Research Branch Staff Publications

Water use of interior Douglas-fir.

Citation:

Simpson, D.G. 2000. Water use of interior Douglas-fir. Can.J.For.Res. 30:534-547

Abstract:

Water use of individual Douglas-fir (pseudotsuga menziesii var. glauca (Beissn.) Franco) trees was measured in two plots at a forest site in southern British Columbia, Canada. Average daily early summer water use by trees with diameters of 7.5-70 cm varied from 1.8 to 166 L. Sap flux density (cm³ water/cm² sapwood per hour) was linearly related to shoot xylem pressure potential and was found to increase with increasing vapour pressure deficit (VPD) and short-wave irradiance (I), reaching maximum rates with VPD > 0.6 kPa and I > 200 Wm². Daily sap flux density varied among trees but was not related to tree diameter, so an average value of 1137.4 Lm² sapwood area was used to estimate average early summer stand transpiration for the two plots of 1.08 and 1.5 mmd. A close curvilinear relationship (r² = 0.85) was found between stem cross-sectional area increment and sapwood area. The relationship was only slightly better (r² = 0.89) between area increment and early summer individual tree water use. Stand volume growth for 1988-1998 for the two plots was 36-47 m³/ha. Stem volume relative growth rate over this 10-year period is estimated at 0.027 and 0.029 m3?m?3?a?'.

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