BIOMASS, PRODUCTION, AND LITTERFALL IN THE COASTAL SAGE SCRUB OF SOUTHERN CALIFORNIA

A 22-year-old stand of coastal sage scrub in the coastal mountains of southern California had a peak standing aboveground biomass of 1,417 g/m2, determined by dimension analysis. Annual aboveground net primary production was 255 g/m2/yr, determined by monthly twig harvests of dominant species and the clipping production of subordinate species. The stand was codominated by two drought-deciduous species, Salvia leucophylla and Artemisia californica, which together comprised 81% of the biomass. Annual litterfall was measured at 194 gIm2/yr. These biomass, production, and litterfall values are less than those measured in most evergreen chaparral communities in California. Seasonally, the two dominant shrubs began aboveground production in the winter soon after the first rains and continued growth for six months until early summer. A massive leaf fall occurred in May-June as the summer drought began, but twig and inflorescence production for both species continued at a high rate into the summer months. Salvia leucophylla had two shoot types: 1) an early spring canopy shoot that elongated rapidly, produced the inflorescence, and died in mid-summer; and 2) a short side shoot produced in late spring with small dense leaves that were retained during the summer drought and early winter. Artemisia californica produced a single cohort of twigs in the early spring, most of which carried inflorescences by late summer. COASTAL SAGE SCRUB and evergreen chaparral are plant communities closely associated with one another over a wide geographic range in the mountains of southern California (Epling and Lewis, 1942). The distribution of these communities has been described by Harrison, Small and Mooney (1971), who found that the drought-deciduous species of coastal sage scrub occur on sites where there is less soil moisture due to low rainfall, slope aspect, or edaphic factors. In the coastal mountains of southern California, coastal sage scrub is found on steep ocean-facing slopes below 300 m, and is replaced by evergreen chaparral at higher elevations (Harrison et al., 1971). Coastal sage scrub also occurs on the interior slopes of these mountains, where a "rain shadow" is present. In contrast to evergreen chaparral shrubs, the dominant species of coastal sage scrub are drought-deciduous. These shrubs are usually 0.5-1.5 m tall and commonly have aromatic, soft, mesophytic leaves, hence the local name "soft chaparral." The woody stems are light 1 Received for publication 30 November 1979; revision accepted 20 February 1980. This study was supported by NSF Grants DEB77-14415 and DEB79-11753 to WHS, and a Sigma-Xi Grant to JTG. Special thanks are given to the California Department of Parks and Recreation for granting permission to conduct research on Leo Carrillo State Beach Park property. We gratefully acknowledge reviews of the manuscript by J. R. Haller and B. E. Mahall. We also thank Mavis Hasey for the illustrations. and brittle and the root systems are typically shallow (Hellmers et al., 1955). The most common species are Artemisia californica, several species of Salvia, Encelia californica, and Eriogonum fasciculatum (Nomenclature follows Munz, 1974). Evergreen chaparral has received considerable attention by ecologists dating from the work of Cooper (1922), to recent research associated with the International Biological Programme (Mooney, 1977a). However, despite its widespread distribution and its close association with chaparral, the coastal sage scrub has received relatively little intensive research (Mooney, 1977b). The work to date has described community distribution (Harrison et al., 1971), water relations (Miller and Poole, 1979; Poole and Miller, 1975), composition (Kirkpatrick and Hutchinson, 1977), origin (Axelrod, 1978), response to pollution (Westman, 1979), and allelopathic potential (Muller, Hanawalt and McPherson, 1968). Although several estimates of biomass and/ or production in the chaparral exist (DeBano and Conrad, 1978; Mooney et al., 1977; Mooney and Rundel, 1979; Schlesinger and Gill, 1980; Specht, 1969), virtually no data are available for the coastal sage scrub. In the present study, the research objectives were to: 1) describe community composition, structure, and biomass in a typical stand of coastal sage scrub; 2) measure the seasonal pattern and magnitude of net primary production and lit-