Atmospheric Precipitation as a Source of Nutrients in Chaparral Ecosystems1

Assistant Professor of Botany, Duke University, Durham, N.C. 27706; and Research Assistant, Department of Biological Sciences, University of California, Santa Barbara, CA 93106 Abstract: Precipitation and dry fallout were collected over a 2-year period at a remote site in the Santa Ynez Mountains, Santa Barbara County, California, USA and analyzed for nutrient content. Mean annual depositions of Ca (2.2 kg/ha), K (0.7 kg/ha), NH4-N (0.5 kg/ha), and NO3-N (1.5 kg/ha) were largely derived from dryfall; depositions of Na (7.2 kg/ha) and Mg (1.2 kg/ha) were important in both rainfall and dry fallout. These inputs are equal to or larger than the typical losses reported in runoff from mature chaparral, but these values imply that long periods are necessary to replace losses measured in volatilization and exacerbated runoff after fire.