An electrical analogue describing the phase and amplitude relations between transpiration, water potential and stem shrinkage for trees was developed. Observations of shrinking and swelling at various heights up a Pinus radiata tree were obtained over several weeks in summer and autumn. The relative amplitude in shrinkage increased by a factor of two up the stem, but phase lags were small. The data obtained were used in conjunction with the electrical analogue of the How pathway to obtain an estimate of the relative magnitude of the capacitance of the living bark and the sapwood, and to predict phase lags between transpiration and leaf water potential, and lags in transpirational flux up the stem. The results suggest that if water potentials recover by dawn, phase lags in water potential down tree stems arc small and that the exchange between water stored in the sapwood and the transpiration stream is irreversible over the diurnal time scale.

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Thirteen sites were examined and the permeabilities determined by a combination of the two-well (Childs) and the single-tube (Kirkham) methods. Anisotropy occurred in less than half of these sites. The range of permeabilities encountered was ten-thousand fold. Two of the clay soils have permeabilities comparable with those of gravelly sands.An argument is presented for the use of permeability as an objective measure of structure in the field and the principal disadvantages of the permeability method are listed.Variability in field structure is considered from the aspect of the ratio between the size of the well sample and the size of the structural units. Four cases of variability are interpreted in terms of their effect on the standard error and the asymmetry of results obtained by the two-well method. This interpretation is shown to allow of the assessment of field structure from the permeability results. When sub-units of structure and the experimental equipment have similar dimensions, individual determinations have questionable validity.The method of calculating permeability and anisotropy from field data is given in an Appendix. A comparison of the field descriptions with the permeability results for the experimental sites indicates that qualitative profile differentiation does not always imply a change of permeability; neither can visual profile uniformity be taken to indicate uniform permeability.