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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.


Relationship between DBH and (A) averaged daily transpiration (ET), (B) averaged total nocturnal sap flow (ET-NOC). Data are mean ± SE, and all linear fittings are significant at the p < 0.05 level. The insets in the figure represent the mean ET(A) and ET-NOC(B) of all 15 trees in dry and wet seasons respectively. Different letters indicate a significant difference between dry and wet seasons.
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Figure 2: Relationship between DBH and (A) averaged daily transpiration (ET), (B) averaged total nocturnal sap flow (ET-NOC). Data are mean ± SE, and all linear fittings are significant at the p < 0.05 level. The insets in the figure represent the mean ET(A) and ET-NOC(B) of all 15 trees in dry and wet seasons respectively. Different letters indicate a significant difference between dry and wet seasons.

Mentions: A boundary line analysis of the relationship between Fd and Q0 was conducted, and the maximum Fd was derived from the exponential relationship. The mean Fd of the 15 trees was 41.03 ± 7.97 and 38.82 ± 13.16 g m-2 s-1 in the dry and wet seasons, respectively, consistent with the pattern of D (Figure 1). Overall, Fd was not affected by tree size, although it was weakly related to DBH in the dry season (R2 = 0.19, p = 0.06). The wet/dry ratio of Fd varied from 0.4 to 0.8 and was not significantly related to the tree size (R2 = 0.03). Average ET in the dry season (5.7 ± 2.9 kg d-1) was 58.0% higher than that in the wet season (3.6 ± 2.3 kg d-1) (Figure 2A, p < 0.01), and linearly increased with tree size (p = 0.003). ET-NOC was 0.18 ± 0.021 kg d-1 in wet and 0.11 ± 0.01 kg d-1 in dry seasons (Figure 2B, p = 0.047), which contributed 1.82 ± 0.45% and 4.51 ± 1.34% to daily ET in dry and wet seasons, respectively. ET-NOC was also linearly related with tree size (p < 0.01).


Hydraulic Balance of a Eucalyptus urophylla Plantation in Response to Periodic Drought in Low Subtropical China
Relationship between DBH and (A) averaged daily transpiration (ET), (B) averaged total nocturnal sap flow (ET-NOC). Data are mean ± SE, and all linear fittings are significant at the p < 0.05 level. The insets in the figure represent the mean ET(A) and ET-NOC(B) of all 15 trees in dry and wet seasons respectively. Different letters indicate a significant difference between dry and wet seasons.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 2: Relationship between DBH and (A) averaged daily transpiration (ET), (B) averaged total nocturnal sap flow (ET-NOC). Data are mean ± SE, and all linear fittings are significant at the p < 0.05 level. The insets in the figure represent the mean ET(A) and ET-NOC(B) of all 15 trees in dry and wet seasons respectively. Different letters indicate a significant difference between dry and wet seasons.
Mentions: A boundary line analysis of the relationship between Fd and Q0 was conducted, and the maximum Fd was derived from the exponential relationship. The mean Fd of the 15 trees was 41.03 ± 7.97 and 38.82 ± 13.16 g m-2 s-1 in the dry and wet seasons, respectively, consistent with the pattern of D (Figure 1). Overall, Fd was not affected by tree size, although it was weakly related to DBH in the dry season (R2 = 0.19, p = 0.06). The wet/dry ratio of Fd varied from 0.4 to 0.8 and was not significantly related to the tree size (R2 = 0.03). Average ET in the dry season (5.7 ± 2.9 kg d-1) was 58.0% higher than that in the wet season (3.6 ± 2.3 kg d-1) (Figure 2A, p < 0.01), and linearly increased with tree size (p = 0.003). ET-NOC was 0.18 ± 0.021 kg d-1 in wet and 0.11 ± 0.01 kg d-1 in dry seasons (Figure 2B, p = 0.047), which contributed 1.82 ± 0.45% and 4.51 ± 1.34% to daily ET in dry and wet seasons, respectively. ET-NOC was also linearly related with tree size (p < 0.01).

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.