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Biogeosciences An interactive open-access journal of the European Geosciences Union
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Volume 14, issue 19
Biogeosciences, 14, 4533–4544, 2017
https://doi.org/10.5194/bg-14-4533-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Special issue: Ecosystem processes and functioning across current and future...

Biogeosciences, 14, 4533–4544, 2017
https://doi.org/10.5194/bg-14-4533-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 13 Oct 2017

Research article | 13 Oct 2017

Soil moisture control of sap-flow response to biophysical factors in a desert-shrub species, Artemisia ordosica

Tianshan Zha1,3,*, Duo Qian2,*, Xin Jia1,3, Yujie Bai1, Yun Tian1, Charles P.-A. Bourque4, Jingyong Ma1, Wei Feng1, Bin Wu1, and Heli Peltola5 Tianshan Zha et al.
  • 1Yanchi Research Station, School of Soil and Water Conservation, Beijing Forestry University, Beijing 100083, China
  • 2Beijing Vocational College of Agriculture, Beijing 102442, China
  • 3Key Laboratory of State Forestry Administration on Soil and Water Conservation, Beijing Forestry University, Beijing, China
  • 4Faculty of Forestry and Environmental Management, 28 Dineen Drive, P.O. Box 4400, University of New Brunswick, New Brunswick, E3B5A3, Canada
  • 5Faculty of Science and Forestry, School of Forest Sciences, University of Eastern Finland, Joensuu, 80101, Finland
  • *These authors contributed equally to this work.

Abstract. The current understanding of acclimation processes in desert-shrub species to drought stress in dryland ecosystems is still incomplete. In this study, we measured sap flow in Artemisia ordosica and associated environmental variables throughout the growing seasons of 2013 and 2014 (May–September period of each year) to better understand the environmental controls on the temporal dynamics of sap flow. We found that the occurrence of drought in the dry year of 2013 during the leaf-expansion and leaf-expanded periods caused sap flow per leaf area (Js) to decline significantly, resulting in transpiration being 34 % lower in 2013 than in 2014. Sap flow per leaf area correlated positively with radiation (Rs), air temperature (T), and water vapor pressure deficit (VPD) when volumetric soil water content (VWC) was greater than 0.10 m3 m−3. Diurnal Js was generally ahead of Rs by as much as 6 hours. This time lag, however, decreased with increasing VWC. The relative response of Js to the environmental variables (i.e., Rs, T, and VPD) varied with VWC, Js being more strongly controlled by plant-physiological processes during periods of dryness indicated by a low decoupling coefficient and low sensitivity to the environmental variables. According to this study, soil moisture is shown to control sap-flow (and, therefore, plant-transpiration) response in Artemisia ordosica to diurnal variations in biophysical factors. This species escaped (acclimated to) water limitations by invoking a water-conservation strategy with the regulation of stomatal conductance and advancement of Js peaking time, manifesting in a hysteresis effect. The findings of this study add to the knowledge of acclimation processes in desert-shrub species under drought-associated stress. This knowledge is essential in modeling desert-shrub-ecosystem functioning under changing climatic conditions.

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According to this study, Artemisia ordosica escaped water limitations by invoking a water-conservation strategy with the regulation of stomatal conductance and advancement of sap-flow peaking time, manifesting in a hysteresis effect. This study provides a significant contribution to the understanding of acclimation processes in desert-shrub species to drought-associated stress in dryland ecosystems.
According to this study, Artemisia ordosica escaped water limitations by invoking a...
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