CA native grass species thrive beside this Yolo County road.

Newsletter - Spring 2008

Current Research - Landscape Processes

Native grasses offer advantages along roadsides.

Soil scientists from the Soils and Revegetation lab are taking a close look at a landscape that most of us forget is there: the strips of vegetation along roadsides.  At the interface between farm land, natural systems, urban areas and the roads that connect them, there is usually a narrow strip of land that is most often a dense stand of invasive annual grasses.  State and county agencies manage these areas by mowing them and spraying herbicides, an expensive practice that costs millions of dollars each year.  Alternatives that may save some money as well as provide ecological benefits to the landscape and reduce pesticide use in the environment are of interest.

Graduate students Steve Young and Ryan O’Dell investigated the use of native perennial grasses in roadside strips as an alternative to the weedy annual grass mix that typically grows.  The annuals pose a fire threat if not mowed, and allow weeds to establish and create “weed corridors” along roadsides that encroach on agricultural fields and natural areas around the state. 

They also change the hydrology of the landscape.  The Central Valley was historically populated with deep rooted perennial grasses that dried the soil deeply.  Currently, annual grasses leave so much water in the soil surface that other weed seeds are quickly able to establish.  “The annual grasses leave a huge resource (water) open to the next generation of weeds,” says principal investigator Vic Claassen. 

In contrast to shallow rooted annual grasses, experiments with native grass stands indicate that they increase infiltration, decrease soil erosion, and can reduce herbicide use.  Native species also serve other important functions, such as providing habitat.  It may take several years to establish a good stand of perennials, but once the stand is established, the site maintains a reduced weed population, and could likely be mowed only once every several years. 

Claassen points out that “even cutting in half the number of times the state has to mow these areas would be a major savings in fuel use and management effort”.