Atmospheric deposition processes and their importance as sources of nutrients in a chaparral ecosystem of southern California

Abstract

Precipitation and dry fallout were collected over a 2‐year period in the Santa Ynez Mountains, Santa Barbara County, California, and analyzed for nutrient content. Mean annual depositions of Ca (2.2 kg/ha), K (0.7 kg/ha), NH 4 + ‐N (0.5 kg/ha), and NO 3 − ‐N (1.5 kg/ha) were largely derived from dryfall; depositions of Na (7.2 kg/ha), Mg (1.2 kg/ha), and SO 4 = ‐S (3.6 kg/ha) were important in both rainfall and dry fallout. These atmospheric inputs are equal to or larger than the typical annual losses reported in runoff from mature chaparral shrublands, but on the basis of these inputs, more than 70 years may be necessary to replace the nitrogen losses measured in volatilization and runoff after fire. The depositions of NO 3 − ‐N and SO 4 = ‐S at this remote site may be indicative of the natural levels of these ions which, in many other areas of California, are derived from anthropogenic sources.