HR: 1330h
AN: H32C-0594    [PDF]
TI: How Does Canopy Structure Influence Interception and Canopy Storage of Rainfall in Young and Old Douglas-Fir Forests?
AU: * Pypker, T G
EM: tom.pypker@orst.edu
AF: Oregon State University, Department of Forest Science, Richardson Hall, Oregon State University, Corvallis, OR 97331 United States
AU: Bond, B J
EM: barbara.bond@orst.edu
AF: Oregon State University, Department of Forest Science, Richardson Hall, Oregon State University, Corvallis, OR 97331 United States
AU: Link, T E
EM: tlink@uidaho.edu
AF: University of Idaho, Department of Forest Resources,University of Idaho, Corvallis, ID 83844 United States
AU: Unsworth, M H
EM: unswortm@coas.oregonstate.edu
AF: Oregon State University, College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, OR 97333 United States
AB: To predict the canopy storage, interception loss and throughfall of rainfall under a forest some modelers have relied on the leaf area index (LAI). However, the use of LAI may not be applicable in old growth forests in the Pacific Northwest because they frequently have complex canopies that are heavily populated with epiphytes. These epiphytes may increase the storage and interception loss of rainfall in old growth forests relative to young forests because of their ability to store many times their mass in water. To investigate the effect of canopy structure on canopy hydrology, we compared and contrasted the interception loss, throughfall and spatial variability of rainfall in a young (24 year-old) and an old ($>$450 year-old) Douglas-fir forest with very similar LAI (LAI = 10 $\pm$1 young; = 9.6 $\pm$0.5 old) in the Pacific Northwest (Wind River Canopy Crane Research Forest, South-central Washington, USA). Rainfall was monitored using an array of tipping bucket rain gauges (25), and PVC rain collectors (50). We found that young forests have one third the canopy storage (young - 1.10 mm; old growth - 3.32 mm) and direct throughfall (young - 0.1; old growth - 0.36) relative to the old growth stand even though they have a very similar LAI. Furthermore, the spatial distribution of rainfall beneath the old growth stand was skewed with many locations below the canopy receiving more precipitation than above the canopy. Hence, it may not be applicable to use LAI to predict canopy variables in old growth Douglas-fir forests.
DE: 1655 Water cycles (1836)
DE: 1818 Evapotranspiration
DE: 1836 Hydrologic budget (1655)
DE: 1875 Unsaturated zone
SC: Hydrology [H]
MN: 2003 Fall Meeting