scholarly journals Measurements of Water Use by Prairie Grasses with Heat Balance Sap Flow Gauges

1995 ◽  
Vol 48 (2) ◽  
pp. 150 ◽  
Author(s):  
R. S. Senock ◽  
J. M. Ham
Keyword(s):  
Water Use ◽  
Heat Balance ◽  
Sap Flow ◽  
Prairie Grasses

Determination of the water use of two pairs of soybean isolines differing in stomatal frequency using a heat balance stem flow gauge

1995 ◽  
Vol 75 (1) ◽  
pp. 99-103 ◽  
Author(s):  
C. S. Tan ◽  
B. R. Buttery
Keyword(s):  
Soil Moisture ◽  
Water Use ◽  
Heat Balance ◽  
Sap Flow ◽  
Stomatal Frequency ◽  
Flow Rates ◽  
High Soil Moisture ◽  
Stem Flow ◽  
Glycine Max L

Using heat-balance stem flow gauges, we were able to measure directly and continuously the sap flow rates in two pairs of soybean [Glycine max (L.) Merr.] isolines differing in stomatal frequency. Plants with high stomatal frequency transpired significantly more water than the low stomatal frequency plants at high soil moisture levels. Under low soil moisture levels, the water use rate decreased greatly for the high stomatal frequency plants. Plants with low stomatal frequency were able to maintain greater sap flow rates than those with high stomatal frequency. Higher leaf temperatures associated with the low stomatal frequency plants were likely due to lower transpiration rates which reduced evaporative cooling especially under well-watered conditions. Key words:Glycine max (L.) Merr., transpiration, water deficits

Determination of the water use and water use response of canola to solar radiation and temperature by using heat balance stem flow gauges

2003 ◽  
Vol 83 (1) ◽  
pp. 31-38 ◽  
Author(s):  
S. V. Angadi ◽  
H. W. Cutforth ◽  
B. G. McConkey
Keyword(s):  
Solar Radiation ◽  
Real Time ◽  
Heat Loss ◽  
Water Use ◽  
Heat Balance ◽  
Heat Input ◽  
Sap Flow ◽  
Flow System ◽  
Major Portion ◽  
Flow Rates

Sap flow gauges using a heat balance have been reliable for measuring real-time transpiration in a number of crops. However, information on the accuracy of sap flow gauges in canola is lacking. Therefore, a study was conducted to validate the sap flow system in canola and to observe sap flow response to variations in temperature and solar radiation. There were strong relationships between sap flow measured with sap flow gauges and actual transpiration measured by the gravimetric method over short periods of 1 h (r2 = 0.93 and RMSE = 2.34 g h-1), and over longer periods of 1 d (r2 = 0.83 and RMSE = 48 g d-1), although sap flow slightly overestimated transpiration. In both cases the slope was not significantly different from 1. Water use in canola, estimated with sap flow gauges or from actual transpiration measurement, was dependent upon temperature (r2 = 0.94 to 0.96). Water use increased until daytime temperatures reached 36°C, after which water use decreased. Sap flow followed solar radiation trends in the field. Heat is lost or dissipated from the gauges convectively as the sap flows through the stem, conductively through the solid stem material, and radially into the surrounding air. As the convective proportion of the heat loss from the gauge increased, the accuracy of the water use estimation using the sap flow gauges increased. For sunny days, convective heat loss through sap flow accounted for a major portion of the total heat input to the gauges, while on cloudy days radial heat loss from the gauges accounted for a major portion of the heat input. Thus, at low sap flow rates during cloudy days, the possibility of error in the sap flow system was high. Overall, sap flow in canola was strongly related to daily solar radiation (r2 = 0.92). The sensitive response to weather variations and the possibility of improving the accuracy at high flow rates in the field makes the use of sap flow gauges a viable option for measuring real-time transpiration in canola. Key words: Brassica napus, canola, heat balance, sap flow, transpiration, temperature, solar radiation

scholarly journals 583 Scaling-up Heat-balance Sap Flow Sensors for the High Flow Rates of Mature Grape Vines

HortScience ◽  
2000 ◽  
Vol 35 (3) ◽  
pp. 497A-497
Author(s):  
J.M. Tarara ◽  
J.C. Ferguson
Keyword(s):  
Water Use ◽  
Water Loss ◽  
Heat Balance ◽  
Sap Flow ◽  
Management Strategies ◽  
Absolute Error ◽  
Stem Segment ◽  
Maximum Absolute Error ◽  
The Heat Balance ◽  
Zero Flow

Management strategies like “deficit irrigation” in wine grapes require accurate, reliable information on vine water use, making direct measurements of vine transpiration highly desirable. The heat-balance sap flow method has the advantages of being non-invasive and requiring no other calibration beyond a zero-flow set. Potential violations of the method's assumptions were dealt with and the heat balance method successfully applied to mature grape vines under conditions of extremely high sap flow. Greenhouse studies suggested that vines transpire at night, up to 9.5% of the total 24-h water loss, thus violating the zero-flow assumption for setting the gauge constant. Using a predetermined gauge constant caused smaller errors than using daily, pre-dawn constants set in situ. The steady-state assumption was violated only in early and late hours of the day, and the inclusion of a term to account for the change in heat stored by the stem only marginally improved daily estimates of water use. The assumption of radially uniform temperature across the heated stem segment is violated at very high flows (e.g., >700 g·h–1), but can be corrected for by using wider heaters and adjusting the placement of thermocouples. For a mature, potted vine in the greenhouse, the maximum absolute error in cumulative daytime water use between a sap gauge and a precision load cell was about –10%, with the gauge almost exclusively underestimating water loss. A custom-built, 20-gauge system was run continuously in the field for 90 days. Vine-to-vine variability in water use was not accounted for by normalizing sap flow by leaf area, suggesting that it is critical to include in any field study the largest number of gauges that are technically feasible.

scholarly journals Transpiration by Crape Myrtle Cultivars Surrounded by Mulch, Soil, and Turfgrass Surfaces

HortScience ◽  
1991 ◽  
Vol 26 (9) ◽  
pp. 1207-1210 ◽  
Author(s):  
Jayne M. Zajicek ◽  
J.L. Heilman
Keyword(s):  
Vapor Pressure ◽  
Water Use ◽  
Heat Balance ◽  
Sap Flow ◽  
Longwave Radiation ◽  
Soil Surface ◽  
Bare Soil ◽  
The Other ◽  
Stem Flow ◽  
Daily Water

A study was conducted to explore how surface materials, including pine bark mulch, bare soil, and turfgrass, affect water use of diverse cultivars (dwarf weeping, dwarf upright, standard weeping, and standard upright) of crape myrtle (Lagerstroemia indica L.). Daily water use was measured gravimetrically, and instantaneous rates of sap flow were measured using heat balance stem flow gauges. Plants of all cultivars surrounded by the mulched surface lost 0.63 to 1.25 kg·m-2·day-1 more water than plants on the soil surface and 0.83 to 1.09 kg·m-2·day-1 more than plants surrounded by turf. The surface temperature of the mulch was higher than that of the other surfaces, resulting in greater fluxes of longwave radiation from the surface. Because of the greater energy load, plants on the mulched surface had higher leaf temperatures and higher leaf-air vapor pressure deficits (VPD) throughout the day. Plants on the mulched area also had higher stomata1 conductances during most of the day compared with those on bare soil and turfgrass surfaces.

An Empirical Calibration for Heat-Balance Sap-Flow Sensors in Maize

2017 ◽  
Vol 109 (3) ◽  
pp. 1122-1128 ◽  
Author(s):  
Yueyue Wang ◽  
Xiao Zhang ◽  
Xinhua Xiao ◽  
Joshua Heitman ◽  
Robert Horton ◽  
...  
Keyword(s):  
Heat Balance ◽  
Sap Flow ◽  
Flow Sensors ◽  
Empirical Calibration ◽  
Sap Flow Sensors

scholarly journals Water-use dynamics of an alien-invaded riparian forest within the Mediterranean climate zone of the Western Cape, South Africa

2017 ◽  
Vol 21 (9) ◽  
pp. 4551-4562 ◽  
Author(s):  
Bruce C. Scott-Shaw ◽  
Colin S. Everson ◽  
Alistair D. Clulow
Keyword(s):  
South Africa ◽  
Water Use ◽  
Sap Flow ◽  
Riparian Forest ◽  
Riparian Forests ◽  
Ratio Method ◽  
Natural State ◽  
Indigenous Species ◽  
Western Cape ◽  
Selection Of

Abstract. In South Africa, the invasion of riparian forests by alien trees has the potential to affect the country's limited water resources. Tree water-use measurements have therefore become an important component of recent hydrological studies. It is difficult for South African government initiatives, such as the Working for Water (WfW) alien clearing program, to justify alien tree removal and implement rehabilitation unless hydrological benefits are known. Consequently, water use within a riparian forest along the Buffeljags River in the Western Cape of South Africa was monitored over a 3-year period. The site consisted of an indigenous stand of Western Cape afrotemperate forest adjacent to a large stand of introduced Acacia mearnsii. The heat ratio method of the heat pulse velocity sap flow technique was used to measure the sap flow of a selection of indigenous species in the indigenous stand, a selection of A. mearnsii trees in the alien stand and two clusters of indigenous species within the alien stand. The indigenous trees in the alien stand at Buffeljags River showed significant intraspecific differences in the daily sap flow rates varying from 15 to 32 L day−1 in summer (sap flow being directly proportional to tree size). In winter (June), this was reduced to only 7 L day−1 when limited energy was available to drive the transpiration process. The water use in the A. mearnsii trees showed peaks in transpiration during the months of March 2012, September 2012 and February 2013. These periods had high average temperatures, rainfall and high daily vapor pressure deficits (VPDs – average of 1.26 kPa). The average daily sap flow ranged from 25 to 35 L in summer and approximately 10 L in the winter. The combined accumulated daily sap flow per year for the three Vepris lanceolata and three A. mearnsii trees was 5700 and 9200 L, respectively, clearly demonstrating the higher water use of the introduced Acacia trees during the winter months. After spatially upscaling the findings, it was concluded that, annually, the alien stand used nearly 6 times more water per unit area than the indigenous stand (585 mm a−1 compared to 101 mm a−1). This finding indicates that there would be a gain in groundwater recharge and/or streamflow if the alien species are removed from riparian forests and rehabilitated back to their natural state.

scholarly journals Stand-Level Transpiration Increases after Eastern Redcedar (Juniperus virginiana L.) Encroachment into the Midstory of Oak Forests

Forests ◽  
2020 ◽  
Vol 11 (9) ◽  
pp. 901 ◽  
Author(s):  
Patricia R. Torquato ◽  
Rodney E. Will ◽  
Bo Zhang ◽  
Chris B. Zou
Keyword(s):  
Water Use ◽  
Sap Flow ◽  
Structural Equation ◽  
Mixed Forest ◽  
Flow Density ◽  
Juniperus Virginiana ◽  
Cross Timbers ◽  
Eastern Redcedar ◽  
Mixed Species ◽  
Mixed Stands

Eastern redcedar (Juniperus virginiana L., redcedar) encroachment is transitioning the oak-dominated Cross-Timbers of the southern Great Plain of the USA into mixed-species forests. However, it remains unknown how the re-assemblage of tree species in a semiarid to sub-humid climate affects species-specific water use and competition, and ultimately the ecosystem-level water budget. We selected three sites representative of oak, redcedar, and oak and redcedar mixed stands with a similar total basal area (BA) in a Cross-Timbers forest near Stillwater, Oklahoma. Sap flow sensors were installed in a subset of trees in each stand representing the distribution of diameter at breast height (DBH). Sap flow of each selected tree was continuously monitored over a period of 20 months, encompassing two growing seasons between May 2017 and December 2018. Results showed that the mean sap flow density (Sd) of redcedar was usually higher than post oaks (Quercus stellata Wangenh.). A structural equation model showed a significant correlation between Sd and shallow soil moisture for redcedar but not for post oak. At the stand level, the annual water use of the mixed species stand was greater than the redcedar or oak stand of similar total BA. The transition of oak-dominated Cross-Timbers to redcedar and oak mixed forest will increase stand-level transpiration, potentially reducing the water available for runoff or recharge to groundwater.

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