Robert L. Bugg, Cynthia S. Brown, and John H. Anderson
Restoration Ecology, 5(3):214-228. 1997
Reprinted by permission of Blackwell Science, Inc.

Editor’s Note: Roadside management schemes in rural California emphasize herbicides and tillage to suppress resident vegetation and weeds. An alternative approach could involve the establishment and maintenance of native perennial grasses that suppress the growth of weeds. These grasses can be grown in conjunction with other native flora and may provide habitat for desirable wildlife while potentially reducing the threat of flooding, erosion and siltation, and wildfire.

Along rural roadsides of the Sacramento Valley of California, [the authors] seeded native and non-native perennial grasses to gauge their potential value in roadside vegetation management programs. In Trial I (polycultures), three seeded complexes and a control (resident vegetation only) were tested. Each seeded plant complex included a different mix of perennial grasses seeded into each of several roadside topographic zones. The seeded levels of Plant Complex were: Native Perennial Grasses 1 (8 species); Native Perennial Grasses 2 (13 species); and Non-Native Perennial Grasses (3 species). In Trial II, plots were seeded to monocultural plots of 15 accessions of native Californian and 3 cultivars of non-native perennial grasses. Plots in both trials were seeded during January 1992, and evaluated for three successive years.

In Trial I polycultures during 1993, canopy cover by seeded species was not significantly different among the three seeded complexes. The three seeded complexes showed statistically equivalent reduction of canopy cover by resident plant species. Biomass of seeded perennial grasses was greater for Non-Native Perennial Grasses than for Native Perennial Grasses 1 or Native Perennial Grasses 2. Total biomass (seeded + resident species) was greatest for Non-Native Perennial Grasses.

In Trial II monocultures during 1993, the non-native Thinopyrum intermedium ssp. trichophorum (pubescent wheatgrass) attained the greatest height, followed by the native species Nassella (Stipa) cernua (nodding needlegrass), Nassella (Stipa) pulchra (purple needlegrass), and Elymus trachycaulus var. majus (slender wheatgrass). By contrast, the non-native Festuca ovina (sheep fescue) and the native Poa secunda ssp. secunda (pine bluegrass) were particularly short. N. cernua, N. pulchra, E. trachycaulus, and T. intermedium ssp. trichophorum showed particularly great canopy cover, whereas particularly low values of canopy cover were obtained for F. ovina and P. secunda ssp. secunda. A highly significant inverse linear relationship was obtained by regression analysis when canopy cover for seeded perennial grasses was used to predict canopy cover for resident plant species (p<0.0001, r²=0.297, slope=-0.336, intercept= 39.442).

In 1994, the following native perennial grasses showed substantial canopy cover in Trial II monocultures, and appear promising for use in Sacramento Valley rights-of-way: Bromus carinatus (California brome), Elymus glaucus (blue wildrye), E. trachycaulus, all accessions of Hordeum brachyantherum ssp. brachyantherum (meadow barley), a prostrate accession of Hordeum brachyantherum ssp. californicum (California barley), N. cernua, and N. pulchra. In addition, the non-native T. intermedium ssp. trichophorum performed well. By contrast, virtual failure of stands was observed for the non-native F. ovina and the following native species: Elymus multisetus (squirreltail), two accessions of the Festuca idahoensis (Idaho fescue), Festuca rubra (creeping red fescue), and P. secunda ssp. secunda.

For more information: Robert L. Bugg, Sustainable Agriculture Research & Education Program, University of California, One Shields Ave., Davis, CA 95616. rlbugg@ucdavis.edu