Shorelines are a type of habitat with strong environmental gradients and high biological diversity.  Many, but not all, shorelines are also wetlands, and these wetlands can intergrade with sand dunes and upland forests. Shorelines also offer natural biological corridors through landscapes. Because of the strong environmental gradients, plants (and some animals) often occur in visually distinctive zones.


Shorelines often have a wide array of wetland vegetation types. This is primarily the result of interactions between two environmental factors: (1) gradients of exposure to waves/ ice scour and (2) fluctuation in water levels, which change environmental conditions both within and among years. Waves, ice scour and water level fluctuations in combination also reduce shrub cover on shorelines, thereby allowing a rich herbaceous flora to occur. Paul Keddy and his associates have studied these factors over many years, with particular emphasis on the rare vegetation types that occur upon infertile, wave-washed shorelines. This work has important lessons for managing lakes and reservoirs, and indeed, floodplains in general.

The following resources fall into three categories.  First, there is a short set of readings on shorelines in general, with particular emphasis upon environmental gradients.  Then there are some key readings on water level fluctuations. Finally, there are some readings on exposure gradients, which are relatively overlooked in plant ecology, but which were a particular focus of Paul Keddy’s wetland work between 1975 and 1995. Exposure gradients are of paraticular interest to plant ecologists because they combine stress and distrubance gradients.

General Readings

Keddy, P.A. and L.H. Fraser. 2000. Four general principles for the management and conservation of wetlands in large lakes: the role of water levels, nutrients, competitive hierarchies and centrifugal organization. Lakes and Reservoirs: Research and Management 5:177-185. (Download PDF)The four major causal factors that control species composition on shorelines.

Keddy, P.A.1991. Working with heterogeneity:  an operator’s guide to environmental gradients. in J. Kolasa and S.T.A. Pickett (eds.) Ecological Heterogeneity, Springer Verlag, New York. (Download PDF)

How to take advantage of natural gradients in planning ecological research.

Keddy, P.A. and A.A. Reznicek.  1986.  Great Lakes vegetation dynamics:  the role of fluctuating water levels and buried seeds.  Journal of Great Lakes Research 12: 25-36. (Download PDF).

The importance of natural water level fluctuations on shorelines.  These principles apply to all shorelines, not just the Great Lakes.

Keddy, P.A. 2010. Zonation: shorelines as a prism. Chapter 10 in Wetland Ecology: Principles and Conservation. (Pages 268-299) Cambridge University Press, Cambridge, UK.

An overview of shoreline zonation, with a particular emphasis upon field experimentsthat have explored causal mechanisms, and statistical techniques that have sought general patterns.

Keddy, P.A. 2017. Gradients and plant communities. Chapter 11 in Plant Ecology: Origins, Processes, Consequences. (Pages 410-449). Cambridge University Press, Cambridge, UK.

An overview of the role of gradients in shaping plant communities, and the tools available for studying them, drawing upon a wide array of examples from mountainsides to lakeshores. Thus, this chapter provides the larger context for work on shorelines.

Water Levels and Water-Level Fluctuations

  • Hill, N. M., P.A. Keddy and I. C. Wisheu. 1998. A hydrological model for predicting the effects of dams on the shoreline vegetation of lakes and reservoirs. Environmental Management 22: 723-736.
  • Toner, M., and P. Keddy. 1997. River hydrology and riparian wetlands: a predictive model for ecological assembly. Ecological Applications 7: 236-246.
  • Weiher, E., I. C. Wisheu, P.A. Keddy and D.R.J. Moore. 1996. Establishment, persistence, and management implications of experimental wetland plant communities. Wetlands 16: 208-218.
  • Boutin, C. and P. A. Keddy. 1993. A functional classification of wetland plants. Journal of Vegetation Science 4: 591-600.
  • Hill, N. and P.A. Keddy. 1992. Predicting numbers of rarities from habitat variables: coastal plain plants of Nova Scotian lakeshores. Ecology 73: 1852-1859
  • Shipley, B. S., P.A. Keddy and L. P. Lefkovitch. 1991. Mechanisms producing plant zonation along a water depth gradient: a comparison with the exposure gradient. Canadian Journal of Botany 69: 1420-1424.
  • Wisheu, I. C. and P.A. Keddy. 1991. Seed banks of a rare wetland plant community: distribution patterns and effects of human induced disturbance. Journal of Vegetation Science 2: 181-188.
  • Shipley, B., P.A. Keddy, D.R.J. Moore and K. Lemky. 1990. Regeneration and establishment strategies of emergent macrophytes. Journal of Ecology 77: 1093-1110.
  • Keddy, P.A. 1989. Effects of competition from shrubs on herbaceous wetland plants: a four year field experiment. Canadian Journal of Botany 67: 708-716.
  • Nilsson, C. and P.A. Keddy. 1988. Predictability of change in shoreline vegetation along a hydro electric reservoir, Northern Sweden. Canadian Journal of Fisheries and Aquatic Sciences 45:1896-1904.
  • Keddy, P.A. and A. A. Reznicek. 1982. The role of seed banks in the persistence of Ontario’s coastal plain flora. American Journal of Botany 69:13-22.  
  • Keddy, P.A. 1985. Lakeshore plants in the Tusket River Valley, Nova Scotia: the distribution and status of some rare species including Coreopsis rosea and Sabatia kennedyana.Rhodora 87:309-320.

Exposure Gradients

  • Weiher, E. and P.A. Keddy. 1995. The assembly of experimental wetland plant communities. Oikos 73: 323-335.
  • Gaudet, C.L. and P.A. Keddy. 1995. Competitive performance and species distribution in shoreline plant communities: a comparative approach. Ecology 76: 280-291.
  • Wisheu, I. C. and P.A. Keddy. 1994. The low competitive ability of Canada’s Atlantic coastal plain shoreline flora: implications for conservation. Biological Conservation 68: 247-252.
  • Wisheu, I. C., C. J. Keddy, P.A. Keddy and N.M. Hill. 1994. Disjunct Atlantic coastal plain species in Nova Scotia: distribution, habitat and conservation priorities. Biological Conservation 68: 217-224.
  • Moore, D.R.J. and P.A. Keddy. 1989. The relationship between species richness and standing crop in wetlands: the importance of scale. Vegetation 79: 99-106.
  • Keddy, P.A. and I. C. Wisheu. 1989. Species richness-standing crop relationships along four lakeshore gradients: constraints on the general model. Canadian Journal of Botany 67: 1609-1617.
  • Keddy, P.A. and I. C. Wisheu. 1989. Ecology, biogeography and conservation of coastal plain plants: some general principles from the study of Nova Scotia wetlands. Rhodora 91: 72-94.
  • Moore, D.R.J., P.A. Keddy, C.L. Gaudet and I. C. Wisheu. 1989. Conservation of wetlands: do infertile wetlands deserve a higher priority? Biological Conservation 47: 203- 217
  • Wilson, S. D. and P.A. Keddy. 1986. Species competitive ability and position along a natural stress/disturbance gradient. Ecology 67:1236-1242.
  • Wilson, S. D. and P.A. Keddy. 1986. Measuring diffuse competition along an environmental gradient: results from a shoreline plant community. The American Naturalist 127: 862-869.
  • Keddy, P.A. 1985. Wave disturbance on lakeshores and the within-lake distribution of Ontario’s Atlantic coastal plain flora. Canadian Journal of Botany 63:656-660.
  • Keddy, P.A. 1984. Quantifying a within-lake gradient of wave energy in Gillfillan Lake, Nova Scotia. Canadian Journal of Botany 62:301-309.
  • Keddy, P.A. 1983. Shoreline vegetation in Axe Lake, Ontario: effects of exposure on zonation patterns. Ecology 64: 331-344.
  • Keddy, P.A. 1982. Quantifying within-lake gradients of wave energy: Inter-relationships of wave energy, substrate particle size and shoreline plants in Axe Lake, Ontario. Aquatic Botany 14:41-58.
  • Keddy, P.A. 1981. Vegetation with Atlantic coastal plain affinities in Axe Lake, near Georgian Bay, Ontario. Canadian Field-Naturalist 95:241-248.