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Hydraulic Balance of a Eucalyptus urophylla Plantation in Response to Periodic Drought in Low Subtropical China

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ABSTRACT

A clear understanding of hydraulic regulation in cultivated plants is crucial for addressing challenges to forest water cycling due to climate changes in low subtropical China. Experiments were conducted to determine the hydrologic balance of a Eucalyptus urophylla plantation in response to periodic drought. Trees displayed lower stomatal conductance (GS) and leaf water potentials (ΨL) during the dry periods. A decrease of 22.4% was found for the maximum reference GS (GS at D = 1 kPa; GSref-max). Accordingly, specific hydraulic conductivity (ks) decreased by 45.3 – 65.6% from the wet to the dry season, depending on the tree size. Fairly stable leaf stomatal conductance (gs) with decreasing ΨL (ΨL < -1.6 MPa) contributed to the high water-use efficiency (WUE) of this Eucalyptus species. Additionally, the lower stomatal sensitivity (-m = 0.53) in the dry season might also be responsible for the high WUE, since we found an anisohydric behavior that was associated with photosynthetically active radiation (Q0). Larger trees were found to use water more efficiently than small trees, due to the higher sensitivity of ks to decreasing ΨL. This was also verified by the decreasing leaf carbon isotope discrimination (Δ13C) with increasing tree diameter. However, further studies are needed to determine the universality of these results for other Eucalyptus species in this region.

No MeSH data available.


Precipitation (P), soil water content (SWC) and evaporative demand (D) during the period of sap flow measurement. SWC data shown in the figure are daily mean ± SE of that month, n = 28–31.
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Figure 1: Precipitation (P), soil water content (SWC) and evaporative demand (D) during the period of sap flow measurement. SWC data shown in the figure are daily mean ± SE of that month, n = 28–31.

Mentions: The precipitation (P) in the research site totaled 2167.6 mm from June 2012 to May 2013 (Figure 1). The water input was mainly contributed by precipitation in late spring and early summer (i.e., from April to June), which accounted for 55.4% of the annual total, while that from October to February (typical dry season in low subtropical China) was only 16%. The SWC in the dry season decreased 32.6% from the wet season, demonstrating a significant difference in the soil water conditions between the wet and dry seasons.


Hydraulic Balance of a Eucalyptus urophylla Plantation in Response to Periodic Drought in Low Subtropical China
Precipitation (P), soil water content (SWC) and evaporative demand (D) during the period of sap flow measurement. SWC data shown in the figure are daily mean ± SE of that month, n = 28–31.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5036442&req=5

Figure 1: Precipitation (P), soil water content (SWC) and evaporative demand (D) during the period of sap flow measurement. SWC data shown in the figure are daily mean ± SE of that month, n = 28–31.
Mentions: The precipitation (P) in the research site totaled 2167.6 mm from June 2012 to May 2013 (Figure 1). The water input was mainly contributed by precipitation in late spring and early summer (i.e., from April to June), which accounted for 55.4% of the annual total, while that from October to February (typical dry season in low subtropical China) was only 16%. The SWC in the dry season decreased 32.6% from the wet season, demonstrating a significant difference in the soil water conditions between the wet and dry seasons.

View Article: PubMed Central - PubMed

ABSTRACT

A clear understanding of hydraulic regulation in cultivated plants is crucial for addressing challenges to forest water cycling due to climate changes in low subtropical China. Experiments were conducted to determine the hydrologic balance of a Eucalyptus urophylla plantation in response to periodic drought. Trees displayed lower stomatal conductance (GS) and leaf water potentials (ΨL) during the dry periods. A decrease of 22.4% was found for the maximum reference GS (GS at D = 1 kPa; GSref-max). Accordingly, specific hydraulic conductivity (ks) decreased by 45.3 – 65.6% from the wet to the dry season, depending on the tree size. Fairly stable leaf stomatal conductance (gs) with decreasing ΨL (ΨL < -1.6 MPa) contributed to the high water-use efficiency (WUE) of this Eucalyptus species. Additionally, the lower stomatal sensitivity (-m = 0.53) in the dry season might also be responsible for the high WUE, since we found an anisohydric behavior that was associated with photosynthetically active radiation (Q0). Larger trees were found to use water more efficiently than small trees, due to the higher sensitivity of ks to decreasing ΨL. This was also verified by the decreasing leaf carbon isotope discrimination (Δ13C) with increasing tree diameter. However, further studies are needed to determine the universality of these results for other Eucalyptus species in this region.

No MeSH data available.