Current Research

My main research focus investigates the role of the factors that regulate the diversity and abundance of vascular plants in forest understories.  These drivers include natural and anthropogenic disturbances, herbivory, competing vegetation, pests and pathogens, and climate change.  I am involved in multiple projects throughout the United States and Canada asking questions on various subsets of these forces on plant diversity.  These projects range from invasive pests decimating Ash populations, to American chestnut reintroduction efforts, to ungulate impacts on plant communities, to the role climate-adaptive management strategies can play in mitigating climate change effects on forests.

Research Interests

I plan on continuing my research programs on the maintenance of tree and herbaceous species diversity in both temperate hardwood and mixed-wood systems in the tension zone between the temperate hardwoods and boreal systems.

Past Research

Past research had a focus on the maintenance of herbaceous species diversity in both temperate and tropical systems and the role of seed-banking as a mechanism to retain and promote diversity in forests.  A substantial part of my early work was on the role of recalcitrant understory layers inhibiting plant diversity, the impact of soil-borne pathogens on early tree establishment, and forest recovery following catastrophic wind disturbance and salvage logging.

Why This Research is Important

Among the many factors that determine forest understory diversity prior to any overstory disturbance, competition and herbivory are typically thought of as preeminent. Understanding how these two factors, alone and in concert, act to promote or reduce plant diversity is key to the sustainable management of forest resources.

Education

• University of Pittsburgh, Ph.D. Ecology and Evolutionary Biology 2005
• University of North Carolina, Greensboro, M.S. Department of Biological Sciences 1998
• University of North Carolina, Greensboro, B.A. Department of Biological Sciences 1993
• University of Pittsburgh, Graduate Certificate Latin American Studies 2005

Professional Organizations

• Ecological Society of America

Featured Publications & Products

• Royo, Alejandro A.; Kramer, David W.; Miller, Karl V.; Nibbelink, Nathan P.; Stout, Susan L. 2017. Spatio-temporal variation in foodscapes modifies deer browsing impact on vegetation.
• De Jager, Nathan R.; Drohan, Patrick J.; Miranda, Brian M.; Sturtevant, Brian R.; Stout, Susan L.; Royo, Alejandro A.; Gustafson, Eric J.; Romanski, Mark C. 2017. Simulating ungulate herbivory across forest landscapes: A browsing extension for LANDIS-II.
• Royo, Alex; Peterson, Chris J.; Stanovick, John S.; Carson, Walter P. 2016. Evaluating the ecological impacts of salvage logging: can natural and anthropogenic disturbances promote coexistence.
• Morgan, Quinn ; Johnstone-Yellin, Tamara L.; Pinchot, Cornelia C.; Peters, Matthew ; Royo, Alejandro A. 2019. Partitioning and predicting forage biomass from total aboveground biomass of regenerating tree species using dimensional analyses.
• Kern, Christel C.; Burton, Julia I.; Raymond, Patricia; D'Amato, Anthony W.; Keeton, William S.; Royo, Alex; Walters, Michael B.; Webster, Christopher R.; Willis, John L. 2017. Challenges facing gap-based silviculture and possible solutions for mesic northern forests in North America.
• Royo, Alex; Kramer, David W.; Miller, Karl V.; Nibbelink, Nathan P.; Stout, Susan L. 2016. The canary in the coal mine: Sprouts as a rapid indicator of browse impact in managed forests.
• Royo, Alejandro A.; Pinchot, Cornelia C.; Stanovick, John S.; Stout, Susan L. 2019. Timing is Not Everything: Assessing the Efficacy of Pre- Versus Post-Harvest Herbicide Applications in Mitigating the Burgeoning Birch Phenomenon in Regenerating Hardwood Stands.
• Pendergast, Thomas H.; Hanlon, Shane M.; Long, Zachary M.; Royo, Alex; Carson, Walter P. 2016. The legacy of deer overabundance: long-term delays in herbaceous understory recovery.
• 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.
• Leverkus, Alexandro B.; Rey Benayas, José María; Castro, Jorge ; Boucher, Dominique ; Brewer, Stephen ; Collins, Brandon M.; Donato, Daniel ; Fraver, Shawn ; Kishchuk, Barbara E.; Lee, Eun-Jae ; Lindenmayer, David B.; Lingua, Emanuele ; Macdonald, Ellen ; Marzano, Raffaella ; Rhoades, Charles C.; Royo, Alejandro ; Thorn, Simon ; Wagenbrenner, Joseph W.; Waldron, Kaysandra ; Wohlgemuth, Thomas ; Gustafsson, Lena . 2018. Salvage logging effects on regulating and supporting ecosystem services a systematic map.

Publications

• 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.
• Ristau, Todd E.; Royo, Alejandro A. 2020. Influence of stand age, soil attributes, and cover type on Rubus (Rosaceae) seed bank abundance.
• De Vriendt, Laurent ; Thiffault, Nelson ; Royo, Alejandro A.; Barrette, Martin ; Tremblay, Jean-Pierre . 2020. Moose Browsing Tends Spruce Plantations More Efficiently Than a Single Mechanical Release.
• Champagne, Emilie ; Bonin, Michaël ; Royo, Alejandro ; Tremblay, Jean-Pierre ; Raymond, Patricia . 2020. Predicting terpene content in dried conifer shoots using near infrared spectroscopy.
• Pinchot, Cornelia C.; Royo, Alejandro A.; Schlarbaum, Scott E.; Peters, Matthew P.; Sharp, Ami M.; Anagnostakis, Sandra L. 2020. The effect of site quality on performance of American Chestnut (Castanea Dentata) seedlings bred for blight (Cryphonectria Parasitica) resistance.
• Vickers, Lance ; McWilliams, William ; Knapp, Benjamin ; D’Amato, Anthony ; Dey, Daniel ; Dickinson, Yvette ; Kabrick, John ; Kenefic, Laura ; Kern, Christel ; Larsen, David ; Royo, Alejandro ; Saunders, Michael ; Shifley, Stephen ; Westfall, James A. 2019. Are Current Seedling Demographics Poised to Regenerate Northern US Forests.
• Royo, Alejandro A.; Stanovick, John S. 2019. Deer browsing overwhelms extended leaf phenology benefits: A test case with Rubus allegheniensis and a recalcitrant hay-scented fern layer.
• 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.
• Champagne, Emilie ; Royo, Alejandro A.; Tremblay, Jean-Pierre ; Raymond, Patricia . 2019. Phytochemicals Involved in Plant Resistance to Leporids and Cervids: a Systematic Review.
• Slyder, Jacob B.; Wenzel, John W.; Royo, Alejandro A.; Spicer, Michelle Elise; Carson, Walter P. 2019. Post-windthrow salvage logging increases seedling and understory diversity with little impact on composition immediately after logging.
• Royo, Alejandro A.; Stout, Susan L. 2019. Recognition, response, and recovery: Deer impact research in Allegheny hardwood forests.
• Raymond, Patricia ; Royo, Alejandro A.; Prévost, Marcel ; Dumais, Daniel . 2018. Assessing the single-tree and small group selection cutting system as intermediate disturbance to promote regeneration and diversity in temperate mixedwood stands.
• Flower, Charles; Fant, Jeremie; Hoban, Sean; Knight, Kathleen; Steger, Laura; Aubihl, Elijah; Gonzalez-Meler, Miquel; Forry, Stephen; Hille, Andrea; Royo, Alejandro. 2018. Optimizing conservation strategies for a threatened tree species: In situ conservation of white ash (Fraxinus americana L.) genetic diversity through insecticide treatment.
• Flower, Charles E.; Aubihl, Elijah; Fant, Jeremie; Forry, Stephen; Hille, Andrea; Knight, Kathleen S.; Oldland, William K.; Royo, Alejandro A.; Turcotte, Richard M. 2017. In-situ genetic conservation of white ash (Fraxinus americana) at the Allegheny national forest.
• Averill, Kristine M; Mortensen, David A; Smithwick, Erica A H; Kalisz, Susan; McShea, William J; Bourg, Norman A; Parker, John D; Royo, Alejandro A; Abrams, Marc D; Apsley, David K; Blossey, Bernd; Boucher, Douglas H; Caraher, Kai L; DiTommaso, Antonio; Johnson, Sarah E; Masson, Robert; Nuzzo, Victoria A. 2017. A regional assessment of white-tailed deer effects on plant invasion.
• 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.
• Barrette, Martin; Bélanger, Louis; De Grandpré, Louis; Royo, Alejandro A. 2017. Demographic disequilibrium caused by canopy gap expansion and recruitment failure triggers forest cover loss.
• Sinacore, Katherine; Hall, Jefferson Scott; Potvin, Catherine; Royo, Alejandro A.; Ducey, Mark J.; Ashton, Mark S.; Joseph, Shijo. 2017. Unearthing the hidden world of roots: Root biomass and architecture differ among species within the same guild.
• 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.
• Chips, Michael J.; Yerger, Ellen H.; Hervanek, Arpad; Nuttle, Tim; Royo, Alex; Pruitt, Jonathan N.; McGlynn, Terrence P.; Riggall, Cynthia L.; Carson, Walter P. 2015. The indirect impact of long-term overbrowsing on insects in the Allegheny National Forest region of Pennsylvania.
• 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.
• 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.
• Peterson, Chris J.; Krueger, Lisa M.; Royo, Alejandro A.; Stark, Scott; Carson, Walter P. 2013. Disturbance size and severity covary in small and mid-size wind disturbances in Pennsylvania northern hardwoods forests.
• Nuttle, Tim; Royo, Alejandro A.; Adams, Mary Beth; Carson, Walter P. 2013. Historic disturbance regimes promote tree diversity only under low browsing regimes in eastern deciduous forest.
• Royo, Alejandro A.; Ristau, Todd E. 2013. Stochastic and deterministic processes regulate spatio-temporal variation in seed bank diversity.
• Stout, Susan L.; Royo, Alejandro A.; deCalesta, David S.; McAleese, Kevin; Finley, James C. 2013. The Kinzua Quality Deer Cooperative: can adaptive management and local stakeholder engagement sustain reduced impact of ungulate browsers in forest systems.
• 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.
• Dey, Daniel C.; Royo, Alejandro A.; Gardiner, Emile S.; Cardenas, Luis Mario. 2012. Sustaining Quercus humboltii and Colombobalanus excelsa on the Colombian landscape: preservation or conservation - a research perspective.
• Dey, Daniel C.; Royo, Alejandro A.; Gardiner, Emile S.; Cardenas, Luis Mario. 2012. Sustaining Quercus humboldtii and Colombobalanus excelsa on the Colombian landscape: preservation or conservation - a research perspective.
• Royo, Alejandro A.; Knight, Kathleen S. 2012. White ash (Fraxinus americana) decline and mortality: the role of site nutrition and stress history.
• Royo, Alejandro A.; Knight, Kathleen S.; Himes, Jamie M.; Will, Ashley N. 2012. White ash (Fraxinus americana) health in the Allegheny plateau region, Pennsylvania: Evaluating the relationship between FIA phase 3 crown variables and a categorical rating system.
• 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.
• Royo, Alejandro A.; Heartsill-Scalley, Tamara; Moya, Samuel; Scatena, Fred N. 2011. Non-arborescent vegetation trajectories following repeated hurricane disturbance: ephemeral versus enduring responses.
• Kain, Morgan; Battaglia, Loretta; Royo, Alejandro; Carson, Walter P. 2011. Over-browsing in Pennsylvania creates a depauperate forest dominated by an understory tree: results from a 60-year-old deer exclosure.
• Dey, Daniel C.; Royo, Alejandro A.; Brose, Patrick H.; Hutchinson, Todd F.; Spetich, Martin A.; Stoleson, Scott H. 2010. An ecologically based approach to oak silviculture: a synthesis of 50 years of oak ecosystem research in North America.
• Reinhart, Kurt O.; Royo, Alejandro A.; Kageyama, Stacie A.; Clay, Keith. 2010. Canopy gaps decrease microbial densities and disease risk for a shade-intolerant tree species.
• Knight, Kathleen S.; Herms, Daniel A.; Cardina, John; Long, Robert; Rebbeck, Joanne; Gandhi, Kamal J.K.; Smith, Annemarie; Klooster, Wendy S.; Herms, Catherine P.; Royo, Alejandro A. 2010. Emerald ash borer aftermath forests: The dynamics of ash mortality and the responses of other plant species.
• Royo, Alejandro A.; Collins, Rachel; Adams, Mary Beth; Kirschbaum, Chad; Carson, Walter P. 2010. Pervasive interactions between ungulate browsers and disturbance regimes promote temperate forest herbaceous diversity.
• Royo, Alejandro A.; Stout, Susan L.; deCalesta, David S.; Pierson, Timothy G. 2010. Restoring forest herb communities through landscape-level deer herd reductions: Is recovery limited by legacy effects.
• Royo, Alejandro A.; Carson, Walter P. 2010. The formation of dense understory layers in forests worldwide: consequences and implications for forest dynamics, biodiversity, and succession.
• Krueger, Lisa M.; Peterson, Chris J.; Royo, Alejandro ; Carson, Walter P. 2009. Evaluating relationships among tree growth rate, shade tolerance, and browse tolerance following disturbance in an eastern deciduous forest.
• Royo, Alejandro A.; Bates, Ramona M.; Lacey, Elizabeth P. 2008. Demographic constraints in three populations of Lobelia boykinii, a rare wetland endemic.
• Royo, Alejandro A.; Carson, Walter P. 2008. Direct and indirect effects of a dense understory on tree seedling recruitment in temperate forests: habitat-mediated predation versus competition.
• Royo, A.A. 2008. P.A. Thomas and J. Packham: Ecology of woodlands and forests: Description, dynamics, and diversity book review.
• Royo, Alejandro ; Carson, Walter P. 2006. On the formation of dense understory layers in forests worldwide: consequences and implications for forest dynamics, biodiversity, and succession.
• Comisky, Lauren ; Royo, Alejandro A.; Carson, Walter P. 2005. Deer Browsing Creates Rock Refugia Gardens on Large Boulders in the Allegheny National Forest, Pennsylvania.
• Carson, Walter P.; Banta, Joshua A.; Royo, Alejandro A.; Kirschbaum, Chad. 2005. Plant communities growing on boulders in the Allegheny National Forest: Evidence for boulders as refugia from deer and as a bioassay of overbrowsing.
• Reinhart, Kurt O.; Royo, Alejandro A.; Van Der Putten, Wim H.; Clay, Keith . 2005. Soil feedback and pathogen activity in Prunus serotina throughout its native range.
• Royo, Alejandro A.; Carson, Walter P. 2005. The herb community of a tropical forest in central Panama: dynamics and impact of mammalian herbivores.

Research Highlights

Highlight	Title	Year
NRS-2012-09	Can We Bank on Forest Seed Banks Community composition of seeds stored in forest soils becomes increasingly divergent over time	2012
NRS-2018-106	Genetic Information on Ash Informs Treatments for Emerald Ash Borer  Forest managers can use insecticide treatments to protect ash trees from emerald ash borer to conserve the genetic diversity of ash. But which t ...	2018
NRS-2011-20	Hurricanes Disturb Non-tree Subtropical Wet Forest Species Composition Hurricane disturbance caused pronounced and persistent changes in the non-tree species composition of a subtropical wet forest. A unique long-te ...	2011
NRS-2015-117	International Symposium Improves Understanding of Disturbance and Salvage Logging and Forest Sustainability The Forest Service’s Northern Research Station along with the University of Pittsburgh and the Carnegie Museum of Natural History sponsored an ...	2015
NRS-2010-020	Landscape-level Deer Herd Reductions Restore Forest Understory Plant Communities but Not Species Diversity Since 2001, NRS scientist Alejandro Royo has tracked the response of herbaceous plant communities to deer herd reductions throughout the 70,000- ...	2010
NRS-2017-16	Managing the foodscape to alleviate deer browsing Forest plant biodiversity is being degraded by browsing from overabundant deer herds, but forest management can alleviate impacts. Research by F ...	2017
NRS-2016-97	Sprouts as Rapid Bioassays of Browse Impact Effective browse pressure indicators are necessary to adaptively manage forest landscapes with resident deer. Hardwood tree stump sprouts are a ...	2016