Native plant establishment along West Virginia Highways.

Abstract:

Most state highway departments in the US are required to use native plants for re-vegetating highway rights-of-way and thereby reduce the potential for introducing invasive species along roads. Often, native plants can be seeded alone or in combination with non-native species. On roadsides with established stands of non-native species, disturbance of existing vegetation can facilitate native species establishment. Two field studies in West Virginia were conducted to assess native plant establishment under these conditions.

In the first study, 4 seed mixtures comprised of combinations of seeds of native and non-native species, and 2 NPK fertilizer treatments were applied at 3 newly-constructed roadsides. After 3 growing seasons, fertilizer showed little to no influence on increasing native or non-native species cover, but the fertilizer rate was only 150 kg/ha of 10-20-10. Natives were slower to establish and only contributed 25% cover in some plots after 3 years. Indiangrass (Sorghastrum nutans (L.) Nash), big bluestem (Andropogon gerardii Vitman), brown-eyed Susan (Rudbeckia triloba L.), and wild senna (Cassia hebecarpa Fernald) were the only seeded native species observed in these plots.

In the second study, 3 different-aged established stands of vegetation composed of tall fescue Festuca arundinacea Screb.), red fescue (F. rubra L.), and crownvetch (Coronilla varia L.) were disturbed by mowing, herbicide, or tillage, and native plants were seeded with and without fertilizer. Native cover was <10% at all sites and in all treatments during the first year in spite of destruction of the established vegetation by herbicide and tillage. But native cover greatly increased by the second year, reaching 45% in disturbed plots, indicating that disturbance was needed for natives to become important vegetation components within two years.

Fertilizer treatment did not increase total plant or native cover on these sites. Only switchgrass (Panicum virgatum L.), little bluestem (Andropogon scoparius Vitman), partridge pea (Chamaecrista fasciculate Michx.), and brown-eyed Susan were observed in plots. Results of these experiments suggest that introducing or increasing the cover of native species along roadsides require 1) reducing competition from non-native species, and 2) patience to allow these slower-establishing species to be observed.