AU2020104203A4

AU2020104203A4 - Device and method for measuring forward and reverse sap flow density of tree trunks

Info

Publication number: AU2020104203A4
Application number: AU2020104203A
Authority: AU
Inventors: Chunxia He; Hui Huang; Changming Ma; Shengjin Shi; Sheng Sun; Shoujia Sun; Changjun YIN; Jinsong Zhang
Original assignee: Research Institute of Forestry of Chinese Academy of Forestry
Current assignee: Research Institute of Forestry of Chinese Academy of Forestry
Priority date: 2020-12-21
Filing date: 2020-12-21
Publication date: 2021-03-11
Anticipated expiration: 2028-12-21

Abstract

Disclosed is a device and a method for measuring forward and reverse sap flow densities of tree trunks. The device comprises a sensor and a controller; the sensor comprising an upper probe, a middle probe and a lower probe that are equally spaced 5 from top to bottom along an extending direction of a tree; each of the upper probe, the middle probe and the lower probe is provided with a temperature measuring component; the middle probe is further provided with a heating component; and the controller is used for controlling the temperature measuring component to collect temperature data and controlling the heating component to heat. According to the present disclosure, traditional 10 Granier-type thermal diffusion (TDP) method commonly used in conventional method for measuring the sap flow density is replaced for solving the problems of low precision, high power consumption, and poor practicability. 1/1 FIG. 1

Description

1/1

FIG. 1

DEVICE AND METHOD FOR MEASURING FORWARD AND REVERSE SAP FLOW DENSITY OF TREE TRUNKS TECHNICAL FIELD

[0001] The present disclosure relates to sap flow density measurement, in particular to a device and a method for measuring forward and reverse sap flow densities of tree trunks.

BACKGROUND

[0002] Sap flow is a tree physiological and ecological indicator on water transportation. The direction of sap flow includes upward and downward. Sap flow is not only an important component of heat balance and water balance, but also an important process of water and heat transfer in soil-plant-atmosphere continuum space) . Meanwhile, the tree sap flow density is a necessary parameter for determining the sap flow rate of an individual plant and forest stand and is one of key indicators for analyzing water transportation mechanism and water consumption of forests and guiding the water management of forest ecology. Therefore, measurements on the sap flow density of tree trunk have always been a hot spot of research on tree physiology and ecology, forest hydrology and forest meteorology.

[0003] However, conventional devices for measuring sap flow densities can only measure the forward sap flow density. That is, they cannot be used to measure the reversed direction. Furthermore, due to the defects of the structure and the measurement methods of the conventional device, their measurement precision is relatively lower, and the power consumption is quite higher.

SUMMARY

[0004] In view of this, the object of the present disclosure is to provide a device and a method for measuring forward and reverse sap flow densities of tree trunks, so as to solve problems such as unobtainable reverse sap flow density and lower measurement precision .

[0005] For the above object, the present disclosure provides a device for measuring forward and reverse sap flow densities of tree trunks, including: a sensor and a controller; wherein, the sensor comprises an upper probe, a middle probe and a lower probe spaced equally from top to bottom along an extending direction of a tree trunk; the upper probe, the middle probe and the lower probe are all provided with a temperature measuring component; the middle probe is further provided with a heating component; and the controller is used to control the temperature measuring component, collect temperature data and control the heating component.

[0006] Wherein, the inner diameters and the lengths of the upper probe, the middle probe and the lower probe are 1.7 mm and between 10 and 30 mm.

[0007] Wherein, the spaces between probes of the upper and middle and the middle and lower are both 40 mm.

[0008] Wherein, the temperature measuring component is a miniature thermistor.

[0009] Wherein, the heating component is a heating resistor.

[0010] Wherein, the heating component is a constantan wire or a tungsten wire with a resistance value of 43Q; and the heating component has a heating voltage of 2V.

[0011] Wherein, the upper probe, the middle probe, and the lower probe all comprise an elongated probe body; and the heating component is equipped in a direction along with the elongated probe body.

[0012] Based on the above device, the present disclosure also provides a method of how to use the device, comprising: insert the upper probe, the middle probe and the lower probe of the sensor into a sapwood part of a tree trunk; the controller control the heating component to perform at least one cycle of intermittent heating; wherein, one cycle of the intermittent heating comprises a heating period and a cooling period with an equal duration; in each cycle of the intermittent heating, the controller is used to control the temperature measuring components of the upper probe, the middle probe, and the lower probe; collect temperature data in the last minute of each heating period and each cooling period, respectively; and obtain the first temperature differences between the middle and upper, as well as middle and lower probe, and the second temperature differences between the middle and upper, and as well as the middle and lower probe. Wherein, the first and second middle and upper temperature differences refers to a temperature difference between the middle probe and the upper probe in the heating period and in the cooling period, respectively. The first and second middle and lower temperature differences refers to a temperature difference between the middle probe and the lower probe in the heating period and in the cooling period, respectively. for one cycle of intermittent heating, when AT 30< ATdS, the forward sap flow density is calculated; and otherwise, the reverse sap flow density is calculated; wherein, the forward and reverse sap flow densities may be calculated by the formulas as follows:

Fa f orwara = A 1 -B -d-AT~, ATd - ATma

F reverse =A (AT-AT - 1- B

[0013] Wherein, Fdforward represents the forward sap flow density; Fdreverse represents the reverse sap flow density; AT, represents the first and second middle and upper temperature differences; ATd represents the first and second middle and lower temperature differences; ATO represents an average value of the first and second upper and middle temperature difference and the first and second lower and middle temperature difference; (ATd - ATo)max represents the maximum value of the difference of ATd - ATO in all cycles of the intermittent heating in a day; (AT, - ATo)max represents the maximum value of the difference of AT, - ATO in all cycles of the intermittent heating in a day; and A and B represent characteristic coefficients corresponding to different tree species.

[0014] Wherein, when the trees are poplars, the characteristic coefficient A is 0.255 and the characteristic coefficient B is 0.011.

[0015] Wherein, one cycle of the intermittent heating is 1 hour; the heating period is 30 minutes; and the cooling period is 30 minutes.

[0016] As can be seen from the aforementioned, the present disclosure provides a device and a method for measuring forward and reverse sap flow densities of tree trunks. For different tree species, different characteristic coefficients are set in established calculating formulas accordingly. Further, intermittent heating used is helpful to reduce thermal damage, improve observation precision, decrease power consumption, and enhance practicability. Also, a "three-probe type" sensor is used to measure the forward and reverse sap flow densities and absolute temperatures of sapwoods, and then to calculate temperature differences of different parts of the tree, thereby to eliminate the influence of natural temperature difference on the precision of sap flow density measurement and facilitate to show a response mechanism of sap flow density to natural temperature changes quantitatively. Compared with conventional devices and methods, the device and method provided by examples of the present disclosure may obtain characteristic coefficients of different tree species by correcting and greatly improve the precision of measurements on the forward and reverse sap flow densities of the trees by changing the heating mode and the structure of the device.

BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly explain the embodiments of the present disclosure or the technical solutions in the prior art, the accompanying drawings needed in the description of the embodiments or the prior arts are briefly introduced. Obviously, the accompanying drawings described below are only some embodiments of the present disclosure. Those of ordinary skill in the art may further obtain other accompanying drawings based on these accompanying drawings without paying any creative work.

[0018] FIG. 1 is a schematic diagram of a device for measuring forward and reverse sap flow densities of trees according to some examples of present disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0019] In order to make the objectives, technical solutions, and advantages of the present disclosure clearer, the present disclosure will be further described in detail with reference to specific embodiments described below together with the accompanying drawings.

[0020] An example of the present disclosure provides a device for measuring forward and reverse sap flow densities of tree trunks. Referring to FIG. 1, the device may include a sensor and a controller 4. Wherein, the sensor includes an upper probe 1, a middle probe 2 and a lower probe 3 may be equally spaced from top to bottom along an extending direction of a tree. Each of the upper probe 1, the middle probe 2 and the lower probe 3 may be provided with a temperature measurement component. The middle probe 2 may be further provided with a heating component 5. The controller 4 may be used for controlling the temperature measurement component to collect temperature data and controlling the heating component to heat.

[0021] The "top" in the extending direction of the tree from top to bottom refers to a crown part, and the "bottom" thereof refers to a root part. The forward sap flow refers to an upward sap flow. That is, the forward sap flow refers to a sap flow from the root part to the crown part. Moreover, the reverse sap flow refers to a downward sap flow. That is, the reverse sap flow refers to a sap flow from the crown part to the root part.

[0022] The upper probe 1 and the lower probe 3 are named according to relative position relationships thereof with the middle probe 2. In fact, the upper probe 1 and the lower probe 3 have the same structure and function. Thus, in actual operations, the final desired technical effect may not be influenced regardless that the upper probe 1 or the lower probe 3 is positioned on top or at bottom. That is, in actual operations, the probe on the top is the upper probe 1 and the probe at bottom is the lower probe 3, and the functions of the probes is not restricted by their names.

[0023] In some examples of the present disclosure, the inner diameters the upper probe, the middle probe and the lower probe may be set as 1.7 mm, so that the overall diameter of the probe can be reduced, and the probes can be easily inserted into tree trunks. The outer surfaces of the upper probe 1, the middle probe 2 and the lower probe 3 may be coated with Teflon materials individually or simultaneously, so that the probes are evenly heated.

[0024] The lengths of the upper probe, the middle probe and the lower probe may be set between 10 and 30 mm, usually 20 mm is preferred. Further, the length may be set as other values as required.

[0025] In some examples of the present disclosure, the space between each two of the upper probe, the middle probe and the lower probe may be 40 mm. In some examples of the present disclosure, the space may be set as other values that meet a standard, as long as the upper probe, the middle probe, and the lower probe are equally spaced.

[0026] In some examples of the present disclosure, the temperature measuring component may be a miniature thermistor that has the advantages of high sensitivity, good linear relationship, and easiness in welding and manufacturing.

[0027] In some examples of the present disclosure, the heating component may be a heating resistor.

[0028] The heating resistor may be a resistance wire of many materials, such as chromium wires, nickel wires, and the like. In some examples of the present disclosure, the heating component may be a constantan wire or a tungsten wire with a resistance value of 43Q. Specifically, a constantan wire or a tungsten wire may be shorter than a heating resistor 5 with a same resistance value due to high resistance coefficients of constantan and tungsten. Thus, the difficulty of a manufacturing process of integrating a resistor into the probe is greatly reduced. Wherein, the heating component has a heating voltage of 2V.

[0029] In some examples of the present disclosure, the upper probe, the middle probe and the lower probe may include an elongated probe body. The heating component may be equipped in a direction along with the body of the probe.

[0030] Most of the sensors in conventional devices for measuring sap flow density may adopt a "two-probe type" sensor, which can only measure the forward sap flow, and cannot measure the reverse sap flow. Therefore, a conventional device may not satisfy demands of studies on strategy mechanism for moisture adaptive status of trees. However, the device proposed by examples of the present disclosure uses a "three-probe type" sensor, which can measure both the forward sap flow density and the reverse sap flow density. Thus, complete data can be measured, and the water physiological ecology can be well characterized.

[0031] Based on the structure of the device provided by examples of the present disclosure, a method for measuring forward and reverse sap flow densities of forest trees is further provided by examples of the present disclosure. The method may include the following steps.

[0032] In step 101, the upper probe, the middle probe and the lower probe of the sensor are inserted into a sapwood part of a tree to be measured.

[0033] In step 102, the heating component is controlled by the controller to perform at least one cycle of intermittent heating.

[0034] Wherein, one cycle of intermittent heating may include a heating period and a cooling period with an equal duration. That is, in each cycle of intermittent heating, the controller may be used to control the temperature measurement components of the upper probe, the middle probe, and the lower probe to collect temperature data in the last minute of each heating period and each cooling period, respectively, and obtain a first middle and upper temperature difference, a first middle and lower temperature difference, a second middle and upper temperature difference, and a second middle and lower temperature difference. Wherein, the first middle and upper temperature difference refers to a temperature difference between the middle probe and the upper probe in the heating period. The first middle and lower temperature difference refers to a temperature difference between the middle probe and the lower probe in the heating period. The second middle and upper temperature difference refers to a temperature difference between the middle probe and the upper probe in the cooling period. The second middle and lower temperature difference refers to a temperature difference between the middle probe and the lower probe in the cooling period.

[0035] In step 103, for one cycle of intermittent heating, when ATo 3 0 < ATdSO, the

forward sap flow density may be calculated; and otherwise, the reverse sap flow density may be calculated.

[0036] The forward and reverse sap flow densities may be calculated by the formulas (1) and (2) as follows:

F forward-= A (ATd-To)ax- 1)- B (1) (ATd-ATO

F reverse - A ((ATuTo)max- 1)- B (2) ATU-ATO

[0037] Wherein, Fdforward represents the forward sap flow density; Fdreverse represents the reverse sap flow density; ATu represents the first and second middle and upper temperature differences; ATd represents the first and second middle and lower temperature differences; ATO represents an average value of the first and second upper and middle temperature difference and the first and second lower and middle temperature difference; (ATd - ATo)max represents the maximum value of the difference of ATd - ATO in all cycles of the intermittent heating in a day; (AT, - ATo)max represents the maximum value of the difference of AT, - ATO in all cycles of the intermittent heating in a day; and A and B represent characteristic coefficients corresponding to different tree species.

[0038] In some examples of the present disclosure, the tree is poplar, the characteristic coefficient A can be determined as 0.255 and the characteristic coefficient B can be determined as 0.011 through a field measurement method by weighing potted trees through correcting. One cycle of the intermittent heating can be set as 1 hour. That is, a heating period and a cooling period are both 30 minutes. In some other examples of the present disclosure, one cycle of intermittent heating may be set, for example, as 0.5h, 2h, or 3h, as long as the heating period and the cooling period are set with the same duration.

[0039] The device and the method of the present disclosure may use an intermittent heating method to replace a continuous heating method. On one hand, the continuous heating method has defects such as thermal damage to the sapwood and increased thermal contact resistance, resulting in a gradual decrease in precision. On the other hand, the continuous heating method has a relatively higher power consumption. Therefore, it is difficult for the forest levels to satisfy a long-term positioning and observation demands due to limitations of AC power supply. Therefore, the practicality of the conventional method and device is reduced. The intermittent heating method used in examples of the present disclosure may not only reduce the thermal damage and power consumption of the device, but also help improving the observation precision. Moreover, the practicality of the device and method can be significantly improved.

[0040] As can be seen from the aforementioned example, in which poplar trees are taken as an example, and the characteristic coefficient A can be determined as 0.255 and the characteristic coefficient B can be determined as 0.011 through a field measurement method by weighing potted trees through correcting. For other trees, the above-mentioned formula (1) and formula (2) can still be used for calculating the forward and reverse sap flow densities, under the condition that the characteristic coefficients are redetermined for calculating the forward and reverse sap flow densities. The device and method proposed by examples of the present disclosure may perform a difference measurement and calculation for different tree species. While in conventional devices and methods, Granier-type thermal diffusion (TDP) technology is commonly used, the original

Granier-type calculation formula for sap flow density is Fd = a(TM ), where the

coefficients a and # represent the differences of tree species, but they are unified as a = 118.99 x 10-6, f = 1.231. This method does not take the difference in hydraulic characteristics of different tree species into account and thus has poor adaptability. Although Granier (1985) claimed that the formula may be adapted to different tree species, many subsequent studies (Smith et al., 1996; Bush, 2010; Hultine et al. 2010; Steppe et al., 2010; Sun et al., 2102) have shown that the formula has large errors for different tree species, and a correction formula should be established for different tree species. Compared with the conventional method, the device and method provided by examples of the present disclosure considers the differences in hydraulic characteristics of different species and obtains the characteristic coefficients of different species by a correction method, so that the device and the method proposed by examples of the present disclosure can be applied to all forest trees, and the calculation errors can be reduced.

[0041] The conventional method neither takes the influences of natural temperature differences between the upper trunk and the lower trunk into consideration, nor can show a response mechanism of the sap flow density to natural temperature changes quantitatively. In view of this, the device and the method provided by examples of the present disclosure can measure absolute temperatures of the sapwoods and then calculate the temperature differences of different parts, thereby eliminating the influences of natural temperature differences on the precision of the sap flow density measurement and facilitating to show the response mechanism of sap flow density to natural temperature changes quantitatively.

[0042] In some examples of the present disclosure, referring to FIG. 1, an average value of the temperature differences of the upper probe 1, the middle probe 2 and the lower probe 3 at the end of the cooling period is used to correct the temperature difference between the middle and lower probes and the temperature difference between the middle and upper probes in the heating period. When a forward (upward) sap flow occurs, the heat of the middle probe 2 diffuses upwards with the flowing of the sap flow, and therefore, the middle probe 2 is cooled. At this time, the temperature difference between the middle and lower probes is greater than that of the middle and upper probes. When the sap flow density of the tree is zero or reaches the minimum value, the temperature difference between the middle and lower probes reaches the maximum value. As the sap flow density of the tree increases, the thermal conductivity of the sapwood increases accordingly and the temperature difference between the two probes decreases. There is a quantitative relationship between the temperature difference of the middle and lower probes and the tree sap flow density, thus, the forward sap flow density can be obtained by calculation. Similarly, when a reverse (downward) sap flow occurs, the temperature difference between the middle and upper probes has a quantitative relationship with the sap flow density of the tree, thus, the reverse sap flow density can be calculated.

[0043] It should be understood by those of ordinary skill in the art that the above-described examples are only exemplary and are not intended to imply that the scope of the present disclosure (including the claims) is limited to these examples. Under the idea of the present disclosure, the above-described examples or technical features in different examples may further be combined, the steps may be implemented in any order, and many other variations in different aspects of the present disclosure as described above may exist, which are not provided in detail for the sake of conciseness.

[0044] Furthermore, in order to simplify the explanation and discussion and easily understand by the present disclosure, the accompanying drawings provided may or may not show the known connections with a sensor, a controller and other components (i.e., these details should be completely within the understanding of those skilled in the art). In the case where specific details (for example, the inner diameter of each of the upper probe, the middle probe and the lower probe can be set 1.7 mm) are set forth to describe the examples of the present disclosure, it is apparent to those skilled in the art that the present disclosure may be implemented without these specific details or when these specific details are changed. Therefore, these descriptions are to be constructed as illustrative rather than limiting.

[0045] Although the present disclosure has been described by way of specific examples, based on the foregoing description, many substitutions, modifications and variations of

In these embodiments will be apparent to those of ordinary skill in the art.

[0046] The examples of the present disclosure are intended to cover all such substitutions, modifications and variations that fall within the broad scope of the appended claims. Therefore, within the spirit and principle of the present disclosure, any omissions, modifications, equivalent substitutions, improvements and the like made thereto should be within the scope of the protection of the present disclosure.

Claims

What is claimed is: 1. A device for measuring forward and reverse sap flow densities of trees, comprising: a sensor and a controller; wherein, the sensor comprises an upper probe, a middle probe and a lower probe spaced equally from top to bottom along an extending direction of a tree; each of the upper probe, the middle probe and the lower probe is provided with a temperature measurement component; the middle probe is further provided with a heating component; and the controller is to control the temperature measurement component, to collect temperature data and control the heating component to heat.
2. The device of claim 1, wherein, the inner diameter of each of the upper probe, the middle probe and the lower probe is 1.7 mm; and the length of each of the upper probe, the middle probe and the lower probe is 10 to 30 mm.
3. The device of claim 1, wherein, the space between each two of the upper probe, the middle probe and the lower probe is 40 mm.
4. The device of claim 1, wherein, the temperature measurement component is a miniature thermistor.
5. The device of claim 1, wherein, the heating component is a heating resistor.
6. The device of claim 5, wherein, the heating component is a constantan wire or a tungsten wire with a resistance value of 43Q; and the heating component has a heating voltage of 2V.
7. The device of any of claims 1 to 6, wherein, each of the upper probe, the middle probe, and the lower probe comprises an elongated probe body; and the heating component is equipped in a direction along with the elongated probe body.
8. A method for measuring forward and reverse sap flow densities of trees using the device of any one of claims I to 7, comprising: inserting the upper probe, the middle probe and the lower probe of the sensor into a sapwood part of a tree to be measured; controlling, by the controller, the heating component to perform at least one cycle of intermittent heating; wherein, one cycle of the intermittent heating comprises a heating period and a cooling period with an equal duration; in each cycle of the intermittent heating, the controller is used to control the temperature measurement components of the upper probe, the middle probe, and the lower probe; collect temperature data in the last minute of each heating period and each cooling period, respectively; and obtain the first middle and upper temperature difference, the first middle and lower temperature difference, the second middle and upper temperature difference, and the second middle and lower temperature difference; wherein, the first middle and upper temperature difference refers to a temperature difference between the middle probe and the upper probe in the heating period; the first middle and lower temperature difference refers to a temperature difference between the middle probe and the lower probe in the heating period; the second middle and upper temperature difference refers to a temperature difference between the middle probe and the upper probe in the cooling period; the second middle and lower temperature difference refers to a temperature difference between the middle probe and the lower probe in the cooling period; for one cycle of intermittent heating, when ATo 3 0 < ATdS, the forward sap flow density is calculated; and otherwise, the reverse sap flow density is calculated; wherein, the forward and reverse sap flow densities may be calculated by the formulas as follows:

Fa f orwara = A 1 -B -d-AT~, ATd - ATma

F reverse =A (AT; ATOma- 1- B

wherein, Fdforward represents the forward sap flow density; Fdreverse represents

the reverse sap flow density; AT, represents the first and second middle and upper temperature differences; ATd represents the first and second middle and lower temperature differences; ATO represents an average value of the first and second upper and middle temperature difference and the first and second lower and middle temperature difference; (ATd - ATo)max represents the maximum value of the difference of

1A

ATd - ATO in all cycles of the intermittent heating in a day; (AT, - ATo)max represents the maximum value of the difference of AT, - ATO in all cycles of the intermittent heating in a day; and A and B represent characteristic coefficients corresponding to different forest tree species.
9. The method of claim 8, wherein, when the forest trees are poplars, the characteristic coefficient A is 0.255 and the characteristic coefficient B is 0.011.
10. The method of claim 9, wherein, one cycle of the intermittent heating is 1 hour; the heating period is 30 minutes; and the cooling period is 30 minutes.

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