A method to improve the accuracy and speed of soil methane uptake simulation

Abstract

A method for improving the accuracy and speed of soil methane uptake simulation is characterized by: first, obtaining driving data; second, substituting the obtained driving data into the R99 model to simulate the national soil methane uptake monthly scale data to obtain the optimal temperature range of R99; third, fitting the measured values ​​with the R99 temperature sensitivity value of 2.0 and finally inferring the new temperature response factor r T response curve; finally, the new temperature response factor r T Substituting this into the R99 model quickly yields high-precision methane absorption data. By collecting measured data from sites and adjusting the temperature response curve of the temperature impact adjustment factor in R99, the improved model significantly improves the simulation of soil methane absorption in various ecosystems across my country.

Description

Technical Field

[0001] The present invention relates to an environmental protection technology, in particular to a technology for monitoring the absorption of methane, one of the greenhouse gases, and more specifically to a method for improving the accuracy and speed of soil methane absorption simulation. Background Art

[0002] Methane is a major greenhouse gas and the second-largest contributor to human-induced climate change, contributing 20% ​​to global warming and having a 100-year warming potential (GWP100) 28 times that of the leading greenhouse gas, CO2. Its short atmospheric lifetime makes it an ideal target for climate change mitigation. Atmospheric methane concentrations depend on the strength of various sources and sinks. Methane absorption by soils primarily relies on the enzymatic breakdown of methane by methanotrophic bacteria. Methane absorption by soil methanotrophs is the only biological sink, and quantifying this methane sink provides crucial insights into predicting global climate change trends and developing feasible climate change mitigation policies.

[0003] Currently, there are two main methods for quantifying soil methane uptake at different scales or in different ecosystems. 1) Using a static chamber method combined with gas chromatography, soil methane uptake is measured at a given experimental site over a specific time period. Regional uptake is then extrapolated from this point data. While this type of site-based data accurately reflects soil methane uptake over a specific time period, it exhibits high variability and poorly predicts uptake for unmeasured periods and regions. Current research primarily uses this method for small-scale, single-ecosystem predictions, but it performs poorly for large, complex regions. 2) Predicting large-scale soil methane uptake through modeling. Several process-based soil methane uptake models exist that predict global-scale soil methane uptake, including the Global Soil Methane Uptake Model (R99) developed by Ridgwell et al., the Global Soil Methane Uptake Model (C07) developed by Curry et al., and the Methanotrophy Model (memo1.0) developed by Murguia-Flores et al. These models derive soil methane uptake by quantifying the effects of environmental factors on soil oxidative microbial oxidation reactions and soil texture on gas flow rates. These models effectively capture the spatial and temporal heterogeneity of soil methane uptake, but are limited by dataset resolution and do not account for regional geographic characteristics. Local-scale models, such as the Arctic Mineral Soil Methane Consumption Model (HXAM) and the New Zealand Denitrification Decomposition Model (NZDNDC), can effectively address these issues. These models utilize local field data to develop or improve existing models to quantify soil methane uptake in local areas.

[0004] my country's soil methane uptake monitoring has primarily focused on single ecosystems or small-scale studies, relying primarily on field data from sites with relatively scattered distribution. Forests and grasslands are the most commonly monitored ecosystems, and in recent years, soil methane uptake monitoring in desert ecosystems has also emerged. However, there remains a technology that can comprehensively monitor soil methane uptake across multiple ecosystems nationwide.

[0005] Based on existing datasets, we chose to use the R99 model to predict soil methane uptake across China. However, the model's fit with measured data was poor, with particularly significant deviations from measured values ​​at high and low latitudes. Existing observational and experimental data in my country primarily explore the influence of specific factors on local soil methane uptake. These experiments include experimental groups that manipulate influencing factors and control groups that remain in natural conditions. The control groups help refine and validate the model. Improving the model based on these measured data makes it more suitable for simulating the spatiotemporal distribution of soil methane uptake in my country. Summary of the Invention

[0006] The purpose of the present invention is to invent a method to improve the accuracy and speed of soil methane uptake simulation to address the problem that the speed and accuracy cannot be matched when using a model to detect long-term series of soil methane uptake in China, making it difficult to adapt to the simulation accuracy of methane uptake in multiple ecosystems in China.

[0007] The technical solution of the present invention is:

[0008] A method for improving the accuracy and speed of soil methane uptake simulation is characterized by: first, obtaining driving data; second, substituting the obtained driving data into the R99 model to simulate 30 years of national soil methane uptake monthly data, and combining it with the collected measured data to obtain the optimal temperature range of R99; third, fitting the measured values ​​based on the temperature sensitivity of R99 with a value of 2.0, and finally inferring the new temperature response factor r T response curve; finally, the new temperature response factor r T Substitute it into the R99 model to quickly obtain high-precision methane absorption.

[0009] The calculation formula for soil methane absorption in the R99 model is:

[0010]

[0011] Among them J CH4 is the soil methane absorption, F is a coefficient, taken as 616.9mg ppmv -1 cm -1 , C 0CH4 is the atmospheric methane concentration, which is set to 1.72 ppmv for the convenience of calculation. dThe soil depth where the oxidation reaction occurs; since oxidation activities are mostly concentrated at a depth of 5-7 cm, 6 cm is used here, D CH4 and k d represent the soil diffusion coefficient and the oxidation rate of soil oxidizing bacteria respectively;

[0012] D CH4 The calculation formula is as follows:

[0013] D CH4 =G soil ×G T ×D 0CH4

[0014] D 0CH4 is the methane diffusion coefficient, which is 0.196 cm 2 s -1 , G soil The soil texture is a scalar that takes into account environmental factors. It is usually determined by the soil texture. G T A scalar that takes into account the environmental influence of temperature;

[0015] G soil The calculation formula is as follows:

[0016]

[0017]

[0018]

[0019] b=-3.140-0.000222(clay) -2 -3.484x10 -5 (sand) 2

[0020] Where Φ is the porosity (cm 3 cm -3 ), ε is the air-filled porosity (cm 3 cm -3 ), b is the soil texture constant, ρ b is the soil bulk density, ρ s is the soil particle size, θ v is the soil water content, Clay and Sand are the percentage contents of clay and sand in the soil;

[0021] G soil The calculation formula is as follows:

[0022] G T =1.0+0.0055T

[0023] Where T is the temperature in degrees Celsius;

[0024] K d The calculation formula is as follows:

[0025] K d =r N ×r sm ×r T ×k0

[0026] Where k0 is the oxidation rate constant, which is 8.7x10 -4 s -1 , r N , r sm , r T They are agricultural impact regulating factor, water regulation regulating factor, and temperature impact regulating factor;

[0027] The calculation formula of the agricultural impact adjustment factor is as follows:

[0028] r N =1.0-(0.75×I cult )

[0029] Among them I cult is the farming intensity score, expressed as the proportion of cultivated land;

[0030] The calculation formula of soil moisture impact adjustment factor is as follows:

[0031]

[0032] Where P is monthly rainfall, SM is soil surface moisture, and ETp is potential evapotranspiration;

[0033] r T is the temperature impact adjustment factor, and its calculation formula is as follows:

[0034]

[0035] Where T is temperature in °C.

[0036] Note: The formula for rt in the traditional R99 model is:

[0037]

[0038] Beneficial effects of the present invention:

[0039] This study collects field data and adjusts the temperature response curve of the temperature impact adjustment factor in R99. This model establishes a temperature response curve for temperatures below 0°C, altering the optimal temperature range for soil methane absorption and adjusting the overall temperature response curve above 0°C downward. This improved model significantly improves the simulation of soil methane absorption across ecosystems in my country.

[0040] The present invention simulates the driving data, and the modified model has a better performance than the R99 model in each temperature range ( Figure 3 ), and at a single point measurement, R 2 Increased from 0.46 to 0.65 ( Figure 4 ).

[0041] The improved model of the present invention modifies the original model by T The temperature response curve of the improved model has greatly improved the simulation effect of the soil methane absorption of multiple ecosystems in China. The model analytical formula applicable to multiple ecosystems across the country is used to quantify the soil methane absorption, which reduces the trouble caused by using different models for calculations in different ecosystems in the past. While reducing the amount of calculation, it also effectively improves the simulation accuracy.

[0042] The present invention realizes grid output, so that the soil methane absorption amount is displayed in a visual (tiff) form. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 The original model of the present invention and the improved model r T Response curve to temperature.

[0044] Figure 2 It is an implementation flow chart of the present invention.

[0045] Figure 3 It is a schematic diagram showing that the model of the present invention has a better performance than the R99 model in each temperature range.

[0046] Figure 4 R is the value measured at a single point 2 Schematic diagram of the change (from 0.46 to 0.65). DETAILED DESCRIPTION

[0047] The present invention will be further described below with reference to the accompanying drawings and examples.

[0048] like Figure 1-4 shown.

[0049] A method for improving the accuracy and speed of soil methane uptake simulation is characterized by: first, obtaining driving data, including temperature, rainfall, potential evapotranspiration, soil clay and sand percentage, soil moisture content, soil volumetric moisture content, soil particle size, and land use data, all of which are in the form of a monthly grid, and the final simulation results are also in the form of a monthly grid.

[0050] To this end, we collected 186 field-measured soil methane uptake data from 32 sites across China for different ecosystems. These data included 112 data points from 14 sites for forest ecosystems, 72 data points from 16 sites for grassland ecosystems, and two data points from two sites for desert ecosystems. We categorized these data across different locations and vegetation types and then 1) validated the model results. 2) Based on the longitude and latitude of the field data locations, we used the temperature at the corresponding locations and time periods in the driving data to infer theoretical values ​​of RT. These RT values ​​were then fitted to generate a new RT-temperature response curve.

[0051] Secondly, the obtained driving data were substituted into the R99 model to simulate the monthly data of soil methane absorption across the country. The soil methane absorption calculation formula is:

[0052]

[0053] Among them J CH4 is the soil methane absorption, F is a coefficient, taken as 616.9mg ppmv -1 cm -1 , C 0CH4 is the atmospheric methane concentration, which is set to 1.72 ppmv for the convenience of calculation. d The soil depth where the oxidation reaction occurs; since oxidation activities are mostly concentrated at a depth of 5-7 cm, 6 cm is used here, D CH4 and k d represent the soil diffusion coefficient and the oxidation rate of soil oxidizing bacteria respectively;

[0054] D CH4 The calculation formula is as follows:

[0055] D CH4 =G soil ×G T ×D OCH4

[0056] D 0CH4 is the methane diffusion coefficient, which is 0.196 cm 2 s -1 , G soil The soil texture is a scalar that takes into account environmental factors. It is usually determined by the soil texture. G T A scalar that takes into account the environmental influence of temperature;

[0057] G soil The calculation formula is as follows:

[0058]

[0059]

[0060]

[0061] b=-3.140-0.000222(clay) -2 -3.484×10 -5 (sand) 2

[0062] Where Φ is the porosity (cm 3 cm -3 ), ε is the air-filled porosity (cm 3 cm -3 ), b is the soil texture constant, ρ b is the soil bulk density, ρ s is the soil particle size, θ v is the soil water content, Clay and Sand are the percentage contents of clay and sand in the soil;

[0063] G soil The calculation formula is as follows:

[0064] G T =1.0+0.0055T

[0065] Where T is the temperature in degrees Celsius;

[0066] K d The calculation formula is as follows:

[0067] K d =r N ×r sm ×r T ×k0

[0068] Where k0 is the oxidation rate constant, which is 8.7x10 -4 s -1 , r N , r sm , r T They are agricultural impact regulating factor, water regulation regulating factor, and temperature impact regulating factor;

[0069] The calculation formula of the agricultural impact adjustment factor is as follows:

[0070] r N =1.0-(0.75×I cult )

[0071] Among them I cult is the farming intensity score, expressed as the proportion of cultivated land;

[0072] The calculation formula of soil moisture impact adjustment factor is as follows:

[0073]

[0074] Where P is monthly rainfall, SM is soil surface moisture, and ETp is potential evapotranspiration;

[0075] r T is the temperature impact adjustment factor, and its calculation formula is as follows:

[0076]

[0077] Where T is temperature in °C.

[0078] Note: The formula for rt in the traditional R99 model is:

[0079]

[0080] It was found that the R99 model had poor simulation effects in high temperature areas and low temperature areas, and there were large deviations in the simulation effects in summer and spring, and the overall effect was poor (R 2 =0.46). In areas below 0°C, the original R99 model assumes that the soil surface freezes below zero, stopping methane absorption. However, measured data shows that soil water does not freeze at a surface temperature of 0°C, and this absorption effect does not stop when the surface temperature reaches below zero. In areas with higher temperatures (T≥18°C), the measured values ​​drop significantly. R99 confirms that the optimal temperature range is 25-30°C, so the optimal temperature is brought forward. In the range of 5-18°C, the R99 simulation value is slightly higher than the measured value, while the corresponding effect is relatively good at 0-5°C. Since the r T It grows exponentially, so it is fitted according to the exponential function. Above 0℃, R99 is fitted to the measured value according to the temperature sensitivity (Q10) of 2.0. The present invention is based on the r obtained by reverse deduction based on the measured value of methane absorption and environmental variable data. T The new temperature response curve ( Figure 1 ).

[0081] Third, through simulation of driving data, the modified model has a good performance compared with the R99 model in each temperature range ( Figure 3 ), and at a single point measurement, R 2 Increased from 0.46 to 0.65 ( Figure 4 ).

[0082] In general, the new improved model modifies r based on the original model. TThe temperature response curve of the improved model has greatly improved the simulation effect of the soil methane absorption of multiple ecosystems in China. The model analytical formula applicable to multiple ecosystems across the country is used to quantify the soil methane absorption, which reduces the trouble caused by using different models for calculations in different ecosystems in the past. While reducing the amount of calculation, it also effectively improves the simulation accuracy.

[0083] The parts not involved in the present invention are the same as the existing technology or can be implemented by using the existing technology.

Claims

1. A method for improving the accuracy and speed of soil methane uptake simulation, characterized by: first, obtaining driving data; second, substituting the obtained driving data into the R99 model to simulate monthly soil methane uptake data across China, and combining it with collected measured data to obtain the optimal temperature range for the R99 model; third, fitting the measured data with the R99 model based on a temperature sensitivity of 2.0, and finally inferring a new temperature response factor r. T response curve; finally, the new temperature response factor r T Substitute into the R99 model to quickly obtain high-precision methane absorption, r T The calculation formula is as follows: Where T is temperature in °C.

2. The method according to claim 1, wherein: The driving data include temperature, rainfall, potential evapotranspiration, soil clay and sand percentage, soil moisture content, soil volumetric moisture content, soil particle size, and land use data, all of which are in monthly grid format.

3. The method according to claim 1, wherein: The calculation formula for soil methane absorption in the R99 model is: Among them J CH4 is the soil methane absorption, F is a coefficient, taken as 616.9mg ppmv -1 cm -1 , C 0CH4 is the atmospheric methane concentration, which is set to 1.72 ppmv for the convenience of calculation. d The soil depth where the oxidation reaction occurs; since oxidation activities are mostly concentrated at a depth of 5-7 cm, 6 cm is used here, D CH4 and k d represent the soil diffusion coefficient and the oxidation rate of soil oxidizing bacteria respectively; D CH4 The calculation formula is as follows: D CH4 =G soil ×G T ×D OCH4 D 0CH4 is the methane diffusion coefficient, which is 0.196 cm 2 s -1 , G soil The soil texture is a scalar that takes into account environmental factors. It is usually determined by the soil texture. G T A scalar that takes into account the environmental influence of temperature; G soil The calculation formula is as follows: b=-3.140-0.000222(clay) -2 3.484×10 -5 (sand) 2 Where Φ is the porosity (cm 3 cm -3 ), ε is the air-filled porosity (cm 3 cm -3 ), b is the soil texture constant, ρ b is the soil bulk density, ρ s is the soil particle size, θ v is the soil water content, Clay and Sand are the percentages of clay and sand in the soil; G T The calculation formula is as follows: G T =1.0+0.0055T Where T is the temperature in degrees Celsius; K d The calculation formula is as follows: K d =r N ×r sm ×r T ×k0 Where k0 is the oxidation rate constant, which is 8.7x10 -4 s -1 , r N ,r sm ,r T They are agricultural impact regulating factor, water regulation regulating factor, and temperature impact regulating factor; The calculation formula of the agricultural impact adjustment factor is as follows: r N ＝1.0-(0.75×I cult ) Among them I cult is the farming intensity score, expressed as the proportion of cultivated land; The calculation formula of soil moisture impact adjustment factor is as follows: Where P is monthly rainfall, SM is soil surface moisture, and ETp is potential evapotranspiration.

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