The Nutrient Content of Precipitation, Dry Fallout, and Intercepted Aerosols in the Chaparral of Southern California

Abstract

In the Santa Ynez Mountains of southern California, precipitation increases with elevation. Concentrations and depositions of ions in bulk precipitation (rainfall + dry fallout) from the atmosphere are greatest at high elevations. Mg and Na+ are deposited primarily during storms; Ca2+, K+ and NO3--N are also deposited in rainfall, but a significant amount of these ions may also enter these ecosystems as dry fallout. Estimated total annual inputs are 1.4 kg/ha for Ca2+, 0.8 for Mg+2, 6.1 for Na+, 0.4 for K+ and 1.0 for N. At a ridgetop site, 1050 m elevation, additional precipitation is received as fog drip from the chaparral shrubs during winter storms. Fog precipitation is not significant at lower elevations in winter, but may occur at sites below 400 m during the summer. At all sites, the deposition of nutrient ions in collectors containing plastic, artificial foliage is significantly greater than in open collectors. The increased deposition in the foliar collectors is primarily due to the interception of dry aerosols. Deposition of N from the atmosphere is likely to exceed the input by symbiotic N fixation by chaparral shrubs.