Bart R. JohnsonAssociate Professor | Department of Landscape Architecture | University of Oregon e-mail: bartj@uoregon.edu


Home Current Research and Scholarship
Oak Savanna Landscape Planning and Restoration Upland Prairie Fire Ecology And Restoration Wetland Prairie Restoration Plant Introduction Genetics Oak Savanna Aesthetics Ecology and Restoration of Rock Outcrop Plant Communities
Past Research and Scholarship
Urban Ecology Education Salmon-Friendly Urban Riverfront Design Urban Riverfront Design Ecology and Design Education Ecology and Participation in Landscape-based Planning Little Applegate Watershed Design The Ecology and Restoration of a High Montane Rare Plant Community Biodiversity in the Klamath-Siskiyou Mountains
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Recent Publications  

Ecology and Restoration of Rock Outcrop Plant Communities

Starting in 1987, I began conducting research on the ecology and restoration of a rare plant community found on high montane outcrops in the Southern Appalachian Mountains of North Carolina and Tennessee. This work has included investigations of the impacts of visitor trampling and woody plant succession on rare plant populations; an assessment of rare species microhabitats; rare plant demography and population genetics; and methods of habitat protection and restoration.

I am currently building on past research to examine the joint cultural and ecological roles rock outcrops play in landscapes around the world, and the conflicts engendered by their dual roles for people and other species. Part of this research focuses on how rock outcrops serve as refugia for many species, including a large number of threatened and endangered plants.

Peer-Reviewed Publications

Johnson, B. R. 1996. Southern Appalachian rare plant reintroductions on granite outcrops. Pages 433-443 in D.A. Falk, C.I. Millar and M. Olwell, eds., Restoring diversity, strategies for reintroduction of endangered plants. Washington, D.C.: Island Press.

Godt, M. J., B. R. Johnson and J.L. Hamrick. 1996. Genetic diversity and population size in four rare Southern Appalachian plant species. Conservation Biology 10(3): 796-805. (download PDF)

Technical Reports, Theses and Other Publications

Johnson, B. R. 1995. The ecology and restoration of a high montane rare plant community. Ph.D. Diss., University of Georgia, Athens. 199 pp.

Johnson, B. R., N. Murdock and C. Frost. 1993. Spreading Avens management plan. U.S. Fish and Wildlife Service, Atlanta, GA. 19 pp.

Johnson, B. R. 1992. Mitigation of visitor impacts on high montane rare plant habitat: habitat protection through an integrated strategy of design, interpretation and restoration, Craggy Gardens, Blue Ridge Parkway, North Carolina. MLA thesis, University of Georgia, Athens. 143 pp. Printed as National Park Service Technical Report. NPS Southeast Region, Atlanta, GA.

Hamrick, J. L., M. Godt and B. R. Johnson. 1991. Levels and distribution of genetic diversity in four rare vascular plant species. Final report. National Park Service Cooperative Studies Unit, University of Georgia, Athens, GA.

Johnson, B. R. 1989. Visitor use at Craggy Pinnacle, Blue Ridge Parkway: Its impacts on rare plants and implications for site management. CPSU Technical Report No. 54. National Park Service Cooperative Studies Unit, Institute of Ecology, University of Georgia, Athens, GA. 69 pp.

Johnson, B. R. 1989. Detailed microhabitat assessment accompanies restoration of rare plants, outcrop communities. Restoration & Management Notes 7(2): 97-98.

Johnson, B. R. 1989. Interpretive signs increase effectiveness of brush-pile barriers. Restoration & Management Notes 7(2): 97-98.

Johnson, B., S. Bratton & B. Teague. 1989. Rare plants protected on Blue Ridge Parkway. Highlights of Natural Resources Management 1988. Natural Resources Report NPS-NR-89-01.

Johnson. B. R. 1989. Footprints on rare plants: habitat protection through design, interpretation and restoration. Georgia Landscape, Spring 1989:12-13.

Johnson, B.R., S.P. Bratton and I. Firth. 1988. The feasibility of using brushing to deter visitor use of unofficial trails at Craggy Gardens, Blue Ridge Parkway, North Carolina. CPSU Technical Report No. 43. National Park Service Cooperative Studies Unit, Institute of Ecology, University of Georgia, Athens, GA. 32 pp.

Johnson, B. R., S. P. Bratton and I. Firth. 1988. Brushing alone of limited value in deterring use of unofficial trails. Restoration and Management Notes 6(2):102-103.

Past Projects

1992-97 Habitat Protection and Restoration of Geum radiatum. U.S. Fish and Wildlife contracts. $33,000 (P.I.).
1992-93 Odum Foundation Research Grants. $850 (P.I.).
1988-91 Habitat Restoration and Landscape Design. National Park Service contracts. $15,200 (P.I.).

Johnson, B.R. 1995. The ecology and restoration of a high montane rare plant community. Ph.D. Diss., University of Georgia, Athens. 199 pp.

Rare plant conservation efforts increasingly call for restoration, not just protection, of extant habitat. Restoration initiatives can be strengthened by knowledge of ecological processes that occur across a range of spatial and temporal scales. In the Southern Appalachian Mountains of the United States, 15 rare herbs are restricted to high montane rock outcrops. My studies of six species indicate that the interaction of three primary factors explains both the distribution of the rare herbs and their declines:

  1. the evolutionary history of the species as arctic-alpine relicts;
  2. the combined influences of physiological tolerances and competitive relationships; and
  3. human impacts through direct effects of trampling and indirect effects on plant succession.

At broad spatial and temporal scales, ecological processes associated with global climate change have restricted elements of a former alpine flora to rock outcrops on cool, moist, mountain summits. Visitor disturbance and woody plant succession appear to be the primary agents of recent population declines; within sites, their effects occur primarily at the scale of individual outcrops, and habitat patches are affected according to their position on the outcrops Within and among habitat patches, a moisture gradient best differentiates the microhabitats of different rare species. Experimental plant introductions showed that the rare species can grow to reproductive maturity over a broader range of microhabitat conditions than those in which they naturally occur. The combined influences of physiological tolerances and competitive relationships appear to be the primary determinant of species distributions at both site and microhabitat scales.

If these species survive in their outcrop refugia, they may be able to reoccupy the zonal vegetation during the next period of global cooling. Thus, the high montane rock outcrops may play an important ecological role in larger landscape processes occurring over longer temporal scales. The long-term ecological role of the rare herbs is not evident from their current distribution, but rather in the context of such broader spatial and temporal processes. A hierarchical approach to habitat protection and restoration offers a practical way to place human influences within the context of broader and finer scales of influence.