© 2000 Heron Publishing—Victoria, Canada
Spatial variations in xylem sap flux density in the trunk of orchard-grown, mature mango trees under changing soil water conditions
Ping Lu (1), Warren J. Müller (2) and Elias K. Chacko (1, 3)
1. CSIRO Plant Industry, Horticulture Unit, Darwin Laboratory, PMB 44, Winnellie, NT 0822, Australia / 2. CSIRO Mathematical and Information Sciences, GPO Box 664, Canberra ACT 2601, Australia / 3. Deceased August 21, 1997 / Received July 21, 1999
Summary
Circumferential and radial variations in xylem sap flux density in trunks of 13-year-old mango (Mangifera indica L.) trees were investigated with Granier sap flow sensor probes under limiting and non-limiting soil water conditions. Under
non-limiting soil water conditions, circumferential variation was substantial, but there was no apparent relationship between
sap flux density and aspect (i.e., the radial position of the sensor probes on the trunk relative to the compass). Hourly
sap flux densities over 24 hours at different aspects were highly pair-wise correlated. The relationships between different
aspects were constant during well-watered periods but highly variable under changing soil water conditions. Sap flux density
showed marked radial variation within the trunk and a substantial flux was observed at the center of the trunk. For each selected
aspect on each tree, changes in sap flux densities over time at different depths were closely correlated, so flux at a particular
depth could be extrapolated as a multiple of flux from 0 to 2 cm beneath the cambium. However, depth profiles of sap flux
density differed between trees and even between aspects within a tree, and also varied in an unpredictable manner as soil
water conditions changed. Nevertheless, over a period of non-limiting soil water conditions, depth profiles remained relatively
constant. Based on the depth profiles obtained during these periods, a method is described for calculating total sap flow
in a mango tree from sap flux density at 0–2 cm beneath the cambium. Total daily sap flows obtained were consistent with water
use estimated from soil water balance.
Keywords:
irrigation, Mangifera indica, sap flow, sapwood, transpiration, water stress, water use.
