A calibration device and method for measuring tree trunk sap flow based on heat dissipation method

Abstract

The present invention relates to the field of calibration of trunk sap flow measurement, and specifically to a calibration device and method for measuring trunk sap flow based on a heat dissipation method. In the calibration device, a water tank is controlled by a Malvern flask to form a stable water potential difference with a water tray, and water in the sealed water tray is pressed into the trunk segment and collected at the top of the trunk segment, entering the volumetric flask through a water inlet; the side of the trunk segment is wrapped with a sealing film, the lower end of which is sealed with the water tray, and the top cross-section is inclined and connected to an acrylic cover plate; after the test is completed, the weight of water passing through the trunk segment per unit time is weighed, and the average trunk sap flow density is calculated based on the cross-sectional area of ​​the trunk's water-conducting xylem. This value is used as the actual measured value and fitted with the temperature difference of the upper and lower probes inserted into the trunk segment's xylem, thereby correcting the empirical relationship between the average trunk sap flow density and the temperature difference of the sensor probes. The present invention is suitable for measuring and calibrating trunk sap flow.

Description

Technical Field

[0001] The present 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 estimates are typically based on measurements of xylem sap flow in individual trees, assuming that the sum of the mass flow through the trunk equals transpiration from 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 exhibits significant variation within the xylem cross-section of the same plant and between different plants. Furthermore, because the pin-type heat dissipation method is based on the thermal conductivity of wood, factors such as the position of the sensor probe and the wound effect caused by the probe's insertion into the tree contribute to uncertainty in the method's estimated results. Furthermore, sap flux density measurements based on the pin-type heat dissipation method only measure the sap flux density within the sapwood that the probe can penetrate. Studies have found that the sap flux density is unevenly distributed radially across the tree's cross-section, so the original pin-type heat dissipation method's estimation of trunk sap flow will contain certain errors. To accurately amplify the sap flow velocity of a monitored portion of the trunk to the level of the entire plant, radial differences in xylem sap flux density need to be considered. Summary of the Invention

[0004] The purpose of the present invention is to overcome the shortcomings of the existing technology and provide a calibration device and method for measuring trunk sap flow based on the thermal dissipation method, so as to realize the correction of 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 objectives. In a first aspect, the present invention provides a calibration device for measuring tree trunk sap flow based on a heat dissipation method. The calibration device includes a closed water tray, a tree trunk segment, an acrylic cover plate, a protective film, a pin-type sap flow sensor, a data logger, a connecting tube, a volumetric flask, an electronic balance, a water tank, and a Malvern flask.

[0006] The trunk segment is erected in its natural growth direction, its side surfaces are covered by a closed protective film, its lower end is immersed in the closed water tray, its top cross-section is inclined and connected to the acrylic cover plate at the top, and the bottom end of the inclined surface is connected to the volumetric flask via 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. The water in the closed water tray is pressed into the tree trunk section by the water potential difference. The water passes through the tree trunk section, is collected in the inclined acrylic cover plate, and enters the volumetric flask through the water outlet.

[0008] The Malchow flask consists of an air inlet pipe, an air outlet pipe, and a water outlet. It uses the principle of pressure and communicating vessels 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 trunk section.

[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 through the air inlet pipe. When the water level of the Malchnitz flask is insufficient, it serves as a water inlet to replenish water to the Malchnitz flask;

[0010] The Malchnitz flask outlet pipe is provided with a valve, which is closed when the Malchnitz flask is operating 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 consists 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, while 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, 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 of the trunk;

[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 described above. The calibration method comprises:

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

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

[0019] S3. Calculate the sap flux density based on the actual weight of water passing through the trunk segment per unit time and the cross-sectional area of ​​the water-conducting xylem, and use this to calibrate 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 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 portion 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 sap flux density of the tree under a certain water potential difference as follows:

[0028] Fs 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 Malvern 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 sap flow of the tree is calculated based on the calibrated 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, 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 the two parameters can be fitted linearly or nonlinearly to obtain the corrected values ​​of the a and b parameters. This can provide a method for measuring sap flow density when there is a lack of observation data for specific species or specific locations, realize the correction of the original empirical relationship, and provide an important reference basis for the accurate measurement of sap flow based on the use of the heat dissipation method. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This 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 solutions and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to 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 cross-section is inclined and 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. The water in the closed water tray is pressed into the tree trunk section by the water potential difference. The water passes through the tree trunk section, is collected in the inclined acrylic cover plate, and enters the volumetric flask through the water outlet.

[0041] The Malvern flask consists of an air inlet pipe, an air outlet pipe, and a water outlet. It uses 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 section.

[0042] 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 the outside air enters the cavity of the bottle through the air inlet pipe. When the water level of the Malchnitz flask is insufficient, it serves as a water inlet to replenish water to the Malchnitz 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 it 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 consists 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, while the lower probe is not heated. 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. Prepare the trunk segment used in the experiment and measure the size of the trunk segment;

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

[0052] S3. Calculate the sap flux density based on the actual weight of water passing through the trunk segment per unit time and the cross-sectional area of ​​the water-conducting xylem, and use this to calibrate 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 increase of the liquid level in the volumetric flask per unit time), 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, representing the original empirical parameters of sap flux density and the temperature difference between the 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 image processing tools to obtain the cross-sectional area As of the water-conducting xylem (or sapwood);

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

[0063] Fs 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 Malvern 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 foregoing description is merely 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 construed as excluding other embodiments. Rather, the present invention 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 techniques or knowledge in the relevant field. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention are intended to be protected by the appended claims.

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 surfaces are covered by a closed protective film, its lower end is immersed in the closed water tray, its top cross-section is inclined and connected to the acrylic cover plate at the top, and the bottom end of the inclined surface is connected to the volumetric flask via 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 this 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 flask through the water outlet. The Malchow flask consists of an air inlet pipe, an air outlet pipe, and a water outlet. It uses the principle of pressure and communicating vessels 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 trunk section. 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 through the air inlet pipe. When the water level of the Malchnitz flask is insufficient, it serves as a water inlet to replenish water to the Malchnitz flask; The Malchnitz flask outlet pipe is provided with a valve, which is closed when the Malchnitz flask is operating normally and needs to be opened when the air pressure needs to be balanced; 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 per unit time; The needle-type liquid flow sensor consists 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, while 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, 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 of the trunk; 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 a heat dissipation method, applied to the calibration device for measuring trunk sap flow based on a heat dissipation method as claimed in claim 1, characterized in that: The calibration method includes: S1. Prepare the trunk segments used in the experiment. The trunk segments are freshly felled trees, and measure the length L and the radius R of the trunk segments excluding bark. S2. Using the pin-type heat dissipation method in a calibration device to measure the trunk sap flux density, while using the actual weight of water passing through the trunk segment as a reference standard; The pin-type heat dissipation method is used to measure the trunk sap flux density, including: After the water flow into the volumetric flask stabilizes, the sap flux density is calculated using Granier's original empirical equation, which is determined by the rate of increase of the liquid level in the volumetric flask 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; S3. Calculate the sap flux density based on the actual weight of water passing through the trunk segment per unit time and the cross-sectional area of ​​the water-conducting xylem, and use this to calibrate the parameters in the empirical relationship between the sap flux density and the temperature difference between the upper and lower probes of the sensor; 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 portion is dyed, the boundary between the sapwood and the heartwood is visually observed based on the dyeing results. The dyed area is quantified using an image processing tool to obtain the cross-sectional area of ​​the water-conducting xylem. Calculate the actual sap flux density of the tree under a certain water potential difference as follows: Fs 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 (unit: 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 Malvern 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' ; S4, calculating the total trunk sap flow of the tree based on the calibrated parameters; F d =F' s ×As,F d Indicates the total trunk sap flow of trees, in g·s -1 .

Images