Method for assessing carbon source or carbon sink of blue carbon ecosystem based on net ecosystem carbon budget framework

Abstract

This invention discloses a method for assessing carbon sources or sinks in blue carbon ecosystems based on a net ecosystem carbon budget framework. It integrates multiple disciplines and technologies, including satellite remote sensing, ecosystem flux observation, determination of water and soil carbon biogeochemical indicators, hydrological observation and simulation, and model simulation and analysis, to establish a system for assessing carbon sources or sinks in coastal wetlands based on the net ecosystem carbon budget framework. An application practice was conducted using the Yellow River Estuary salt marsh tidal flat wetland as an example. The method for estimating carbon sources or sinks in coastal wetlands provided by this invention simultaneously considers key processes such as surface-atmosphere exchange and the carbon budget of river inputs and outputs to the nearshore area, achieving accurate assessment of carbon sources or sinks in coastal wetlands.

Description

Technical Field

[0001] This invention relates to the field of monitoring and assessing ecosystem carbon sources or sinks, and in particular to a method for assessing blue carbon ecosystem carbon sources or sinks based on a net ecosystem carbon budget framework. Background Technology

[0002] Coastal wetland blue carbon ecosystems are among the ecosystems with the highest carbon absorption rates and storage densities globally. Their average carbon absorption rate and carbon density are approximately 10 times and 3-5 times that of mature tropical forest ecosystems, respectively, and they are considered another important "nature-based climate solution" besides terrestrial ecosystems. Accurately understanding the carbon sink function of coastal wetlands and comprehending their key influencing processes and mechanisms is of paramount importance for ecosystem carbon sink management and the ecological protection and management of coastal areas.

[0003] Unlike terrestrial ecosystems, the carbon budget processes in coastal wetlands are highly complex, involving not only vertical surface-atmosphere exchange and sediment burial, but also river inputs and nearshore exchange. Figure 1 Therefore, understanding the carbon sinks and key impact processes and mechanisms of coastal wetland blue carbon ecosystems requires establishing a net ecosystem carbon budget (NECB) framework that simultaneously considers these four key carbon budget processes. However, current research on coastal wetland blue carbon ecosystem carbon sinks remains at the stage of analyzing carbon source or sink characteristics and their environmental impact factors based on single flux observations at the site scale or estuarine carbon burial rate data, without fully considering horizontal river inputs and nearshore exchange processes. This deficiency leads to significant uncertainty in the current understanding of coastal wetland carbon sinks and also obscures the important scientific question of how each key carbon budget process affects coastal wetland carbon sinks. To address this, there is an urgent need to establish a comprehensive NECB carbon source or sink assessment methodology for coastal wetlands, integrating multidisciplinary methods and multi-source data, including ecosystem observation, geochemical index testing, hydrological observation and simulation, and model simulation and analysis, to reassess coastal wetland carbon sinks and their key impact processes based on the NECB framework. Summary of the Invention

[0004] The purpose of this invention is to address the technical deficiencies in the existing technology by providing a method for assessing carbon sources or sinks in blue carbon ecosystems based on the net ecosystem carbon budget framework.

[0005] The technical solution adopted to achieve the purpose of this invention is: The blue carbon ecosystem carbon source or sink assessment method based on the net ecosystem carbon budget framework includes the following steps: Step 1: Establish a carbon budget framework for organic carbon, inorganic carbon, and total carbon sources in the coastal wetland blue carbon ecosystem, and calculate the organic carbon source or carbon sink value of the net ecosystem carbon budget. Inorganic carbon source or carbon sink value and total carbon source or carbon sink value ,in: The carbon budget framework for organic carbon is as follows: (1) In the formula, Positive values ​​indicate carbon sink ecosystems, while negative values ​​indicate carbon sources; NEP w Indicates net ecosystem productivity; and These represent the DOC flux input to coastal wetlands from rivers and the DOC flux output from coastal wetlands to the nearshore area, respectively. and These represent the POC flux input from rivers to coastal wetlands and the POC flux output from coastal wetlands to nearshore waters, respectively. CH4 emission flux from coastal wetlands; and These represent the DOC and POC fluxes discharged from coastal wetlands into the nearshore waters via groundwater, respectively. The inorganic carbon support framework is as follows: (2) In the formula, Positive values ​​indicate carbon sink ecosystems, while negative values ​​indicate carbon sources; For the absorption / emission of CO2 flux in coastal wetland waters; and These represent the DIC flux input from rivers to coastal wetlands and the DIC flux output from coastal wetlands to the nearshore area, respectively. and These represent the PIC flux input from rivers to coastal wetlands and the PIC flux output from coastal wetlands to nearshore waters, respectively. and These represent the DIC and PIC fluxes discharged from coastal wetlands into the nearshore waters via groundwater, respectively. The overall carbon source budget framework equation is as follows: (3) Based on the net ecosystem carbon budget, the total carbon source or carbon sink value, This represents the net CO2 exchange flux between coastal wetlands and the atmosphere.

[0006] Step 2, based on the calculations obtained in Step 1 , as well as Appropriate environmental protection measures should be taken.

[0007] In the above technical solution, in step 1, , , The calculation method is as follows: First, station-scale CO2 or CH4 flux observation data are obtained using eddy covariance or box method. Then, grid-scale CO2 and CH4 flux data are obtained through data-driven models using statistical relationships.

[0008] In the above technical solution, in step 1, , , , The method to obtain it is as follows: Regularly collect river water samples from major rivers flowing into the sea, and obtain DOC, POC, PIC and DIC concentration data for different months through laboratory testing and analysis. Calculate the ratio between DIC and DOC and establish a relationship model between PIC and POC or DOC. A satellite remote sensing DOC and POC inversion algorithm model was constructed. DOC and POC concentration data for coastal wetland water bodies were obtained through satellite remote sensing inversion methods, and finally, combined with flow observation data, the final results were obtained. , ; Based on the ratio between DIC and DOC, by Get ; Based on the relationship model between PIC and POC or DOC, by or Get .

[0009] In the above technical solution, step 1 uses a method combining nonlinear regression modeling and quality balancing to obtain... , , , The specific steps are as follows: Based on observational data, a nonlinear model of the DIC flux output from coastal wetlands to nearshore areas was constructed to estimate the output. and utilize and The proportional relationship is determined by Calculation output ; Assuming annual scale and equal, and They are equal, and thus the calculation is obtained. and .

[0010] In the above technical solution, in step 1, , , and The method for obtaining δ is selected 18 O / δ 2 H-terminal model method 222 Rn isotope balance method, or through and , and , and ,as well as and The corresponding ratio relationship is obtained.

[0011] In the above technical solution, in step 2, if A positive result is achieved by maintaining hydrological stability and preventing carbon leakage, thereby improving the efficiency of ecosystem carbon sequestration. like The negative value can be achieved by reducing ecosystem carbon emissions and improving carbon sequestration efficiency through hydrological restoration, vegetation restoration and reconstruction, or reducing human interference.

[0012] Compared with the prior art, the beneficial effects of the present invention are: The carbon source and sink assessment method for coastal wetlands provided by this invention addresses the challenges in research on carbon sources or sinks in coastal wetlands. Through multidisciplinary collaboration and multi-source data integration, it achieves a truly meaningful estimation of carbon sources or sinks based on the NECB framework. Compared to traditional methods that assess carbon sources or sinks by observing surface-atmospheric carbon fluxes at a station-scale flux tower to obtain sediment carbon burial rates, this invention is strictly based on the entire ecosystem's carbon budget process. The method is more scientific and rational, representing the true carbon sources or sinks of the blue carbon ecosystem in coastal wetlands. It achieves accurate assessment of carbon sources or sinks in complex coastal wetland ecosystems, enhances the scientific understanding of blue carbon, and provides scientific support for the management of carbon sinks and the protection and governance of the ecological environment in coastal wetlands. Attached Figure Description

[0013] Figure 1 The diagram shows the carbon budget process of coastal wetlands.

[0014] Figure 2 The diagram shows a multidisciplinary and multi-technology integrated assessment methodology for net carbon balance, carbon source, or carbon sink in coastal wetlands. Detailed Implementation

[0015] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0016] Example 1 The blue carbon ecosystem carbon source or sink assessment method based on the net ecosystem carbon budget framework includes the following steps: Step 1: Establish a carbon budget framework for organic carbon, inorganic carbon, and total carbon sources in the coastal wetland blue carbon ecosystem, and calculate the organic carbon source or carbon sink value of the net ecosystem carbon budget. Inorganic carbon source or carbon sink value and total carbon source or carbon sink value ,in: The carbon budget framework for organic carbon is as follows: (1) In the formula, Positive values ​​indicate carbon sink ecosystems, while negative values ​​indicate carbon sources; NEP w Indicates net ecosystem productivity; and These represent the flux of dissolved organic carbon (DOC) input into coastal wetlands from rivers and the flux of DOC output from coastal wetlands to the nearshore area, respectively. and These represent the particulate organic carbon (POC) flux input from rivers to coastal wetlands and the nearshore POC flux output from coastal wetlands, respectively. For methane (CH4) emission flux in coastal wetlands; and These represent the DOC and POC fluxes discharged from coastal wetlands into the nearshore waters via groundwater, respectively. The inorganic carbon support framework is as follows: (2) In the formula, Positive values ​​indicate carbon sink ecosystems, while negative values ​​indicate carbon sources; For the absorption / emission of CO2 flux in coastal wetland waters; and These represent the flux of dissolved inorganic carbon (DIC) input into coastal wetlands from rivers and the flux of DIC output from coastal wetlands to the nearshore area, respectively. and These represent the particulate inorganic carbon (PIC) flux input from rivers to coastal wetlands and the nearshore PIC flux output from coastal wetlands, respectively. and These represent the DIC and PIC fluxes discharged from coastal wetlands into the nearshore area via groundwater, respectively.

[0017] The overall carbon source budget framework equation is as follows: (3) Based on the net ecosystem carbon budget, the total carbon source or carbon sink value, This represents the net CO2 exchange flux between coastal wetlands and the atmosphere.

[0018] Step 2, based on the calculations obtained in Step 1 , as well as Appropriate environmental protection measures should be taken.

[0019] like A positive sign indicates that the coastal wetland ecosystem is a carbon sink ecosystem. The value reflects the system's carbon sink intensity, indicating the overall health of the ecosystem. Ecosystem carbon sink efficiency can be improved through restoration / management measures such as maintaining hydrological stability and preventing carbon leakage. like A negative value indicates that the coastal wetland ecosystem is a net carbon source. The absolute value reflects the size of the carbon source in the system. A negative value... A negative value typically indicates a decline in ecosystem net primary productivity, increased soil carbon mineralization, increased external disturbances (reclamation, drainage, aquaculture), and increased methane or dissolved organic carbon output. From a carbon sequestration management perspective, targeted restoration and management measures can be taken to reduce ecosystem carbon emissions and improve carbon sequestration efficiency. (1) Hydrological restoration By restoring tidal exchange, sealing drainage ditches, reducing groundwater level fluctuations, and reducing long-term exposure to oxidation, the anaerobic environment can be restored and soil organic carbon oxidation can be inhibited. (2) Vegetation restoration and reconstruction By restoring typical dominant species (such as salt marsh herbs or mangroves), aboveground and belowground biomass can be increased, root carbon input can be enhanced, thereby increasing soil carbon deposition.

[0020] (3) Control human interference Human interference can be reduced by limiting land reclamation and expansion, optimizing aquaculture methods, and establishing buffer zones.

[0021] Example 2 In Example 1, the calculation method for each parameter in step 1 is as follows: (1) , , Data on CH4 flux, CO2 exchange flux between water bodies and the atmosphere, or net CO2 exchange flux of ecosystems are obtained through the following steps: First, station-scale CO2 or CH4 flux observation data are obtained using eddy covariance or box method. Then, grid-scale CO2 and CH4 flux data are obtained through statistical relational data-driven models.

[0022] (2) , , , The method to obtain it is as follows: River water samples from major rivers flowing into the sea were collected regularly. Laboratory tests and analyses were conducted to obtain monthly DOC, POC, PIC, and DIC concentration data. The proportional relationship between DIC and DOC was calculated, and a model was established to correlate PIC with POC or DOC. A satellite remote sensing DOC and POC inversion algorithm model was constructed. DOC and POC concentration data for coastal wetland water bodies were obtained through satellite remote sensing inversion methods. Combined with flow observation data, the final DOC and POC flux data input to coastal wetlands were obtained. , Based on the ratio between DIC and DOC, DIC flux data of river input to coastal wetlands were obtained from the DOC estimation results. Based on the relationship model between PIC and POC or DOC, PIC throughput data is obtained from the POC or DOC throughput. ).

[0023] (3) Obtaining the results by combining nonlinear regression modeling with quality balance. , , , The specific method is as follows: Based on observational data, a nonlinear relationship model for DIC flux output from coastal wetlands to nearshore areas was constructed to estimate the DIC flux output to nearshore areas. ), and uses the ratio of DOC to DIC flux to calculate and output the nearshore DOC flux from the DIC flux ( Assuming annual coastal wetland output of nearshore POC (… ) and PIC flux ( ) and river input POC ( ) and PIC flux ( The values ​​are equal, and then the river input POC ( ) and PIC flux ( Estimate the nearshore POC output from coastal wetlands ( ), ) and PIC flux ( ).

[0024] (4) , , and The method to obtain it is as follows: The carbon flux released from coastal wetlands into the nearshore waters via groundwater is difficult to observe directly, but can be measured using delta-coulometric methods. 18 O / δ 2 H three-terminal, 222 Estimated by methods such as the Rn isotope balance method. δ 18 O / δ 2 H. The three-terminal component model method utilizes δ 18O and δ 2 Significant differences in H were used to construct a linear mixture model to distinguish whether the carbon source of freshwater was from the erosion of terrestrial soil organic matter or from recycling after infiltration into the sea. 222 Rn isotope methods utilize groundwater (endmembers) 222 Given that radon concentrations are significantly higher than in seawater, continuous monitoring of radon dynamics in water bodies, after deducting losses due to atmospheric escape, radioactive decay, and tidal mixing, indicates that the remaining "surplus" represents groundwater input. However, isotopic methods for monitoring / analysis are costly and their spatial representativeness is limited by the number of monitoring stations. In practical calculations of carbon flux discharged from coastal wetlands to the nearshore, a simplified approach can be taken based on the ratio of the carbon flux discharged from the coastal wetlands to the nearshore. For example, based on experimental testing and analysis data, it is generally considered that the DIC discharged from the Yellow River Estuary coastal wetlands to the nearshore via groundwater accounts for 23-53% of the total nearshore input flux from the estuary.

[0025] After calculating in step 1 , as well as Then, it can be compared with the organic carbon burial rate. CAR o Inorganic carbon burial rate CAR i and total carbon burial rate CAR tc Compare and verify , as well as Reliability of settlement results.

[0026] NEBC calculations reflect whether an ecosystem is a carbon sink (net carbon absorber) or a carbon source (net carbon releaser) over a specific time scale (usually an year). A positive NEBC value indicates that the wetland system is a carbon sink, while a negative value indicates a carbon source. CAR reflects the long-term carbon accumulation in coastal wetland ecosystems, i.e., the process of carbon "fixation" in sediments. Theoretically, the NEBC carbon source or sink should be close to the CAR, especially when carbon flow and exchange rates are high. If a coastal wetland is a long-term carbon sink, the NEBC (positive value) should be aligned with the CAR value, meaning both indicate the ecosystem's ability to fix carbon.

[0027] CAR o , CAR i and CAR tc The calculation steps are as follows: The carbon burial rate of coastal wetland sediments can be obtained through field surveys and analysis of sediment samples from typical coastal wetland areas. 210 Pb- 137Cs dating (SAR) deposition rate is calculated by multiplying organic carbon, inorganic carbon, and total carbon concentrations by the SAR. CAR o , CAR i and CAR tc .

[0028] Example 2 The collaborative assessment of carbon sources or sinks in the Yellow River Estuary salt marsh tidal flat wetlands based on multi-source data includes the following steps: Step 1: Net Ecosystem Carbon Budget Framework for Coastal Wetland Blue Carbon Ecosystems Considering the vertical carbon flux and total carbon between the surface and atmosphere of coastal wetlands, the horizontal carbon flux and total carbon input from rivers, and the nearshore carbon flux and total carbon output from coastal wetlands, we define a framework equation for assessing the carbon sources or sinks of organic carbon, inorganic carbon, and total carbon in coastal wetlands: (1) (2) (3) Considering the cost of data acquisition, the average carbon balance of each item in equations (1)-(3) is obtained mainly through published literature methods based on multidisciplinary methods such as ecosystem flux observation, river hydrological observation, river and wetland water sample testing and analysis, and sediment sample testing and analysis. The NECB carbon source or carbon sink value is calculated respectively and compared with the average carbon burial rate of coastal wetland sediments for verification.

[0029] The specific steps for obtaining flux data for various carbon budget items in the Yellow River Estuary salt marsh tidal flat wetlands are as follows: Land-atmosphere CO2 and CH4 flux data based on eddy covariance flux tower observations were obtained through literature review and supplementary observations. 210 Pb- 137 Sedimentary carbon flux data obtained from Cs dating of sedimentation rates, and river transport carbon flux data based on flow observations and water sample testing analysis.

[0030] Based on the carbon flux data of the Yellow River Estuary coastal wetland carbon budget obtained in step 3, and using the NECB net carbon budget framework of equations (1)-(3) in step 2, the carbon source or sink characteristics of the coastal wetland are evaluated and compared with the organic carbon burial rate. CAR o Inorganic carbon burial rate ( CAR i ) and total carbon burial rate ( CAR tcThe results were compared and verified (Table 1). The assessment results show that the Yellow River Estuary salt marsh tidal flat wetland exhibits a weak organic carbon sink ecosystem with an annual carbon sink of 0.038 Tg C, and also a significant inorganic carbon sink ecosystem with an annual inorganic carbon sink of 0.74 Tg C. Considering both inorganic and organic carbon budgets, the Yellow River Estuary coastal wetland as a whole exhibits a significant blue carbon sink ecosystem with an annual carbon uptake of approximately 0.895 Tg C. The long-term organic carbon, inorganic carbon, and total carbon sequestration rates characterized by carbon sequestration rate measurements also corroborate this assessment result.

[0031] Table 1. Assessment Results of Carbon Sources or Sinks in Yellow River Estuary Salt Marsh Tidal Flat Wetlands Based on Net Ecosystem Carbon Budget Framework a a. Estimated based on multi-year averages.

[0032] b. , , These represent the burial rates of organic carbon, inorganic carbon, and total carbon, respectively.

[0033] c. and Rivers flow into coastal wetlands ( ) and coastal wetland output near the sea ( Total organic carbon flux.

[0034] d. and These respectively represent the river's input into the coastal wetland ( ) and coastal wetland output near the sea ( Total inorganic carbon flux.

[0035] at the same time, , as well as respectively with CAR o , CAR i and CAR tc The comparison shows that the positive and negative directions are consistent, which indirectly verifies the reliability of the carbon source or carbon sink assessment method of the present invention.

[0036] The above description is only a preferred embodiment of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for assessing carbon sources or sinks in blue carbon ecosystems based on the net ecosystem carbon budget framework, characterized in that, Includes the following steps: Step 1: Establish a carbon budget framework for organic carbon, inorganic carbon, and total carbon sources in the coastal wetland blue carbon ecosystem, and calculate the organic carbon source or carbon sink value of the net ecosystem carbon budget. Inorganic carbon source or carbon sink value and total carbon source or carbon sink value ,in: The carbon budget framework for organic carbon is as follows: (1) In the formula, Positive values ​​indicate carbon sink ecosystems, while negative values ​​indicate carbon sources; NEP w Indicates net ecosystem productivity; and These represent the DOC flux input to coastal wetlands from rivers and the DOC flux output from coastal wetlands to the nearshore area, respectively. and These represent the POC flux input from rivers to coastal wetlands and the POC flux output from coastal wetlands to nearshore waters, respectively. CH4 emission flux from coastal wetlands; and These represent the DOC and POC fluxes discharged from coastal wetlands into the nearshore waters via groundwater, respectively. The inorganic carbon support framework is as follows: (2) In the formula, Positive values ​​indicate carbon sink ecosystems, while negative values ​​indicate carbon sources; For the absorption / emission of CO2 flux in coastal wetland waters; and These represent the DIC flux input from rivers to coastal wetlands and the DIC flux output from coastal wetlands to the nearshore area, respectively. and These represent the PIC flux input from rivers to coastal wetlands and the PIC flux output from coastal wetlands to nearshore waters, respectively. and These represent the DIC and PIC fluxes discharged from coastal wetlands into the nearshore waters via groundwater, respectively. The overall carbon source budget framework equation is as follows: (3) Based on the net ecosystem carbon budget, the total carbon source or carbon sink value, This represents the net CO2 exchange flux between coastal wetlands and the atmosphere. Step 2, based on the calculations obtained in Step 1 , as well as Appropriate environmental protection measures should be taken.

2. The method for assessing carbon sources or sinks in blue carbon ecosystems as described in claim 1, characterized in that, In step 1, , , The calculation method is as follows: First, station-scale CO2 or CH4 flux observation data are obtained using eddy covariance or box method. Then, grid-scale CO2 and CH4 flux data are obtained through data-driven models using statistical relationships.

3. The method for assessing carbon sources or sinks in blue carbon ecosystems as described in claim 1, characterized in that, In step 1, , , , The method to obtain it is as follows: Regularly collect river water samples from major rivers flowing into the sea, and obtain DOC, POC, PIC and DIC concentration data for different months through laboratory testing and analysis. Calculate the ratio between DIC and DOC and establish a relationship model between PIC and POC or DOC. A satellite remote sensing DOC and POC inversion algorithm model was constructed. DOC and POC concentration data for coastal wetland water bodies were obtained through satellite remote sensing inversion methods, and finally, combined with flow observation data, the final results were obtained. , ; Based on the ratio between DIC and DOC, by Get ; Based on the relationship model between PIC and POC or DOC, by or Get .

4. The method for assessing carbon sources or sinks in blue carbon ecosystems as described in claim 1, characterized in that, In step 1, a method combining nonlinear regression modeling and quality balance is used to obtain... , , , The specific steps are as follows: Based on observational data, a nonlinear model of the DIC flux output from coastal wetlands to nearshore areas was constructed to estimate the output. and utilize and The proportional relationship is determined by Calculation output ; Assuming annual scale and equal, and They are equal, and thus the calculation is obtained. and .

5. The method for assessing carbon sources or sinks in blue carbon ecosystems as described in claim 1, characterized in that, In step 1, , , and The method for obtaining δ is selected 18 O / δ 2 H-terminal model method 222 Rn isotope balance method, or through and , and , and ,as well as and The corresponding ratio relationship is obtained.

6. The method for assessing carbon sources or sinks in blue carbon ecosystems as described in claim 1, characterized in that, In step 2, if A positive result is achieved by maintaining hydrological stability and preventing carbon leakage, thereby improving the efficiency of ecosystem carbon sequestration. like The negative value can be achieved by reducing ecosystem carbon emissions and improving carbon sequestration efficiency through hydrological restoration, vegetation restoration and reconstruction, or reducing human interference.

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