Tree nighttime transpiration and xylem filling separation method and system

Abstract

The invention relates to a tree nighttime transpiration and xylem filling separation method and system, and belongs to the field of tree nighttime water consumption detection. According to the method, the night water consumption of the tree is calculated through monitored tree liquid flow data and downward short wave radiation data, a night change curve is fitted according to the initial slope of a night xylem filling curve, and the night water consumption of the tree is divided into night transpiration and xylem filling. The system executes the process steps of the method. According to the nighttime transpiration and xylem filling separation method provided by the invention, a nighttime xylem filling curve is simulated by adopting a logarithmic function, so that the method is simple, better conforms to plant physiological conditions, and xylem filling and nighttime transpiration can be relatively accurately and continuously separated.

Description

Technical Field

[0001] The invention belongs to the field of nighttime water consumption detection for trees, and in particular relates to a method and system for separating nighttime transpiration and xylem filling of trees. Background Art

[0002] Nighttime water consumption is mainly the absorption of water by plants at night to replenish the water consumed by the xylem during the day, which is an important physiological process to prevent plants from withering at night, and can accelerate the acquisition of nutrients by plants at night. Plant nighttime water consumption is mainly used in two aspects-xylem filling and nighttime transpiration. The thermal diffusion method has been widely used in the measurement of plant stem water consumption due to its many advantages such as simplicity, high accuracy, low cost, easy automatic measurement, and continuous measurement. Among them, the method of monitoring plant water consumption based on Grainer thermal diffusion probe is the most commonly used method in thermal diffusion methods. It can continuously monitor the trunk sap flow by monitoring the temperature difference at both ends of the probe. However, this method cannot separate nighttime transpiration and xylem filling from nighttime water consumption. Therefore, many studies have proposed a variety of methods to separate xylem filling from nighttime transpiration. The first is the dual sap flow curve separation method. This method continuously monitors sap flow by installing probes at the base of the canopy and the lowest end of the trunk. It is assumed that the positive part of the difference curve of the two sap flow curves is night transpiration, and the negative part is xylem filling, such as "Rates of nocturnal transpiration in two evergreen temperate woodland species with differing water-use strategies". Although this method has a strong physical mechanism, it is difficult to install probes at the canopy, and the "base" position is difficult to determine, which leads to deviations in the separation results of xylem filling and night transpiration. The second is an empirical method based on VPD division. This method determines two consecutive days with similar daytime VPD and one high and one low nighttime VPD. It is assumed that the night with high VPD is the sum of nighttime transpiration and xylem filling, and the sap flow with low VPD on the second night is caused by xylem filling. Such as "Inter and intraspecific variation in nocturnal water transport in Eucalyptus". This method will overestimate xylem filling and nighttime transpiration, and will be limited by application conditions. The third is a resistance network model separation method, which proposes a flow model that uses the ratio of stem water storage to stem resistance as a parameter based on the resistance network to separate stem water filling and nocturnal transpiration. For example, "Nocturnal water loss in mature subalpine Eucalyptus delegatensis tall open forests and adjacent E. pauciflora woodlands".Although this method quantifies the duration of water filling and can track the time process of water loss, it is difficult to obtain the key model parameters required by this method. The fourth is a predictive backfilling method. This method assumes that xylem filling and night transpiration will occur simultaneously. The exponential function fitting method is used to fit the initial slope of the night water consumption curve. It is considered that the area below the curve is xylem filling and the area above is night transpiration. For example, "Depressed hydraulic redistribution of roots more by stem refillingthan by nocturnal transpiration for Populus euphratica Oliv.in situmeasurement". The fitting method of this method indicates that xylem filling always exists at night, which is inconsistent with the actual physiological phenomenon of plants. Therefore, how to find a method to separate xylem filling and night transpiration that is simple to operate, not limited by application conditions, has a strong physical mechanism and conforms to the real physiological phenomenon of plants is a technical difficulty that needs to be solved urgently.

[0003] Due to the advantages of Grainer thermal diffusion probe, such as simplicity, high accuracy, and low cost, using Grainer thermal diffusion probe to monitor trunk sap flow in real time is a more practical method. Trees will give priority to replenishing the water lost in their xylem during the day at night, and will start transpiration at night after a period of time, and xylem filling and night transpiration will occur simultaneously. Therefore, the present invention uses Grainer thermal diffusion probe to monitor trunk sap flow, and uses a logarithmic function to fit the nighttime plant xylem filling curve to separate xylem filling and night transpiration. Summary of the invention

[0004] The purpose of the present invention is to solve some technical and universal problems existing in the previous methods for separating xylem filling and night transpiration, and to provide a method and system for separating night transpiration and xylem filling of trees. Grainer thermal diffusion probe is used to monitor the trunk sap flow, and a logarithmic function is used to fit the nighttime plant xylem filling curve to separate xylem filling and nighttime transpiration.

[0005] To achieve the above-mentioned purpose, the technical solution of the present invention is: a method for separating nighttime transpiration and xylem filling of trees, which calculates the nighttime water consumption of trees by monitoring tree sap flow data and downward shortwave radiation data, and fits the nighttime xylem filling curve according to the initial slope of the nighttime xylem filling curve, thereby dividing the nighttime water consumption of trees into nighttime transpiration and xylem filling.

[0006] In one embodiment of the present invention, a Grainer thermal diffusion probe is used to monitor the trunk sap flow data, and a logarithmic function is used to fit the nighttime xylem filling curve to separate nighttime transpiration and xylem filling.

[0007] In one embodiment of the present invention, the method comprises the following steps:

[0008] Step S1, calculating the temperature difference data collected by the Grainer thermal diffusion probe as the instantaneous sap flow density of the tree based on the Grainer formula;

[0009] Step S2, combining the sapwood area of ​​the corresponding tree species with the stand density data to calculate the instantaneous sap flow density of the trees as the stand nighttime water consumption, and dividing the daytime and nighttime data by the downward shortwave radiation data;

[0010] Step S3, using a logarithmic function to fit the nighttime xylem filling curve according to the initial slope of the xylem filling curve;

[0011] Step S4, integrating the area below the fitting curve to obtain the xylem filling volume, and calculating the night transpiration volume by the difference between the night water consumption and the xylem filling volume.

[0012] In one embodiment of the present invention, in step S1, a group of Grainer thermal diffusion probes consists of two probes, namely a heating probe and a control probe; when liquid flows through, the temperature on the heating probe will be reduced, and the data collector monitors the temperature difference data at both ends of the probe in real time and saves it.

[0013] In one embodiment of the present invention, in step S1, the temperature difference data collected by the Grainer thermal diffusion probe needs to remove abnormal data before use. Since the thermal diffusion probe liquid flow experimental instrument needs to be placed in the forest for a long time to monitor the data in real time, it is easy to be damaged by weather or other factors, and regular data review and maintenance are required.

[0014] In one embodiment of the present invention, in step S2, it is necessary to obtain the relationship between the sapwood area of ​​the corresponding tree species and its diameter at breast height, and use a growth cone to collect the core of the tree of the corresponding tree species outdoors to obtain the sapwood area and establish a relationship between it and its diameter at breast height; the water consumption at night is based on the downward shortwave radiation <10W / m 2 Divide.

[0015] In one embodiment of the present invention, in step S3, it is assumed that the plant replenishes the water lost in the xylem first at night, and after a period of time, the xylem begins to transpire at night while the water is filled, until the xylem is completely filled, and then all the water consumed at night is used for transpiration at night.

[0016] In one embodiment of the present invention, in step S3, Matlab software is used to fit the nighttime xylem filling curve according to the initial slope of the nighttime xylem filling curve of the tree using a logarithmic function.

[0017] In one embodiment of the present invention, in step S4, Matlab software is used to integrate the area below the fitting curve to obtain the xylem filling amount; the night water consumption is calculated according to the night water consumption calculation formula, and the night transpiration is obtained by subtracting it from the xylem filling amount.

[0018] The present invention also provides a method and system for separating nighttime transpiration and xylem filling of trees, comprising:

[0019] The data acquisition module obtains the tree sap flow density, downward shortwave radiation, sapwood area and stand density in the target area through direct measurement by instruments or indirect calculation based on formulas;

[0020] The night water consumption calculation module inputs the tree sap flow density, downward shortwave radiation, sapwood area and stand density observed in the target area into the night water consumption calculation model to obtain the night water consumption of the stand;

[0021] The xylem filling and night transpiration separation module is based on a logarithmic function. The night xylem filling curve is fitted using the predictive backfill method according to the initial slope of the night xylem filling curve, and the night water consumption is divided into xylem filling and night transpiration.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention uses a Grainer thermal diffusion probe to observe the trunk sap flow, and obtains downward shortwave radiation, sapwood area and stand density data by direct instrument measurement or indirect calculation based on a formula. The operation is simple, the data acquisition difficulty is low and the accuracy is high, and the shortcomings of the sap flow data acquisition difficulty and ambiguity in accuracy are overcome. The prediction backfill method based on logarithmic function used in the present invention can be applied on any non-rainy day, and is more in line with the normal physiological conditions of plants, improving the applicability and accuracy of the model. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following is a brief introduction to the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application, and those skilled in the art can also obtain other drawings based on these drawings without creative work.

[0025] Figure 1The present invention discloses a process for separating tree nighttime transpiration and xylem filling based on a Grainer thermal diffusion probe.

[0026] Figure 2 This is a structural diagram of the tree night transpiration and xylem filling separation system based on the Grainer thermal diffusion probe of the present invention.

[0027] Figure 3 Schematic diagram of the method for separating xylem filling and nocturnal transpiration. DETAILED DESCRIPTION

[0028] The technical solution of the present invention is described in detail below in conjunction with the accompanying drawings.

[0029] The technical solutions in the embodiments of the present invention are clearly and completely described in conjunction with the drawings in the embodiments of the present invention. The described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field without creative work based on the embodiments of the present invention are within the scope of protection of the present invention.

[0030] The present invention provides a method for separating nighttime transpiration and xylem filling of trees. The nighttime water consumption of trees is calculated by monitoring tree sap flow data and downward shortwave radiation data, and the nighttime xylem filling curve is fitted according to the initial slope of the nighttime xylem filling curve to divide the nighttime water consumption of trees into nighttime transpiration and xylem filling. A Grainer thermal diffusion probe is selected to monitor the trunk sap flow data, and a logarithmic function is used to fit the nighttime xylem filling curve to separate nighttime transpiration and xylem filling. The method comprises the following steps:

[0031] Step S1, calculating the temperature difference data collected by the Grainer thermal diffusion probe as the instantaneous sap flow density of the tree based on the Grainer formula;

[0032] Step S2, combining the sapwood area of ​​the corresponding tree species with the stand density data to calculate the instantaneous sap flow density of the trees as the stand nighttime water consumption, and dividing the daytime and nighttime data by the downward shortwave radiation data;

[0033] Step S3, using a logarithmic function to fit the nighttime xylem filling curve according to the initial slope of the xylem filling curve;

[0034] Step S4, integrating the area below the fitting curve to obtain the xylem filling volume, and calculating the night transpiration volume by the difference between the night water consumption and the xylem filling volume.

[0035] The present invention also provides a method and system for separating nighttime transpiration and xylem filling of trees, comprising:

[0036] The data acquisition module obtains the tree sap flow density, downward shortwave radiation, sapwood area and stand density in the target area through direct measurement by instruments or indirect calculation based on formulas;

[0037] The night water consumption calculation module inputs the tree sap flow density, downward shortwave radiation, sapwood area and stand density observed in the target area into the night water consumption calculation model to obtain the night water consumption of the stand;

[0038] The xylem filling and night transpiration separation module is based on a logarithmic function. The night xylem filling curve is fitted using the predictive backfill method according to the initial slope of the night xylem filling curve, and the night water consumption is divided into xylem filling and night transpiration.

[0039] The following are specific implementation examples of the present invention.

[0040] The process of the method for separating tree nighttime transpiration and xylem filling based on Grainer thermal diffusion probe of the present invention is specifically referred to Figure 1 In actual application, the following steps S1 to S4 are specifically performed.

[0041] S1-acquire the instantaneous temperature difference data monitored in real time by the outdoor Grainer thermal diffusion probe, and calculate the temperature difference data into the instantaneous liquid flow density according to the Grainer formula, and then enter step S2.

[0042] The data used in the present invention is the instantaneous temperature difference data monitored in real time by the Grainer thermal diffusion probe. A group of Grainer thermal diffusion probes consists of two probes, namely a heating probe and a control probe. When liquid flows through, the temperature on the heating probe will be reduced, and the data collector can monitor the temperature difference between the two ends of the probe in real time and save it. Using DTU, data can be collected remotely, so that data abnormalities can be checked in time, and instrument maintenance and abnormal data processing can be carried out in time. Afterwards, the collected temperature difference data is calculated as instantaneous liquid flow density according to the Grainer formula. The specific calculation formula is as follows:

[0043] K=(ΔT max -ΔT) / ΔT (1)

[0044] SFD=119×K 1.231 (2)

[0045] Where: K represents the sap flow index, SFD represents the instantaneous sap flow density of the tree (g / m 2 / s), ΔTmax represents the maximum temperature difference between the two probes over a period of time (°C), and ΔT represents the actual temperature difference between the heating probe and the control probe (°C). Considering the data quality issue and avoiding underestimation of ΔTmax, Baseliner software is used to process the temperature difference data collected by the data logger. The software can automatically find the time of the daily "zero" trunk sap flow density based on the two environmental factors of saturated water vapor pressure difference and photosynthetically active radiation with the same recording frequency as the trunk sap flow probe. It can also be manually adjusted to the time of the day when the temperature difference is the largest, and a smooth curve is used to fit the baseline of zero trunk sap flow density over a period of time, and then the sap flow index K value is derived from the software.

[0046] S2-get the calculation formula of the sapwood area of ​​the corresponding trees and the stand density of the forest land, calculate the instantaneous sap flow density calculated in S1 as the water consumption, and divide the night water consumption according to the downward shortwave data, and then enter S3.

[0047] The calculation formula of sapwood area can be obtained by using growth cones to drill the core of the corresponding tree species from four different directions, observing the color change to obtain the sapwood area, taking the average of different directions and establishing a relationship with the breast diameter to obtain the sapwood area calculation formula of the tree species, which can be used to calculate the sapwood area of ​​the tree species in the forest. Combined with the stand density, the instantaneous liquid flow density calculated by S1 is calculated as the water consumption during the day or night. The specific calculation formula is as follows:

[0048] NWC=SFD night ×t night ×SA / A G (3)

[0049] DWC=SFD day ×t day ×SA / A G (4)

[0050]

[0051] Where: NWC and DWC are nighttime and daytime water consumption respectively; SFD a is the average sap flow density; n is the number of trees with thermal diffusion probes installed; SDF i are the instantaneous sap flow density of each tree. SFD night and SFD day are the average liquid flow density at night and during the day, respectively; t night and t day are the duration of night and day, respectively; SA is the average sapwood area of ​​trees with heat diffusion probes installed; A G is the forest area. The downward shortwave radiation is 10W / m 2As the dividing point, the water consumption at night and during the day is divided, and the downward shortwave radiation is less than 10W / m 2 The water consumption during the period is considered as nighttime water consumption, and the downward shortwave radiation is greater than 10W / m 2 The water consumption during the day is considered as daytime water consumption.

[0052] S3-Use Matlab software to fit the change trend of the xylem filling curve using a logarithmic function according to the initial slope of the xylem filling curve to obtain the complete curve of the xylem filling, and then enter S4.

[0053] It is assumed that trees will give priority to filling the water lost in their xylem during the day at night, and the filling rate will gradually decrease over time. After a period of filling, night transpiration is carried out synchronously until the xylem filling rate is reduced to 0, after which all water is used for night transpiration. Considering that the change in water consumption at night can be reflected by the change in sap flow density, the present invention uses Matlab software to fit the night sap flow density curve according to its initial slope in the form of a logarithmic function, thereby obtaining the sap flow density curve for the xylem filling part, and then calculating it as xylem filling. The specific logarithmic function fitting form is as follows:

[0054] f(t)=a×log(SFD)+b (6)

[0055] Where: f(t) is the logarithmic function fitting form, a and b are fitting parameters respectively.

[0056] S4-Use the fitted curve, use Matlab software to integrate the curve below, and combine it with the night water consumption calculation formula (Formula 3) to obtain the xylem filling volume, and subtract it from the total night water consumption to obtain the night transpiration (see Figure 3 ). Part of the nighttime water consumption of plants is used for xylem filling, and the other part is used for nighttime transpiration. Integrate the nighttime sap flow curve caused by xylem filling, and then use Formula 3 to calculate the xylem filling amount, and subtract it from the total nighttime water consumption calculated by Formula 3 to obtain the nighttime transpiration amount. The specific formula is as follows:

[0057]

[0058] NT=NWC-SR (8)

[0059] Where SR is xylem filling, NT is night transpiration, c is the start time of night, d is the time when xylem filling is 0, and f(t) is the logarithmic function fitting form of xylem filling, see Formula 6.

[0060] Correspondingly, the present invention also provides a tree night transpiration and xylem filling separation system based on a Grainer thermal diffusion probe, comprising:

[0061] A data acquisition module is used to obtain the sap flow density, downward shortwave radiation, sapwood area and stand density of trees in the target area by direct measurement with instruments or indirect calculation based on formulas;

[0062] The night water consumption calculation module is used to input the tree sap flow density, downward shortwave radiation, sapwood area and stand density observed in the target area into the night water consumption calculation model to obtain the night water consumption of the stand

[0063] The module for separating xylem filling and night transpiration is used to fit the change curve of the xylem filling curve based on the logarithmic function and the predictive backfill method according to the initial slope of the xylem filling curve, and divide the night water consumption into xylem filling and night transpiration.

[0064] like Figure 2 As shown, the separation system in this embodiment includes: a data module 1, liquid flow density 2, downward shortwave radiation 3, sapwood area 4, forest stand density 5 and a wood filling and night transpiration separation module 6 based on a logarithmic function. Among them, data module 1 is used to obtain the input data required for xylem filling and night transpiration separation of the prediction backfill method based on the logarithmic function; sap flow density 2 is used for the input data required for xylem filling and night transpiration separation of the prediction backfill method based on the logarithmic function, and calculates the tree sap flow density; downward shortwave radiation 3 is used for the input data required for xylem filling and night transpiration separation of the prediction backfill method based on the logarithmic function, and calculates the downward shortwave radiation; sapwood area 4 is used for the input data required for xylem filling and night transpiration separation of the prediction backfill method based on the logarithmic function, and calculates the sapwood area; forest stand density 5 is used for the input data required for xylem filling and night transpiration separation of the prediction backfill method based on the logarithmic function, and calculates the forest stand density; xylem filling and night transpiration separation module 6 is used to separate xylem filling and night transpiration by using the prediction backfill method based on the logarithmic function based on the sap flow density, the downward shortwave radiation, the sapwood area and the forest stand density. The specific xylem filling and night transpiration separation method can be referred to the above embodiment, and the embodiment of the present invention will not be repeated here.

[0065] The above are preferred embodiments of the present invention. Any changes made according to the technical solution of the present invention, as long as the resulting functions do not exceed the scope of the technical solution of the present invention, belong to the protection scope of the present invention.

Claims

1. A method for separating nighttime transpiration and xylem filling of trees, characterized in that: The nighttime water consumption of trees was calculated by monitoring tree sap flow data and downward shortwave radiation data, and the nighttime xylem filling curve was fitted according to the initial slope of the nighttime xylem filling curve to divide the nighttime water consumption of trees into nighttime transpiration and xylem filling.

2. A method for separating nighttime transpiration and xylem filling of trees according to claim 1, characterized in that: Grainer heat diffusion probe was used to monitor the trunk sap flow data, and a logarithmic function was used to fit the nighttime xylem filling curve to separate nighttime transpiration from xylem filling.

3. The method for separating nighttime transpiration and xylem filling of trees according to claim 1, characterized in that: The method comprises the following steps: Step S1, calculating the temperature difference data collected by the Grainer thermal diffusion probe as the instantaneous sap flow density of the tree based on the Grainer formula; Step S2, combining the sapwood area of ​​the corresponding tree species with the stand density data to calculate the instantaneous sap flow density of the trees as the stand nighttime water consumption, and dividing the daytime and nighttime data by the downward shortwave radiation data; Step S3, using a logarithmic function to fit the nighttime xylem filling curve according to the initial slope of the xylem filling curve; Step S4, integrating the area below the fitting curve to obtain the xylem filling volume, and calculating the night transpiration volume by the difference between the night water consumption and the xylem filling volume.

4. A method for separating nighttime transpiration and xylem filling of trees according to claim 3, characterized in that: In step S1, a group of Grainer thermal diffusion probes consists of two probes, namely a heating probe and a control probe; when liquid flows through, the temperature on the heating probe will be reduced, and the data collector monitors the temperature difference data at both ends of the probe in real time and saves it.

5. The method for separating nighttime transpiration and xylem filling of trees according to claim 3, characterized in that: In step S1, the temperature difference data collected by the Grainer thermal diffusion probe needs to remove abnormal data before use.

6. The method for separating nighttime transpiration and xylem filling of trees according to claim 3, characterized in that: In step S2, it is necessary to obtain the relationship between the sapwood area of ​​the corresponding tree species and its diameter at breast height. The growth cone is used to collect the core of the tree of the corresponding tree species outdoors to obtain the sapwood area and establish a relationship between it and its diameter at breast height. The water consumption at night is based on the downward shortwave radiation <10W / m 2 Divide.

7. The method for separating nighttime transpiration and xylem filling of trees according to claim 3, characterized in that: In step S3, it is assumed that the plant replenishes the water lost in the xylem first at night, and after a period of time, the xylem begins to transpire at night while the water is filled, until the xylem is completely filled, and then all the water consumed at night is used for transpiration at night.

8. A method for separating nighttime transpiration and xylem filling of trees according to claim 7, characterized in that: In step S3, Matlab software is used to fit the nighttime xylem filling curve according to the initial slope of the nighttime xylem filling curve of the tree using a logarithmic function.

9. The method for separating nighttime transpiration and xylem filling of trees according to claim 3, characterized in that: In step S4, the area below the fitting curve is integrated using Matlab software to obtain the xylem filling volume; the night water consumption is calculated according to the night water consumption calculation formula, and the night transpiration is obtained by subtracting it from the xylem filling volume.

10. A system for separating tree night transpiration and xylem filling, characterized in that: include: The data acquisition module obtains the tree sap flow density, downward shortwave radiation, sapwood area and stand density in the target area through direct measurement by instruments or indirect calculation based on formulas; The night water consumption calculation module inputs the tree sap flow density, downward shortwave radiation, sapwood area and stand density observed in the target area into the night water consumption calculation model to obtain the night water consumption of the stand; The xylem filling and night transpiration separation module is based on a logarithmic function. The night xylem filling curve is fitted using the predictive backfill method according to the initial slope of the night xylem filling curve, and the night water consumption is divided into xylem filling and night transpiration.

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