Fog Precipitation in Coastal California Forests

TLDR

Fog precipitation in coastal California forests typically begins late evening, can last several days, and delivers up to 8 cm of drip, influencing water balances, nutrient cycling, and species composition. The study measured summer fog precipitation at two ridge sites in the Eel River Valley using bottle‑funnel and mechanical gauges on the forest floor and screened bottle‑funnels to capture fog in open areas. Up to 42.5 cm of fog water was collected beneath the forest crown during the summer season, with large variability in seasonal totals among individual trees due to differences in crown exposure and size.

Abstract

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.