Scientists & Staff

Todd Ristau
P.O. Box 267
Current Research
- Influence of nitrogen deposition changes on black cherry seed production and seedling development in a changing environment following the reduced nitrate and sulfate emissions and deposition.
- Recognizing silvicultural problems and opportunities during the early stem exclusion phase of stand development including competition and use of treatments such as herbicides and fertilizers to enhance seedling development.
- Long term changes in old growth forests of the Allegheny Plateau region with focus on Hearts Content, Cook Forest and Tionesta Natural Area.
- Enhancement of regeneration guidelines for northern hardwood forests, especially as related to herbicide and fertilizer use.
Research Interests
- I am interested in how both woody and herbaceous plant communities respond to disturbances.
- I am interested in understanding the conditions that result in monoculture following overstory removal and how to apply existing or novel silvicultural techniques to prevent monoculture and promote mixed species regeneration.
- I am interested in how unmanaged old growth forests differ from or are similar to managed second growth forests in terms of both woody and herbaceous species composition following disturbances.
- I work to develop guidelines for forest management that are used in the SILVAH system of stand inventory, analysis and prescription used by many foresters in the northcentral and northeastern states use as a tool for forest management.
Why This Research is Important
Our mission is to enhance the basic understanding of Allegheny Plateau forest ecosystems while developing resource management guidelines. Understanding how management activities alter the herbaceous plant community in stands under a variety of management strategies is critical to the practice of ecosystem management. Understanding the competitive ability of species like black birch, black cherry, and pin cherry are important. Understanding establishment requirements and creating conditions favorable for a variety of species to become established where they are best suited is critical to achieving our mission goals.Education
- The State University of New York, College of Env. Sci. and For., Ph.D. Plant Ecology, 2010
- The Pennsylvania State University, M.S. Forest Science, 1997
- Houghton College, B.S. Biology, 1991
Professional Organizations
- Ecological Society of America (1995 - Present)
- Torrey Botanical Society (1998 - Present)
- Society of American Foresters (SAF) (1995 - Present)
Featured Publications & Products
- Long, Robert P.; Ristau, Todd E. 2020. Changes in Black Cherry Seed Production: Is Stand Age a Factor?. Northeastern Naturalist
- Royo, Alejandro ; Vickers, Lance ; Long, Robert ; Ristau, Todd ; Stoleson, Scott ; Stout, Susan L. 2021. The Forest of Unintended Consequences: Anthropogenic Actions Trigger the Rise and Fall of Black Cherry. BioScience
- Ristau, Todd. 2019. Using herbicides to control interfering understories in the Allegheny hardwood stands, 2. Sharpening the tools in the toolbox. In: Stout, Susan L., ed. SILVAH: 50 years of science-management cooperation. Proceedings of the Allegheny Society of American Foresters training session; 2017 Sept. 20-22; Clarion, PA. Gen. Tech. Rep. NRS-P-186. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northern Research Station: 44-55.
- Ristau, Todd E.; Royo, Alejandro A. 2020. Influence of stand age, soil attributes, and cover type on Rubus (Rosaceae) seed bank abundance. The Journal of the Torrey Botanical Society
- Ristau, Todd E. 2017. Control of hay-scented and New York ferns with Oust Xp® herbicide: Revisiting rate and timing required in mixed oak and northern hardwood stands. In: Kabrick, John M.; Dey, Daniel C.; Knapp, Benjamin O.; Larsen, David R.; Shifley, Stephen R.; Stelzer, Henry E., eds. Proceedings of the 20th Central Hardwood Forest Conference; 2016 March 28-April 1; Columbia, MO. General Technical Report NRS-P-167. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northern Research Station: 11-18.
- Ristau, Todd E.; Stoleson, Scott H.; Horsley, Stephen B.; deCalesta, David S. 2011. Ten-year response of the herbaceous layer to an operational herbicide-shelterwood treatment in a northern hardwood forest. Forest Ecology and Management. 262: 970-979.
- Horsley, Stephen B.; Bailey, Scott W.; Ristau, Todd E.; Long, Robert P.; Hallett, Richard A. 2008. Linking environmental gradients, species composition, and vegetation indicators of sugar maple health in the northeastern United States. Canadian Journal of Forest Research. 38: 1761-1774.
- Nuttle, Tim; Yerger, Ellen H.; Stoleson, Scott H.; Ristau, Todd E. 2011. Legacy of top-down herbivore pressure ricochets back up multiple trophic levels in forest canopies over 30 years. Ecosphere. 2(1): Article 4.
- Royo, Alejandro A.; Ristau, Todd E. 2013. Stochastic and deterministic processes regulate spatio-temporal variation in seed bank diversity. Journal of Vegetation Science. 24: 724-734.
- Ristau, Todd E.; Horsley, Stephen B. 1999. Pin cherry effects on Allegheny hardwood stand development. Canadian Journal of Forest Research. 29: 73-84.
Publications & Products
- Stout, Susan L.; Brose, Patrick H.; Cleveland, Helene ; Long, Robert P.; McGuinness, Barbara ; Peters, Matthew P.; Rebbeck, Joanne ; Ristau, Todd ; Royo, Alejandro A.; Stoleson, Scott H.; Thomasma, Scott ; Twery, Mark J.; Wurzbacher, Sarah. 2019. Fifty years of science-management cooperation from the SILVAH community of practice. In: Stout, Susan L., ed. SILVAH: 50 years of science-management cooperation. Proceedings of the Allegheny Society of American Foresters training session; 2017 Sept. 20-22; Clarion, PA. Gen. Tech. Rep. NRS-P-186. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northern Research Station: 8-25.
- McWilliams, William H.; Westfall, James A.; Brose, Patrick H.; Dey, Daniel C.; D'Amato, Anthony W.; Dickinson, Yvette L.; Fajvan, Mary Ann; Kenefic, Laura S.; Kern, Christel C.; Laustsen, Kenneth M.; Lehman, Shawn L.; Morin, Randall S.; Ristau, Todd E.; Royo, Alejandro A.; Stoltman, Andrew M.; Stout, Susan L. 2018. Subcontinental-scale patterns of large-ungulate herbivory and synoptic review of restoration management implications for midwestern and northeastern forests. Gen. Tech. Rep. NRS-182. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northern Research Station. 24 p.
- McWilliams, William H.; Westfall, James A.; Brose, Patrick H.; Lehman, Shawn L.; Morin, Randall S.; Ristau, Todd E.; Royo, Alejandro A.; Stout, Susan L. 2017. After 25 years, what does the Pennsylvania Regeneration Study tell us about oak/hickory forests under stress?. In: Kabrick, John M.; Dey, Daniel C.; Knapp, Benjamin O.; Larsen, David R.; Shifley, Stephen R.; Stelzer, Henry E., eds. Proceedings of the 20th Central Hardwood Forest Conference; 2016 March 28-April 1; Columbia, MO. General Technical Report NRS-P-167. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northern Research Station: 280-290.
- McWilliams, William H.; Westfall, James A.; Brose, Patrick H.; Dey, Daniel C.; Hatfield, Mark; Johnson, Katherine; Laustsen, Kenneth M.; Lehman, Shawn L.; Morin, Randall S.; Nelson, Mark D.; Ristau, Todd E.; Royo, Alejandro A.; Stout, Susan L.; Willard, Thomas; Woodall, Christopher W. 2015. A regeneration indicator for Forest Inventory and Analysis: history, sampling, estimation, analytics, and potential use in the midwest and northeast United States. Gen. Tech. Rep. NRS-148. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northern Research Station. 74 p.
- Huebner, Cynthia D.; Steinman, Jim; Hutchinson, Todd F.; Ristau, Todd E.; Royo, Alejandro A. 2014. The distribution of a non-native (Rosa multiflora) and native (Kalmia latifolia) shrub in mature closed-canopy forests across soil fertility gradients. Plant and Soil. 377(1-2): 259-276.
- Nuttle, Tim; Ristau, Todd E.; Royo, Alejandro A. 2014. Long-term biological legacies of herbivore density in a landscape-scale experiment: forest understories reflect past deer density treatments for at least 20 years. Journal of Ecology. 102: 221-228.
- Ristau, Todd E.; Stout, Susan L. 2014. Can cover data be used as a surrogate for seedling counts in regeneration stocking evaluations in northern hardwood forests?. Res. Note NRS-198. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northern Research Station. 10 p.
- Trager, Matthew D.; Ristau, Todd E.; Stoleson, Scott H.; Davidson, Robert L.; Acciavatti, Robert E. 2013. Carabid beetle responses to herbicide application, shelterwood seed cut and insect defoliator outbreaks. Forest Ecology and Management. 289: 269-288.
- Huebner, Cynthia D.; Hutchinson, Todd; Ristau, Todd; Royo, Alejandro; Steinman, James. 2012. Documenting the Regional and local distribution of Kalmia latifolia and Rosa multiflora in West Virginia, Ohio, and Pennsylvania Forests along a soil fertility gradient. In: Potter, Kevin M.; Conkling, Barbara L., eds. 2012. Forest health monitoring: 2009 national technical report. Gen. Tech. Rep. SRS-167. Asheville, NC: U.S. Department of Agriculture Forest Service, Southern Research Station. 211-217.
- Goetsch, Chandra ; Wigg, Jennifer ; Royo, Alejandro A.; Ristau, Todd ; Carson, Walter P. 2011. Chronic over browsing and biodiversity collapse in a forest understory in Pennsylvania: Results from a 60 year-old deer exclusion plot. The Journal of the Torrey Botanical Society
- Stoleson, Scott H.; Ristau, Todd E.; deCalesta, David S.; Horsley, Stephen B. 2011. Ten-year response of a forest bird community to an operational herbicide-shelterwood treatment in Allegheny hardwoods. Forest Ecology and Management. 262: 1205-1214.
- Brose, Patrick H.; Gottschalk, Kurt W.; Horsley, Stephen B.; Knopp, Peter D.; Kochenderfer, James N.; McGuinness, Barbara J.; Miller, Gary W.; Ristau, Todd E.; Stoleson, Scott H.; Stout, Susan L. 2008. Prescribing regeneration treatments for mixed-oak forests in the Mid-Atlantic region. Gen. Tech. Rep. NRS-33. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northern Research Station. 100 p.
- Morin, Randall S.; Liebhold, Andrew M; Gottschalk, K.W.; Woodall, Chris W.; Twardus, Daniel B.; White, Robert L.; Horsley, Stephen B.; Ristau, Todd E. 2006. Analysis of forest health monitoring surveys on the Allegheny National Forest (1998-2001). Gen. Tech. Rep. NE-339. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northeastern Research Station. 102 p.
- Ristau, Todd E.; Horsley, Stephen B. 2006. When is pin cherry (Prunus pensylvanica L.) a problem in Allegheny hardwoods?. Northern Journal of Applied Forestry 23(3):204-210
- Stout, Susan L.; Hoover, Coeli M.; Ristau, Todd E. 2006. Listening to old beech and young cherry trees - long-term research in the Alleghenies. In: Irland, Lloyd C.; Camp, Ann E.; Brissette, John C.; and Donohew, Zachary R., eds. Long-term Silvicultural & Ecological Studies: Results for Science and Management. New Haven, CT: Yale University: 10-25
- Stout, Susan L.; Ristau, Todd E. 2005. Long-term Research on the USFS Kane Experimental Forest in Northwestern Pennsylvania. In: Kenefic, Laura S.; Twery, Mark J., eds. Changing Forests - Challenging Times: Proceedings of the New England Society of American Foresters 85th Winter Meeting; 2005 March 16-18; Gen. Tech. Rep. NE-325. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northeastern Research Station: 76
- Ristau, Todd E.; Horsley, Stephen B.; McCormick, Larry H. 2001. Sampling to assess species diversity of herbaceous layer vegetation in Allegheny hardwood forests. Journal of the Torrey Botanical Society. 128(2): 150-164.
- McCormick, Larry H.; Groninger, John W.; Penrod, Kathy A.; Ristau, Todd E. 1993. Deer exclusion effects on understory development following partial cutting in a Pennsylvania oak stand. In: Gillespie, Andrew R.; Parker, George R.; Pope, Phillip E.; Rink, George: eds. Proceedings of the 9th Central Hardwood Forest Conference; Gen. Tech. Rep. NC-161. St. Paul, MN: U.S. Department of Agriculture, Forest Service, North Central Forest Experiment Station: 418-427
National Research Highlights
Black cherry regeneration difficulties: Are They Related to Stand Age or Something Else?
Year: 2017
Forest managers report that black cherry regeneration is impeded by poor and erratic seed production. Tree stand age has been suggested as one of the causal factors affecting seed production. Forest Service scientists monitored black cherry seed production over seven years to see whether stand age affects seed production.
Using fertilizer to promote diverse seedling development in Allegheny hardwood forests
Year: 2017
Fertilizing the forest understory slows the development of dominance by sweet birch, favors development of black cherry following overstory removal, and favors red maple in partial cut shelterwood stands.
Changes in Black Cherry on the Allegheny Plateau
Year: 2016
Increased tree mortality, decreased seed production, and seedling growth. Managers and scientists have been observing these changes in black cherry on the Allegheny Plateau and are working together to sharpen the research focus and utilize long-term research to improve forest management.
Fine-tuning Herbicide Prescriptions in Northern Hardwood Forests
Year: 2016
Fine-tuning existing herbicide prescriptions leads to better results for forest managers and landowners.
Pennsylvania Regeneration Study Assesses Overstory and Understory Tree Species Communities
Year: 2014
In 2001, the Commonwealth of Pennsylvania and Forest Service's Forest Inventory & Analysis (FIA) program launched the "Pennsylvania Regeneration Study" to gain a better understanding of understory conditions across Pennsylvania. The landscape-level study was incorporated into a subset of the existing FIA sample locations. At each selected plot, composition and abundance of established tree seedlings and associated non-tree vegetation were recorded. Forest Service scientists analyzed the 2001 to 2005 data to determine whether overstory and understory species composition was similar by forest type or ecoregion and to test various hypotheses about causes for dissimilarity.
Scientists Study Long-term Response of Ground Beetle Communities to an Operational Herbicide Application
Year: 2013
Ground beetles comprise a large and diverse group of mostly predatory beetles that have long been recognized as a useful barometer of ecosystem health. As part of a long-term, large-scale study of the impacts of an operational herbicide-shelterwood treatment, Forest Service scientists found no treatment response by ground beetles as measured by abundance or diversity. However, their numbers and diversity were strongly correlated with natural outbreaks of forest lepidopterans, an order of insects that include moths and butterflies.
Long-Term Differences in Forests With Different Deer Densities
Year: 2011
Thirty years after a study on the effects of deer on forest ecosystems established new forest stands at deer densities ranging from 10 to 64 deer per square mile, Forest Service scientists found that tree species diversity, canopy foliage density, insect density and bird density, all decreased significantly as the deer density at stand initiation increased. If deer densities were high initially, the effects carried over, even if densities were lower later.