Xylem anatomy and hydraulic conductivity of three co-occurring desert phreatophytes |
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| Authors: | A RzepeckiF Zeng FM Thomas |
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| Institution: | a Geobotany, Faculty of Geography and Geosciences, University of Trier, Behringstraße 21, 54296 Trier, Germanyb Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, 40 South Beijing Road, 830011 Urumqi, China |
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| Abstract: | The tree species Populus euphratica, the shrub Tamarix ramosissima and the sub-shrub Alhagi sparsifolia are phreatophytes that grow along the southern fringe of the Taklamakan Desert (NW China). We hypothesised that in the shoot xylem of these species, the fraction of conduits with a large cross-sectional area and the hydraulic conductivity decrease in the sequence A. sparsifolia > T. ramosissima > P. euphratica according to the different ground water distances at the typical sites of the species’ occurrence. The theoretical hydraulic conductivity related to the total cross-sectional xylem area (kttot) or to the cross-sectional area of the conduits (ktcond) was computed using a modified Hagen-Poiseuille equation. The percentage of wide conduits and ktcond were highest in A. sparsifolia, and smallest, in P. euphratica. With regard to kttot, the diffuse-porous to semi-ring-porous P. euphratica occupied an intermediate position due to an increased percentage of conducting area related to the total cross-sectional xylem area. This figure as well as kttot were lowest in the semi-ring-porous to ring-porous T. ramosissima. The kttot values corresponded to the leaf area-related hydraulic conductivity calculated from measurements in the field. Altogether, our results match the typical occurrence of the species with respect to the ground water depth. |
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| Keywords: | Digital image analysis Hydraulic conductance Light microscopy Poplar Saltcedar Xylem vessel |
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