Summer fog drip in the coastal redwood forest

Fog drip was studied in the virgin redwood forest at Lady Bird Johnson Grove near Orick, California during the period July 4, 1970 through September 15, 1970. Four one-fourth acre plots were placed on the southwest aspect of the study area to sample fog drip. Two plots, plots B and B' were placed at the 1,000-foot elevation and a single plot was placed at both the 800-(plot C) and 1,200-foot (plot A) elevations. Fifty open-end aluminum beer cans were attached to stakes and were randomly placed at each of the four plots. In addition, 100 cans were randomly placed on the ground at plots A, B, and c. Control cans were placed in an adjacent open area at each elevation to record any condensation or rainfall. Results show that during the ten-week study period, 0.12 inch of fog drip was collected at the 1,200-foot elevation, trace amounts at the 1,000-foot, and no drip at the 800-foot elevation. Fog drip occurred only when wet fog was present and air temperature was 49°F or cooler. Fog drip was more frequent in August than July and no fog drip occurred during September. High relative humidity and reduced insulation as a result of fog appear to be more important than drip in reducing summer water losses in the coastal redwood forest.