Fog Precipitation in Coastal California Forests

Summer fog precipitation beneath coastal forests was examined at two forested sites on ridges bordering the Eel River Valley in northern California. Each site was outfitted with bottle—funnel gauges and standard mechanical gauges placed on the forest floor and screened bottle—funnel gauges to trap fog in open areas. As much as 42.5 cm of fog water were collected beneath the forest crown during the summer fog season although differences in crown exposure and dimension caused high variability in seasonal totals caught beneath individual trees. A typical fog precipitation event begins during late evening and ends just after sunrise. It sometimes continues for several days and produces fog drip amounts of up to 8 cm. The nutrients and water captured form drifting fog by intercepting trees, shrubs, and grasses affect water balances and nutrient cycling within such coastal ecosystems. Fog may influence species composition, and the character of the soils and vegetation of such coastal forests must certainly reflect to some degree the prevalence of summer fog.