PARENT SESSION
Poster Session #9: Water Relations.
Monday, August 6, 2001. Presentation from 3:30 PM to 5:00 PM. Exhibition Hall
Relationships between stem diameter and sapwood area for ring- and diffuse-porous tree species.
WULLSCHLEGER, STAN1, SILLETTI, ANDREA 1, HANSON, PAUL1, TODD, DON1, 1
ABSTRACT- Canopy transpiration and forest water use are increasingly being estimated as the product of sap velocity measured on individual trees and cross-sectional sapwood area. Few studies, however, report sapwood area for trees of mixed deciduous forests and there is a need to better quantify sapwood area from biometric measurements. Therefore, species-specific allometric equations were developed for estimating sapwood area from measured stem diameter (dbh) for twelve temperate tree species. Sapwood area was calculated for ring- (Quercus) and diffuse-porous (Acer, Liriodendron, Nyssa) species growing in closed-canopy stands. Stem diameter was an excellent predictor of sapwood area. In all species, sapwood area increased exponentially with increasing stem diameter. Sapwood areas for similar sized individuals were 3 to 4-fold greater in diffuse-porous than in ring-porous trees. Application of these allometric equations to inventory data for a 40 to 70-year-old forest stand in east Tennessee indicated that diffuse-porous species accounted for roughly 72% of total stand sapwood area, whereas the remainder was accounted for by ring-porous species. Chestnut oak (Q. Prinus L.), which accounted for 27% of the stand basal area, contributed only 12% of stand sapwood area. Such information is critical for scaling individual tree water use observations to whole-stand estimates of transpiration and for better understanding how species composition potentially affects forest water use.
KEY WORDS: sap flow, sapwood area, transpiration, water use