Journal of Plant Ecology Advance Access originally published online on October 31, 2008
Journal of Plant Ecology 2008 1(4):227-235; doi:10.1093/jpe/rtn023
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Regulation of the water status in three co-occurring phreatophytes at the southern fringe of the Taklamakan Desert
1 Department of Plant Ecology, Albrecht von Haller Institute for Plant Sciences, Georg-August-Universität Göttingen, Untere Karspüle 2, 37073 Göttingen, Germany
2 Present address: Department of Geobotany, University of Trier, Behringstraße 21, 54296 Trier, Germany
3 Present address: Eidgenössisches Institut für Agrarökologie und Landwirtschaft, Forschungsanstalt Agroscope, Reckenholzstrasse 191, 8046 Zürich, Switzerland
4 Present address: Institute of Geobotany and Botanical Garden, Martin Luther University Halle-Wittenberg, Am Kirchtor 1, 06108 Halle (Saale), Germany
5 Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, 40 South Beijing Road, 830011 Urumqi, China
* Correspondence address. Department of Geobotany, University of Trier, Behringstraße 21, 54296 Trier, Germany. Tel: +49-651-2012393; Fax: +49-651-2013808; E-mail: thomasf{at}uni-trier.de
Aims: We investigated the regulation of the water status in three predominant perennial C3 phreatophytes (Alhagi sparsifolia, Populus euphratica, Tamarix ramosissima) at typical sites of their occurrence at the southern fringe of the hyperarid Taklamakan Desert (north-west China).
Methods: In the foreland of the river oasis of Qira (Cele), we determined meteorological variables, plant biomass production, plant water potentials (
L) and the water flux through the plants. We calculated the hydraulic conductance on the flow path from the soil to the leaves (kSL) and tested the effects of kSL, L and the leaf-to-air difference in the partial pressure of water vapour (
w) on stomatal regulation using regression analyses.
Important Findings: Despite high values of plant water potential at the point of turgor loss, all plants sustained L at levels that were high enough to maintain transpiration throughout the growing season. In A. sparsifolia, stomatal resistance (rs; related to leaf area or leaf mass) was most closely correlated with kSL; whereas in P. euphratica, 
70% of the variation in rs was explained by w. In T. ramosissima, leaf area-related rs was significantly correlated with L and kSL. The regulation mechanisms are in accordance with the growth patterns and the occurrence of the species in relation to their distance to the ground water.
Keywords: aboveground growth • extreme aridity • stomatal conductance • transpirational demand • vapour pressure deficit