Joan L. Walker

Emeritus Scientist

Department of Forest Resources
233 Lehotsky Hall
Clemson, SC 29634-0001

Phone: 864-656-4822
joan.walker@usda.gov

Research
Education
and Experience
Publications
and Products

Current Research

I am studying the population dynamics, breeding system, habitat requirements of, and fire effects on rare plants in longleaf pine communities.Specifically, I am working on Macbridea alba, Harperocallis flava, Scutellaria floridana, and Echinacea laevigata (not longleaf systems).I am also working in the fall-line sandhills of South Carolina to develop strategies for restoring structure and composition in the ground layer vegetation of altered longleaf pine communities.Sandhills work includes evaluating the effects and interactions of mechanical treatments and prescribed fire on midstory reduction, and describing life histories and establishment requirements for common sandhills herbs.I am working with others to develop a monitoring strategy for Allium tricoccum (ramps) and to model population processes of this species in the Southern Appalachians.

Education

Ph.D. in Biology, 1985: University of North Carolina at Chapel Hill

Featured Publications and Products

Mudder, Bryan T.; Wang, G. Geoff; Walker, Joan L.; Lanham, J. Drew; Costa, Ralph. 2010. Effects of fire season on vegetation in longleaf pine (Pinus palustris) forests.
Walker, Joan L.; Silletti, Andrea M.; Cohen, Susan. 2010. Composition and structure of managed pine stands compared to reference longleaf pine sites on Marine Corps Base Camp Lejeune, North Carolina.
Knapp, Benjamin O.; Wang, G. Geoff; Walker, Joan L. 2010. Artificially regenerating longleaf pine on wet sites: preliminary analysis of effects of site preparation treatments on early survival and growth.
Knapp, Benjamin O.; Wang, G. Geoff; Van Lear, David H.; Walker, Joan L. 2006. Predicting root biomass of burned and unburned white oak advance reproduction from diameter and height.
Knapp, Benjamin O.; Wang, G. Geoff; Walker, Joan L.; Cohen, Susan. 2006. Effects of site preparation treatments on early growth and survival of planted longleaf pine (Pinus palustris Mill.) seedlings in North Carolina.

Publications

Crouch, Connor D.; Knapp, Benjamin O.; Stambaugh, Michael C.; Cohen, Susan ; Walker, Joan L.; Wang, G. Geoff. 2020. Site preparation for longleaf pine restoration on hydric sites: tree- and stand-level responses 15 years after planting.
Knapp, Benjamin O.; Pile, Lauren S.; Walker, Joan L.; Geoff Wang, G. . 2018. Fire effects on a fire-adapted species: response of grass stage longleaf pine seedlings to experimental burning.
Pile, Lauren ; Wang, G. Geoff; Walker, Joan ; Layton, Patricia A. 2018. Plant community response to the management of an invasive tree.
Pile, Lauren S.; Wang, G. Geoff; Knapp, Benjamin O.; Walker, Joan L.; Stambaugh, Michael C. 2017. Chinese tallow (Triadica sebifera) invasion in maritime forests: the role of anthropogenic disturbance and its management implication.
Pile, Lauren S.; Wang, G. Geoff; Waldrop, Thomas A.; Walker, Joan L.; Bridges, William C.; Layton, Patricia A. 2017. Managing an established tree invader: developing control methods for Chinese tallow (Triadica sebifera) in maritime forests.
Knapp, Benjamin O.; Wang, G. Geoff; Walker, Joan L.; Addington, Robert N. 2016. Fate of residual canopy trees following harvesting to underplant longleaf pine seedlings in loblolly pine stands in Georgia.
Reid, Shawna L.; Walker, Joan L.; Schaaf, Abigail. 2016. Using multi-spectral landsat imagery to examine forest health trends at Fort Benning, Georgia.
Knapp, Benjamin O.; Wang, G. Geoff; Walker, Joan L.; Hu, Huifeng. 2016. Using silvicultural practices to regulate competition, resource availability, and growing conditions for Pinus palustris seedlings underplanted in Pinus taeda forests.
Addington, Robert N.; Knapp, Benjamin O.; Sorrell, Geoffrey G.; Elmore, Michele L.; Wang, G. Geoff; Walker, Joan L. 2015. Factors affecting broadleaf woody vegetation in upland pine forests managed for longleaf pine restoration.
Knapp, Benjamin O.; Wang, G. Geoff; Walker, Joan L.; Hu, Huifeng. 2015. From loblolly to longleaf: fifth-year results of a longleaf pine restoration study at two ecologically distinct sites.
Mattingly, W. Brett; Orrock, John L.; Collins, Cathy D.; Brudvig, Lars A.; Damschen, Ellen I.; Veldman, Joseph W.; Walker, Joan L. 2015. Historical agriculture alters the effects of fire on understory plant beta diversity.
Knapp, Benjamin O.; Walker, Joan L.; Wang, G. Geoff; Hu, Huifeng; Addington, Robert N. . 2014. Effects of overstory retention, herbicides, and fertilization on sub-canopy vegetation structure and functional group composition in loblolly pine forests restored to longleaf pine.
Veldman, Joseph W.; Brudvig, Lars A.; Damschen, Ellen I.; Orrock, John L.; Mattingly, W. Brett; Walker, Joan L. 2014. Fire frequency, agricultural history and the multivariate control of pine savanna understorey plant diversity.
Brudvig, Lars A.; Orrock, John L.; Damschen, Ellen I.; Collins, Cathy D.; Hahn, Philip G.; Mattingly, W. Brett; Veldman, Joseph W.; Walker, Joan L. 2014. Land-use history and contemporary management inform an ecological reference model for longleaf pine woodland understory plant communities.
Knapp, Benjamin O.; Wang, G. Geoff; Walker, Joan L. 2013. Effects of canopy structure and cultural treatments on the survival and growth of Pinus palustris Mill. seedlings underplanted in Pinus taeda L. stands.
Hu, Huifeng; Knapp, Benjamin O.; Wang, G. Geoff; Walker, Joan L. 2013. Effects of canopy treatments on early growth of planted longleaf pine seedlings and ground vegetation in North Carolina: a preliminary study.
Ryu, Soung Ryoul; Wang, G. Geoff; Walker, Joan L. 2013. Factors influencing loblolly pine stand health in Fort Benning, Georgia, USA.
Ryu, Soung-Ryoul; Wang, G. Geoff; Walker, Joan L. 2013. The health of loblolly pine stands at Fort Benning, GA.
Wenk, Evelyn S.; Wang, G. Geoff; Walker, Joan L. 2013. Understory fuel variation at the Carolina Sandhills National Wildlife Refuge: a description of chemical and physical properties.
Knapp, Benjamin O.; Walker, Joan L. 2013. Using existing growth models to predict RCW habitat development following site preparation: pitfalls of the process and potential growth response.
Oswalt, Christopher M.; Cooper, Jason A.; Brockway, Dale G.; Brooks, Horace W.; Walker, Joan L.; Connor, Kristina F.; Oswalt, Sonja N.; Conner, Roger C. 2012. History and current condition of longleaf pine in the Southern United States.
Hu, Huifeng; Wang, G.Geoff; Walker, Joan L.; Knapp, Benjamin O. 2012. Silvicultural treatments for converting loblolly pine to longleaf pine dominance: Effects on planted longleaf pine seedlings.
Hu, Huifeng; Wang, G.Geoff; Walker, Joan L.; Knapp, Benjamin O. 2012. Silvicultural treatments for converting loblolly pine to longleaf pine dominance: Effects on resource availability and their relationships with planted longleaf pine seedlings.
Knapp, Ben; Geoff, Wang; Hu, Huifeng; Walker, Joan; Tennant, Carsyn. 2011. Restoring longleaf pine (Pinus palustris Mill.) in loblolly pine (Pinus taeda L.) stands: Effects of restoration treatments on natural loblolly pine regeneration.
Wenk, Evelyn S.; Wang, G. Geoff; Walker, Joan L. 2011. Within-stand variation in understorey vegetation affects fire behaviour in longleaf pine xeric sandhills.
Knapp, Benjamin O.; Wang, G. Geoff; Walker, Joan L.; van Lear, David H. 2006. Can root biomass of white oak advance regeneration be reliably predicted from diameter and height?.
Knapp, Benjamin O.; Wang, G. Geoff; Walker, Joan L. 2006. Early growth of planted longleaf pine seedlings in relation to light, soil moisture, and soil temperature.
Cohen, Susan; Walker, Joan. 2006. Early longleaf pine seedling survivorship on hydric soils.
Walker, Joan L.; Silletti, Andrea M. 2006. Restoring the ground layer of longleaf pine ecosystems.
Walker, Joan L.; Silletti, Andrea M. 2005. A three-year demographic study of Harper's beauty (Harperocallis flava McDaniel), an endangered Florida endemic.
Brockway, Dale G.; Outcalt, Kenneth W.; Guldin, James M.; Boyer, William D.; Walker, Joan L.; Rudolph, D. Craig; Rummer, Robert B.; Barnett, James P.; Jose, Shibu; Nowak, Jarek. 2005. Uneven-aged management of longleaf pine forests: a scientist and manager dialogue.
Godt, M.J.W.; Walker, Joan L.; Hamrick, J.L. 2004. Allozyme diversity in Macbridea alba (Lamiaceae), an endemic Florida mint.
Walker, Joan L.; van Eerden, Brian P.; Robinson, David; Hausch, Mike. 2004. Burning and chopping for woodpeckers and wiregrass?.
Silletti, Andrea M.; Walker, Joan. 2003. Adaptive cluster sampling: An efficient method for assessing inconspicuous species.
Schulze, Dana Madsen; Walker, Joan; Spira, Timothy P. 2002. Germination and Seed Bank Studies of Macbridea alba (Lamiaceae), a Federally Theatened Plant.
Pitts-Singer, Theresa; Hanula, James L.; Walker, Joan L. 2002. Insect Pollinators of Three Rare Plants in a Florida Longleaf Pine Forest.
Smith, Gregory P.; Shelburne, Victor B.; Walker, Joan L. 2002. Structure and Composition of Vegetation of Longleaf Pine Plantations Compared to Natural Stands Occurring Along an Environmental Gradient at the Savannah River Site.
White, Peter S.; Harrod, Jonathan; Walker, Joan L.; Jentsch, Anke. 2000. Disturbance, Scale, and Boundary in Wilderness Management.
White, Peter S.; Harrod, Jonathan; Walker, Joan L.; Jentsch, Anke. 2000. Disturbance, scale, and boundary in wilderness management.
Barnett, Jim; Busby, Rod; Bridgwater, Floyd; English, Don; Hanula, Jim; Herbert, Nancy; Johnsen, Kurt; Kard, Brad; Klepzig, Kier; McMahon, Charlie; Prestemon, Jeff; Rials, Tim; Rummer, Bob; Shelton, Mike; Thill, Ron; Waldrop, Tom; Walker, Joan; Walters, Nancy. 2000. Sustainability and productivity of southern pine ecosystems.
Walker, Joan L. 1999. Longleaf Pine Ecosystem Restoration on Small and Mid-Sized Tracts.
Walker, Joan L. 1999. Longleaf pine forests and woodlands: old growth under fire!.
Covington, Wallace; Niering, William A.; Starkey, Ed; Walker, Joan. 1998. Ecosystem Restoration and Management: Scientific Principles and Concepts\t.
Walker, Joan; Peet, Robert K. 1983. Composition and species diversity of pine-wiregrass savannas of the Green Swamp, North Carolina.

Research Highlights

A Roadmap to Recovery for Degraded Longleaf Pine Plant Communities (2014): Less than 3 percent of the historical longleaf pine ecosystem remains; although much of the southeastern United States has the potential for recovery. Forest Service and university researchers joined forces to develop a roadmap for the recovery of degraded longleaf pine plant communities. Determining how the many possible factors influence recovery is imperative for directing restoration efforts.
Strategic treatments to control Chinese tallow tree in maritime forest (2017): Chinese tallow tree is an aggressive and successful invader in coastal forests of the southeastern US. Forest Service researchers were part of a team that studied how land use history related to successful tallow invasions in a South Carolina maritime forest. They used current understanding of the tallow tree to develop and test alternative strategies for controlling this invasive species while promoting native plant community resilience and restoration.