Abstract
We investigated the occurrence of freezing-induced cavitation in the evergreen desert shrub Larrea tridentata and compared it to co-occurring, winter-deciduous Prosopis velutina. Field measurements indicated that xylem sap in L. tridentata froze at temperatures below c. –5°C, and that this caused no measurable cavitation for minimum temperatures above –7°C. During the same period P. velutina cavitated almost completely. In the laboratory, we cooled stems of L. tridentata to temperatures ranging from –5 to –20°C, held them at temperature for 1 or 12 h, thawed the stems at a constant rate and measured cavitation by the decrease in hydraulic conductivity of stem segments. As observed in the field, freezing exotherms occurred at temperatures between –6.5 and –9°C and as long as temperatures were held above –11°C there was no change in hydraulic conductivity after thawing. However, when stems were cooled to between –11°C and –20°C, stem hydraulic conductivity decreased linearly with minimum temperature. Minimum temperatures between –16 and –20°C were sufficient to completely eliminate hydraulic conductance. Record (>20 year) minimum isotherms in this same range of temperatures corresponded closely with the northern limit of L. tridentata in the Mojave and Sonoran deserts.
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Received: 11 June 1996 / Accepted: 29 August 1996
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Pockman, W., Sperry, J. Freezing-induced xylem cavitation and the northern limit of Larrea tridentata . Oecologia 109, 19–27 (1996). https://doi.org/10.1007/s004420050053
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DOI: https://doi.org/10.1007/s004420050053