A method for measuring water storage capacity of forest floor litter based on field forest

Abstract

The present application belongs to the technical field of measuring the water storage capacity of the litter layer, and specifically discloses a method for measuring the water storage capacity of the litter layer based on a field forest, which comprises the following steps: collecting initial acoustic characteristic parameters of a target measuring point, applying non-impact atomized water, monitoring real-time parameters to adjust the water application rate, collecting parameter changes after water absorption when the stable termination condition is met, matching a preset response relationship according to the pore distribution type of the target measuring point, generating water storage capacity characteristic values and converting them into water holding capacity per unit area and grades, and then evaluating the water storage capacity of the target measuring point. Through the fixing of the acoustic probe laser ranging, the calibration of the atomizing nozzle, and the non-impact water application, the present application realizes pore zero disturbance measurement in combination with acoustic parameter dynamic feedback, solves the problem of structure damage caused by manual laying, and realizes the evaluation of the water storage capacity of the target measuring point through pore characteristic classification and differential response relationship matching.

Description

Technical Field

[0001] The invention belongs to the technical field of measuring the water storage capacity of a litter layer, and relates to a method for measuring the water storage capacity of a litter layer based on a wild forest. Background Art

[0002] Litter, the organic matter cover of forest floors formed by the decomposition of plant litter, plays a key ecological role in maintaining soil structure, regulating the hydrological cycle, and conserving water resources. Accurately quantifying its water storage capacity is fundamental to uncovering the mechanisms of hydrological processes such as precipitation interception, runoff reduction from the measured litter layer, and groundwater recharge. Therefore, measurement and analysis of this water storage capacity is essential.

[0003] Current technologies for measuring the water storage capacity of litter layers have significant limitations. For example, Chinese invention patent publication number CN108226448B discloses a device and method for measuring the hydrological function of litter. By combining a split-type trough design with a flow collection assembly and graduated cylinder measurement, this approach attempts to separate the surface transport of rainfall from its vertical infiltration, enabling a precise assessment of the water-handling benefits of the litter layer. Furthermore, comparative measurements can address the critical bottleneck of low precision in litter layer water-holding capacity assessment.

[0004] The above existing technologies have the following deficiencies: 1. Currently, they rely on artificial laying of litter and soil indoors to construct an ex-situ environment, which destroys the original spatial distribution structure and natural pore network of the litter layer in the field, resulting in systematic deviations from the key characteristics of the litter layer, such as its interlayer connectivity, pore morphology and density, and the state of the litter layer. As a result, the measurement results cannot reflect the actual water storage behavior.

[0005] 2. Currently, water storage capacity is only indirectly estimated by collecting macro-hydrological output data such as runoff and seepage water volume. Microstructural parameters such as pore density, connectivity and size distribution are not detected. It is impossible to analyze the inherent physical mechanism of the difference in water storage capacity of litter layers with different pore structures. The measurement results lack universality for complex field scenarios. Summary of the Invention

[0006] In view of this, in order to solve the problems raised in the above background technology, a method for measuring the water storage capacity of the litter layer based on wild forest land is proposed.

[0007] The purpose of the present invention can be achieved through the following technical solutions: The present invention provides a method for measuring the water storage capacity of the dead branch and leaf layer based on the wild forest, including: S1, emitting sound waves to the target measuring point of the dead branch and leaf layer to be measured, and collecting the initial acoustic characteristic parameters of the reflected acoustic signal.

[0008] S2. Apply a small amount of atomized water without impact to the target measuring point, and continuously collect the real-time acoustic characteristic parameters of the reflected acoustic signal during the application process.

[0009] S3. Adjust the application rate of the trace atomized water according to the initial acoustic characteristic parameters and the real-time acoustic characteristic parameters until any preset termination condition is met and stop applying. When the preset termination condition is a safety termination condition, trigger a secondary measurement operation.

[0010] S4. When the preset termination condition is a stable termination condition, the post-water absorption acoustic characteristic parameters of the reflected acoustic signal are collected after the target measuring point absorbs a trace amount of atomized water.

[0011] S5. Calculate the change in the acoustic characteristic parameters before and after water absorption based on the initial acoustic characteristic parameters and the acoustic characteristic parameters after water absorption.

[0012] S6. Based on the initial amplitude, initial phase lag, and initial spectrum half-width in the initial acoustic characteristic parameters, determine the pore distribution type of the target measuring point and select a matching preset response relationship.

[0013] S7. Input the change in the acoustic characteristic parameter into the corresponding preset response relationship to evaluate the water storage capacity of the target measuring point.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The present invention directly measures the dead branches and leaves layer to be measured in a natural state by fixing the acoustic probe laser distance measurement and calibrating the overlap of the atomizing nozzle with the acoustic wave detection area. At the same time, the impact-free application of trace atomized water and the dynamic feedback of acoustic parameters are combined to achieve zero-disturbance water application in the pores, solve the problem of interlayer structure damage caused by artificial paving, and make the water storage capacity truly reflect the state of the dead branches and leaves layer to be measured.

[0015] (2) The present invention determines the pore density level by inverting the initial amplitude, determines the pore connectivity by the phase lag, and identifies the pore size distribution by the spectrum half-width, thereby determining the pore distribution type. This solves the problem that the existing technology cannot analyze the microscopic causes of the water storage mechanism, and provides a structural basis for the subsequent selection of differentiated response relationships.

[0016] (3) The present invention controls the water application rate by dynamically comparing the threshold value and the ratio algorithm of the phase lag increment, and at the same time combines the dual termination conditions of the amplitude change rate threshold and the upper limit of the water application amount to solve the problem of inaccurate determination of the water absorption saturation point, and realizes non-destructive and accurate measurement of the water storage capacity of the dead branches and leaves layer to be measured.

[0017] (4) The present invention solves the problem of single output dimension in the existing technology by weighted fusion calculation of acoustic feature variation, and based on the mapping rules between characteristic values ​​and actual water holding capacity and the water storage capacity level matching method, realizes the synchronous output of three parameters: water holding capacity per unit area, pore distribution type and water storage capacity level.

[0018] (5) The present invention starts secondary measurement when the safety termination condition is triggered, demarcates an area with the target measurement point as the center and arranges points, selects the best adjacent unmeasured point through preset influence distance screening and similarity calculation based on amplitude, phase and spectrum parameters, and restarts the process at the adjusted rate, thereby improving regional measurement efficiency and data reliability through dual protection of space and features. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0020] Figure 1 Schematic diagram of the connection of each step of the method of the present invention.

[0021] Figure 2 Schematic diagram of the connection steps for collecting initial acoustic characteristic parameters of the reflected acoustic signal of the present invention.

[0022] Figure 3 Schematic diagram of the connection steps for determining the pore distribution type of the target measuring point of the present invention. DETAILED DESCRIPTION

[0023] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0024] See also Figure 1 As shown, the present invention provides a method for measuring the water storage capacity of a litter layer based on a wild forest, the method comprising: S1, transmitting an acoustic wave to a target measuring point of the litter layer to be measured, and collecting initial acoustic characteristic parameters of the reflected acoustic signal.

[0025] See also Figure 2 As shown, exemplarily, the collecting of initial acoustic characteristic parameters of the reflected acoustic signal includes: fixing the acoustic probe at a vertical distance of the probe above the target measuring point through a laser rangefinder.

[0026] Among them, the vertical distance of the probe is obtained as follows: based on the emission angle of the sound wave transducer, the radius of the acoustic detection area is calculated by a formula to ensure that the radius completely covers the target measuring point area. At the same time, combined with the frequency range of the ultrasonic transmitter and the sensitivity of the receiver, an indoor calibration experiment is carried out through pre-collected representative samples of the dead branches and leaves to be tested, and the stability of the reflected signal at different vertical distances is tested. The optimal vertical distance that can stably extract the initial acoustic characteristic parameters is selected as the vertical distance of the probe.

[0027] The ultrasonic transmitter is controlled to transmit pulsed sound wave signals within a preset frequency range, wherein the preset frequency range refers to the frequency interval of the ultrasonic transmitter transmitting the pulsed sound wave signals, which is pre-set before measurement based on the physical characteristics of the target measuring point, such as thickness, looseness, dead branch type, etc.

[0028] The reflected acoustic signal is captured by the receiver, and after low-noise amplification and analog-to-digital conversion, the initial amplitude, initial phase lag and initial spectrum half-width of the reflected acoustic signal are extracted and used as the initial acoustic characteristic parameters.

[0029] It should be noted that the indoor calibration experiments were completed during a separate preparatory phase from the measurement process, using independent samples collected from the area surrounding the target measurement point. The parameters generated during the calibration were directly applied to the field measurement, ensuring zero-contact measurement of the target measurement point.

[0030] S2. Apply a small amount of atomized water without impact to the target measuring point, and continuously collect the real-time acoustic characteristic parameters of the reflected acoustic signal during the application process.

[0031] It should be added that the method for collecting the real-time acoustic characteristic parameters is the same as the method for collecting the initial acoustic characteristic parameters, and will not be repeated here.

[0032] Exemplarily, applying a small amount of impact-free atomized water to the target measuring point includes: calculating the radius of the acoustic detection area based on the emission angle of the acoustic wave transducer and the vertical distance of the probe, wherein the emission angle is an inherent technical parameter of the transmitter.

[0033] It should be added that, through the formula Calculate the radius of the acoustic detection area, where: is the radius of the acoustic detection area, is the vertical distance of the probe, is the launch angle.

[0034] Install the pneumatic atomizing nozzle at an angle and adjust the atomizing fan angle to cover the acoustic detection area using the nozzle angle adjustment knob.

[0035] Before applying water, the boundary of the acoustic detection area is projected by a laser locator, and the angle of the nozzle is adjusted so that the atomization coverage area coincides with the laser marked area.

[0036] The preset initial water application rate is controlled by the flow control valve, and the diameter of the atomized water droplets is ensured to be within the atomized water droplet particle size range.

[0037] It should be added that the preset initial water application rate refers to the amount of atomized water applied per unit time that is pre-set by the flow control valve at the initial stage of water application. The setting basis includes: based on the initial pore density level of the target measuring point, the initial water application rate in the high pore density area can be appropriately increased, while that in the low pore density area can be reduced to avoid structural disturbance caused by excessive water accumulation. Combined with the area of ​​the acoustic detection area, the water application per unit area is ensured to be evenly covered. The initial rate is the product of the water application per unit area and the area of ​​the acoustic detection area.

[0038] The atomized water droplet size range refers to the maximum diameter limit set for impact-free water application. Specific control methods include: using high-precision pneumatic atomizing nozzles and adjusting the air pressure source output to match the nozzle aperture to ensure that the droplet diameter remains within the preset range. Before water application, atomized water droplets are sampled and tested using a laser particle size analyzer. If the particle size exceeds the range, the nozzle angle or air pressure parameters are adjusted until the atomized water droplet diameter is controlled within the atomized water droplet size range.

[0039] During the water application process, the nozzle outlet pressure is monitored in real time through a pressure sensor. If the pressure fluctuation exceeds the nozzle pressure tolerance range, the air pressure source output is dynamically adjusted through a closed-loop control system to maintain atomization stability.

[0040] The nozzle pressure tolerance range refers to the maximum allowable deviation of the nozzle outlet pressure from the target pressure value during water application to maintain atomization stability. This range is typically set as a percentage of the target pressure. When the pressure sensor detects that the actual pressure exceeds this range, the closed-loop control system's adjustment mechanism is triggered.

[0041] The nozzle pressure tolerance range is set based on the following factors: nozzle outlet pressure directly affects atomization quality. Excessive pressure fluctuations can cause droplet diameters to deviate from the preset range. Indoor calibration experiments measure droplet diameter changes under varying pressure fluctuations, and the pressure fluctuation range that maintains droplet diameters within the preset range is defined as the nozzle pressure tolerance range.

[0042] The embodiment of the present invention directly measures the dead branch and leaf layer to be measured in a natural state through the laser ranging fixation of the acoustic probe and the overlap calibration of the atomizing nozzle and the sound wave detection area. At the same time, the impact-free application of trace atomized water and the dynamic feedback of acoustic parameters are combined to achieve zero-disturbance water application in the pores, solve the problem of interlayer structure damage caused by artificial paving, and make the water storage capacity truly reflect the state of the dead branch and leaf layer to be measured.

[0043] S3. Adjust the application rate of the trace atomized water according to the initial acoustic characteristic parameters and the real-time acoustic characteristic parameters until any preset termination condition is met and stop applying. When the preset termination condition is a safety termination condition, trigger a secondary measurement operation.

[0044] Exemplarily, the adjusting the water application rate of the micro-atomized water includes: taking the difference between the real-time phase lag in the real-time acoustic characteristic parameters and the initial phase lag in the initial acoustic characteristic parameters as the phase lag increment, and comparing it with the pre-set water phase lag threshold.

[0045] Among them, the pre-watering phase lag threshold refers to the critical reference value used to judge whether the change in phase lag requires adjustment of the watering rate during the watering process. It is an important reference indicator for measuring changes in the water absorption state of the dead branches and leaves layer to be tested. The method of obtaining it is: based on the field measurement database of the same type of dead branches and leaves layer to be tested, the phase lag threshold of similar samples is called, the average is calculated, and the calculation result is used as the pre-watering phase lag threshold.

[0046] If the phase lag increment is greater than the preset water phase lag threshold, the ratio of the threshold to the increment is used as the attenuation factor, which is multiplied by the current water application rate to generate the adjusted water application rate. Otherwise, the current water application rate is used as the adjusted water application rate.

[0047] It should be added that the phase lag is a core acoustic parameter that reflects the dynamic changes in pore water in the litter layer, and its increment directly reflects the matching state between the water penetration rate and the pore absorption capacity. When the phase lag increment is greater than the pre-set water phase lag threshold, it indicates that the water filling speed at the current water application rate has exceeded the stable pore absorption range, which may lead to surface water accumulation or pore structure disturbance. At this time, the water application rate is reduced by generating an attenuation factor based on the ratio of the threshold to the increment, which can achieve dynamic adaptation of the water application amount and the real-time water absorption capacity, ensure uniform water penetration, maintain stable changes in acoustic parameters, and provide guarantees for the subsequent triggering of stable termination conditions and effective data collection.

[0048] Exemplarily, the preset termination condition includes: calculating an amplitude change rate based on an initial amplitude in the initial acoustic characteristic parameter and a real-time amplitude in the real-time acoustic characteristic parameter.

[0049] The amplitude change rate being continuously less than the preset amplitude change rate threshold is used as a stable termination condition, and the cumulative amount of trace atomized water applied reaching the preset maximum cumulative water application amount is used as a safe termination condition.

[0050] It should be noted that the preset amplitude change rate threshold is the critical value for determining whether the amplitude change rate has reached a stable state. It is used to represent the upper limit of the fluctuation range of the acoustic amplitude characteristics during the water absorption process of the test litter layer. When the amplitude change rate is continuously less than this threshold, it indicates that the water absorption of the test litter layer has stabilized and the acoustic characteristics are no longer changing significantly. The process of obtaining this threshold involves accessing a field measurement database of similar test litter layers and extracting the statistical mean of the amplitude change rate during the stable water absorption phase as the preset amplitude change rate threshold.

[0051] The preset maximum cumulative water application volume refers to the maximum value of the cumulative application volume of trace atomized water allowed during the water application process. It is used to avoid structural damage or water loss of the dead branches and leaves layer to be measured due to excessive water application, and to ensure the safety of the water application process and measurement accuracy.

[0052] The specific process for obtaining the preset maximum cumulative watering volume involves conducting a small-scale pilot test at the target measurement point before watering. A representative sub-area within the test area is selected, and atomized water is applied at a low rate while simultaneously monitoring the amplitude change rate and water penetration depth. When the amplitude change rate in the sub-area first falls below the temporary reference threshold, the cumulative watering volume at that time is recorded and used as the preset maximum cumulative watering volume.

[0053] The embodiment of the present invention controls the water application rate through a dynamic comparison threshold and ratio algorithm of the phase lag increment, and at the same time combines the dual termination conditions of the amplitude change rate threshold and the upper limit of the water application amount to solve the problem of inaccurate determination of the water absorption saturation point, and realizes non-destructive and accurate measurement of the water storage capacity of the dead branches and leaves layer to be measured.

[0054] Exemplarily, the triggering of the secondary measurement operation includes: defining a circular associated area with the position of the target measuring point as the center, evenly distributing a number of measuring points within the circular associated area, calculating the straight-line distance between each measuring point and the target measuring point, and selecting measuring points whose distance is greater than a preset influence distance as adjacent unmeasured points.

[0055] It should be added that the preset influence distance refers to the critical spatial distance centered on the target measuring point, which defines the significant impact of its acoustic characteristics and moisture effects on the surrounding area. Its core function is to distinguish between areas directly affected by the target measuring point and unaffected areas, ensuring the independence of the secondary measurement point selection. Among them, the preset influence distance is based on the decisive effect of the pore distribution type of the dead branches and leaves layer on the water diffusion characteristics, and is determined in combination with experimental verification data. The fast-penetrating pore structure has strong connectivity and a wide pore size distribution range, a fast water penetration rate, and a large lateral diffusion range. Experimental verification shows that under this type of pore distribution, the target measuring point has the largest water interference range in the surrounding area within a short period of time after water is applied, so the preset influence distance is set to the maximum value.

[0056] High-water-holding pores have a dense structure and poor connectivity, with water primarily retained and weak lateral diffusion. Experimental verification shows that this type of pore structure minimizes the impact of water on the surrounding area when water is applied to the target measuring point, so the preset impact distance is set to the minimum value.

[0057] The pore density and connectivity of the slow-release water storage type fall between the two aforementioned types, with a medium water diffusion rate and range. Experimental verification indicates that this type of water storage has a moderate water interference range, so the default impact distance is set midway between the maximum and minimum values.

[0058] The initial acoustic characteristic parameters of each adjacent unmeasured point are collected, and the initial amplitude, initial phase lag and initial spectrum half-width of each adjacent unmeasured point and the target measured point are similarly calculated to obtain the acoustic characteristic similarity between each adjacent unmeasured point and the target measured point.

[0059] It should be added that the calculation process of the acoustic feature similarity is as follows: the relative deviation of the initial amplitude, the relative deviation of the initial phase lag, and the relative deviation of the initial spectrum half-width are calculated, and their averages are calculated to obtain the comprehensive difference coefficient, and then the value 1 minus the comprehensive difference coefficient is used as the acoustic feature similarity between each adjacent unmeasured point and the target measured point.

[0060] The adjacent unmeasured point with the maximum value in the acoustic feature similarity is selected as a new measuring point, the adjusted water application rate is used as the initial water application rate of the new measuring point, and the process returns to step S1 to restart the process with the new measuring point as the target measuring point.

[0061] The embodiment of the present invention initiates secondary measurement when a safety termination condition is triggered, demarcates an area and arranges points with the target measurement point as the center, selects the optimal adjacent unmeasured point through preset influence distance screening and similarity calculation based on amplitude, phase and spectral parameters, and restarts the process at an adjusted rate. This improves regional measurement efficiency and data reliability through dual spatial and feature protection.

[0062] S4. When the preset termination condition is a stable termination condition, the post-water absorption acoustic characteristic parameters of the reflected acoustic signal are collected after the target measuring point absorbs a trace amount of atomized water.

[0063] It should be added that the method for collecting the acoustic characteristic parameters after water absorption is the same as the method for collecting the initial acoustic characteristic parameters, and will not be repeated here.

[0064] S5. Calculate the change in the acoustic characteristic parameters before and after water absorption based on the initial acoustic characteristic parameters and the acoustic characteristic parameters after water absorption.

[0065] Exemplarily, the calculating of the change in acoustic characteristic parameters before and after water absorption includes: taking the initial amplitude in the initial acoustic characteristic parameters as a reference, and taking the absolute difference between the amplitude after water absorption and the initial amplitude in the acoustic characteristic parameters after water absorption as the amplitude change.

[0066] The difference between the phase lag after water absorption and the initial phase lag is taken as the total phase lag change.

[0067] The ratio of the initial spectrum half-width to the spectrum half-width after water absorption is taken as the spectrum width attenuation coefficient.

[0068] The amplitude change, total phase lag change and spectrum width attenuation coefficient are summarized as the acoustic characteristic parameter changes.

[0069] The embodiment of the present invention determines the pore density level by inverting the initial amplitude, determines the pore connectivity by the phase lag, and identifies the pore size distribution by the spectrum half-width, thereby determining the pore distribution type. This solves the problem that the existing technology cannot analyze the microscopic causes of the water storage mechanism, and provides a structural basis for the subsequent selection of differentiated response relationships.

[0070] S6. Based on the initial amplitude, initial phase lag, and initial spectrum half-width in the initial acoustic characteristic parameters, determine the pore distribution type of the target measuring point and select a matching preset response relationship.

[0071] It should be added that the preset response relationship is an acoustic characteristic change-water storage capacity mapping model established in advance through indoor calibration experiments. It is divided into three categories corresponding to different pore distribution types of target measuring points. The preset response relationships are the first preset response relationship, the second preset response relationship, and the third preset response relationship.

[0072] See also Figure 3 As shown, illustratively, determining the pore distribution type of the target measuring point includes: inverting the pore density level according to the initial amplitude, and determining that the initial amplitude is less than the lower limit of the preset amplitude range as high pore density, such as fluffy ash layer.

[0073] It should be noted that the preset amplitude interval refers to the acoustic amplitude reference range used to invert the pore density level of the litter layer to be measured. By comparing the initial amplitude with this interval, the pore density level can be determined.

[0074] The preset amplitude range is verified through indoor calibration experiments. The specific acquisition process includes: selecting litter samples with known porosity to be tested, simulating a field acoustic detection environment in the laboratory, and using the same parameters as in the field, such as the acoustic wave emission frequency and probe vertical distance, to collect reflected acoustic amplitude data for samples with different porosity densities. The maximum amplitude of the high-porosity sample is used as the lower limit of the range, and the minimum amplitude of the low-porosity sample is used as the upper limit of the range to form the preset amplitude range. The lower limit of the preset amplitude range is the statistical maximum amplitude of the high-porosity sample, and the upper limit of the preset amplitude range is the statistical minimum amplitude of the low-porosity sample.

[0075] An initial amplitude within the preset amplitude range is determined as a medium pore density, such as a semi-carbonized dead leaf layer; an initial amplitude greater than the upper limit of the preset amplitude range is determined as a low pore density, such as a compacted unburned layer.

[0076] Pore ​​connectivity is determined based on the initial phase lag. When the initial phase lag is greater than the preset pore connectivity threshold, the pores are considered highly connected. Otherwise, the pores are considered poorly connected. High pore connectivity refers to when the initial phase lag is greater than the preset pore connectivity threshold, indicating good inter-pore connectivity and low water infiltration resistance. Low pore connectivity refers to when the initial phase lag is less than or equal to the threshold, indicating that the pores are tortuous or clogged, leading to high water infiltration resistance.

[0077] The pore size distribution is identified in combination with the initial spectrum half-width amplitude. An initial spectrum half-width amplitude greater than the preset spectrum half-width threshold is judged as a wide spectrum, otherwise it is judged as a narrow spectrum. A wide spectrum indicates that the pore size distribution is highly discrete, and the sound waves are scattered in pores of various scales, resulting in spectrum broadening. A narrow spectrum reflects uniform pore size.

[0078] It should be added that the preset spectrum half-width threshold refers to the critical value used to distinguish the pore size distribution type of the litter layer to be tested. By comparing the initial spectrum half-width amplitude with the threshold, it can be determined whether the pore size distribution is a wide spectrum or a narrow spectrum.

[0079] The preset spectral half-width threshold is derived from indoor calibration experiments. The specific acquisition process involves selecting litter samples with known pore size distribution, simulating field acoustic detection conditions in the laboratory, and collecting initial spectral half-width amplitude data for different samples. The minimum spectral half-width amplitude for the wide-spectrum samples and the maximum spectral half-width amplitude for the narrow-spectrum samples are then calculated. The midpoint between the minimum and maximum spectral half-width amplitudes is then taken as the preset spectral half-width threshold.

[0080] The pore distribution type that meets the conditions of high pore density, high pore connectivity and wide spectrum is defined as fast permeability type, the pore distribution type that meets the conditions of medium pore density, low pore connectivity and wide spectrum is defined as slow-release water storage type, and the pore distribution type that meets the conditions of low pore density, low pore connectivity and narrow spectrum is defined as high water retention type.

[0081] It should be added that, for pore distributions that do not fall into the above types, they are classified as slow-release water storage type by default and matched with the second preset response relationship.

[0082] Exemplarily, the selected matching preset response relationship includes: if the pore distribution type of the target measuring point is a fast permeability type, matching the first preset response relationship in the preset response relationship, which uses the spectrum width attenuation coefficient as the core input parameter, and the amplitude change and the total change of the phase lag as auxiliary input parameters.

[0083] If the pore distribution type of the target measuring point is slow-release water storage type, the second preset response relationship in the preset response relationship is matched, in which the amplitude change, the total change of phase lag and the spectrum width attenuation coefficient are equally weighted input parameters.

[0084] If the pore distribution type of the target measuring point is high water holding type, the third preset response relationship in the preset response relationship is matched. This relationship uses the amplitude change as the core input parameter, and the total change of phase lag and the spectrum width attenuation coefficient as auxiliary input parameters.

[0085] It should be noted that due to the high pore density, high connectivity, and wide spectrum characteristics of the rapid permeability type, water quickly infiltrates, resulting in a narrow spectral scattering range. The spectrum width attenuation coefficient accurately reflects the integrity and rate of permeation and is therefore a core parameter. Rapid water flow causes synchronous fluctuations in amplitude and phase, and the variation pattern is dominated by the permeation dynamics, making it an auxiliary parameter. The slow-release water storage type, characterized by medium pore density, low connectivity, and a wide spectrum, exhibits a complex process of slow permeation and gradual saturation. The spectrum width attenuation coefficient reflects the overall degree of saturation, the amplitude change corresponds to the energy attenuation difference, and the total phase lag change reflects the permeation lag effect. These three parameters characterize the water storage process from the perspectives of saturation progress, energy pattern, and temporal characteristics, respectively, and are therefore equally weighted. Due to the low pore density, low connectivity, and narrow spectrum characteristics of the high water retention type, water is primarily retained in dense pores, resulting in significant acoustic energy attenuation. The amplitude change directly reflects water holding capacity, while the phase and spectrum changes are less affected by pore uniformity. Therefore, the amplitude change is the core parameter, and the others are auxiliary. By setting differentiated parameter weights, the water storage mechanism of various pore distribution types can be accurately adapted to achieve effective evaluation of water storage capacity.

[0086] S7. Input the change in the acoustic characteristic parameter into the corresponding preset response relationship to evaluate the water storage capacity of the target measuring point.

[0087] Exemplarily, the evaluation of the water storage capacity of the target measuring point includes: performing weighted fusion calculation on the amplitude change, the total phase lag change and the spectrum width attenuation coefficient according to a matching preset response relationship to generate a water storage capacity characteristic value.

[0088] The water storage capacity characteristic value is input into the mapping rule between the characteristic value and the actual water holding capacity in the preset response relationship to obtain the water holding capacity per unit area.

[0089] It should be added that the mapping rule between characteristic value and actual water holding capacity is a mathematical association rule for converting the water storage capacity characteristic value generated by weighted fusion of acoustic characteristic parameters into a specific water holding capacity per unit area. The construction method includes: selecting samples of the dead branches and leaves layer to be tested with different pore distribution types such as fast infiltration type, slow-release water storage type, and high water holding type, collecting the changes in acoustic characteristic parameters of each sample before and after water absorption through the measurement method of the present invention, and performing weighted fusion calculation according to the corresponding preset response relationship to obtain the water storage capacity characteristic value of each sample.

[0090] While obtaining the characteristic values, the weight method was used to accurately measure the actual water holding capacity per unit area of ​​each sample, and a one-to-one corresponding data pair between the characteristic value of water storage capacity and the actual water holding capacity per unit area was established. Based on these data pairs, mathematical correlation models were fitted for different pore distribution types, so that the models could accurately reflect the quantitative correspondence between the characteristic values ​​and the actual water holding capacity, and finally a mapping rule between the characteristic values ​​and the actual water holding capacity of different pore distribution types was formed.

[0091] The water holding capacity per unit area is matched with the water holding capacity intervals corresponding to each water storage capacity level to obtain the water storage capacity level. This results in a water storage capacity assessment result for the target measurement point, including the water holding capacity per unit area, pore distribution type, and water storage capacity level. The water storage capacity levels are classified as strong, medium, and weak.

[0092] It's important to note that the water holding capacity per unit area range corresponding to the water storage capacity class is the range of water holding capacity per unit area, determined through systematic experimental calibration based on pore distribution type. This range serves as a quantitative criterion linking water holding capacity per unit area to water storage capacity class. This range is obtained by conducting indoor water absorption and saturation experiments for three pore distribution types: rapid permeability, slow-release storage, and high water retention. For rapid permeability samples, the focus is on analyzing the water holding range corresponding to their high pore connectivity and rapid water infiltration.

[0093] For slow-release water storage samples, the focus is on the water holding characteristic range with medium pore density and the combined process of water retention and infiltration.

[0094] For high water-holding samples, emphasis is placed on the water-holding value range corresponding to the strong water-holding capacity of the pores.

[0095] By statistically analyzing the saturated water holding capacity data of multiple groups of samples, the boundaries of the water holding capacity per unit area corresponding to each type are determined.

[0096] The embodiment of the present invention solves the problem of single output dimension in the existing technology through weighted fusion calculation of acoustic feature changes, and based on the mapping rules between characteristic values ​​and actual water holding capacity and the water storage capacity level matching method, realizes the synchronous output of three parameters: water holding capacity per unit area, pore distribution type and water storage capacity level.

[0097] The above embodiments may be implemented in whole or in part through software, hardware, firmware, or any other combination thereof. When implemented using software, the above embodiments may be implemented in whole or in part in the form of a computer program product.

[0098] Those skilled in the art will appreciate that the modules and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0099] In addition, each functional module in each embodiment of the present application may be integrated into one processing module, or each module may exist physically separately, or two or more modules may be integrated into one module.

[0100] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

[0101] Finally, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for measuring the water storage capacity of litter in a wild forest, characterized by: The method includes: S1, transmitting an acoustic wave to a target measuring point of the litter layer to be measured, and collecting initial acoustic characteristic parameters of the reflected acoustic signal; S2, applying a small amount of atomized water without impact to the target measuring point, and continuously collecting the real-time acoustic characteristic parameters of the reflected acoustic signal during the application process; S3. Adjusting the rate of applying the micro-atomized water according to the initial acoustic characteristic parameters and the real-time acoustic characteristic parameters until any preset termination condition is met and stopping the application. When the preset termination condition is a safety termination condition, triggering a secondary measurement operation; The preset termination conditions include: calculating the amplitude change rate based on the initial amplitude in the initial acoustic characteristic parameters and the real-time amplitude in the real-time acoustic characteristic parameters; taking the amplitude change rate being continuously less than a preset amplitude change rate threshold as a stable termination condition; and taking the cumulative amount of micro-atomized water applied reaching a preset maximum cumulative amount of water applied as a safe termination condition; The triggering of the secondary measurement operation includes: defining a circular associated area with the position of the target measuring point as the center, evenly distributing a number of measuring points within the circular associated area, calculating the straight-line distance between each measuring point and the target measuring point, and selecting measuring points with a distance greater than a preset influence distance as adjacent unmeasured points; collecting initial acoustic feature parameters of each adjacent unmeasured point, performing similarity calculation on the initial amplitude, initial phase lag, and initial spectrum half-width of each adjacent unmeasured point and the target measuring point to obtain acoustic feature similarity between each adjacent unmeasured point and the target measuring point; selecting the adjacent unmeasured point with the maximum value in the acoustic feature similarity as a new measuring point, using the adjusted water application rate as the initial water application rate of the new measuring point, returning to step S1, and restarting the process with the new measuring point as the target measuring point; S4. When the preset termination condition is a stable termination condition, collecting acoustic characteristic parameters of the reflected acoustic signal after absorbing a small amount of atomized water at the target measuring point; S5. Calculating the change in the acoustic characteristic parameters before and after water absorption based on the initial acoustic characteristic parameters and the acoustic characteristic parameters after water absorption; S6. Based on the initial amplitude, initial phase lag, and initial spectrum half-width in the initial acoustic characteristic parameters, determine the pore distribution type of the target measuring point and select a matching preset response relationship; S7. Input the change in the acoustic characteristic parameter into the corresponding preset response relationship to evaluate the water storage capacity of the target measuring point.

2. The method for measuring water storage capacity of litter in a wild forest according to claim 1, characterized in that: The initial acoustic characteristic parameters of the collected reflected acoustic signal include: Fix the acoustic probe at the vertical distance of the probe above the target measuring point through the laser rangefinder; Controlling the ultrasonic transmitter to emit pulsed sound wave signals within a preset frequency range; The reflected acoustic signal is captured by the receiver, and after low-noise amplification and analog-to-digital conversion, the initial amplitude, initial phase lag and initial spectrum half-width of the reflected acoustic signal are extracted and used as the initial acoustic characteristic parameters.

3. The method for measuring water storage capacity of litter layer in wild forest land according to claim 1, characterized in that: The step of applying a small amount of atomized water without impact to the target measuring point comprises: Calculate the radius of the acoustic detection area based on the emission angle of the acoustic transducer and the vertical distance of the probe; Install the pneumatic atomizing nozzle at an angle and adjust the atomizing fan angle to cover the acoustic detection area using the nozzle angle adjustment knob. Before applying water, the boundary of the acoustic detection area is projected by a laser locator, and the angle of the nozzle is adjusted so that the atomization coverage area coincides with the laser marked area; The preset initial water application rate is controlled by the flow control valve, and the diameter of the atomized water droplets is ensured to be within the atomized water droplet particle size range; During the water application process, the nozzle outlet pressure is monitored in real time through a pressure sensor. If the pressure fluctuation exceeds the nozzle pressure tolerance range, the air pressure source output is dynamically adjusted through a closed-loop control system to maintain atomization stability.

4. The method for measuring water storage capacity of litter in a wild forest according to claim 1, characterized in that: The adjustment of the water application rate of the trace atomized water comprises: The difference between the real-time phase lag in the real-time acoustic characteristic parameters and the initial phase lag in the initial acoustic characteristic parameters is used as the phase lag increment, and the difference is compared with the pre-set phase lag threshold; If the phase lag increment is greater than the preset water phase lag threshold, the ratio of the threshold to the increment is used as the attenuation factor, which is multiplied by the current water application rate to generate the adjusted water application rate. Otherwise, the current water application rate is used as the adjusted water application rate.

5. The method for measuring water storage capacity of litter layer in wild forest land according to claim 1, characterized in that: The calculation of the change in acoustic characteristic parameters before and after water absorption includes: Taking the initial amplitude in the initial acoustic characteristic parameters as a reference, the absolute difference between the amplitude after water absorption and the initial amplitude in the acoustic characteristic parameters after water absorption is taken as the amplitude change; The difference between the phase lag after water absorption and the initial phase lag is taken as the total phase lag change; The ratio of the initial spectrum half-width to the spectrum half-width after water absorption is taken as the spectrum width attenuation coefficient; The amplitude change, total phase lag change and spectrum width attenuation coefficient are summarized as the acoustic characteristic parameter changes.

6. The method for measuring water storage capacity of litter layer in wild forest land according to claim 1, characterized in that: Determining the pore distribution type of the target measuring point includes: The pore density level is inverted based on the initial amplitude, and the initial amplitude less than the lower limit of the preset amplitude range is determined as high pore density; If the initial amplitude is within the preset amplitude range, it is determined as medium pore density; if the initial amplitude is greater than the upper limit of the preset amplitude range, it is determined as low pore density; The pore connectivity is judged based on the initial phase lag. If the initial phase lag is greater than the preset pore connectivity judgment phase lag threshold, the pore is judged to be highly connected. Otherwise, it is judged to be poorly connected. The pore size distribution is identified by combining the initial spectrum half-width amplitude. If the initial spectrum half-width amplitude is greater than the preset spectrum half-width threshold, it is determined to be a wide spectrum; otherwise, it is determined to be a narrow spectrum. The pore distribution type that meets the conditions of high pore density, high pore connectivity and wide spectrum is defined as fast permeability type, the pore distribution type that meets the conditions of medium pore density, low pore connectivity and wide spectrum is defined as slow-release water storage type, and the pore distribution type that meets the conditions of low pore density, low pore connectivity and narrow spectrum is defined as high water retention type.

7. The method for measuring water storage capacity of litter layer in wild forest land according to claim 1, characterized in that: The preset response relationship selected for matching includes: If the pore distribution type of the target measuring point is a fast permeability type, the first preset response relationship in the preset response relationship is matched, which uses the spectrum width attenuation coefficient as the core input parameter and the amplitude change and the total phase lag change as auxiliary input parameters; If the pore distribution type of the target measuring point is slow-release water storage type, the second preset response relationship in the preset response relationship is matched, in which the amplitude change, the total change of phase lag and the spectrum width attenuation coefficient are input parameters with equal weights; If the pore distribution type of the target measuring point is high water holding type, the third preset response relationship in the preset response relationship is matched. This relationship uses the amplitude change as the core input parameter, and the total change of phase lag and the spectrum width attenuation coefficient as auxiliary input parameters.

8. The method for measuring water storage capacity of litter layer in wild forest land according to claim 5, characterized in that: The water storage capacity of the target measuring point to be evaluated includes: The amplitude change, the total phase lag change and the spectrum width attenuation coefficient are weighted and fused according to the matching preset response relationship to generate a water storage capacity characteristic value; The water storage capacity characteristic value is input into the mapping rule between the characteristic value and the actual water holding capacity in the preset response relationship to obtain the water holding capacity per unit area; The water holding capacity per unit area is matched with the water holding capacity interval per unit area corresponding to each water storage capacity level to obtain the water storage capacity level, and then the water storage capacity assessment result of the target measuring point including the water holding capacity per unit area, pore distribution type and water storage capacity level is output.

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