|Link, Timothy - UNIV OF IDAHO|
|Unsworth, Mike - OREGON STATE UNIV|
Submitted to: Agricultural and Forest Meteorology
Publication Type: Abstract Only
Publication Acceptance Date: January 29, 2004
Publication Date: January 29, 2004
Citation: Link, Timothy E., Unsworth, Mike, and Marks, D., Agricultural and Forest Meteorology, 2004; The dynamics of rainfall interception by a seasonal temperate rainforest, abstract, vol. 124, pp. 171-191. Technical Abstract: Net canopy interception I net during rainfall in an old-growth Douglas-fir'western hemlock ecosystem was 22.8 and 25.0 percent of the gross rainfall (PG) for 1999 and 2000, respectively. The average direct throughfall proportion (p) and canopy storage capacity (S) derived from high-temporal resolution throughfall measurements were 0.36 and 3.3 mm, respectively. Derived values of S were very sensitive to the estimated evaporation during canopy wetting Iw. Evaporation during wetting was typically small due to low vapor pressure deficits that usually occur at the start of an event, therefore Iw is best estimated using the Penman method during canopy wetting, rather than assuming a constant evaporation rate over an entire event. S varied seasonally, from an average of 3.0mm in the spring and fall, to 4.1mm in the summer, coincident with canopy phenology changes. Interception losses during large storms that saturated the canopy accounted for 81 percent of I net. Canopy drying after events comprised 47percent of I net, evaporation during rainfall comprised 33 percent, and evaporation during wetting accounted for 1 percent. Interception associated with small storms insufficient to saturate the canopy accounted for 19 percent of net. The Gash analytical model accurately estimated both I net and the individual components of I net in this system when applied on an event basis, and when the Penman method was used to compute evaporation during rainfall. The Gash model performed poorly when applied on a daily basis, due to a rainfall regime characterized by long-duration events, which violated the assumption of one rain event per day.