Published online by Cambridge University Press: 03 May 2011
Between 10 July and 25 October 2001, fog interception (CWI) by a Puerto Rican elfin cloud forest at 970 m.a.s.l. was studied. Values of CWI were estimated from the wet-canopy water budget as the sum of throughfall, stemflow, and interception loss, minus rainfall corrected for the effect of slope. CWI was also estimated from throughfall measurements during periods of fog-only. Timing and duration of fog were measured using a wire harp that was protected against rainfall. Estimated rates of CWI correlated significantly (p < 0.01) with collections by the fog gage. Gage to canopy factors were determined from the slopes of these relationships and were considered to integrate differences in fog-catching efficiency of the wire harp and the forest canopy. Applying these factors to the fog gage record yielded an estimated 1.1–1.4 mm day−1 of fog CWI, equivalent to 10–12% of mean daily corrected rainfall (11.3 mm day−1). The wet-canopy water budget method gave the best results when rainfall amounts were small compared to fog, but error bands of estimated CWI became too wide to give meaningful results when rainfall was equal to or larger than the amount of fog. Furthermore, solving the water budget for large rainstorms gave negative values of CWI, possibly because of underestimated stemflow.