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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.


Relationship between DBH and maximum stomatal conductance at reference D (=1 kPa) (GSref-max) derived from Figure 4, and, the AL/(As∗1000) based on the predicted AL and As with DBH. Lines represent least square fits for dry (white circle) and wet (black circle) seasons respectively; data are mean ± SE.
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Figure 6: Relationship between DBH and maximum stomatal conductance at reference D (=1 kPa) (GSref-max) derived from Figure 4, and, the AL/(As∗1000) based on the predicted AL and As with DBH. Lines represent least square fits for dry (white circle) and wet (black circle) seasons respectively; data are mean ± SE.

Mentions: We estimated the max Gs (GSref-max) of each tree from the exponential function (equation 4, corresponding to a) before it was normalized and fitted to DBH (Figure 6). GSref-max was found to increase with DBH in the wet season before reaching the maximum when DBH > 9 cm. While no clear relationship in the dry season was observed, the mean GSref-max was higher in the wet season (88.6 mmol m-2 s-1) than in the dry season (68.8 mmol m-2 s-1)(p < 0.01). The ratio of GSref-max in the dry to wet season ranged from 0.58 to 1.26 (0.81 on average), decreasing rapidly when DBH < 9 cm and stabilizing when DBH > 9 cm.


Hydraulic Balance of a Eucalyptus urophylla Plantation in Response to Periodic Drought in Low Subtropical China
Relationship between DBH and maximum stomatal conductance at reference D (=1 kPa) (GSref-max) derived from Figure 4, and, the AL/(As∗1000) based on the predicted AL and As with DBH. Lines represent least square fits for dry (white circle) and wet (black circle) seasons respectively; data are mean ± SE.
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Related In: Results  -  Collection

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

Figure 6: Relationship between DBH and maximum stomatal conductance at reference D (=1 kPa) (GSref-max) derived from Figure 4, and, the AL/(As∗1000) based on the predicted AL and As with DBH. Lines represent least square fits for dry (white circle) and wet (black circle) seasons respectively; data are mean ± SE.
Mentions: We estimated the max Gs (GSref-max) of each tree from the exponential function (equation 4, corresponding to a) before it was normalized and fitted to DBH (Figure 6). GSref-max was found to increase with DBH in the wet season before reaching the maximum when DBH > 9 cm. While no clear relationship in the dry season was observed, the mean GSref-max was higher in the wet season (88.6 mmol m-2 s-1) than in the dry season (68.8 mmol m-2 s-1)(p < 0.01). The ratio of GSref-max in the dry to wet season ranged from 0.58 to 1.26 (0.81 on average), decreasing rapidly when DBH < 9 cm and stabilizing when DBH > 9 cm.

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.