Roadside Use of Native Plants

Working With Succession — An Ecological Approach in Preserving Biodiversity

William A. Niering, Connecticut College, New London

The highway rights-of-ways across America represent a vast potential ecological resource in terms of supporting a diversity of natural and semi-natural plant communities. These rights-of-way can contribute significantly in promoting and preserving biodiversity which is now a current environmental issue of international concern. This brief paper will address the potential that exists nationwide along the rights-of-way of our nation. Here is an untapped landscape resource which, if managed creatively, can support a rich array of plant and animal species and at the same time restore elements of the natural landscape that have been and are being continuously destroyed by development. For example, in the Midwest grassland region, most of the original prairie has been converted to agricultural land supporting agricultural crops. Thus restoring elements of the prairie grassland along highway rights- of- way provides a way to recreate elements of native prairie with their diversity of grasses and colorful forbs. Elsewhere, in the West, the State of Texas has been a leader in promoting colorful floristic roadsides thanks in part to Ladybird Johnson. In even drier regions- the deserts of the Southwest, the Great Basin and Mojave Desert, the sparse native desert vegetation is the logical plant cover to promote along these arid roadsides. Here no mowing is needed and plants are adapted to the extreme xeric conditions.

Elsewhere in forested regions of the nation, there also exists unlimited potential to promote both natural grasslands and shrublands in lieu of a continuum of frequently mowed landscapes along roadside rights-of-way. The extent of regularly mowed areas varies with States — some have extensive areas, others have reduced such activity to a minimum. In terms of roadside management needs, the presence of a regularly mowed strip immediately adjacent to the highways is usually deemed necessary and justified based on visibility and fire hazard conditions. However, beyond this belt, possibly 25–50 feet or less in width, there are opportunities to favor natural meadows with a mixture of native and introduced grasses and showy broad-leaved flowering plants such as goldenrod, asters, and blazing star. Such meadows will develop with the mere cessation of regular mowing. In addition, shrublands can also be favored either by native plantings or by allowing thickets to develop naturally. Trees are associated with such thickets and deemed undesirable. They can be removed with selected herbicides, and the resulting shrubland will remain remarkably stable, as has been documented by numerous studies in the Northeast (Niering & Goodwin 1974, Dreyer & Niering 1986, Niering et al 1986, Canham et al 1993). This idea of shrub stability somewhat counters traditional succession theory; however the ability of many kinds of shrub thickets to arrest tree establishment is an example of the inhibition model of Connell & Slatyer (1977) in which certain shrubby plant communities can arrest forest development. Thus shrub communities represent a low maintenance vegetation type with high wildlife values. As to meadow maintenance, mowing once a year is adequate to suppress woody development. By integrating natural plant communities into the management of the nation's roadside rights-of-way, maintenance costs and air pollution will be reduced. Adoption of these innovative vegetation management strategies will be the wave of the future for the environmentally enlighten since they favor energy conservation and the preservation of biodiversity (Niering & Goodwin 1975, Taylor et al. 1987).

Literature Cited

• Canham, C.D., A.R. Berkowitz, J.B. McAninch, M.J. McDonnell and R.S. Ostfeld. 1993. Vegetation dynamics along utility rights-of-way: factors affecting the ability of shrub and herbaceous communities to resist invasion by trees. Final Technical Report, Central Hudson Gas and Electric Corp. and Empire State Electric Energy Research Corporation. Institute of Ecosystem Studies, Millbrook, N.Y.
• Connell, J.H. and R.O. Slatyer. 1977. Mechanisms of succession in natural communities and their role in community stability and organization. American Naturalist III:1119–1177.
• Dreyer, G.D. and W.A. Niering. 1986. Evolution of two herbicide techniques in electric transmission rights-of-way: development of relatively stable shrublands. Environmental Management 10:113–118.
• Niering, W.A. and R.H. Goodwin. 1974. Creation of relatively stable shrublands with herbicides: arresting "succession" on rights-of-way and pasturelands. Ecology 55: 784–795.
• Niering, W.A. and R.H. Goodwin. (eds.) 1975. Energy Conservation on the Home Grounds, The Role of Naturalistic Landscaping. Connecticut College Arboretum Bulletin No. 21.
• Niering, W.A., G.D. Dreyer, F.E. Egler and J.P. Anderson Jr. 1986. Stability of a Viburnum lentago-shrub community after 30 years. Bulletin of the Torrey Botanical Club 113:23–27.
• Taylor S.L., G.D. Dreyer and W.A. Niering. 1987. Native Shrubs for Landscaping. Connecticut College Arboretum Bulletin. No. 30.