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Reliance on shallow soil water in a mixed-hardwood forest in central Pennsylvania.

Gaines KP, Stanley JW, Meinzer FC, McCulloh KA, Woodruff DR, Chen W, Adams TS, Lin H, Eissenstat DM - Tree Physiol. (2015)

Bottom Line: Based on multiple lines of evidence, including stable isotope natural abundance, sap flux and soil moisture depletion patterns with depth, the majority of water uptake during the dry part of the growing season occurred, on average, at less than ∼60 cm soil depth throughout the catchment.While there were some trends in depth of water uptake related to genus, tree size and soil depth, water uptake was more uniformly shallow than we expected.Our results suggest that these types of forests may rely considerably on water sources that are quite shallow, even in the drier parts of the growing season.

View Article: PubMed Central - PubMed

Affiliation: Department of Ecosystem Science and Management, Pennsylvania State University, University Park, PA 16802, USA.

No MeSH data available.


(a) Soil moisture depletion and precipitation during a soil drying and rewetting cycle for one hillslope site in August 2009. Total soil water from 0 to 44 cm (closed circles) and 73–123 cm (open circles) is shown. Values were weighted by midpoint between sensor depths. (b) Daytime (7 am to 7 pm) VPD in kPa for the dry week and recovery, with values <0.1 kPa omitted. (c) Crown conductance (Gc,% maximum) based on sap flux and VPD for Acer, Quercus and Pinus individuals at the south ridge site during the same soil drying and rewetting cycle. (d) Sap flux (% maximum) for individuals at the south ridge site. For (c) and (d), values for individuals of each genus, Quercus (n = 3) and Acer (n = 2) are shown with bars representing standard errors of the mean (Pinus, n = 1). Average values for crown conductance and sap flux were normalized by the percentage of maximum over the dry cycle and recovery. Day of year 239, 240 and 241 were omitted due to precipitation events.
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TPV113F7: (a) Soil moisture depletion and precipitation during a soil drying and rewetting cycle for one hillslope site in August 2009. Total soil water from 0 to 44 cm (closed circles) and 73–123 cm (open circles) is shown. Values were weighted by midpoint between sensor depths. (b) Daytime (7 am to 7 pm) VPD in kPa for the dry week and recovery, with values <0.1 kPa omitted. (c) Crown conductance (Gc,% maximum) based on sap flux and VPD for Acer, Quercus and Pinus individuals at the south ridge site during the same soil drying and rewetting cycle. (d) Sap flux (% maximum) for individuals at the south ridge site. For (c) and (d), values for individuals of each genus, Quercus (n = 3) and Acer (n = 2) are shown with bars representing standard errors of the mean (Pinus, n = 1). Average values for crown conductance and sap flux were normalized by the percentage of maximum over the dry cycle and recovery. Day of year 239, 240 and 241 were omitted due to precipitation events.

Mentions: Isotopic-based estimates of mean depth of soil water extraction should correspond to patterns of soil moisture depletion. If trees were using significant amounts of deep water, we expected to observe sizable depletions in soil moisture at ≥1 m. The average amount of depletion of soil water storage over a dry week in July 2009 for three hillslope sites was 10.5 ± 1.6 mm for depths shallower than 40 cm and 3.8 ± 0.5 mm for depths >40 cm (Figure 7a). The rate of soil moisture depletion slowed by the end of the dry week before rewetting occurred, which provided evidence of decreasing soil moisture availability in the shallow layers. Similarly, average volumetric water content (m3 m−3) at the same locations declined significantly over the dry cycle in 2009 (P < 0.01) at all sensor depths measured. Soil moisture at depths shallower than 40 cm declined the greatest (10.2, 14.3 and 7.1% depletion for 0–10, 10–20 and 20–40 cm depths, respectively) with minor depletions observed in the deeper soil (3.9, 2.0 and 1.3% decline for 60–80, 80–100 cm and over 100 cm, respectively) (see Figure S3 available as Supplementary Data at Tree Physiology Online).Figure 7.


Reliance on shallow soil water in a mixed-hardwood forest in central Pennsylvania.

Gaines KP, Stanley JW, Meinzer FC, McCulloh KA, Woodruff DR, Chen W, Adams TS, Lin H, Eissenstat DM - Tree Physiol. (2015)

(a) Soil moisture depletion and precipitation during a soil drying and rewetting cycle for one hillslope site in August 2009. Total soil water from 0 to 44 cm (closed circles) and 73–123 cm (open circles) is shown. Values were weighted by midpoint between sensor depths. (b) Daytime (7 am to 7 pm) VPD in kPa for the dry week and recovery, with values <0.1 kPa omitted. (c) Crown conductance (Gc,% maximum) based on sap flux and VPD for Acer, Quercus and Pinus individuals at the south ridge site during the same soil drying and rewetting cycle. (d) Sap flux (% maximum) for individuals at the south ridge site. For (c) and (d), values for individuals of each genus, Quercus (n = 3) and Acer (n = 2) are shown with bars representing standard errors of the mean (Pinus, n = 1). Average values for crown conductance and sap flux were normalized by the percentage of maximum over the dry cycle and recovery. Day of year 239, 240 and 241 were omitted due to precipitation events.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4835221&req=5

TPV113F7: (a) Soil moisture depletion and precipitation during a soil drying and rewetting cycle for one hillslope site in August 2009. Total soil water from 0 to 44 cm (closed circles) and 73–123 cm (open circles) is shown. Values were weighted by midpoint between sensor depths. (b) Daytime (7 am to 7 pm) VPD in kPa for the dry week and recovery, with values <0.1 kPa omitted. (c) Crown conductance (Gc,% maximum) based on sap flux and VPD for Acer, Quercus and Pinus individuals at the south ridge site during the same soil drying and rewetting cycle. (d) Sap flux (% maximum) for individuals at the south ridge site. For (c) and (d), values for individuals of each genus, Quercus (n = 3) and Acer (n = 2) are shown with bars representing standard errors of the mean (Pinus, n = 1). Average values for crown conductance and sap flux were normalized by the percentage of maximum over the dry cycle and recovery. Day of year 239, 240 and 241 were omitted due to precipitation events.
Mentions: Isotopic-based estimates of mean depth of soil water extraction should correspond to patterns of soil moisture depletion. If trees were using significant amounts of deep water, we expected to observe sizable depletions in soil moisture at ≥1 m. The average amount of depletion of soil water storage over a dry week in July 2009 for three hillslope sites was 10.5 ± 1.6 mm for depths shallower than 40 cm and 3.8 ± 0.5 mm for depths >40 cm (Figure 7a). The rate of soil moisture depletion slowed by the end of the dry week before rewetting occurred, which provided evidence of decreasing soil moisture availability in the shallow layers. Similarly, average volumetric water content (m3 m−3) at the same locations declined significantly over the dry cycle in 2009 (P < 0.01) at all sensor depths measured. Soil moisture at depths shallower than 40 cm declined the greatest (10.2, 14.3 and 7.1% depletion for 0–10, 10–20 and 20–40 cm depths, respectively) with minor depletions observed in the deeper soil (3.9, 2.0 and 1.3% decline for 60–80, 80–100 cm and over 100 cm, respectively) (see Figure S3 available as Supplementary Data at Tree Physiology Online).Figure 7.

Bottom Line: Based on multiple lines of evidence, including stable isotope natural abundance, sap flux and soil moisture depletion patterns with depth, the majority of water uptake during the dry part of the growing season occurred, on average, at less than ∼60 cm soil depth throughout the catchment.While there were some trends in depth of water uptake related to genus, tree size and soil depth, water uptake was more uniformly shallow than we expected.Our results suggest that these types of forests may rely considerably on water sources that are quite shallow, even in the drier parts of the growing season.

View Article: PubMed Central - PubMed

Affiliation: Department of Ecosystem Science and Management, Pennsylvania State University, University Park, PA 16802, USA.

No MeSH data available.