Postfire Succession of the Herbaceous Flora in Southern California Chaparral

Abstract

Postfire succession of the temporary herbaceous and suffrutescent cover was studied after chaparral fires in San Diego County, California, USA. Four categories of species make up the temporary cover. (I) "Generalized herbaceous perennials" are present before and after fire. Populations of these herbs are sparse under the shrub canopy. They resprout after fire from bulbs or other underground parts and postfire populations are sparse. (2) "Generalized annuals" are present in openings before fire but produce their peak population size in the first few years after fire. (3) Specialized "fire-annuals" are more or less restricted to the 1st postfire yr. (4) Specialized "fire-perennials" (subshrubs) are uncommon before fire, establish from seed in the 1st postfire yr and reach maximum cover in the 3rd and 4th yr.Community-level changes in cover and diversity are interpreted in light of differences in population dynamics of the four groups. Species richness was highest in the 1st yr after fire because this was the only time all four groups were present together. Throughout succession herbaceous species richness was positively related to herb cover, negatively related to elevation and unrelated to slope aspect. The number of annual species fluctuated greatly through succession at all sites, but the number of herbaceous perennials did not. Herb cover fluctuated markedly from year to year and was positively related to amount of annual precipitation and negatively related to subshrub or "fire-perennial" cover.Artificial seeding with annual rye grass Lolium multiflorum had no apparent effect on total herb cover since sites with poor Lolium establishment had as high or higher herb cover as sites with high Lolium establishment. Lolium success was at the expense of the native cover and this negative effect was greatest on the "fire annuals."

Aspects of Demography in Post-Fire Mediterranean Plant Communities of Greece

“…This is unlikely to happen for many reasons, mainly because of the distances involved, the weakness of wind dispersal (Harper 1977;Cook 1980) and the rapid appearance of the herbs in the burned sites (Keeley 1980;Keeley et al 1981). It is likely that the fire annuals of the chaparral behave like fugitive species, but since any single chaparral site is inevitably subjected to fire there is little selection towards long-range dispersal.…”

Seedling growth of four fire‐following Mediterranean plant species deprived of single mineral nutrients

“…A phenomenon common to such fire-prone communities is the flush of germination and growth that follows a burn (Christensen & Muller 1975a;Cowling, Lamont & Pierce 1987;Whelan 1988;Thanos et al 1989). In the interval between fires, mature vegetation is usually dominated by a few species of long-lived shrubs with very little recruitment in the understorey (Sampson 1944;Hanes 1971;Christensen & Muller 1975b) and significant seedling establishment occurs only in the first few years following fire (Sampson 1944;Keeley et al 1981;Keeley & Keeley 1988). Several direct and indirect mechanisms may account for the flush in seedling germination observed in postfire communities.…”

Restoration of A. fasciculatum at Rocky Canyon Granite Quarry, San Luis Obispo, CA

“…The proportion of annuals to perennials in the native seed mixture was typical of that reported after fire in previous studies (Keeley 1981). Each species was treated specifically for fire-stimulated germination requirements (Table 2), and planted in approximately equal densities.…”

“…The seed amounts in the table below vary as shown, due to differences in individual seed weight (Appendix C). The species used for the seed mixture were selected from those native to Rocky Canyon, or a nearby fire site on Cuesta Grade and described as being common in the immediate post-fire environment (Keeley 1981 .54…”

“…Significant seedling establishment only occurs in the first few years following fire because of the requirement of most chaparral species to have fire related cues for regeneration (Tyler 1995, Hanes 1971, Keeley 1981. Chaparral fires typically occur in late summer and early fall, and are usually stand0-replacing crown fires that destroy all above ground biomass (Keeley and Fotheringham 2001).…”