| Abstrakt: |
The relationships between volumetric soil water content (?), in situ soil water potential (?soil) and predawn xylem pressure potential (?predawn) were quantified in four contrasting lodgepole pine ecosystems in Wyoming, USA. On three of the sites, changes in ?soil correlated closely with ?predawn, but on a porous soil derived from coarse granitic parent material, ?predawn declines occurred much sooner than corresponding declines in ?soil, possibly because of local depletion of rhizosphere moisture and low molecular diffusivity of water in that soil. Exptrapolation of laboratory-derived characteristic curves for soil moisture to field conditions yielded different relationships between ? and ?soil than curves derived from in situ measurements, probably because of disruption of soil structure and porosity during sample collection and handling in laboratory studies. Although a close correlation between ? and ?predawn was observed, future efforts at modelling the soil-plant-atmosphere continuum should be directed towards a more detailed understanding of the complex relationships between ?soil at varying depths and plant water stress. |
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