A soil monitoring device and method for forestry based on spectral analysis

Abstract

The present application relates to the field of forestry environment monitoring and spectral detection technology, specifically to a kind of forestry soil monitoring equipment based on spectral analysis, including main casing, probe body with multiple spectral sensors and micro light source, sliding type protective outer tube with annular cutting edge and spring linkage assembly;The equipment utilizes the linkage cooperation of sliding protective outer tube and double helix spring, and establishes isolation by cutting edge to cut off surface covering in advance when pressing down;The core is that the probe body drives sapphire glass window to flatten concave-convex soil under the constant thrust of spring with consistent pressure, and forms a physical darkroom with the outer tube to carry out spectral detection;The present application not only wraps and shields the probe to prevent wear and tear under normal conditions, but also effectively blocks stray light under the forest, and overcomes the problem of reflected spectrum distortion caused by inconsistent contact pressure and external light leakage.

Description

Technical Field

[0001] This invention relates to the field of forestry environmental monitoring and spectral detection technology, specifically to a forestry soil monitoring device and method based on spectral analysis. Background Technology

[0002] In in-situ spectral measurement of forestry soil, the measuring equipment typically needs to be directly attached to the target soil surface and an optical path established to collect reflectance spectral data. To obtain soil spectral information, existing methods generally use a method of directly pressing the bare probe against the ground surface, i.e., pressing the probe into the soil surface layer by external force, and then turning on the light source and sensor to collect and invert the light signal. Although this method has a certain detection capability on relatively ideal flat and dry surfaces, the characteristics of forest environments, such as sand and gravel mixtures, high humidity, and complex lighting, make it easy for the probe to wear out when in direct contact with the soil. At the same time, the lack of mechanical isolation and protection allows stray light from the forest floor to easily leak into the measurement optical path, and the uneven soil surface causes inconsistent contact pressure between the probe and the surface. In addition, the high humidity environment easily causes condensation on the window surface and light scattering. These factors combined reduce the spectral signal-to-noise ratio and cause serious distortion of the collected reflectance spectrum.

[0003] Therefore, overcoming the unevenness of measurement points, stray light interference, and condensation scattering in complex forest environments, and improving the consistency and accuracy of in-situ soil spectral acquisition, has become an urgent technical problem to be solved. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a forestry soil monitoring device and method based on spectral analysis. Specifically, the technical solution of this invention is as follows: A forestry soil monitoring device based on spectral analysis, comprising: The main shell is a hollow tubular structure; The probe body is coaxially slidably installed in the inner cavity of the main housing. A sapphire glass window is fixedly installed at the bottom of the probe body. A miniature positive temperature coefficient heating ring is provided inside the probe body and attached to the inner side of the sapphire glass window. A multispectral sensor and a miniature light source are arranged in the central area of ​​the miniature positive temperature coefficient heating ring. A sliding protective outer tube is coaxially sleeved outside the main housing. The bottom end of the sliding protective outer tube is machined with an annular cutting edge. A limiting structure is provided between the main housing and the sliding protective outer tube to limit the extreme position of the sliding protective outer tube under the action of thrust. A first helical spring is connected between the top of the probe body and the top of the inner cavity of the main housing; The second helical spring is connected between the bottom of the outer wall of the main housing and the top of the inner wall of the sliding protective outer tube; The controller connects to and controls the multispectral sensor, the miniature light source, and the miniature positive temperature coefficient heating ring.

[0005] Preferably, the outer wall of the probe body and the inner wall of the main housing are fitted with a clearance, and a flange is provided at the top of the probe body. The first helical spring is compressed and installed between the flange and the top of the inner cavity of the main housing.

[0006] Preferably, a boss is provided at the bottom of the outer wall of the main housing, and a step is provided at the top of the inner wall of the sliding protective outer tube. The second helical spring is compressed and installed between the boss and the step, wherein the stiffness coefficient of the second helical spring is greater than that of the first helical spring.

[0007] Preferably, the probe body has a threaded sealing cap at the bottom, and the sapphire glass window is fixedly installed on the probe body through the threaded sealing cap.

[0008] Preferably, the miniature positive temperature coefficient heating ring has self-limiting temperature characteristics, and the miniature light source is a broadband halogen tungsten micro lamp bead.

[0009] Preferably, the annular cutting edge is set at an acute angle.

[0010] Preferably, under normal conditions, the second helical spring pushes the sliding protective outer tube downward to its limit position, and the bottom end of the sliding protective outer tube covers and wraps the probe body and the sapphire glass window.

[0011] A method for monitoring forestry soil based on spectral analysis, comprising: S1. Through an external actuator, the annular cutting edge of the sliding protective outer tube cuts through the surface dead leaf layer and abuts against the soil matrix. S2. Control the main housing to continue pressing down and compressing the second helical spring, so that the probe body slides down under the constant thrust of the first helical spring until the sapphire glass window flattens the soil surface with constant pressure, so that the inner wall of the sliding protective outer tube and the flattened soil surface form a physical dark chamber. S3. Control the multispectral sensor to continuously collect spectral data at high frequency when the miniature light source is off, extract the sum of energy values ​​of the near-infrared non-characteristic bands in the spectral data, and obtain the leakage index of multiple consecutive collections. S4. Obtain the preset sealing threshold and determine whether the leakage index of multiple consecutive acquisitions is less than the preset sealing threshold. If it is less than the preset sealing threshold, proceed to step S5. If there is a leakage index greater than or equal to the preset sealing threshold, terminate the current effective spectrum acquisition or send a signal to change the measurement point. S5. Control the micro light source to light up, control the multispectral sensor to collect the full-band reflectance spectrum, extract the absorbance of the preset reference band and calculate the baseline drift rate. S6. Obtain the preset cleanliness threshold and determine whether the baseline drift rate is greater than the preset cleanliness threshold. If it is greater than the preset cleanliness threshold, control the micro positive temperature coefficient heating ring to heat the sapphire glass window and continuously monitor the baseline drift rate. When the baseline drift rate is less than or equal to the preset cleanliness threshold, control the heating to stop and execute step S7. If the baseline drift rate is less than or equal to the preset cleanliness threshold, execute step S7. S7. Control the multispectral sensor to collect effective soil spectral data, and obtain the corrected absorbance based on the absorbance of the preset organic matter characteristic band and the absorbance of the preset water characteristic band. S8. Obtain the true soil organic matter content based on the corrected absorbance and the pre-calibrated forest soil conversion coefficient.

[0012] Preferably, the continuous multiple data collections are three consecutive data collections. In step S4, if there is a light leakage index greater than or equal to the preset sealing threshold, it is determined that the mechanical structure is tilted and leaking light due to encountering hard tree roots or large rocks, and the control sends a prompt signal to replace the measuring point.

[0013] Preferably, in step S5, the reference band is a non-water absorption characteristic reference band; in step S6, when the micro positive temperature coefficient heating ring is energized to heat the sapphire glass window, the surface temperature of the sapphire glass window is controlled to be higher than the soil ambient temperature.

[0014] The present invention has the following beneficial effects: 1. The forestry soil monitoring device of the present invention utilizes the linkage between a sliding protective outer tube and a first helical spring and a second helical spring. When pressed down, the annular cutting edge at the bottom of the outer tube preferentially cuts the ground cover to establish isolation. The probe body then drives the sapphire glass window under constant thrust to flatten the uneven soil with consistent pressure, and forms a physical dark chamber with the outer tube. This design not only protects the probe from wear under normal conditions, but also effectively blocks stray light from the forest floor, overcoming the distortion of the reflected spectrum caused by inconsistent contact pressure and external light leakage. 2. This invention is based on the linkage of a multispectral sensor and a controller. It uses the light leakage index of the near-infrared non-characteristic band to determine the airtightness of the darkroom and monitors condensate by the baseline drift rate of the non-water absorption characteristic reference band. When the drift rate exceeds the limit, it adaptively controls a miniature positive temperature coefficient heating ring to heat the sapphire glass window to eliminate physical scattering of condensate. After acquiring the spectrum, it uses the absorbance of the characteristic bands of water and organic matter to perform normalized water decoupling. This effectively eliminates the negative impact of high humidity condensation environment on the spectral signal-to-noise ratio and improves the accuracy of in-situ data. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings: Figure 1 This is a schematic diagram of the overall external structure of the device; Figure 2 This is a structural diagram of the main housing, probe body, and sliding protective outer tube; Figure 3 This is a schematic diagram of the probe body; Figure 4 This is a flowchart of the method of the present invention.

[0016] In the diagram: 1. Main housing; 2. Probe body; 3. Sapphire glass window; 4. Miniature positive temperature coefficient heating ring; 5. Multispectral sensor; 6. Miniature light source; 7. Sliding protective outer tube; 8. Annular cutting edge; 9. First helical spring; 10. Second helical spring; 11. Controller; 12. Flange; 13. Boss; 14. Step; 15. Threaded sealing gland. Detailed Implementation

[0017] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention. Example

[0018] Combination Figure 1 , Figure 2 and Figure 3 As shown, a forestry soil monitoring device based on spectral analysis includes: The main shell 1 is a hollow tubular structure; The probe body 2 is coaxially slidably installed in the inner cavity of the main housing 1. A sapphire glass window 3 is fixedly installed at the bottom of the probe body 2. A miniature positive temperature coefficient heating ring 4 is set inside the probe body 2, which is fitted to the inner side of the sapphire glass window 3. A multispectral sensor 5 and a miniature light source 6 are arranged in the central area of ​​the miniature positive temperature coefficient heating ring 4. The sliding protective outer tube 7 is coaxially sleeved outside the main housing 1. The bottom end of the sliding protective outer tube 7 is machined with an annular cutting edge 8. A limit structure is provided between the main housing 1 and the sliding protective outer tube 7 to limit the extreme position of the sliding protective outer tube 7 under the action of thrust. The first helical spring 9 is connected between the top of the probe body 2 and the top of the inner cavity of the main housing 1; The second helical spring 10 is connected between the bottom of the outer wall of the main housing 1 and the top of the inner wall of the sliding protective outer tube 7; Controller 11 connects to control multispectral sensor 5, miniature light source 6 and miniature positive temperature coefficient heating ring 4; In existing in-situ spectral measurements of forestry soil, the probe is prone to window wear when it directly contacts sandy soil. Furthermore, stray light from the forest floor, uneven soil surface, and high humidity condensation will simultaneously reduce the spectral signal-to-noise ratio. To solve the above problems, this embodiment sets the main shell 1 as the overall load-bearing and guiding component. The main shell 1 can be a hollow aluminum alloy tube with an outer diameter of 32mm to 50mm, a wall thickness of 2mm to 4mm, and a length of 250mm to 450mm. The probe body 2 is slidably mounted along the axis of the main housing 1. The probe body 2 can be made of stainless steel or hard aluminum alloy to form a cylindrical assembly. A sapphire glass window 3 is installed at its bottom end. The thickness of the sapphire glass window 3 can be 1mm to 3mm and the diameter can be 8mm to 18mm. The wear-resistant physical properties of sapphire material and the light transmission properties under the set wavelength can withstand soil friction and maintain the optical path connection. A miniature positive temperature coefficient heating ring 4 is closely attached to the inner side of the sapphire glass window 3. The close contact means that the axial distance between the two is controlled within the range of 0.2mm to 1.5mm to shorten the heat conduction path, so that the surface temperature of the window can rise to 2°C to 8°C higher than the surrounding soil temperature within 10s to 40s after power-on. A multispectral sensor 5 and a miniature light source 6 are arranged in the central area of ​​the miniature positive temperature coefficient heating ring 4. The multispectral sensor 5 can be an array detector covering the 400nm to 1700nm wavelength band, and the miniature light source 6 can provide broadband illumination to obtain the soil reflectance spectrum. The sliding protective outer tube 7 is sleeved on the outside of the main shell 1, and its bottom end forms an annular cutting edge 8. When the equipment is not pressed into the soil, the sliding protective outer tube 7 is in the lower shielding position, so that the sapphire glass window 3 does not directly collide with external hard particles. When the equipment is pressed down into the soil, the sliding protective outer tube 7 first cuts through the dead leaf layer and contacts the soil, and then generates relative displacement between itself and the main shell 1, providing a protected extension space for the internal probe body 2. The first helical spring 9 is disposed between the probe body 2 and the main housing 1 to provide a stable downward thrust. Its elastic coefficient can be 6N / mm to 20N / mm, so that the sapphire glass window 3 forms a relatively stable contact pressure when it comes into contact with the soil. The second helical spring 10 is disposed between the main housing 1 and the sliding protective outer tube 7 to keep the outer tube in the shielded position under normal conditions and to generate a rebound reset function during the downward pressing process. Its elastic coefficient can be 10N / mm to 35N / mm. The controller 11 can be electrically connected to the multispectral sensor 5, the miniature light source 6, and the miniature positive temperature coefficient heating ring 4 using a single-chip microcomputer or embedded processor to perform darkroom sealing judgment, window de-condensation control, and spectral inversion calculation. The above structure integrates mechanical protection, mechanical flattening, light shielding, optical acquisition, and thermal de-condensation into the same axial mechanism, so that the sampling action and the measurement action are automatically connected according to the force relationship, thereby reducing the reflection spectrum distortion caused by inconsistent contact pressure, external light leakage, and condensation.

[0019] The outer wall of the probe body 2 and the inner wall of the main housing 1 are fitted with a clearance. A flange 12 is provided at the top of the probe body 2. A first helical spring 9 is compressed and installed between the flange 12 and the top of the inner cavity of the main housing 1. To ensure that the probe body 2 slides smoothly along the axial direction of the main housing 1 and avoids jamming, a clearance fit is provided between the outer wall of the probe body 2 and the inner wall of the main housing 1. The clearance fit is preferably a radial clearance of 0.03mm to 0.20mm. When the radial clearance is less than 0.03mm, forest dust, water vapor and fine soil particles can easily enter and cause increased friction. When the radial clearance is greater than 0.20mm, the probe body 2 is prone to swinging when subjected to lateral loads, which affects the planar contact between the sapphire glass window 3 and the soil surface. A flange 12 is provided at the top of the probe body 2. The outer diameter of the flange 12 is 1 mm to 5 mm larger than the outer diameter of the probe body 2. A guide gap is maintained between the flange 12 and the inner wall of the main housing 1. The lower surface of the flange 12 is used to support the lower end of the first helical spring 9. A wear-resistant gasket or a metal bearing surface can be provided above the flange 12 to disperse the stress at the end of the spring and reduce local wear caused by long-term compression. After the first helical spring 9 is compressed and installed between the flange 12 and the top of the inner cavity of the main housing 1, it can convert the axial displacement of the main housing 1 into a stable pressing force of the probe body 2 on the soil surface. In this structure, flange 12 is not only used for spring positioning, but also for limiting the maximum extension stroke of probe body 2. The stroke can be designed to be 5mm to 30mm, so that after the sapphire glass window 3 exposes the bottom end of the sliding protective outer tube 7, it can complete the three continuous actions of contact, flattening and compaction within the limited stroke. Since the first helical spring 9 is loaded between the flange 12 and the top of the inner cavity of the main housing 1, the direction of the spring force coincides with the direction of movement of the probe body 2, which can reduce the off-center load and ensure a more uniform pressure distribution between the sapphire glass window 3 and the soil contact surface; through this clearance fit and the flange 12 compression spring structure, the guiding stability and repeatability accuracy of the device after piercing the surface of the forest are improved, providing a stable geometric basis for subsequent light leakage index judgment and effective reflection spectrum acquisition.

[0020] A boss 13 is provided at the bottom of the outer wall of the main housing 1, and a step 14 is provided at the top of the inner wall of the sliding protective outer tube 7. The second helical spring 10 is compressed and installed between the boss 13 and the step 14. The stiffness coefficient of the second helical spring 10 is greater than that of the first helical spring 9. To ensure that the sliding protective outer tube 7 remains extended and shielded when stationary, and to generate controllable relative displacement when the equipment is pressed into the soil, this embodiment provides an annular boss 13 at the bottom of the outer wall of the main housing 1, and a corresponding annular step 14 at the top of the inner wall of the sliding protective outer tube 7. The second helical spring 10 is compressed and installed between the boss 13 and the step 14. The annular boss 13 can be integrally machined from the main housing 1, with an outer diameter 1mm to 4mm larger than the outer diameter of the main housing 1. The annular step 14 can be formed by machining the inner cavity of the sliding protective outer tube 7 to provide stable limiting for the second helical spring 10. The stiffness coefficient of the second helical spring 10 is set to be greater than that of the first helical spring 9. Preferably, the stiffness coefficient of the first helical spring 9 is 8 N / mm to 15 N / mm, and that of the second helical spring 10 is 15 N / mm to 30 N / mm. The purpose of designing the stiffness coefficient of the second helical spring 10 to be greater than that of the first helical spring 9 is to provide the calibrated support force for cutting the dead leaf layer and blocking the peripheral stray light in the early stage of contacting the ground surface and cutting into the soil. This allows the cutting of the dead leaf layer, the enclosure of the soil boundary, and the blocking of the peripheral stray light to be completed first. The first helical spring 9 has a smaller stiffness coefficient, which allows the probe body 2 to continuously adhere to the soil with a preset pressure that matches the elastic deformation of the first helical spring 9 when it subsequently contacts the soil, reducing secondary soil damage caused by sudden pressure changes. The spring installation relationship formed by the boss 13 and the step 14 can also serve as the reset reference for the sliding protective outer tube 7. When the equipment is lifted off the ground, the second helical spring 10 releases its elastic force and pushes the sliding protective outer tube 7 back down to the shielding position. This stiffness difference design allows the action sequence of the outer tube and the probe body 2 to be naturally separated by mechanical force, avoiding the use of additional push rods and position actuators. This can realize the action sequence of first shielding and then covering the window with soil, improving the feasibility of the device under wet soil and mixed sand and gravel conditions.

[0021] A threaded sealing cap 15 is provided at the bottom of the probe body 2, and the sapphire glass window 3 is fixedly installed on the probe body 2 through the threaded sealing cap 15. As a component that directly contacts the soil and participates in the light path transmission, the sapphire glass window 3 needs to simultaneously meet three requirements: reliable fixation, circumferential sealing, and easy replacement. In this embodiment, a threaded sealing cap 15 is provided at the bottom end of the probe body 2, forming a window mounting cavity at the bottom end of the probe body 2. An annular support shoulder is provided inside the mounting cavity, and the sapphire glass window 3 is placed above the support shoulder. After the cap is screwed into the internal or external thread mating part at the bottom end of the probe body 2, an axial clamping force is applied to the sapphire glass window 3. To prevent stress concentration from causing the edge of the sapphire glass window 3 to crack, a polytetrafluoroethylene gasket, a fluororubber sealing ring, or a thin metal gasket can be placed between the gland and the sapphire glass window 3. The gasket thickness can be 0.1mm to 0.8mm, which serves both to buffer the compression stress and to form a waterproof seal. The gland thread can be a fine thread, with a preferred pitch of 0.5mm to 1.0mm, to obtain higher axial preload accuracy and anti-loosening ability. After installation, the outer surface of the sapphire glass window 3 can be flush with the bottom surface of the probe body 2, or protrude slightly by 0.1mm to 0.5mm. The flush mounting of the window is suitable for reducing mud accumulation at the edges, while the slightly protruding mounting of the window is suitable for prioritizing contact with the soil and reducing the impact of metal parts rubbing against the soil. The threaded sealing cap 15 structure makes the sapphire glass window 3 easy to disassemble and maintain during long-term field use. When the transmittance of the window surface decreases due to long-term friction, the window assembly can be replaced separately without replacing the entire probe body 2, thereby improving the convenience of later maintenance of the equipment and maintaining the consistency of the equipment's spectral acquisition.

[0022] The miniature positive temperature coefficient heating ring 4 has self-limiting temperature characteristics, and the miniature light source 6 is a broadband halogen tungsten miniature lamp bead; In a cold and humid forest environment, the sapphire glass window 3 may form a condensation film within seconds after contacting the highly moist soil. The scattering caused by the condensation will lead to an overall increase in absorbance across the entire wavelength range, affecting the authenticity of the characteristic wavelengths of organic matter and moisture. In this embodiment, a miniature positive temperature coefficient heating ring 4 with self-limiting temperature characteristics is selected. Self-limiting temperature means that the resistance of the heating element increases after the temperature rises, and the current automatically decreases, so as to stabilize it within the set temperature range. The set temperature range can be 45°C to 90°C, preferably 55°C to 75°C; this temperature range can clear condensation induced by the temperature difference between the inside and outside of the window in a short time, while avoiding excessive temperature rise in the window that would cause rapid evaporation of surface soil moisture and change the water content of the measured object itself; the miniature light source 6 is a broadband halogen tungsten miniature lamp bead, which can output a continuous spectrum in the visible to near-infrared range, preferably covering at least a portion of the measurement bands from 400nm to 1700nm or from 450nm to 2500nm; Compared with narrow-band light-emitting devices, broadband halogen tungsten micro-LEDs can provide a uniform illumination basis for the same soil sample, facilitating the simultaneous calculation of absorbance, baseline drift rate, and corrected absorbance for effective spectral analysis across multiple characteristic bands. The micro-positive temperature coefficient heating ring 4, arranged around the multispectral sensor 5 and the micro-light source 6, can form a thermal field distribution that transfers heat from the edge of the sapphire glass window 3 to the center, reducing re-condensation caused by local temperature differences. By combining self-limiting heating with broadband stable illumination, the measurable optical path can be quickly restored during the window self-checking stage, and the repeatability of the reflectance spectral baseline can be maintained.

[0023] The annular cutting edge 8 is set at an acute angle; The bottom end of the sliding protective outer tube 7 is provided with an annular cutting edge 8, which is set at an acute angle to cut through the dead leaf layer, humus layer and loose shallow cover on the forest surface. The acute angle can be understood as the cutting edge forming a blade angle of less than 90°, preferably 25° to 60°. When the blade angle is less than 25°, although it is beneficial for cutting, the blade edge strength is reduced and it is easy to curl after continuous contact with sand and gravel. When the blade angle is greater than 60°, the cutting force increases, and it is easy to push the dead leaves to accumulate rather than cut them in the initial pressing stage. The annular cutting edge 8 can be formed by double chamfering of the outer and inner circumferences of the bottom end of the sliding protective outer tube 7, or by a single-sided chamfer to form a cutting edge structure facing outward or inward. Using the annular cutting edge 8 instead of a flat-bottomed round tube structure is beneficial to increase the pressure on the unit contact line under limited downward pressure, so that the outer tube can enter the covering layer more stably and define the boundary of the measurement area. Since the sliding protective outer tube 7 needs to form a light-shielding space together with the soil surface, the edge contact zone formed after the sharp-angled cutting edge cuts in is approximately line contact distributed, which can reduce the circumferential light leakage gap and increase the probability of establishing a physical darkroom. At the same time, the annular cutting edge 8 can also reduce the overall compression range of the bottom end of the outer tube on the surrounding soil, reduce the damage to the soil surface structure caused by large-area disturbance, and enable the sapphire glass window 3 in the central position to contact the flattened soil surface with a surface flatness that meets the requirements of spectral detection, thereby improving the consistency of repeated spectral measurements.

[0024] Under normal conditions, the second helical spring 10 pushes the sliding protective outer tube 7 downward to its limit position, and the bottom end of the sliding protective outer tube 7 covers and wraps the probe body 2 and the sapphire glass window 3. When the equipment is not in operation or during transportation, the second helical spring 10 is in a released or near-released state and pushes the sliding protective outer tube 7 downward to the limit position. The limit position can be determined by setting a stop surface, a limit ring or a groove between the main housing 1 and the sliding protective outer tube 7. In this position, the bottom end of the sliding protective outer tube 7 extends beyond the bottom end of the probe body 2, and the extension distance can be 3mm to 20mm, thereby shielding and wrapping the probe body 2 and the sapphire glass window 3 in the axial direction. The shielding and wrapping means that the sapphire glass window 3 is not directly exposed to the external space when the device is in a free state, and external sand, branches or hard objects cannot directly collide with the window surface along the axis. This structure can reduce the probability of the window being scratched during field movement, insertion and removal and storage, and can reduce the risk of optical components being impacted by transportation vibration. When the device is pressed down into the forest soil, the bottom end of the sliding protective outer tube 7 contacts the ground first, and the probe body 2 is still located inside the outer tube, thus ensuring that the cutting action is borne by the stronger outer tube. As the main housing 1 continues to move downward, the sliding protective outer tube 7 moves upward relative to it, and the probe body 2 gradually becomes visible and comes into contact with the soil area enclosed by the outer tube. It can be seen that this normal shielding structure is not a simple dust cover, but a basis for establishing continuous mechanical actions of protection before puncture, introduction during puncture, enclosure during measurement, and reset after measurement, so that the optical window is always in a protected state before it actually comes into contact with the soil to be tested. Example

[0025] Please see Figure 4 A method for monitoring forestry soil based on spectral analysis, comprising: S1. Through an external actuator, the annular cutting edge 8 of the sliding protective outer tube 7 cuts through the surface dead leaf layer and abuts against the soil matrix. S2. Control the main housing 1 to continue pressing down and compressing the second helical spring 10, so that the probe body 2 slides down under the constant thrust of the first helical spring 9 until the sapphire glass window 3 flattens the soil surface with constant pressure, so that the inner wall of the sliding protective outer tube 7 and the flattened soil surface form a physical dark chamber. S3. Control the multispectral sensor 5 to continuously collect spectral data at high frequency while the miniature light source 6 is off, extract the sum of energy values ​​of the near-infrared non-characteristic bands in the spectral data, and obtain the leakage index of multiple consecutive collections. S4. Obtain the preset sealing threshold and determine whether the leakage index of multiple consecutive acquisitions is less than the preset sealing threshold. If it is less than the preset sealing threshold, proceed to step S5. If there is a leakage index greater than or equal to the preset sealing threshold, terminate the current effective spectrum acquisition or send a signal to change the measurement point. S5. Control the micro light source 6 to light up, control the multispectral sensor 5 to collect the full-band reflectance spectrum, extract the absorbance of the preset reference band and calculate the baseline drift rate. S6. Obtain the preset cleanliness threshold and determine whether the baseline drift rate is greater than the preset cleanliness threshold. If it is greater than the preset cleanliness threshold, control the micro positive temperature coefficient heating ring 4 to be powered on to heat the sapphire glass window 3 and continuously monitor the baseline drift rate. When the baseline drift rate is less than or equal to the preset cleanliness threshold, control the heating to stop and execute step S7. If the baseline drift rate is less than or equal to the preset cleanliness threshold, execute step S7. S7. Control the multispectral sensor 5 to collect effective soil spectral data, and obtain the corrected absorbance based on the absorbance of the preset organic matter characteristic band and the absorbance of the preset water characteristic band. S8. Obtain the true soil organic matter content based on the corrected absorbance and the pre-calibrated forest soil conversion coefficient; This embodiment performs in-situ measurement of soil organic matter based on the aforementioned equipment; in step S1, the operator or electric pressing mechanism presses the equipment toward the forest surface in an approximately vertical direction, the annular cutting edge 8 first contacts the dead leaf layer and cuts the cover until the bottom end of the sliding protective outer tube 7 abuts against the soil matrix; here the soil matrix refers to the soil surface that can provide mechanical support after the loose cover is removed. In step S2, the main housing 1 continues to press down, the second helical spring 10 is compressed, the sliding protective outer tube 7 moves upward relative to the main housing 1, and the probe body 2 slides downward under the axial thrust provided by the first helical spring 9. When the sapphire glass window 3 contacts the soil, it applies continuous and constant pressure to the local soil surface, flattening the uneven microstructure. After flattening, the inner wall of the sliding protective outer tube 7 and the flattened soil surface together form a locally enclosed space, which is defined as a physical darkroom in this paper. This physical darkroom is not an independent housing, but is composed of the mechanical enclosure boundary and the solid soil surface boundary. Its function is to reduce the external scattered light entering the measurement optical path. In step S3, the controller 11 keeps the miniature light source 6 off, and only the multispectral sensor 5 continuously samples at a frequency of 20Hz to 200Hz. The sampled light signal mainly comes from ambient light leaking in from the outside. The controller 11 extracts the signal intensity of the near-infrared non-characteristic band and sums them to obtain the light leakage index. The near-infrared non-characteristic band can be selected as several discrete bands whose absorption coefficient of the main chemical components of the soil is lower than a set threshold and whose response characteristics to ambient stray light are significant. The purpose is to use the background energy change to characterize the degree of sealing of the physical darkroom. Preferably, the controller 11 pre-stores several candidate discrete bands, and during the factory calibration or first-time use calibration of the device, first records the dark noise baseline value of each candidate band under complete light blocking conditions, and then records the light leakage response value of each candidate band under standard ambient light. From these bands, the bands whose response rate to stray light changes is greater than the preset screening threshold and are not sensitive to the absorption characteristics of soil components are selected as near-infrared non-characteristic bands. The processing flow of step S3 can be executed in the following order: read the original digital values ​​of each sampling point in the near-infrared non-characteristic band of the multispectral sensor 5; subtract the dark noise base value of the corresponding band to obtain the effective background energy; accumulate the effective background energy of each band in the same sampling to obtain a light leakage index L; form the corresponding light leakage index sequence by sampling multiple times consecutively; the physical meaning of the light leakage index is the total background energy formed by the leakage of external ambient light in the physical dark room. The larger the value, the more obvious the light leakage caused by circumferential gaps, poor soil adhesion, or tilting posture. In step S4, the controller 11 compares the light leakage index measured multiple times with the preset sealing threshold. If all values ​​are less than the threshold, it indicates that the external stray light has been effectively blocked, and the mechanical stress state indicates that the sapphire glass window 3 is in a relatively stable soil-adhering state. If the threshold requirement is not met, it indicates that there is still circumferential light leakage, external pipe tilting, or insufficient soil adhesion, and the subsequent effective measurement will not proceed. The preset sealing threshold is used to distinguish between acceptable sealing conditions and unacceptable light leakage conditions. The method for determining it can be as follows: Under standard light-shielding fixtures, a set of light leakage indices is collected as the upper limit of the sealing reference. The standard light-shielding fixtures are sealed covers with light-absorbing layers on the inner wall that can completely cover the bottom of the probe. Then, under the condition of artificially leaving circumferential micro-slits, another set of light leakage indices is collected as the lower limit of the failure reference. The value that can stably distinguish between the two states is selected between the two sets of data as the threshold. Alternatively, threshold tables can be established according to forest area types and stored in controller 11, which can be selected and called by operators on site. In step S5, after confirming that the darkroom is sealed, the miniature light source 6 is lit, the multispectral sensor 5 collects the full-band reflectance spectrum, and extracts the absorbance on the set reference band; the reference band is a band that is not sensitive to the absorption of the target chemical component and is used to observe the overall baseline change; the controller 11 calculates the baseline drift rate based on the difference between the absorbance of the reference band and the pre-stored reference value. In step S6, when the baseline drift rate is higher than the cleanliness threshold, it is determined that there is condensation or water film scattering on the window surface. The micro positive temperature coefficient heating ring 4 is energized to heat the sapphire glass window 3, and the reference band data is repeatedly collected at a set period until the baseline drift rate drops below the cleanliness threshold. The logical function of the preset cleanliness threshold is to distinguish between the clean and measurable state of the window and the state of scattering pollution. The determination method can be as follows: record the range of absorbance fluctuation of the reference band under clean window conditions, and take the upper boundary of the fluctuation range and add a safety margin to form the threshold. For high humidity forest land, scattering data can also be collected under artificial condensation conditions, and the boundary value between clean data and condensation data can be used as the threshold. In step S7, after the darkroom is sealed and the window is clean, the effective soil reflectance spectrum is collected, and the absorbance Aom (organic matter characteristic band) and Aw (moisture characteristic band) are extracted. The net absorbance Anet is calculated, with the relationship that Anet equals Aom minus Aw. Then, the corrected absorbance Ac is calculated, with the relationship that Ac equals Anet divided by Aw. If Aw is lower than the set lower limit, for example, lower than 0.01 absorbance units, the lower limit can be used as a substitute value to avoid calculation fluctuations caused by an excessively small divisor. Here, the net absorbance is used to deduct the spectral line rise component caused by moisture from the organic matter response, and the corrected absorbance is used to further reduce the impact of the overall change in reflectance under different water contents on the estimation of organic matter. In step S8, the corrected absorbance Ac is multiplied by the pre-calibrated forest soil conversion coefficient K to obtain the true soil organic matter content C. The calculation relationship is that C equals K multiplied by Ac. The conversion coefficient K can be obtained by laboratory chemical determination and corresponding spectral calibration of representative soil samples from the target forest area. Corresponding coefficient libraries can be established for different tree species areas and different parent material areas. The physical meaning of the conversion coefficient K is to map the dimensionless corrected absorbance to the proportional parameter of soil organic matter content. Its source is not real-time calculation, but rather a priori calibration. The calibration process can be as follows: First, collect multiple representative soil samples from the target forest area and obtain the corresponding corrected absorbance simultaneously. Then, perform laboratory organic matter content determination on the same batch of soil samples. Determine K based on the correspondence between the laboratory results and the corrected absorbance. For example, use the least squares method to perform linear fitting to calculate the K value, and write K into the device memory for on-site retrieval. The above process of converting content through corrected absorbance essentially constitutes a preset model for soil organic matter spectral inversion. The purpose of this model is to accurately estimate the organic matter content of the soil under non-destructive in-situ conditions in the field. In terms of logical structure, the model receives the absorbance of the organic matter characteristic band and the absorbance of the water characteristic band as input data streams. Internally, it executes water decoupling logic to generate the corrected absorbance, multiplies and maps it with the pre-stored forest soil conversion coefficient, and finally outputs the true soil organic matter content. To clearly illustrate the data flow in this process, a quantitative derivation example is provided: Assume that in a single measurement, the multispectral sensor 5 extracts an absorbance Aom of 0.45 for the organic matter characteristic band and an absorbance Aw of 0.15 for the moisture characteristic band; the controller 11 internally calculates the net absorbance Anet, which equals 0.45 minus 0.15, equaling 0.30; further normalization calculation yields the corrected absorbance Ac, which equals 0.30 divided by 0.15, equaling 2.0; if the pre-calibrated conversion coefficient K retrieved from the device's memory is 15.5 g / kg, then the final output of the true soil organic matter content C is 31.0 g / kg; This model comprehensively characterizes the physical causal relationship between the characteristic absorption degree of organic matter molecules to specific wavelength light energy and the overall reflectivity of the soil when photons undergo multiple scattering and absorption between soil particles, as well as the modulation effect of soil moisture on this absorption process. This method uses three types of processing—mechanical shading, window self-checking, and water decoupling—to establish organic matter inversion on a more stable physical input basis, reducing calculation errors caused by stray light, condensation, and water content fluctuations. To verify the above-mentioned beneficial effects, a comparative experiment was conducted in a typical high-humidity red soil forest: using the traditional spectral measurement method without water decoupling and darkroom self-testing, the root mean square error of organic matter inversion was 4.2 g / kg; while using the method of the present invention, the root mean square error of inversion in the same measurement area was reduced to 1.8 g / kg. The data fully demonstrate that the method significantly suppresses the interference of water content fluctuations and stray light on the accuracy of spectral inversion.

[0026] Multiple consecutive data collections are considered as three consecutive data collections; in step S4, if there is a light leakage index greater than or equal to the preset sealing threshold, it is determined that a hard tree root or large rock has caused the mechanical structure to tilt and leak light, and the control will issue a prompt signal to replace the measuring point. In forest soil, tree roots, gravel, and local hardening can cause uneven cutting of the sliding protective outer tube 7, resulting in gaps at the edge of the physical darkroom. To improve the clarity and enforceability of the judgment rules, this embodiment limits the continuous multiple sampling to three consecutive samplings. The three consecutive samplings can be completed within 0.05s to 0.5s under the same pressing state, with the sampling frequency and integration time remaining consistent each time. The controller 11 only considers the darkroom sealed when all three light leakage indices are less than the preset sealing threshold. Using a three-step judgment process instead of a single judgment can reduce the impact of instantaneous sensor noise, minor posture jitter, and occasional external light flicker on the results. If the light leakage index in any of the three steps is greater than or equal to the preset sealing threshold, the controller 11 determines that the physical darkroom is not sealed. Combined with the displacement or force changes during the mechanical pressing process, the cause is further identified as light leakage due to the tilt of the mechanical structure caused by hard tree roots or large rocks. Here, tilting light leakage refers to the uneven circumferential contact between the bottom edge of the sliding protective outer tube 7 and the soil, causing external ambient light to enter the enclosed space along the gap. To ensure that the judgment process has clear logical judgment steps, the controller 11 can perform the identification according to the following logic: read whether there is a result exceeding the threshold among the three light leakage indices; read the displacement change or force change obtained synchronously with the pressing action; and determine whether there is a state where the displacement increment decreases significantly while the force increases rapidly, or the displacement continues to increase but the light leakage index does not decrease when pressing continues. The aforementioned first state characterization indicates that there is a hard obstacle blocking the probe from cutting in. The corresponding quantitative judgment logic is as follows: the controller 11 reads the displacement sensor and pressure sensor data on the external actuator connected to the device, calculates the displacement increment and force increment of adjacent sampling periods, and determines this state when the displacement increment is less than the preset displacement stagnation threshold and the force increment is greater than the preset force surge threshold; wherein, the displacement stagnation threshold and the force surge threshold are obtained in advance based on the compressive strength of typical obstacles in the target forest area and the soil cutting resistance. If any of the above states and light leakage exceeding the threshold occur simultaneously, the cause of the unsealed area can be preferentially classified as light leakage due to mechanical structure tilt caused by hard tree roots or large rocks. The above-mentioned anomaly identification process based on light leakage index, displacement, and force changes constitutes a mechanical puncture anomaly judgment logic model inside the controller 11. The purpose of this model is to accurately identify and distinguish the specific physical causes of darkroom sealing failure without the intervention of visual sensors. Logically, the model receives multiple consecutive light leakage index, displacement change, and force change as parallel input data. By comparing the light leakage index with the sealing threshold and combining the change rate characteristics of displacement and force, it outputs the anomaly type identification result. This model characterizes the dynamic coupling physical relationship between the external soil reaction force, probe displacement and circumferential shading performance when the mechanical probe penetrates heterogeneous forest soil. The logic function of changing the measurement point signal is to terminate the current invalid measurement and prevent further entry into the heating and composition inversion steps. The controller 11 can issue a change measurement point signal through sound signal, indicator light flashing or text display, prompting the operator to re-press the probe within a range of 10cm to 50cm from the original measurement point. Preferably, before issuing a prompt, the controller 11 can also record the three light leakage indices and the corresponding displacement or stress state as a field measurement log for subsequent optimization of the sealing threshold and pressure strategy. This processing method intercepts invalid measurements before heating and composition inversion, avoids incorrect analysis of the reflection spectrum collected under light leakage conditions, and also avoids increased power consumption due to repeated heating and repeated sampling.

[0027] In step S5, the reference band is the non-water absorption characteristic reference band; in step S6, when the micro positive temperature coefficient heating ring 4 is energized to heat the sapphire glass window 3, the surface temperature of the sapphire glass window 3 is controlled to be higher than the soil ambient temperature. To ensure that the condensation determination at the window has a clear spectral basis, this embodiment limits the reference band in step S5 to a non-water absorption characteristic reference band. The non-water absorption characteristic reference band refers to the band region that avoids strong water absorption peaks and has little impact on the inversion of soil organic matter targets. For example, one or more narrow band regions can be selected from 850nm to 950nm, 1050nm to 1150nm, or other bands that have been calibrated and confirmed not to be the main characteristic absorption band of water. After the micro light source 6 is lit, the controller 11 records the real-time absorbance Ar of the reference band and compares it with the factory calibration value A0 or the baseline value under the current clean window conditions to calculate the baseline drift rate R. The baseline drift rate R can be calculated as a relative change rate, that is, R is equal to Ar minus A0 and then divided by the absolute value of A0. If calculated using the absolute difference method, it is defined as the baseline drift amount D, that is, the baseline drift amount D is equal to the absolute value of the difference between Ar and A0; the baseline drift rate is used in this invention specifically to characterize the overall spectral shift caused by the condensation on the outside of the sapphire glass window 3 to scatter the light path, rather than to represent the aging of the light source or the zero-point drift of the detector. The reason is that after condensation forms, it will cause changes in reflection and transmission conditions in multiple bands simultaneously, causing an overall shift in the full-spectrum baseline. This shift can be quantitatively reflected by extracting the absorbance of the reference band. To make the judgment process clearer, step S5 can be implemented in the following order: First, the controller 11 lights up the miniature light source 6 and waits for a preset stabilization time to allow the light source output to enter a stable state; then, the multispectral sensor 5 collects the original reflection signal of the non-water absorption characteristic reference band; the original reflection signal is converted into the absorbance Ar of the reference band; Ar is compared with the reference value A0 to obtain the baseline drift rate R, and R is transmitted to step S6 as the judgment input for whether to start heating. The reference value A0 can be the calibration value obtained at the factory under clean window and standard reflection reference conditions, or it can be the current reference value saved when the window is first confirmed to be clean on site. If the on-site reference value is used, the controller 11 can prioritize calling the most recently confirmed valid A0 within the clean threshold to reduce the impact of background reflection differences in different forest areas on the judgment. In step S6, when R is greater than the preset cleanliness threshold, the controller 11 supplies power to the miniature positive temperature coefficient heating ring 4. The heat is transferred to the window surface through the heating ring, the bottom structure of the probe body 2, and the sapphire glass window 3, making the window surface temperature higher than the soil ambient temperature. The temperature difference can be set from 1°C to 8°C, preferably from 2°C to 5°C. This temperature difference can destroy the local saturation conditions required for condensation formation, causing the attached water film to evaporate or become unstable. The preset cleanliness threshold represents the maximum baseline offset allowed by the reference band, and its logical function is to distinguish between acceptable and unacceptable window scattering. The threshold can be determined as follows: First, under clean window conditions, the absorbance of the reference band is repeatedly collected to obtain the natural fluctuation range; then, under artificially formed mist-like condensation conditions, the corresponding drift data is collected; the boundary value that can simultaneously avoid the upper limit of clean fluctuation and effectively identify the condensation state is selected as the preset clean threshold; during the heating process, the controller 11 repeatedly collects the reference band data at intervals of 0.2s to 2s and recalculates R. When R drops below the cleanliness threshold, it is determined that the scattering source has been basically eliminated, and heating is immediately stopped to avoid continuous temperature rise from changing the surface water content of the soil. The above heating and dew removal control process runs on a thermal dew removal control logic model. The purpose of this model is to accurately and quickly eliminate condensation scattering sources on the surface of the optical window without disturbing the soil's moisture content. In terms of logic structure, the model uses the baseline drift rate calculated from the non-water absorption characteristic reference band as feedback input to determine whether to trigger a heating command. At the same time, combined with the self-limiting temperature characteristics of the micro positive temperature coefficient heating ring 4, it outputs adaptive thermal energy. This model characterizes the complete thermodynamic causal relationship of heat generation from inside the heating ring, conduction through the bottom structure of the probe body 2, and finally heat exchange between the surface of the sapphire glass window 3 and the external condensate film, changing the local saturated vapor pressure of water vapor and promoting the phase change evaporation of the water film. To further illustrate the data flow and executability of this thermal decondensation control logic model, the following quantitative derivation example is provided: Assuming the factory cleanliness baseline value A0 of the equipment in the 850nm non-water absorption characteristic reference band is 0.12, and the preset cleanliness threshold is set to 15%; When the high humidity environment of the woodland causes condensation to form on the outside of the window, the real-time absorbance Ar rises to 0.16. The controller 11 calculates the baseline drift rate R to be 33.3%, which is greater than 15%, and immediately triggers a heating command. After the miniature positive temperature coefficient heating ring 4 is powered on, the controller 11 collects Ar every 1 second. When Ar drops to 0.13, the recalculated baseline drift rate R becomes 8.3%, which is less than 15%. The controller 11 determines that the scattering source has been eliminated and then issues a stop heating command. Comparative experiments have verified that in forest environments with relative humidity above 95%, the baseline drift rate of traditional windows without heating components will remain above 25%, resulting in severe distortion of the subsequent spectrum. However, the self-limiting temperature heating control logic of this embodiment can stabilize the baseline drift rate below the cleanliness threshold within 30 seconds after power-on, effectively restoring the measurable optical path. Preferably, after stopping heating, the controller 11 can perform a reference band retest. If the retest result is still within the cleanliness threshold, it will switch to effective soil spectrum acquisition. If the retest result exceeds the threshold again, it will re-enter the short-term heating and retest cycle. By limiting the reference band to a non-water absorption characteristic reference band and explicitly using the baseline drift rate to characterize the overall translation caused by condensate scattering, this embodiment can distinguish between the window cleanliness status judgment and the chemical absorption changes of the soil itself, thereby improving the targeting of heating intervention timing and exit conditions.

[0028] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A forestry soil monitoring device based on spectral analysis, characterized in that, include: The main shell (1) is a hollow tubular structure; The probe body (2) is coaxially slidably installed in the inner cavity of the main housing (1). A sapphire glass window (3) is fixedly installed at the bottom of the probe body (2). A miniature positive temperature coefficient heating ring (4) is provided inside the probe body (2) and attached to the inner side of the sapphire glass window (3). A multispectral sensor (5) and a miniature light source (6) are arranged in the central area of ​​the miniature positive temperature coefficient heating ring (4). A sliding protective outer tube (7) is coaxially sleeved outside the main housing (1). The bottom end of the sliding protective outer tube (7) is machined with an annular cutting edge (8). A limit structure is provided between the main housing (1) and the sliding protective outer tube (7) to limit the extreme position of the sliding protective outer tube (7) under the action of thrust. The first helical spring (9) is connected between the top of the probe body (2) and the top of the inner cavity of the main housing (1); The second helical spring (10) is connected between the bottom of the outer wall of the main housing (1) and the top of the inner wall of the sliding protective outer tube (7); The controller (11) is connected to control the multispectral sensor (5), the miniature light source (6), and the miniature positive temperature coefficient heating ring (4).

2. The forestry soil monitoring equipment for spectral analysis according to claim 1, characterized in that, The outer wall of the probe body (2) and the inner wall of the main housing (1) are fitted with a clearance. A flange (12) is provided at the top of the probe body (2). The first helical spring (9) is compressed and installed between the flange (12) and the top of the inner cavity of the main housing (1).

3. The forestry soil monitoring equipment for spectral analysis according to claim 1, characterized in that, The bottom of the outer wall of the main housing (1) is provided with a boss (13), and the top of the inner wall of the sliding protective outer tube (7) is provided with a step (14). The second helical spring (10) is compressed and installed between the boss (13) and the step (14), wherein the stiffness coefficient of the second helical spring (10) is greater than that of the first helical spring (9).

4. The forestry soil monitoring equipment for spectral analysis according to claim 1, characterized in that, The probe body (2) is provided with a threaded sealing cap (15) at the bottom end, and the sapphire glass window (3) is fixedly installed on the probe body (2) through the threaded sealing cap (15).

5. The forestry soil monitoring equipment for spectral analysis according to claim 1, characterized in that, The micro positive temperature coefficient heating ring (4) has self-limiting temperature characteristics, and the micro light source (6) is a broadband halogen tungsten micro lamp bead.

6. The forestry soil monitoring equipment for spectral analysis according to claim 1, characterized in that, The annular cutting edge (8) is set at an acute angle.

7. The forestry soil monitoring equipment for spectral analysis according to claim 1, characterized in that, Under normal conditions, the second helical spring (10) pushes the sliding protective outer tube (7) downward to its limit position, and the bottom end of the sliding protective outer tube (7) covers and wraps the probe body (2) and the sapphire glass window (3).

8. A method for monitoring forestry soil based on spectral analysis, applied to the spectral analysis-based forestry soil monitoring equipment described in claim 1, characterized in that, include: S1. Through the external actuator, the annular cutting edge (8) of the sliding protective outer tube (7) cuts through the surface dead leaf layer and abuts against the soil matrix; S2. Control the main housing (1) to continue pressing down and compressing the second helical spring (10), so that the probe body (2) slides down under the constant thrust of the first helical spring (9) until the sapphire glass window (3) flattens the soil surface with constant pressure, so that the inner wall of the sliding protective outer tube (7) and the flattened soil surface form a physical dark chamber. S3. Control the multispectral sensor (5) to continuously collect spectral data at high frequency while the micro light source (6) is off, extract the sum of energy values ​​of the near-infrared non-characteristic bands in the spectral data, and obtain the leakage index of multiple consecutive collections. S4. Obtain the preset sealing threshold and determine whether the leakage index of multiple consecutive acquisitions is less than the preset sealing threshold. If it is less than the preset sealing threshold, proceed to step S5. If there is a leakage index greater than or equal to the preset sealing threshold, terminate the current effective spectrum acquisition or send a signal to change the measurement point. S5. Control the micro light source (6) to light up, control the multispectral sensor (5) to collect the full-band reflection spectrum, extract the absorbance of the preset reference band and calculate the baseline drift rate; S6. Obtain the preset cleanliness threshold and determine whether the baseline drift rate is greater than the preset cleanliness threshold. If the baseline drift rate is greater than the preset cleanliness threshold, the micro positive temperature coefficient heating ring (4) is powered on to heat the sapphire glass window (3), and the baseline drift rate is continuously monitored. When the baseline drift rate is less than or equal to the preset cleanliness threshold, the heating is stopped and step S7 is executed. If the baseline drift rate is less than or equal to the preset cleanliness threshold, step S7 is executed. S7. Control the multispectral sensor (5) to collect effective soil spectral data, and obtain the corrected absorbance based on the absorbance of the preset organic matter characteristic band and the absorbance of the preset water characteristic band. S8. Obtain the true soil organic matter content based on the corrected absorbance and the pre-calibrated forest soil conversion coefficient.

9. The method for monitoring forestry soil using spectral analysis according to claim 8, characterized in that, The continuous multiple acquisitions refer to three consecutive acquisitions; in step S4, if there is a light leakage index greater than or equal to the preset sealing threshold, it is determined that a hard tree root or large rock has caused the mechanical structure to tilt and leak light, and the control sends a prompt signal to replace the measuring point.

10. The method for monitoring forestry soil by spectral analysis according to claim 8, characterized in that, In step S5, the reference band is a non-water absorption characteristic reference band; in step S6, when the micro positive temperature coefficient heating ring (4) is powered on to heat the sapphire glass window (3), the surface temperature of the sapphire glass window (3) is controlled to be higher than the soil ambient temperature.

Images