Determination of sap flow in Douglas-fir trees using the heat pulse technique

1985 ◽  
Vol 15 (2) ◽  
pp. 422-428 ◽  
Author(s):  
Y. Cohen ◽  
F. M. Kelliher ◽  
T. A. Black
Keyword(s):  
Flow Rate ◽  
Sap Flow ◽  
Water Flow Rate ◽  
Vapour Pressure Deficit ◽  
Heat Pulse ◽  
Douglas Fir ◽  
Temperature Sensing ◽  
Sap Flux ◽  
Pulse Technique ◽  
Laboratory Calibration

A modified heat pulse technique was used to determine volumetric sap flow in 15–17 m tall Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) trees. Laboratory calibration of the heat pulse technique, accomplished by passing water through 200 mm long by 77 mm diameter stem sections with a gas pressure apparatus, showed an underestimation of the actual water flow rate by 47%. Using a six-thermistor temperature sensing probe inserted radially to a depth of 60 mm, field measurements of sap flux density were found to change with depth into the sap wood. Simultaneous measurements using the temperature sensing probes inserted in three azimuthal directions (0, 120, and 240°) showed good agreement during the daytime in three trees, while in another tree the ratio of the three sap flux densities gradually changed during the daytime. Hourly values of sap flow rate in two different trees, obtained using the laboratory calibration factor were 29 and 53% larger than corresponding foliar transpiration rates estimated using measurements of stomatal conductance, tree leaf area and vapour pressure deficit. Using a microprocessor-based data acquisition system, the technique was successfully used to monitor the course of sap flow rate over a 4-month period.

scholarly journals CALIBRATING THE COMPENSATION HEAT-PULSE TECHNIQUE FOR MEASURING SAP FLOW IN OLIVE

1999 ◽  
pp. 455-460 ◽  
Author(s):  
J.E. Fernández ◽  
M.J. Palomo ◽  
A. Díaz-Espejo ◽  
I.F. Girón
Keyword(s):  
Sap Flow ◽  
Heat Pulse ◽  
Pulse Technique

The importance of conduction versus convection in heat pulse sap flow methods

2020 ◽  
Vol 40 (5) ◽  
pp. 683-694
Author(s):  
Michael A Forster
Keyword(s):  
Flux Density ◽  
Sap Flow ◽  
Peclet Number ◽  
Velocity Measurement ◽  
Measurement Range ◽  
Heat Pulse ◽  
Sap Flux ◽  
Sap Flux Density ◽  
Péclet Number ◽  
Fast Methods

Abstract Heat pulse methods are a popular approach for estimating sap flow and transpiration. Yet, many methods are unable to resolve the entire heat velocity measurement range observable in plants. Specifically, the Heat Ratio (HRM) and Tmax heat pulse methods can only resolve slow and fast velocities, respectively. The Dual Method Approach (DMA) combines optimal data from HRM and Tmax to output the entire range of heat velocity. However, the transition between slow and fast methods in the DMA currently does not have a theoretical solution. A re-consideration of the conduction/convection equation demonstrated that the HRM equation is equivalent to the Péclet equation which is the ratio of conduction to convection. This study tested the hypothesis that the transition between slow and fast methods occurs when conduction/convection, or the Péclet number, equals one, and the DMA would be improved via the inclusion of this transition value. Sap flux density was estimated via the HRM, Tmax and DMA methods and compared with gravimetric sap flux density measured via a water pressure system on 113 stems from 15 woody angiosperm species. When the Péclet number ≤ 1, the HRM yielded accurate results and the Tmax was out of range. When the Péclet number > 1, the HRM reached a maximum heat velocity at approximately 15 cm hr −1 and was no longer accurate, whereas the Tmax yielded accurate results. The DMA was able to output accurate data for the entire measurement range observed in this study. The linear regression analysis with gravimetric sap flux showed an r2 of 0.541 for HRM, 0.879 for Tmax and 0.940 for DMA. With the inclusion of the Péclet equation, the DMA resolved the entire heat velocity measurement range observed across 15 taxonomically diverse woody species. Consequently, the HRM and Tmax are redundant sap flow methods and have been superseded by the DMA.

scholarly journals ABA, Hydraulics, and Gas Exchange of Split-rooted Apple Trees

HortScience ◽  
2005 ◽  
Vol 40 (4) ◽  
pp. 1097C-1097
Author(s):  
Todd C. Einhorn ◽  
Horst W. Caspari ◽  
Steve Green
Keyword(s):  
Gas Exchange ◽  
Time Domain ◽  
Sap Flow ◽  
Leaf Gas Exchange ◽  
Heat Pulse ◽  
Time Domain Reflectometry ◽  
Apple Trees ◽  
Pulse Technique ◽  
Predawn Leaf Water Potential ◽  
Single Leaf

Approach-grafted 1-year-old `Gala'/M7 apple trees were grown with both tops for the remainder of the 2003 season in a greenhouse. Trees were supplied with >100% (control, PRD100) or 50% (PRD50, DI50) of daily ETc either applied to one root compartment only (PRD100, PRD50) or divided evenly across both root compartments (control and DI50). ETc was estimated from gravimetric measurements, and irrigation was switched between wet and dry root compartments several times throughout the experiment. Soil moisture was measured both gravimetrically (tripod) and volumetrically (time-domain reflectometry). Predawn leaf water potential (υpd) and single leaf gas exchange (photosynthesis, stomatal conductance, and transpiration) were recorded daily, and sap flow in stems and roots was monitored continuously using the heat-pulse technique. Leaves were collected for abscisic acid (ABA) determination following gas exchange measurements. Regardless of irrigation placement (i.e., PRD or DI), both 50% ETc treatments experienced similar declines in υpd and single leaf gas exchange relative to control levels. In addition, ABA concentrations were similar for PRD50 and DI50, and were significantly higher than the control and PRD100 treatments. PRD100 trees had similar υpd as control trees; however, gas exchange was reduced >25% compared to the control. Bulk leaf ABA concentration did not differ significantly from control levels and does not by itself explain the down regulation of stomata with PRD100.

Xylem Sap Velocity in Relation to Weather and Air Pollution

IAWA Journal ◽  
1989 ◽  
Vol 10 (4) ◽  
pp. 427-439 ◽  
Author(s):  
Hans Visser ◽  
Frank Noppert ◽  
Han van Wakeren ◽  
Jens Vaessen
Keyword(s):  
Air Pollutants ◽  
Xylem Sap ◽  
Vapour Pressure Deficit ◽  
Weather Conditions ◽  
Heat Pulse ◽  
Atmospheric Conditions ◽  
Air Humidity ◽  
Stochastic Response ◽  
Pulse Technique ◽  
Hourly Basis

Measurements of xylem sap velocities have been used to assess the influence of atmospheric conditions and air pollutants on the transpiration of full-grown trees. For a period of four months sap velocities of oak, beech and Douglas fir were measured on an hourly basis using the heat-pulse technique. Simultaneously, concentrations of S02, NO, N02 and 03 were measured along with air temperature, light intensity, air humidity, precipitation, wind speed and wind direction. To analyse these time series, a technique is introduced which can handle time-dependent relations: the stochastic response model. This statistical model is a submodel of the class of structural models and is estimated by means of the Kalman filter. The influence of weather conditions on heat-pulse velocities (HPV) is prevailing: 80% of the variance is explained by the single variable vapour pressure deficit. No influence of gaseous pollutants on HPV could be assessed. Possible explanations are discussed.

Corrigendum to: Sap-flux density measurement methods: working principles and applicability

2013 ◽  
Vol 40 (10) ◽  
pp. 1088 ◽  
Author(s):  
Maurits W. Vandegehuchte ◽  
Kathy Steppe
Keyword(s):  
Flux Density ◽  
Flow Rate ◽  
Heat Balance ◽  
Sap Flow ◽  
Density Measurement ◽  
Continuous Heating ◽  
Sap Flux ◽  
Sap Flux Density ◽  
Flux Density Measurement ◽  
Density Methods

Sap-flow measurements have become increasingly important in plant science. Since the early experiments with dyes, many methods have been developed. Most of these are based on the application of heat in the sapwood which is transported by the moving sap. By measuring changes in the temperature field around the heater, sap flow can be derived. Although these methods all have the same basis, their working principles vary widely. A first distinction can be made between those measuring the sap-flow rate (g h–1) such as the stem heat balance and trunk sector heat balance method and those measuring sap-flux density (cm3 cm–2 h–1). Within the latter, the thermal dissipation and heat field deformation methods are based on continuous heating, whereas the compensation heat pulse velocity, Tmax, heat ratio, calibrated average gradient and Sapflow+ methods are based on the application of heat pulses. Each of these methods has its advantages and limitations. Although the sap-flow rate methods have been adequately described in previous reviews, recent developments in sap-flux density methods prompted a synthesis of the existing but scattered literature. This paper reviews sap-flux density methods to enable users to make a well founded choice, whether for practical applications or fundamental research questions, and to encourage further improvement in sap-flux density measurement techniques.

Sap-flux density measurement methods: working principles and applicability

2013 ◽  
Vol 40 (3) ◽  
pp. 213 ◽  
Author(s):  
Maurits W. Vandegehuchte ◽  
Kathy Steppe
Keyword(s):  
Flux Density ◽  
Flow Rate ◽  
Heat Balance ◽  
Sap Flow ◽  
Density Measurement ◽  
Continuous Heating ◽  
Sap Flux ◽  
Sap Flux Density ◽  
Flux Density Measurement ◽  
Density Methods

Sap-flow measurements have become increasingly important in plant science. Since the early experiments with dyes, many methods have been developed. Most of these are based on the application of heat in the sapwood which is transported by the moving sap. By measuring changes in the temperature field around the heater, sap flow can be derived. Although these methods all have the same basis, their working principles vary widely. A first distinction can be made between those measuring the sap-flow rate (g h–1) such as the stem heat balance and trunk sector heat balance method and those measuring sap-flux density (cm3 cm–2 h–1). Within the latter, the thermal dissipation and heat field deformation methods are based on continuous heating, whereas the compensation heat pulse velocity, Tmax, heat ratio, calibrated average gradient and Sapflow+ methods are based on the application of heat pulses. Each of these methods has its advantages and limitations. Although the sap-flow rate methods have been adequately described in previous reviews, recent developments in sap-flux density methods prompted a synthesis of the existing but scattered literature. This paper reviews sap-flux density methods to enable users to make a well founded choice, whether for practical applications or fundamental research questions, and to encourage further improvement in sap-flux density measurement techniques.

scholarly journals Effect of Water Flow on Underwater Wet Welded A36 Steel

Metals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 682
Author(s):  
Eko Surojo ◽  
Aziz Harya Gumilang ◽  
Triyono Triyono ◽  
Aditya Rio Prabowo ◽  
Eko Prasetya Budiana ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Water Flow ◽  
Flow Rate ◽  
Water Flow Rate ◽  
Physical And Mechanical Properties ◽  
Shielded Metal Arc Welding ◽  
Effect Of Water ◽  
Bending Effect ◽  
Metal Arc Welding ◽  
A36 Steel

Underwater wet welding (UWW) combined with the shielded metal arc welding (SMAW) method has proven to be an effective way of permanently joining metals that can be performed in water. This research was conducted to determine the effect of water flow rate on the physical and mechanical properties (tensile, hardness, toughness, and bending effect) of underwater welded bead on A36 steel plate. The control variables used were a welding speed of 4 mm/s, a current of 120 A, electrode E7018 with a diameter of 4 mm, and freshwater. The results show that variations in water flow affected defects, microstructure, and mechanical properties of underwater welds. These defects include spatter, porosity, and undercut, which occur in all underwater welding results. The presence of flow and an increased flow rate causes differences in the microstructure, increased porosity on the weld metal, and undercut on the UWW specimen. An increase in water flow rate causes the acicular ferrite microstructure to appear greater, and the heat-affected zone (HAZ) will form finer grains. The best mechanical properties are achieved by welding with the highest flow rate, with a tensile strength of 534.1 MPa, 3.6% elongation, a Vickers microhardness in the HAZ area of 424 HV, and an impact strength of 1.47 J/mm2.

scholarly journals Design and thermal characteristic analysis of motorized spindle cooling system

2021 ◽  
Vol 13 (5) ◽  
pp. 168781402110208
Author(s):  
Yuan Zhang ◽  
Lifeng Wang ◽  
Yaodong Zhang ◽  
Yongde Zhang
Keyword(s):  
Flow Rate ◽  
High Speed ◽  
Thermal Deformation ◽  
Cooling System ◽  
Thermal Characteristic ◽  
Water Flow Rate ◽  
Thermal Characteristics ◽  
Characteristic Analysis ◽  
Motorized Spindle ◽  
Experiment And Simulation

The thermal deformation of high-speed motorized spindle will affect its reliability, so fully considering its thermal characteristics is the premise of optimal design. In order to study the thermal characteristics of high-speed motorized spindles, a coupled model of thermal-flow-structure was established. Through experiment and simulation, the thermal characteristics of spiral cooling motorized spindle are studied, and the U-shaped cooled motorized spindle is designed and optimized. The simulation results show that when the diameter of the cooling channel is 7 mm, the temperature of the spiral cooling system is lower than that of the U-shaped cooling system, but the radial thermal deformation is greater than that of the U-shaped cooling system. As the increase of the channel diameter of U-shaped cooling system, the temperature and radial thermal deformation decrease. When the diameter is 10 mm, the temperature and radial thermal deformation are lower than the spiral cooling system. And as the flow rate increases, the temperature and radial thermal deformation gradually decrease, which provides a basis for a reasonable choice of water flow rate. The maximum error between experiment and simulation is 2°C, and the error is small, which verifies the accuracy and lays the foundation for future research.

Sign in / Sign up

Export Citation Format

Share Document