Device and method for observing rainfall interception and evaporation of forest litter

Abstract

The device and method for observing the interception of rainfall and evaporation of forest litter of the present invention, wherein the observation device includes an observation tray and a self-counting rain gauge, a filter is provided inside the observation tray, and a flow guide hole is provided on the bottom plate inside the observation tray, and the flow guide hole is connected to the leakage water observation tube through a water guide pipe. The observation method of the present invention includes: step one, determining the installation position of the device for observing the interception of rainfall and evaporation of forest litter; step two, installing the device for observing the interception of rainfall and evaporation of forest litter and determining the initial parameters; step three, observing the interception of rainfall and evaporation of forest litter; step four, calculating the interception of rainfall and water evaporation of litter. The technical scheme of the present invention can observe the interception of rainfall of forest litter and the evaporation of water of litter after the end of rainfall, and the measured interception of litter and water evaporation are more accurate; at the same time, long-term continuous dynamic observation can also be carried out, providing a scientific reference for more objective evaluation of hydrological and ecological functions such as the water conservation function of forests.

Description

Technical Field

[0001] The invention relates to the field of testing by means of measuring the physical properties of materials, and in particular to a device and method for observing the interception of rainfall and evaporation of forest litter. Background Art

[0002] The forest litter layer is an important carrier of the ecological hydrological cycle, and plays an important ecological function in intercepting rainfall, preventing soil erosion, and improving soil structure. Part of the precipitation intercepted by the forest litter layer infiltrates into the soil layer, and part is lost to the surrounding environment through evaporation. Therefore, the forest litter layer plays an important role in regulating the hydrological cycle, thereby affecting the forest hydrological ecological process.

[0003] At present, in the study of forest litter interception rainfall, the maximum interception capacity of litter is mostly obtained through laboratory simulation, while in field observation experiments, the dynamics of interception precipitation of forest litter layer is mostly estimated by measuring the dynamics of litter moisture content. Because the structure of litter is destroyed, there are large errors in the measured structure, and it is difficult to observe long-term stable. In the observation of water evaporation of litter layer, the soil layer and litter layer are currently taken as a whole, and the evaporation of soil under the forest is measured by lysimeter method. It is impossible to know the dynamics of interception precipitation and water evaporation of litter layer and its role in the eco-hydrological cycle. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a device and method for observing rainfall interception and evaporation of forest litter, which can carry out dynamic observation of rainfall interception and evaporation of forest litter, so as to clarify the role of forest litter layer in forest hydrological process.

[0005] The device for observing rainfall interception and evaporation of forest litter of the present invention comprises an observation tray for receiving forest litter and precipitation intercepted by forest litter, and also comprises a self-counting rain gauge arranged next to the observation tray, wherein a filter for receiving forest litter is arranged inside the observation tray, and a bottom plate inside the observation tray is provided with diversion holes for outflow of precipitation intercepted by forest litter, and the diversion holes are connected to the leakage water observation cylinder through a water guide pipe.

[0006] The forest litter rainfall interception and evaporation observation device of the present invention comprises the following steps: the filter is detachably arranged inside the observation tray, and a weighing sensor is arranged at the bottom of the filter.

[0007] The device for observing rainfall interception and evaporation of forest litter of the present invention comprises a shielding net disposed above the observation tray.

[0008] The device for observing rainfall interception and evaporation of forest litter of the present invention also comprises a data collector, and a weighing sensor, a self-counting rain gauge and a leakage water observation tube are respectively connected to the data collector.

[0009] The device for observing rainfall interception and evaporation of forest litter of the present invention further comprises a bracket for supporting an observation tray.

[0010] The forest litter rainfall interception and evaporation observation device of the present invention, wherein the observation tray includes a prismatic receiving portion and a pyramidal drainage portion, the tip of the drainage portion is downward, the guide hole is arranged at the tip of the drainage portion, and the filter is arranged between the receiving portion and the drainage portion.

[0011] The method for observing rainfall interception and evaporation of forest litter of the present invention comprises:

[0012] Step 1: Determine the installation location of the forest litter rainfall interception and evaporation observation device;

[0013] Step 2: installing the forest litter rainfall interception and evaporation observation device according to any one of claims 1 to 6 and determining the initial parameters;

[0014] Step 3: Observation of rainfall interception and evaporation of forest litter;

[0015] Step 4: Calculate the rainfall interception and water evaporation of litter.

[0016] The method for observing rainfall interception and evaporation of forest litter of the present invention, wherein the step 1 comprises: starting from the four corners of the observation plot, setting installation positions at 1 / 4, 1 / 2, and 3 / 4 positions along the diagonal, and setting at least 6 observation sites for each observation plot;

[0017] The step 2 comprises: installing the forest litter rainfall interception and evaporation observation device according to any one of claims 1 to 6 at the installation position, measuring the size of the observation tray after the installation, determining the initial mass of the filter, sampling the forest litter according to the undecomposed layer and the semi-decomposed layer, placing the sampled forest litter on the filter, taking part of the litter to determine the moisture content of the litter, and determining the dry weight of the litter in the undecomposed layer and the dry weight of the litter in the semi-decomposed layer;

[0018] The step three comprises: setting parameters of the forest litter rainfall interception and evaporation observation device, connecting the self-counting rain gauge and the leakage water observation tube to the power supply, the self-counting time frequency is 1 time / 30 minutes, the self-counting frequency of the weighing sensor data is also set to 1 time / 30 minutes, and the parameters automatically measured include: precipitation, litter water leakage and dynamic changes in litter quality;

[0019] The step 4 includes: estimating rainfall interception and water evaporation based on continuous observation data, the area of ​​the observation tray is A, the measured mass of litter on the previous day is M1, the mass measured on the next day is M2, the initial dry weight of litter is M0, and the change of water volume per unit area of ​​litter in the observation tray is ΔS:

[0020] △S=(M2-M1) / A,

[0021] If the evaporation E≈0 when rainfall occurs, the mass change of the litter layer is assumed to be the precipitation interception of the litter. According to the total amount of throughfall in the forest, P=△S+seepage L+evaporation E,

[0022] △S=PL,

[0023] The total amount of throughfall in the forest P is calculated based on the arithmetic mean of the observations from the self-counting rain gauge, and the amount of seepage L is calculated based on the observations from the seepage water observation tube;

[0024] After the rain stops, P=0, △S+L+E=0,

[0025] If there is still water leakage after the rainfall ends, assuming that the evaporation is approximately 0, the rainfall interception of a rainfall event is estimated according to the water balance principle. When there is no rainfall and no water leakage, P = 0, L = 0, and the evaporation is the water loss of litter:

[0026] E=-△S.

[0027] The technical solution of the present invention proposes a device and method for observing rainfall interception and evaporation of forest litter, which can observe the intercepted rainfall of forest litter and the evaporation of litter water after the end of rainfall. The measured litter interception and water evaporation are more accurate and the method is simpler; at the same time, long-term continuous dynamic observation can be carried out; dynamic monitoring of rainfall interception and water evaporation of forest litter can more comprehensively understand the role of forest litter in the forest hydrological cycle, and provide a scientific reference for more objective evaluation of hydrological ecological functions such as forest water conservation function. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a main cross-sectional view of the structural schematic diagram of the device for observing rainfall interception and evaporation of forest litter of the present invention;

[0029] Figure 2 It is a top view of the observation tray and the self-counting rain gauge;

[0030] Figure 3 This is a bottom view of the filter. DETAILED DESCRIPTION

[0031] According to the principle of water balance, the total amount of throughfall in the forest (P) should be equal to the sum of the water change in the forest litter layer (△S), the seepage (L), and the evaporation (E).

[0032] That is, P = △S + L + E,

[0033] When rainfall occurs, the relative humidity of the air in the forest is very high and there is no solar radiation. Therefore, it can be approximated that there is no evaporation or it is infinitesimal, that is, E≈0. Therefore, the water balance formula can be simplified to △S=PL, where △S is the interception of rainfall by forest litter.

[0034] When there is no rainfall process, the rainfall input is zero, and the water leakage L of the litter layer can be approximately assumed to be zero. According to the water balance formula, E=△S, the change in the water volume of the litter layer at this time is mainly evaporation loss.

[0035] like Figure 1 , Figure 2 , Figure 3 As shown, the forest litter rainfall interception and evaporation observation device of the present invention includes an observation tray 1 for receiving forest litter and precipitation intercepted by forest litter, and also includes a self-counting rain gauge 2 arranged next to the observation tray, the interior of the observation tray is provided with a filter 3 for receiving forest litter, the bottom plate inside the observation tray is provided with diversion holes 4 for outflow of precipitation intercepted by forest litter, and the diversion holes are connected to the leakage water observation tube 6 through a water guide pipe 5.

[0036] In the device for observing rainfall interception and evaporation of forest litter of the present invention, the filter 3 is detachably arranged inside the observation tray, and a weighing sensor 7 is arranged at the bottom of the filter.

[0037] In the device for observing rainfall interception and evaporation of forest litter of the present invention, a shielding net 8 is arranged above the observation tray 1 .

[0038] The device for observing rainfall interception and evaporation of forest litter of the present invention further comprises a data collector, and the weighing sensor 7, the self-counting rain gauge 2 and the leakage water observation tube 6 are respectively connected to the data collector.

[0039] The device for observing rainfall interception and evaporation of forest litter of the present invention further comprises a bracket 9 for supporting an observation tray.

[0040] The forest litter rainfall interception and evaporation observation device of the present invention, wherein the observation tray 1 includes a prismatic receiving portion 11 and a pyramidal drainage portion 12, the tip of the drainage portion 12 is downward, the guide hole 4 is arranged at the tip of the drainage portion, and the filter is arranged between the receiving portion and the drainage portion.

[0041] The method for observing rainfall interception and evaporation of forest litter of the present invention comprises:

[0042] Step 1: Determine the installation location of the forest litter rainfall interception and evaporation observation device;

[0043] Step 2: installing the forest litter rainfall interception and evaporation observation device according to any one of claims 1 to 6 and determining the initial parameters;

[0044] Step 3: Observation of rainfall interception and evaporation of forest litter;

[0045] Step 4: Calculate the rainfall interception and water evaporation of litter.

[0046] The method for observing rainfall interception and evaporation of forest litter of the present invention comprises:

[0047] Step 1: Determine the installation location of the forest litter rainfall interception and evaporation observation device: starting from the four corners of the observation plot, set the installation locations at 1 / 4, 1 / 2, and 3 / 4 along the diagonal, and set at least 6 observation sites for each observation plot;

[0048] Step 2, installing the forest litter rainfall interception and evaporation observation device and determining initial parameters: installing the forest litter rainfall interception and evaporation observation device of the present invention at the installation position, after the installation is completed, measuring the size of the observation tray, determining the initial mass of the filter, sampling the forest litter according to the undecomposed layer and the semi-decomposed layer, placing the sampled forest litter on the filter, taking part of the litter to determine the moisture content of the litter, and determining the dry weight of the litter in the undecomposed layer and the dry weight of the litter in the semi-decomposed layer;

[0049] Step 3, observation of rainfall interception and evaporation of forest litter: set the parameters of the device for observing rainfall interception and evaporation of forest litter, connect the self-counting rain gauge and the leakage water observation tube to the power supply, set the self-counting time frequency to 1 time / 30min, and the self-counting frequency of the weighing sensor data to 1 time / 30min. The parameters automatically measured include: dynamic changes of precipitation, water leakage of litter and litter quality;

[0050] Step 4: Calculate the rainfall interception and water evaporation of litter: Based on the continuous observation data, estimate the rainfall interception and water evaporation. The area of ​​the observation tray is A, the mass of litter measured on the previous day is M1, the mass measured on the next day is M2, and the initial dry weight of litter is M0. According to the water balance theory, the change in water volume per unit area of ​​litter in the observation tray is △S:

[0051] △S=(M2-M1) / A,

[0052] If rainfall occurs, the evaporation is very small, and the approximate evaporation E≈0. At this time, the mass change of the litter layer can be considered as the precipitation interception of the litter. According to the total amount of throughfall in the forest P=△S+leakage L+evaporation E,

[0053] △S=PL,

[0054] The total amount of throughfall in the forest P is calculated based on the arithmetic mean of the observations from the self-counting rain gauge, and the amount of seepage L is calculated based on the observations from the seepage water observation tube;

[0055] After the rainfall ends, due to the time lag, no precipitation occurs, that is, P = 0. According to the water balance principle, △S + L + E = 0 at this time.

[0056] If there is still water leakage after the rainfall ends, assuming that the evaporation is approximately 0, the rainfall interception of a rainfall event is estimated according to the water balance principle. When there is no rainfall and no water leakage, P = 0, L = 0, and the evaporation is the water loss of litter:

[0057] E=-△S.

[0058] The technical solution of the present invention can carry out dynamic observation of rainfall interception and evaporation of forest litter, so as to clarify the role of the forest litter layer in the forest hydrological process.

[0059] In the forest litter rainfall interception and evaporation observation device of the present invention, the self-counting rain gauge 2 is located around the observation tray 1. The self-counting rain gauge 2 can be provided in multiple numbers, such as 4, 6, 8 or 12. In this embodiment, 4 self-counting rain gauges 2 are provided, and the 4 self-counting rain gauges 2 are respectively located around the observation tray 1. The observation value of the self-counting rain gauge can be the arithmetic average of the observation values ​​of the 4 self-counting rain gauges 2.

[0060] The height of the collection port of the self-counting rain gauge is about 5 cm lower than the upper opening of the observation tray. The opening diameter of the self-counting rain gauge is 20 cm. The tipping bucket type self-counting rain gauge can be used to continuously observe the change of rainfall.

[0061] The litter moisture observation tray (i.e., observation tray) is located in the center of the device. The four walls of the observation tray are 25-30 cm high and the side length is about 0.8-1.0 m. The bottom of the observation tray is "V" shaped, that is, the bottom center of the observation tray is the lowest. A diversion hole is set to facilitate the smooth outflow of water leaking through the litter. The diversion hole is connected to the leakage moisture observation tube through a water guide pipe; the observation tray can be made of transparent plastic material to reduce the weight of the device. A movable stainless steel filter (i.e., filter) is placed at the bottom of the observation tray. The aperture of the stainless steel filter is about 2-5 mm, which is used to carry the forest litter to be observed. A weighing sensor is placed at the bottom of the stainless steel filter to continuously observe the changes in the weight of the litter. The weighing sensor is connected to the data collector through a data cable.

[0062] There can be multiple weighing sensors, such as 4, 6, 8 or 12. In this embodiment, there are 4 weighing sensors, which are evenly distributed on the filter screen. The measured value of the weighing sensor can be the arithmetic average of the measured values ​​of the 4 weighing sensors.

[0063] The shielding net is set up on the upper part of the tray, and its aperture is determined according to the size of the observed litter. If it is a broad-leaved tree, the aperture size of the litter shielding net can be larger. If it is a coniferous tree, the aperture needs to be smaller. Its main function is to prevent newly fallen branches and leaves from entering the observation tray, thereby affecting the observation results.

[0064] The self-counting litter seepage water observation tube (i.e., leakage water observation tube) is located below the litter water observation tray. It collects rainfall leaking from the litter through a water pipe. The tipping bucket-type self-counting litter seepage water observation tube can be used to continuously observe changes in the leakage water volume.

[0065] The bracket is located at the lower part or the periphery of the self-counting rain gauge, the litter moisture observation tray and the leakage moisture observation tube, and plays the role of a fixing device.

[0066] An embodiment of the forest litter rainfall interception and evaporation observation method of the present invention comprises:

[0067] The first step is to select and determine the location for the device installation: Based on the results of the field observation plot forest survey, the ratio of the canopy and forest window area and the spatial distribution characteristics, the appropriate observation location can be determined according to the diagonal principle, such as the 4 corners of the observation plot, 1 / 4, 1 / 2, 3 / 4 of the diagonal, etc. In general, each observation plot (such as an area of ​​100m×100m) is set up with at least 6-10 observation sites, and the observation sites can be installed more densely according to actual needs.

[0068] The second step is to install the forest litter rainfall interception and evaporation observation device and determine the initial parameters: at the determined location, install the components of the above-mentioned device separately. During installation, pay attention to keeping the device level and maintaining the stability of the device.

[0069] After installation, accurately measure the size (length and width) of the litter moisture observation tray and accurately calculate the area (m 2 ); at the same time, the initial mass of the stainless steel filter is accurately determined using an electronic balance (accuracy 0.1g). Then, the sampled forest litter is placed on the stainless steel filter. The forest litter is taken from the surface near the installation location. When sampling, the area of ​​the sampled litter is determined according to the size of the observation tray. Then, the samples are taken according to the undecomposed layer and the semi-decomposed layer, and the wet weight of the litter in each layer is determined. The layers are placed on the stainless steel filter according to the original surface. At the same time, some of the litter is taken back to the room to determine the moisture content of the litter, and the dry weight of the litter in the undecomposed layer and the semi-decomposed layer is determined.

[0070] The third step is field observation of rainfall interception and water evaporation of litter: After the device is installed, set the device parameters, connect the self-counting rain gauge and the self-counting litter seepage observation tube to the power supply (such as battery), set the self-counting time frequency to 1 time / 30min, and set the self-counting frequency of the weighing sensor data to 1 time / 30min. The parameters automatically measured include: dynamic changes in precipitation (mm), litter water seepage (mm) and litter mass (g). In order to maintain the continuity of the data, the device needs to be maintained frequently, such as power supply replacement, device integrity inspection, etc.

[0071] The fourth step is to calculate the rainfall interception and water evaporation of litter, that is, to estimate the rainfall interception and water evaporation based on continuous observation data:

[0072] Assume that the area of ​​the observation tray is A(m 2 ), the mass of litter on the previous day is M1 (g), the mass on the next day is M2 (g), and the initial dry weight of litter is M0 (g). According to the water balance theory, the change in water volume of litter in the tray (△S, mm) can be expressed as:

[0073] △S(mm)=(M2-M1) / (1000×A),

[0074] When rainfall occurs, the evaporation is very small, and the approximate evaporation E≈0. At this time, the mass change of the litter layer can be considered as the precipitation interception of the litter. According to P=△S+L+E,

[0075] △S(mm)=P(mm)-L(mm),

[0076] In practical applications, the rainfall is the arithmetic mean of the observation values ​​of the four self-counting rain gauges, and the water leakage is the corrected result. Due to the difference in the size of the receiving surface between the rainfall receiving interface of the observation tray and the self-counting litter leakage water observation tube, the result needs to be corrected to:

[0077] L a =(L obs πd 2 ) / (400A),

[0078] Where, L a To observe the tray precipitation leakage (mm), L obs is the actual amount of water leakage observed by the self-counting litter seepage observation tube (mm), and A is the area of ​​the receiving interface of the observation tray (m 2 ), d is the diameter of the standard rain gauge (cm);

[0079] When the rainfall ends, due to the time lag, no precipitation occurs, that is, P = 0, but there may be water leakage and evaporation. At this time, according to the water balance principle, △S + L + E = 0,

[0080] In order to estimate the water interception of litter in a rainfall event, if there is still water leakage after the rainfall ends, the precipitation and leakage process can be compared, and the end of leakage can be used as a standard for the end of a rainfall event. At this time, evaporation is assumed to be approximately 0, and the rainfall interception of a rainfall event can be estimated according to the water balance principle.

[0081] When there is no rainfall and no water leakage, P = 0, L = 0, and the evaporation is the water loss of litter:

[0082] E=-△S.

[0083] The technical solution of the present invention proposes a device and method for observing rainfall interception and evaporation of forest litter, which can observe the intercepted rainfall of forest litter and the evaporation of litter water after the end of rainfall. The measured litter interception and water evaporation are more accurate and the method is simpler; at the same time, long-term continuous dynamic observation can be carried out; dynamic monitoring of rainfall interception and water evaporation of forest litter can more comprehensively understand the role of forest litter in the forest hydrological cycle, and provide a scientific reference for more objective evaluation of hydrological ecological functions such as forest water conservation function.

[0084] The above are only preferred embodiments of the present invention. It should be pointed out that for those skilled in the art, without departing from the principles of the present invention, they can also adjust the order of steps, integrate the contents of steps, and make several improvements and modifications. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for observing rainfall interception and evaporation of forest litter, characterized in that: include: Step 1: Determine the installation location of the forest litter rainfall interception and evaporation observation device; Step 2: Install the forest litter rainfall interception and evaporation observation device and determine the initial parameters. The forest litter rainfall interception and evaporation observation device includes an observation tray for receiving forest litter and precipitation intercepted by forest litter, and also includes a self-counting rain gauge arranged next to the observation tray. The interior of the observation tray is provided with a filter for receiving forest litter, and the bottom plate of the interior of the observation tray is provided with a diversion hole for the outflow of precipitation intercepted by forest litter. The diversion hole is connected to the leakage water observation tube through a water guide pipe, and the filter is detachably arranged inside the observation tray. The bottom of the filter is provided with a filter for receiving forest litter. The part is provided with a weighing sensor, and also includes a data collector, the weighing sensor, the self-counting rain gauge, and the leakage water observation tube are respectively connected to the data collector, the observation tray includes a prismatic receiving part and a pyramidal drainage part, the cone tip of the drainage part is downward, the diversion hole is arranged at the cone tip of the drainage part, the filter is arranged between the receiving part and the drainage part, 4 self-counting rain gauges are arranged, and the 4 self-counting rain gauges are respectively located around the observation tray, and a shielding net is arranged above the observation tray, and the forest litter rainfall interception and evaporation observation device also includes a bracket for supporting the observation tray; Step 3: Observation of rainfall interception and evaporation of forest litter; Step 4: Calculate the rainfall interception and water evaporation of litter. The step 1 comprises: starting from the four corners of the observation plot, setting installation positions at 1 / 4, 1 / 2, and 3 / 4 positions along the diagonal, and setting at least 6 observation sites for each observation plot; The step 2 comprises: installing the forest litter rainfall interception and evaporation observation device at the installation position, measuring the size of the observation tray after the installation, determining the initial mass of the filter, sampling the forest litter in layers according to the undecomposed layer and the semi-decomposed layer, placing the sampled forest litter on the filter, taking part of the litter to determine the moisture content of the litter, and determining the dry weight of the litter in the undecomposed layer and the dry weight of the litter in the semi-decomposed layer; The step three comprises: setting parameters of the forest litter rainfall interception and evaporation observation device, connecting the self-counting rain gauge and the leakage water observation tube to the power supply, the self-counting time frequency is 1 time / 30 minutes, the self-counting frequency of the weighing sensor data is also set to 1 time / 30 minutes, and the parameters automatically measured include: precipitation, litter water leakage and dynamic changes in litter quality; The step 4 includes: estimating rainfall interception and water evaporation based on continuous observation data, the area of ​​the observation tray is A, the measured mass of litter on the previous day is M1, the mass measured on the next day is M2, the initial dry weight of litter is M0, and the change of water volume per unit area of ​​litter in the observation tray is ΔS: △S=(M2-M1) / A, If the evaporation E≈0 when rainfall occurs, the mass change of the litter layer is assumed to be the precipitation interception of the litter. According to the total amount of throughfall in the forest, P=△S+seepage L+evaporation E, △S=PL, The total amount of throughfall in the forest P is calculated based on the arithmetic mean of the observations from the self-counting rain gauge, and the amount of seepage L is calculated based on the observations from the seepage water observation tube; After the rain stops, P=0, △S+L+E=0, If there is still water leakage after the rainfall ends, assuming that the evaporation is approximately 0, the rainfall interception of a rainfall event is estimated according to the water balance principle. When there is no rainfall and no water leakage, P = 0, L = 0, and the evaporation is the water loss of litter: E=-△S.

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