Coastal Terrace Prairie

California, which is known for its phenomenal diversity of plant and animal life, is equally remarkable for its diversity of distinct and not-so-distinct plant communities. It has been suggested that California’s biologic diversity is directly related to its geologic diversity (Raven and Axelrod 1978) and is the result of the effects of tremendously varied microclimates, topography, soils, organisms, and time (Kruckeberg 1986).

A discussion of California’s plant communities and community classification is well beyond the scope of this article (for a good synopsis, see the introduction to A Manual of California Vegetation by Sawyer and Keeler-Wolf, 1995). Just as taxonomists can be categorized as “lumpers” or “splitters,” so can ecologists involved in the classification of plant communities. With ecologists, the category to which communities belong usually has more to do with the scale at which they are working. Suffice it to say that many classification schemes have been proposed. The number of habitats, plant communities, or plant associations in California ranges from as few as 15 (Sochava 1964), 29 (Munz and Keck 1959), 230 (Holland 1986), 260 (Sawyer and Keeler-Wolf 1995) to an almost unbelievable 2,073 (CDFG 2003).

When I see the word “prairie,” I usually think of vast expanses of tall grasses on a featureless plain dotted with the occasional buffalo. Prairie (noun): An extensive area of flat or rolling grassland; especially, the plain of central north America. In the United States, grasslands currently cover an estimated 310 million acres of land (over 16 percent of the total land area), more than any other single vegetation type (Barbour and Billings 1988). The California prairie, also known as the foothill-valley grassland, covers approximately 5.35 million acres, with another 3.87 million acres found beneath an oak overstory, occupying over nine percent of the total land area of the state (Barbour and Major 1988).

In keeping with our discussion of the grasses found in San Francisco and nearby coastal areas, I thought I’d switch gears to discuss one of the prominent grassland plant communities found here.

Coastal terrace prairie is typically comprised of a dense, tall grassland dominated by both sod- and tussock-forming native perennial grasses. It is naturally patchy in occurrence and variable in composition, reflecting differences in slope aspect, soil texture, and moisture availability. This vegetation community occurs on sandy loam soils of marine terraces near the coast and is restricted to cooler, more mesic sites within the zone of fog incursion. Although coastal terrace prairie consists of many of the same native species that comprise valley/foothill needlegrass grassland, annual species are less important in community structure. Coastal terrace prairie is distributed from Santa Cruz County to Oregon (Holland 1986) and its range closely matches that of northern coastal scrub (Holland and Keil 1990), with which it is generally associated.

red fescue Like other grassland communities, coastal terrace prairie is characterized by the species which comprise it. The dominant species vary from north to south and with distance from the ocean. Coastal terrace prairie is also commonly referred to as Festuca-Danthonia grassland, for the two most common genera. In our area, characteristic native grass species include California oatgrass (Danthonia californica), red fescue (Festuca rubra), Idaho fescue (Festuca idahoensis), California brome (Bromus carinatus), coastal tufted hairgrass (Deschampsia cespitosa ssp. holciformis), blue wildrye (Elymus glaucus var. glaucus and E. g. var. jepsonii), big squirreltail (Elymus multisetus), Torrey melic (Melica torreyana), Pacific reedgrass (Calamagrostis nutkaensis), purple needlegrass (Nassella pulchra), foothill needlegrass (Nassella lepida), and one-sided bluegrass (Poa secunda).

Like all of California’s grasslands, coastal terrace prairie has been subjected to a long history of human-caused disturbance. Intensive livestock grazing, changes in fire regime, erosion, land development, and invasive exotic species all have resulted in the loss of native grassland habitats throughout the state. Along the coast, the expansion of eucalyptus, Monterey pine, pampas grass, and Cape ivy are readily apparent, overruning many of the remaining stands of coastal terrace prairie. Perhaps surprisingly, it’s not just the exotic interlopers causing the damage. Native shrub species such as coyote bush, poison oak, and California blackberry are also found invading native coastal grasslands, and their spread represents nearly as great a threat as that of non-native species.

Although not as expansive as the prairies of the American Midwest, California’s coastal prairies are a characteristic part of the state’s wind-swept western edge. Dramatic, yet soothing, the coastal grasslands are a sheer joy to drive past and even more enjoyable to explore on foot. Winter is roaring in. Mother Nature is waking from her drought-induced hibernation. I can’t think of a better time to walk across a grassy terrace next to the wild ocean on a stormy day.

Literature Cited:

Barbour, M. and W.D. Billings. 1988. North American Terrestrial Vegetation. Cambridge Univ. Press, Cambridge. 434 pp.
Barbour, M. and J. Major. 1988. Terrestrial Vegetation of California. California Native Plant Society, Special Publ. No. 9, Sacramento. 1020 pp.
California Department of Fish and Game (CDFG). 2003. List of Terrestrial Natural Communities Recognized by the California Natural Diversity Database. Natural Diversity Database, Wildlife and Habitat Data Analysis Branch. September.
Holland, R. 1986. Preliminary Descriptions of the Terrestrial Natural Communities of California. California Department of Fish and Game, The Resources Agency. 156 pp.
Holland, V.L. and D.J. Keil. 1990. California Vegetation. 4th edition. Calif. Polytechnic State University, San Luis Obispo. 318 pp.
Kruckeberg, A.R. 1986. An Essay: the Stimulus of Unusual Geologies for Plant Speciation. Syst. Bot. 11:455-463.
Munz, P.A. and D.D. Keck. 1959. A California Flora. Univ. of Calif. Press, Berkeley. 1681 pp.
Raven, P. and D.I. Axelrod. 1978. Origin and Relationships of the California Flora. Univ. Calif. Publs. In Botany 72:1-134.
Sawyer, J.O. and T. Keeler-Wolf. 1995. A Manual of California Vegetation. California Native Plant Society, Sacramento. 471 pp.
Sochava, V. 1964. [Physicogeographical Atlas of the World.] Acad. Nauk. USSR, Moscow. 298 pp. Translated in: Soviet Geogr., Rev. and Trans. 6(5/6):1-403, 1965.