.; Morgan, T.A. 2019. AB 1504 California Forest Ecosystem and Harvested Wood Product Carbon Inventory: 2017 Reporting Period. Sacramento, CA: California Department of Forestry and Fire Protection. 552 p. https://bof.fire.ca.gov/projects-and-programs/ab-1504/
• Watts, A.; Gray, A.N.; Whittier, T.R. 2017. There’s Carbon in Them Thar Hills: But How Much? Could Pacific Northwest Forests Store More? 195. Portland, Oregon: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 6 p. http://treesearch.fs.fed.us/pubs/53931
• Christensen, G.A.; Gray, A.N.; Kuegler, O.; Tase, N.A.; Rosenberg, M. 2017. AB 1504 California Forest Ecosystem and Harvested Wood Product Carbon Inventory: 2006 – 2015. Sacramento, CA: California Department of Forestry and Fire Protection. 390 p. (“under AB 1504 Report” at: https://bof.fire.ca.gov/projects-and-programs/ab-1504/)

Research Highlights

Highlight	Title	Year
PNW-2015-72	Equations Used to Estimate Regional Tree Biomass and Carbon can be Improved Developing nationally consistent methods for defining, measuring, and calculating biomass components will improve the reliability and applicatio ...	2015
PNW-2013-011	Forest and Agricultural Land Area Declines in Washington State While Residential and Urban Land Use Increases Over Past 30 years Station scientists and partners assessed changes in land use and housing density across Washington state from 1976 to 2006. They found that the ...	2013
PNW-2016-273	Ground-based Estimates of Fire Severity Reveal Information Undetected by Satellite Imagery Analyses A new study provides a broad-scale characterization of the extent of relatively low-severity fires and small fires, including prescribed fires, ...	2016
PNW-2014-197	Increasing Development Near Public Forest Lands in Washington and Oregon Has Implications for Public Land Management and Fire Suppression Areas bordering public forest land in Washington and Oregon are showing substantial increases in development, with the number of structures on p ...	2014
PNW-2014-058	Net Forest Carbon in Oregon Increased Slightly During the Last Decade Gains in forest carbon through tree growth and afforestation in the Pacific Northwest were offset by fire, insects, cutting, and deforestation.	2014
PNW-2017-226	Scientists analyze trends in tree growth to assess change in Interior Alaska’s spruce forest Tree-ring analysis adjusted for age-related changes in growth indicate that recent growth of black and white spruce in Interior Alaska is near t ...	2017
PNW-2017-228	Scientists model four-state region to estimate carbon pools and flux over large domains Variation in climate, disturbance regime, and forest management strongly influence terrestrial carbon sources and sinks.	2017
PNW-2017-215	Wetter, warmer conditions will likely favor biomass accumulation in Douglas-fir Conversely, continued accumulation of forest biomass in drier regions may be more limited.	2017
PNW-2018-82	Working with Cal Fire to monitor carbon sequestration in California Forest Service scientists partnered with California’s Department of Forestry and Fire Protection (Cal Fire) to develop a carbon inventory esse ...	2018