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

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.


The leaf water potential at (A) pre-dawn (Ψpre-dawn) and (B) noon (Ψnoon) along the tree size gradient in dry and wet seasons.
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Figure 3: The leaf water potential at (A) pre-dawn (Ψpre-dawn) and (B) noon (Ψnoon) along the tree size gradient in dry and wet seasons.

Mentions: The average Ψpre-dawn and Ψpre-night was -0.24 ± 0.04 and -0.29 ± 0.02 MPa in the dry season and -0.21 ± 0.03 and -0.31 ± 0.05 MPa in the wet season. Seasonal differences for both were not significant (p > 0.05). The average Ψnoon was higher (-0.75 ± 0.23 MPa) in the wet season than that in the dry season (-1.46 ± 0.23 MPa) (p < 0.01). Ψpre-dawn and Ψnoon versus tree size in both seasons are shown in Figure 3. Tree size was not related to variations in either Ψpre-dawn and Ψnoon. Accordingly, the water potential difference at midday (ΔΨ) had a mean of 0.62 ± 0.66 (wet) and 1.22 ± 0.10 MPa (dry). ΔΨ was much higher in wet than in dry season (p < 0.01). No difference existed among the five trees for the parameters above (p > 0.05).


Hydraulic Balance of a Eucalyptus urophylla Plantation in Response to Periodic Drought in Low Subtropical China
The leaf water potential at (A) pre-dawn (Ψpre-dawn) and (B) noon (Ψnoon) along the tree size gradient in dry and wet seasons.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 3: The leaf water potential at (A) pre-dawn (Ψpre-dawn) and (B) noon (Ψnoon) along the tree size gradient in dry and wet seasons.
Mentions: The average Ψpre-dawn and Ψpre-night was -0.24 ± 0.04 and -0.29 ± 0.02 MPa in the dry season and -0.21 ± 0.03 and -0.31 ± 0.05 MPa in the wet season. Seasonal differences for both were not significant (p > 0.05). The average Ψnoon was higher (-0.75 ± 0.23 MPa) in the wet season than that in the dry season (-1.46 ± 0.23 MPa) (p < 0.01). Ψpre-dawn and Ψnoon versus tree size in both seasons are shown in Figure 3. Tree size was not related to variations in either Ψpre-dawn and Ψnoon. Accordingly, the water potential difference at midday (ΔΨ) had a mean of 0.62 ± 0.66 (wet) and 1.22 ± 0.10 MPa (dry). ΔΨ was much higher in wet than in dry season (p < 0.01). No difference existed among the five trees for the parameters above (p > 0.05).

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 (&Psi;L) 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 &ndash; 65.6% from the wet to the dry season, depending on the tree size. Fairly stable leaf stomatal conductance (gs) with decreasing &Psi;L (&Psi;L &lt; -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 &Psi;L. This was also verified by the decreasing leaf carbon isotope discrimination (&Delta;13C) 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.