Fire Intensity Effects on Germination of Shrubs and Herbs in Southern California Chaparral

Ecology - Tập 72 Số 6 - Trang 1993-2004 - 1991
José M. Moreno, Walter C. Oechel

Tóm tắt

The study reported here investigates the effects of fire intensity and combustion products (ash and char) on shrub and herbaceous seedling emergence in the field in a mixed southern California chaparral, which was dominated by a facultative seeder, Adenostoma fasciculatum, and by an obligate seeder, Ceanothus greggii. Fire effects were studied in two winter burns, one of which as manipulated by adding brush to experimental plots to increase fire intensity. Adenostoma was very sensitive to increasing fire intensity, with decreasing seedling production as fire intensity increased. This was detected within the normal range of fire intensities of a winter burn, and to a greater extent when intensities were experimentally modified. Ceanothus germination was either stimulated by, or very resistant to, increasing fire intensity. Increasing fire intensity also promoted earlier germination of Ceanothus. Herb species were also differentially affected by increasing fire intensities. Among the abundant herbs, fire annuals like Phacelia brachyloba were more resistant to increasing fire intensity than opportunistic annuals like Cryptantha muricata. Seedling production of one opportunistic annual, Lotus strigosus, was however, stimulated by all levels of increased fire intensity. In most cases, ash and char did not affect field germination. Fire intensity can profoundly modify seedling production of shrubs and herbs after a fire. By substantially altering post—fire seedling populations, fire intensity may represent a major factor in controlling species composition and diversity in chaparral.

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