Calibration device and method for measuring trunk liquid flow based on heat dissipation method

Abstract

The invention relates to the field of measurement and calibration of trunk sap flow, in particular to a calibration device and method for measuring trunk sap flow based on a heat dissipation method. A stable water potential difference is formed between a water tank in the calibration device and a water containing tray under the control of a Markov bottle, and water in the closed water containing tray is pressed into a trunk section, is gathered at the top of the trunk section and enters a volumetric flask through a water passing opening; the lower end of the trunk section is hermetically connected with the water containing tray, and the section of the top end of the trunk section is inclined and is connected with the acrylic cover plate; after the test is finished, weighing the weight of water passing through the trunk section in unit time, calculating the average liquid flux density of the trunk according to the cross section area of the water-guiding xylem of the trunk, and fitting the average liquid flux density as a measured value with the temperature difference between the upper probe and the lower probe inserted into the xylem of the trunk section; and correction of the empirical relationship between the average liquid flux density of the trunk and the temperature difference of the sensor probe is realized. The method is suitable for measuring and calibrating the trunk liquid flow.

Description

Technical Field

[0001] The invention relates to the field of trunk sap flow measurement and calibration, and in particular to a calibration device and method for measuring trunk sap flow based on a heat dissipation method. Background Art

[0002] In forest and orchard ecosystems, transpiration estimation is usually based on the measurement of xylem sap flow in individual trees, assuming that the total mass flow of liquid flowing through the trunk is equal to the transpiration of the entire canopy. The pin-type heat dissipation method is a common method for determining tree transpiration.

[0003] However, the xylem sap flux density of plants shows great differences in the xylem cross section of the same plant and between different plants. At the same time, since the pin-type heat dissipation method is based on the thermal conductivity of wood, the position of the sensor probe and the wound effect formed by the probe inserted into the tree will lead to uncertainty in the estimation results of this method. In addition, the sap flux density measurement based on the pin-type heat dissipation method is only for the sapwood range that the probe can penetrate. Studies have found that the sap flux density is unevenly distributed in the radial direction of the tree cross section, so the original pin-type heat dissipation method will have a certain error in estimating the sap flow rate of the trunk. In order to accurately amplify the sap flow velocity of the monitored part of the trunk to the level of the whole plant, it is necessary to consider the radial difference of the xylem sap flux density. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a calibration device and method for measuring trunk sap flow based on the heat dissipation method, so as to correct the relationship between the average sap flux density of the trunk and the temperature difference between the upper and lower probes of the sensor, so as to more accurately monitor the sap flow rate of the trunk.

[0005] The present invention adopts the following technical solutions to achieve the above-mentioned purpose. In a first aspect, the present invention provides a calibration device for measuring trunk sap flow based on a heat dissipation method, the calibration device comprising a closed water tray, a trunk segment, an acrylic cover plate, a protective film, a pin-type sap flow sensor, a data recorder, a connecting tube, a volumetric flask, an electronic balance, a water tank, and a Martens flask;

[0006] The trunk segment is erected in its natural growth direction, its side is covered by a closed protective film, its lower end is immersed in the closed water tray, its top section is inclined, and is connected to the acrylic cover plate at the top, and the bottom end of the inclined surface is connected to the volumetric flask through the connecting pipe;

[0007] A water potential difference is formed between the water tank and the closed water tray on which the tree trunk section is placed, and the water in the closed water tray is pressed into the tree trunk section through the water potential difference. The water passes through the tree trunk section, is collected in the inclined acrylic cover plate, and enters the volumetric bottle through the water opening;

[0008] The Malchow flask is composed of an air inlet pipe, an air outlet pipe, and a water outlet, and utilizes the pressure and communicating vessel principle to maintain a stable water level in the water tank, so as to form a stable water potential difference between the water tank and the closed water tray, thereby forming a stable liquid flow in the tree trunk segment;

[0009] The bottom of the air inlet pipe of the Malchnitz flask is level with the liquid level of the water tank. When the liquid level of the water tank drops, the Malchnitz flask supplies water, and outside air enters the cavity of the flask from the air inlet pipe. When the water level of the Malchnitz flask is insufficient, it serves as a water inlet to add water to the Malchnitz flask.

[0010] The gas outlet pipe of the Malvern flask is provided with a valve, which is closed when the Malvern flask is working normally, and needs to be opened when the air pressure needs to be balanced;

[0011] The volumetric flask is connected to the water outlet and placed on an electronic balance after the test to measure the weight of water passing through the trunk segment;

[0012] The needle-type liquid flow sensor is composed of an upper probe, a lower probe and a T-type thermocouple. The upper probe and the lower probe are radially inserted into the sapwood portion of the trunk segment. The upper probe is continuously heated at a constant power, and the lower probe is not heated. The thermocouple is used to measure the temperature difference between the upper probe and the lower probe.

[0013] The depth of the probe inserted into the wood can be varied to measure the difference in radial sap flow in the trunk;

[0014] The probes are installed at different positions at the same height of the trunk segment, or at different heights at the same position, to study the differences in radial liquid flow at different positions at the same height or at different heights at the same position;

[0015] The data recorder is used to record the weight measured by the electronic balance and the temperature difference measured by the pin-type liquid flow sensor.

[0016] In a second aspect, the present invention provides a calibration method for measuring trunk sap flow based on a heat dissipation method, which is applied to the calibration device for measuring trunk sap flow based on a heat dissipation method as described above. The calibration method comprises:

[0017] S1. Prepare a trunk segment for the experiment, and measure the length L and the radius R of the trunk segment excluding bark;

[0018] S2. Using the pin-type heat dissipation method in the calibration device to measure the trunk sap flux density, while using the actual weight of water passing through the trunk section as a reference standard;

[0019] S3, calculating the sap flux density according to the actual water weight passing through the trunk section per unit time and the cross-sectional area of ​​the water-conducting wood, and using this to correct the parameters in the empirical relationship between the sap flux density and the temperature difference between the upper and lower probes of the sensor;

[0020] S4. Calculate the total trunk sap flow of the tree based on the calibrated parameters.

[0021] Furthermore, in step S1, the tree trunk segments are made of freshly felled trees.

[0022] Furthermore, the pin-type heat dissipation method is used to measure the trunk sap flux density, specifically including:

[0023] After the water flow into the volumetric flask stabilizes (which can be determined by the rate of rise of the liquid level in the volumetric flask per unit time), the sap flux density is calculated using Granier's original empirical equation, Fs = a × K b , Fs represents the sap flux density, a and b represent the original empirical parameters of the calibrated sap flux density and the original empirical parameters of the temperature difference between the upper and lower probes of the sensor, respectively;

[0024] ΔT0 is the ΔT value obtained under zero flow conditions, that is, the maximum temperature difference between the upper and lower probes (°C), and ΔT is the temperature difference between the upper and lower probes measured by the thermocouple (°C).

[0025] Furthermore, step S3 specifically includes:

[0026] A set percentage of acid fuchsin dye is added to the water tray in the calibration system device, and the water tank presses the fuchsin dye into the trunk segment. After the sapwood is dyed, the dyed area is quantified using an image processing tool to obtain the cross-sectional area of ​​the water-conducting xylem;

[0027] Calculate the actual liquid flux density of the tree under a certain water potential difference as follows:

[0028] F G Indicates the water weight flux in g cm -2 ·s -1 , G is the actual water weight obtained by the electronic balance, in g·s -1 , As is the cross-sectional area of ​​the water-conducting xylem, in cm 2 ;

[0029] Change the height of the water tank and the Martens flask, that is, change the water potential difference between the water tank and the closed water tray, record the stable value of K under a certain water potential difference, and record the water volume per unit time during the stable period of K value. G and a×K b The relationship between a and b is linearly or nonlinearly fitted to obtain the correction values ​​a′ and b′ of a and b, and the corrected sap flux density F' is calculated based on the correction values ​​a′ and b′ s , F′ s =a′×K b′ .

[0030] Furthermore, step S4 specifically includes:

[0031] The total tree sap flow is calculated based on the corrected parameters as follows:

[0032] F d =F' s ×As,F d Indicates the total trunk sap flow of the tree, in g·s -1 .

[0033] The beneficial effects of the present invention are:

[0034] The present invention uses a specific calibration device to measure the sap flux density using the heat dissipation method principle, taking into account the position error of the probe piercing the tree, the wound effect, the radial difference and other error sources, and uses the actual water flow Fs passing through the trunk segment. G For reference, according to its relationship with a×K b The relationship between a and b can be linearly or nonlinearly fitted to obtain the corrected values ​​of parameters a and b, which can provide a method for measuring sap flow density for those lacking observation data on specific species or locations, realize the correction of the original empirical relationship, and provide an important reference for accurately measuring sap flow based on the use of the heat dissipation method. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a structural diagram of a calibration device for measuring trunk sap flow based on a heat dissipation method provided by an embodiment of the present invention;

[0036] Figure 2 It is a schematic cross-sectional view of a tree trunk segment provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0037] To make the purpose, technical solution and advantages of the embodiments of the present invention more clear, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0038] The present invention provides a calibration device for measuring trunk sap flow based on the heat dissipation method, such as Figure 1 As shown, the calibration device includes a closed water tray, a tree trunk segment, an acrylic cover plate, a protective film, a pin-type liquid flow sensor, a data logger, a connecting tube, a volumetric flask, an electronic balance, a water tank, and a Martens flask;

[0039] The trunk segment is erected in its natural growth direction, its side is covered by a closed protective film, its lower end is immersed in the closed water tray, its top section is inclined, and is connected to the acrylic cover plate at the top, and the bottom end of the inclined surface is connected to the volumetric flask through the connecting pipe;

[0040] A water potential difference is formed between the water tank and the closed water tray on which the tree trunk section is placed, and the water in the closed water tray is pressed into the tree trunk section through the water potential difference. The water passes through the tree trunk section, is collected in the inclined acrylic cover plate, and enters the volumetric bottle through the water opening;

[0041] The Malvern flask consists of an air inlet pipe, an air outlet pipe, and a water outlet. It uses the pressure and the principle of communicating vessels to maintain a stable water level in the water tank, so that a stable water potential difference is formed between the water tank and the closed water tray, thereby forming a stable liquid flow in the trunk segment.

[0042] The bottom of the air inlet pipe of the Malvern flask is level with the liquid level of the water tank. When the liquid level of the water tank drops, the Malvern flask supplies water, and the outside air enters the cavity of the flask from the air inlet pipe. When the water level of the Malvern flask is insufficient, it serves as a water inlet to add water to the Malvern flask.

[0043] The outlet pipe of the Malvern flask is equipped with a valve. The valve is closed when the Malvern flask is working normally, and the valve needs to be opened when the air pressure needs to be balanced;

[0044] Connect the volumetric flask to the water outlet and place it on an electronic balance after the test to measure the weight of water passing through the trunk segment;

[0045] The needle-type liquid flow sensor is composed of an upper probe, a lower probe and a T-type thermocouple, wherein the upper probe and the lower probe are radially inserted into the sapwood portion of the trunk segment, the upper probe is continuously heated at a constant power, and the lower probe is not heated, and the thermocouple is used to measure the temperature difference between the upper probe and the lower probe;

[0046] The depth of probe insertion into the xylem can be varied to measure differences in radial sap flow in the trunk;

[0047] The probes can be installed at different positions at the same height of the trunk segment (TD1, TD2), or at different heights at the same position (TD2, TD3), to study the differences in radial sap flow at different positions at the same height or at different heights at the same position;

[0048] The data logger is used to record the weight measured by the electronic balance and the temperature difference measured by the pin-type liquid flow sensor.

[0049] Based on the calibration device, the present invention also provides a calibration method for measuring trunk sap flow based on the heat dissipation method, which specifically includes:

[0050] S1. preparing a tree trunk segment for the experiment and measuring the size of the tree trunk segment;

[0051] S2. Using the pin-type heat dissipation method in the calibration device to measure the trunk sap flux density, while using the actual weight of water passing through the trunk section as a reference standard;

[0052] S3, calculating the sap flux density according to the actual water weight passing through the trunk section per unit time and the cross-sectional area of ​​the water-conducting wood, and using this to correct the parameters in the empirical relationship between the sap flux density and the temperature difference between the upper and lower probes of the sensor;

[0053] S4. Calculate the total trunk sap flow of the tree based on the calibrated parameters.

[0054] Specifically, the trunk segment in step S1 is a freshly felled tree, and the length L and the radius R excluding the bark of the trunk are measured.

[0055] In one embodiment of the present invention, the trunk sap flux density measurement in step S2 is specifically as follows:

[0056] First, after the water flow into the volumetric flask is stable (which can be determined by the rate of liquid level rise in the volumetric flask per unit time), Granier's original empirical equation is used to calculate the sap flux density Fs (g·cm -2 ·s -1 ), calculated as follows:

[0057] Fs=a×K b ;

[0058] Where a and b are 0.0119 and 1.231 respectively, which are the original empirical parameters of sap flux density and temperature difference between upper and lower probes of the sensor calibrated by Granier using three tree species (Pseudotsugamenziesii, Pinus nigra and Quercus pedunculata). K is defined as:

[0059]

[0060] Where: ΔT0 is the ΔT value obtained under zero flow conditions or the maximum temperature difference between the upper and lower probes (°C), and ΔT is the temperature difference between the upper and lower probes measured by the thermocouple (°C);

[0061] Then, a set percentage (0.5%) of acid fuchsin dye is added to the water tray in the calibration system device, and the water tank presses the fuchsin dye into the trunk section; Figure 2 As shown, after the sapwood is partially dyed, the dyed area is quantified using an image processing tool to obtain the cross-sectional area As of the water-conducting xylem (or sapwood);

[0062] Calculate the actual liquid flux density of the tree under a certain water potential difference as follows:

[0063] F G Indicates the water weight flux in g cm -2 ·s -1, G is the actual water weight obtained by the electronic balance, in g·s -1 , As is the cross-sectional area of ​​the water-conducting xylem, in cm 2 ;

[0064] Change the height of the water tank and the Martens flask, that is, change the water potential difference between the water tank and the closed water tray, record the stable value of K under a certain water potential difference, and record the water volume per unit time during the stable period of K value. G and a×K b The relationship between a and b is linearly or nonlinearly fitted to obtain the correction values ​​a′ and b′ of a and b, and the corrected sap flux density F' is calculated based on the correction values ​​a′ and b′ s , F′ s =a′×K b′ .

[0065] Finally, the total trunk sap flow of the tree is calculated based on the corrected parameters as follows:

[0066] F d =F' s ×As,F d Represents the total trunk sap flow of a tree.

[0067] The above is only a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art shall not deviate from the spirit and scope of the present invention, and shall be within the scope of protection of the claims attached to the present invention.

Claims

1. A calibration device for measuring trunk sap flow based on the heat dissipation method, characterized in that: The calibration device includes a closed water tray, a tree trunk section, an acrylic cover plate, a protective film, a pin-type liquid flow sensor, a data logger, a connecting tube, a volumetric flask, an electronic balance, a water tank, and a Martens flask; The trunk segment is erected in its natural growth direction, its side is covered by a closed protective film, its lower end is immersed in the closed water tray, its top section is inclined, and is connected to the acrylic cover plate at the top, and the bottom end of the inclined surface is connected to the volumetric flask through the connecting pipe; A water potential difference is formed between the water tank and the closed water tray on which the tree trunk section is placed. Under the pressure of the water potential difference, the water in the closed water tray can be pressed into the tree trunk section. The water passes through the tree trunk section, is collected in the inclined acrylic cover plate, and enters the volumetric bottle through the water opening. The Malchow flask is composed of an air inlet pipe, an air outlet pipe, and a water outlet, and utilizes the pressure and communicating vessel principle to maintain a stable water level in the water tank, so as to form a stable water potential difference between the water tank and the closed water tray, thereby forming a stable liquid flow in the tree trunk segment; The bottom of the air inlet pipe of the Malchnitz flask is level with the liquid level of the water tank. When the liquid level of the water tank drops, the Malchnitz flask supplies water, and outside air enters the cavity of the flask from the air inlet pipe. When the water level of the Malchnitz flask is insufficient, it serves as a water inlet to add water to the Malchnitz flask. The gas outlet pipe of the Malvern flask is provided with a valve, which is closed when the Malvern flask is working normally, and needs to be opened when the air pressure needs to be balanced; The volumetric flask is connected to the water outlet and is placed on an electronic balance after the test to measure the weight of water passing through the trunk segment per unit time; The needle-type liquid flow sensor is composed of an upper probe, a lower probe and a T-type thermocouple. The upper probe and the lower probe are radially inserted into the sapwood portion of the trunk segment. The upper probe is continuously heated at a constant power, and the lower probe is not heated. The thermocouple is used to measure the temperature difference between the upper probe and the lower probe. The depth of the probe inserted into the wood can be varied to measure the difference in radial sap flow in the trunk; The probes are installed at different positions at the same height of the trunk segment, or at different heights at the same position, to study the differences in radial liquid flow at different positions at the same height or at different heights at the same position; The data recorder is used to record the weight measured by the electronic balance and the temperature difference measured by the pin-type liquid flow sensor.

2. A calibration method for measuring trunk sap flow based on heat dissipation method, applied to the calibration device for measuring trunk sap flow based on heat dissipation method as claimed in claim 1, characterized in that: The calibration method includes: S1. Prepare a trunk segment for the experiment, and measure the length L and the radius R of the trunk segment excluding bark; S2. Using the pin-type heat dissipation method in the calibration device to measure the trunk sap flux density, while using the actual weight of water passing through the trunk section as a reference standard; S3, calculating the sap flux density according to the actual water weight passing through the trunk section per unit time and the cross-sectional area of ​​the water-conducting wood, and using this to correct the parameters in the empirical relationship between the sap flux density and the temperature difference between the upper and lower probes of the sensor; S4. Calculate the total trunk sap flow of the tree based on the calibrated parameters.

3. The calibration method for determining trunk sap flow based on the heat dissipation method according to claim 2, characterized in that: In step S1, the trunk segments are freshly felled trees.

4. The calibration method for determining trunk sap flow based on the heat dissipation method according to claim 2, characterized in that: The pin-type heat dissipation method is used to measure the trunk sap flux density, including: After the water flow into the volumetric flask is stable, the sap flux density is calculated using Granier's original empirical equation, which is determined by the rate at which the liquid level in the volumetric flask rises per unit time. Fs=a×K b , Fs represents the sap flux density, a and b represent the original empirical parameters of the calibrated sap flux density and the original empirical parameters of the temperature difference between the upper and lower probes of the sensor, respectively; ΔT0 is the ΔT value obtained under zero liquid flow conditions, that is, the maximum temperature difference between the upper and lower probes, and ΔT is the temperature difference between the upper and lower probes measured in real time by the thermocouple.

5. The calibration method for determining trunk sap flow based on the heat dissipation method according to claim 2, characterized in that: Step S3 specifically includes: A set percentage of acid fuchsin dye is added to the water tray in the calibration system device, and the water tank presses the fuchsin dye into the trunk section. After the sapwood part is dyed, the boundary between the sapwood part and the heartwood part is visually observed according to the dyeing result, and the dyeing area is quantified by an image processing tool to obtain the cross-sectional area of ​​the water-conducting xylem; Calculate the actual liquid flux density of the tree under a certain water potential difference as follows: F G Indicates the water weight flux in g cm -2 ·s -1 , G is the actual water weight per unit time obtained by the electronic balance (in g·s -1 , As is the cross-sectional area of ​​the water-conducting xylem, in cm 2 ; Change the height of the water tank and the Martens flask, that is, change the water potential difference between the water tank and the closed water tray, record the stable value of K under a certain water potential difference, and record the water volume per unit time during the stable period of K value. G and a×K b The relationship between a and b is linearly or nonlinearly fitted to obtain the correction values ​​a′ and b′ of a and b, and the corrected sap flux density F' is calculated based on the correction values ​​a′ and b′ s , F′ s =a′×K b′ .

6. The calibration method for determining trunk sap flow based on the heat dissipation method according to claim 5, characterized in that: Step S4 specifically includes: The total tree sap flow is calculated based on the corrected parameters as follows: F d =F' s ×As,F d Indicates the total trunk sap flow of the tree in g·s -1 .

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