Tree-pasture interactions at a range of tree densities in an agroforestry experiment, 3. Water uptake in relation to soil hydraulic conductivity and rooting patterns [Eucalyptus grandis; Setaria sphacelata].
1990
Eastham J. | Rose C.W. | Charles Edwards D.A. | Cameron D.M. | Rance S.J. | Talsma T.
Tree transpiration of Eucalyptus grandis was studied at 3 tree planting densities in an agroforestry experiment over a period of approximately one year and related to rooting patterns and soil hydraulic properties. Over the range of soil water contents studied, the ratio of tree transpiration rate to equilibrium evaporation rate declined linearly with decreasing mean soil water content at each tree density. Overall soil conductance (K) was calculated. At each tree density, decreases in the ratio were related to decreases in 1n K measured at 1.2 m from the stem. A more rapid decrease in the ratio with decrease in water content observed at low tree density was due to a greater decline in K as mean water contents decreased. The greater decline in K at low tree densities was associated with a larger proportion of water extracted and a higher proportion of total root length in surface soil horizons, which showed a greater decrease in hydraulic conductivity than subsoil horizons for the same decrease in water content.
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