Soil moisture control of sap-flow response to biophysical factors in a desert-shrub species, <i>Artemisia ordosica</i>
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 <i>Artemisia ordosica</i> and associated environmental variables throughout the growing seasons of 2013 and 20...
| Main Authors: | , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-10-01
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| Series: | Biogeosciences |
| Online Access: | https://www.biogeosciences.net/14/4533/2017/bg-14-4533-2017.pdf |
| Summary: | 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 <i>Artemisia ordosica</i> 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 (<i>J</i><sub>s</sub>) to
decline significantly, resulting in transpiration being 34 % lower in
2013 than in 2014. Sap flow per leaf area correlated positively with
radiation (<i>R</i><sub>s</sub>), air temperature (<i>T</i>), and water vapor pressure
deficit (VPD) when volumetric soil water content (VWC) was
greater than 0.10 m<sup>3</sup> m<sup>−3</sup>. Diurnal <i>J</i><sub>s</sub> was generally ahead of
<i>R</i><sub>s</sub> by as much as 6 hours. This time lag, however, decreased
with increasing VWC. The relative response of <i>J</i><sub>s</sub> to the environmental
variables (i.e., <i>R</i><sub>s</sub>, <i>T</i>, and VPD) varied with VWC,
<i>J</i><sub>s</sub> 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 <i>Artemisia ordosica</i> 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 <i>J</i><sub>s</sub> 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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| ISSN: | 1726-4170 1726-4189 |