Prairie:
Vege­­tation Types

Pacific reedgrass stand at Point Reyes National Seasore
Pacific reedgrass stand at Point Reyes National Seasore

Pacific reedgrass stand at Point Reyes National Seashore 2010. Photo by J. Coleman.

Like other vegetation types, coastal prairie community types are named after the species in the stand with the most ground cover. In coastal prairie, these species are often perennial or annual grasses. Native perennial grasses most common in coastal prairies of Sonoma and Marin Counties are California oatgrass (Danthonia californica), tufted hairgrass (Deschampsia cespitosa), and Pacific reedgrass (Calamagrostis nutkaensis).

Many vegetation types have not yet been characterized. The Manual of California Vegetation, an on-going effort to quantitatively identify all of the vegetation types throughout California, identified 4 types associated with coastal prairie in the first edition (Sawyer and Keeler-Wolf 1995) and 9 types (associations) in the second edition (Sawyer, et al. 2009). Grasslands are particularly difficult to characterize due to the changing abundance of cover of species over the season. Moreover, the distinction between coastal prairie and valley grasslands is less clear in areas where coastal influences reach inland (Ford and Hayes 2007).

The coastal prairie mapping project conducted by the Coastal Prairie Enhancement Feasibility Study in 2010 and 2011 identified over 34 types of coastal prairie grasslands in Sonoma and Marin Counties, which constitute from 30-50% of the total number of vegetation types in the two counties (CPEFS 2010).

Species composition in coastal prairie tends to vary with landform, each with distinct differences in the occurrence of dominant grass species (Stromberg, et al. 2001). The following is a partial list of the most common coastal prairie vegetation types (or “alliances”) with associated land forms found in Sonoma and Marin counties (Sawyer et al. 2009).

Native Dominated Stands

Semi-Natural Herbaceous Stands

Sawyer, et al. (2009:1247) describe semi-natural stands as, "Vegetation in which past or present human activities significantly influence composition or structure but do not eliminate or dominate spontaneous ecological processes." The following non-native dominated stands remain valuable in that they can contain a wide variety of native plant species. Futhermore, these grasslands continue to provide important habitat with food, forage, shelter, protection, nesting sites, and hunting grounds for wildlife (Sawyer, et al. 2009).

Common velvet grass-sweet vernal grass meadows (Holcus lanatus-Anthoxanthum odoratum) semi-natural herbaceous stands are dominant or co-dominant along coastal bluffs, terraces and moist pastures. Introduced from Europe, Holcus lanatus populations are increasing in many of California’s coastal prairies including those in Sonoma and Marin Counties.

Bent grass-tall fescue meadows (Agrostis gigantea, A. stolonifera, Festuca arundinacea) semi-natural herbaceous stands are dominant or co-dominant in areas that were once occupied by Pacific reedgrass (Calamagrostis nutkaensis), California oatgrass (Danthonia californica), and tufted hairgrass (Deschampsia cespitosa) alliances.

Annual dogtail grasslands (Cynosurus echinatus)—semi-natural herbaceous stands are dominant or co-dominant with other non-natives in the herbaceous layer. These deteriorated grasslands can contain native plants including California oatgrass (Danthonia californica), blue wild rye (Elymus glaucus), blue-eyed grass (Sisyrinchium bellum), Ithuriel's spear (Triteleia laxa), and other remnants of the pre-invaded community.