A method for tracing the origin of organic carbon in wetlands

Abstract

The present application belongs to the field of environmental monitoring, and discloses a method for tracing the source of organic carbon in wetlands, specifically a method for tracing the source of organic carbon in wetlands, comprising the following steps: (1) collection of sediment samples; (2) determination of the content of biomarkers in the sediment samples, wherein the biomarkers include n-alkanes and amino sugars; (3) based on the determination results of step (2), analyzing the contribution of plant carbon sources and microbial carbon sources to soil organic carbon. The present application combines two biomarkers, n-alkanes and amino sugars, and based on different markers and total carbon content, a calculation process is proposed, which realizes the analysis and comparison of six biological source carbon inputs, i.e. wetland plant sources (herbaceous plants, algal plants, woody plants and aquatic plants) and microbial source carbon (fungal residue carbon and bacterial residue carbon), thereby realizing carbon source tracing in different dimensions.

Description

Technical Field

[0001] This invention belongs to the field of environmental monitoring, specifically relating to a method for comprehensive source tracing of organic carbon sources in wetlands. Background Technology

[0002] Biomarkers are organic compounds from the environment and geological bodies that have a specific biological origin and retain the molecular structure information of the original parent material during sedimentation. They are widely used to identify carbon sources due to their long-term stability. Commonly used biomarkers include amino acids, carbohydrates, alkane lipids, and amino sugars.

[0003] Common lipid molecules include fatty acids, sterols, and n-alkanes. Among these, n-alkanes are widely distributed in various organisms, from lower algae to higher plants, and are a widely used biomarker in sediment research. The carbon number composition and distribution characteristics of n-alkanes from different organisms vary. Generally, it is believed that C... 20 The following n-alkanes are mainly derived from lower organisms, such as bacteria, algae, and marine plankton, with C... 15 and C 17 It is the main peak and does not have a clear odd / even advantage. And C 21 ~C 25 n-Alkanes primarily originate from mosses and aquatic plants. Long-chain n-alkanes (C... 26 ~C 33 It exhibits a significant odd carbon number advantage, primarily produced by the degradation of the surface waxy substance of terrestrial higher plants, with C... 27 C 29 C 31 and C 33 The most abundant, with the main indicator peak for woody plants being C. 27 and C 29 The main indicator peak for herbaceous plants is C. 31 and C 33 As a characterization of the plant parent material source in organic matter, long-chain (C14-C24) alkanes are generally considered to be a significant contributor to organic matter. 31 +C 33 (C) is a marker derived from herbaceous plants. 27 +C 29 () is a marker derived from woody / deciduous plants. The medium chain is mainly produced by aquatic plants such as mosses, floating plants, and submerged plants, while the short chain mainly comes from phytoplankton, algae, etc.

[0004] n-Alkanes primarily characterize the plant parent material source of organic matter, while amino sugars are the main biomarkers of microbial residues in soil. Converting amino sugar content yields the carbon content of microbial residues and its relative contribution to soil organic carbon. Amino sugars are important components of microbial cell walls; compared to other cytoplasmic components, they remain stable in soil for a longer period, making them widely used in studying the contribution of microbial residues to soil organic carbon and various microenvironmental transport. Common amino sugars in soil include glucosamine, galactosamine, mannosamine, and muramic acid, accounting for 2%–5% of soil organic carbon content. Muramic acid in soil originates only from bacteria, while glucosamine mainly comes from fungi. Therefore, the GluN / MurN ratio is commonly used to evaluate the relative contributions of fungal and bacterial residues to soil organic matter transformation.

[0005] Due to the unique nature of their environment, salt marshes can be categorized into endogenous and exogenous carbon sources based on their carbon origin. Endogenous carbon refers to the organic carbon fixed by plants or other photosynthetic organisms within the salt marsh ecosystem through photosynthesis, converting CO2 into biological organic carbon. This organic carbon decomposes slowly due to periodic tidal movements, becoming stable organic carbon stored in sediments. This portion of carbon is produced at the same location as its deposition. In addition to endogenous carbon, salt marshes are frequently disturbed by hydrological processes such as coastal currents, tides, and surface runoff. Sediments and organic debris from near-shore or adjacent terrestrial ecosystems are captured and fixed by the plant canopy or root systems within the salt marsh, becoming part of the coastal wetland carbon pool. This portion of carbon, produced at a different location than its deposition, is called exogenous carbon. The combined input of endogenous and exogenous carbon makes salt marshes a richer source of carbon than terrestrial ecosystems, thus making them one of the highest-density carbon sinks on Earth. The continuous accumulation of organic carbon in salt marsh wetland sediments, along with the suppressed production and emission of CH4, helps mitigate the severe situation of global warming. However, existing methods for tracing the carbon sources of salt marsh wetlands are mainly based on stable isotope and N / C ratio tracing to distinguish and quantify terrestrial, plant (endogenous), and marine carbon sources. More detailed carbon source tracing and quantification lack a theoretical and practical foundation. Summary of the Invention

[0006] The first objective of this invention is to provide a method for tracing the sources of organic carbon in wetlands in a comprehensive manner.

[0007] The second aspect of the present invention aims to provide the application of the method of the first aspect of the present invention in the study of ecosystem carbon cycle processes.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] The first aspect of this invention provides a method for comprehensive source tracing of wetland organic carbon, comprising the following steps:

[0010] (1) Collection of sediment samples;

[0011] (2) Determination of the content of biomarkers in sediment samples, wherein the biomarkers include n-alkanes and amino sugars;

[0012] (3) Based on the measurement results of step (2), analyze the contribution of plant carbon source and microbial carbon source to sediment organic carbon.

[0013] Preferably, the n-alkane comprises C7 to C40; more preferably, it comprises C15, C17, C19, C21, C23, C25, C27, C29, C31 and C33.

[0014] Preferably, the amino sugar includes glucosamine and muramic acid.

[0015] Preferably, the analysis of the contribution of plant carbon sources and microbial carbon sources to sediment organic carbon includes calculating the proportion of herbaceous plants, woody plants, aquatic plants, and algae in plant-derived carbon input, the carbon input content of herbaceous plants, the carbon input content of woody plants, the carbon input content of aquatic plants, the carbon input content of algae, as well as the carbon content of fungal residues and bacterial residues.

[0016] Preferably, the formula for calculating the proportion of herbaceous plants in the plant-derived carbon input is: Herbaceous plants = (C 31 +C 33 ) / (C 15 +C 17 +C 19 +C 21 +C 23 +C 25 +C 27 +C 29 +C 31 +C 33 ).

[0017] Preferably, the formula for calculating the proportion of woody plants in the plant-derived carbon input is: Woody plants = (C 27 +C 29 ) / (C 15 +C 17 +C 19 +C 21 +C 23 +C 25 +C 27 +C 29 +C 31 +C 33 ).

[0018] Preferably, the formula for calculating the proportion of aquatic plants in the plant-derived carbon input is: Aquatic plants = (C 21 +C 23 +C 25 ) / (C 15 +C 17 +C 19 +C 21 +C 23 +C 25 +C 27 +C 29 +C 31 +C 33 ).

[0019] Preferably, the formula for calculating the proportion of algae in plant-derived carbon input is: Algae = (C 15 +C 17 +C 19 ) / (C 15 +C 17 +C 19 +C 21 +C 23 +C 25 +C 27 +C 29 +C 31 +C 33 ).

[0020] Preferably, the carbon content of fungal and bacterial residues is calculated using the following formulas: fungal residue carbon content = F-GluN × 9, bacterial residue carbon content = MurN × 45, where F-GluN is an amino sugar that indicates carbon in fungal microbial residues, and MurN is a cell muramic acid.

[0021] Preferably, the F-GluN is calculated using the following formula: F-GluN = total GluN – 2 × MurN × (179.2 / 251.2), where GluN is glucosamine.

[0022] Preferably, the plant carbon input content is calculated using the following formula: different plant carbon input content = (sediment organic carbon content - microbial residue carbon content) × the proportion of plant in plant-derived carbon input, wherein microbial residue carbon content = fungal residue carbon content + bacterial residue carbon content.

[0023] Preferably, the sediment samples mentioned in (1) include sediments from any one of salt marshes, mangroves, forests, and grasslands.

[0024] Preferably, during the collection of sediment samples, biological cavities are avoided and sediment samples with no obvious biological disturbance are selected.

[0025] Preferably, the sediment samples include sediment samples from at least one of the four wetland types: bare mudflats, Spartina alterniflora, Suaeda salsa, and reeds.

[0026] Preferably, gas chromatography / mass spectrometry is used to determine the content of n-alkanes in the sediment sample, and high performance liquid chromatography is used to determine the content of amino sugars in the sediment sample.

[0027] Preferably, the wetland is a salt marsh wetland.

[0028] Salt marsh wetlands are a special type of coastal wetland ecosystem. Due to their location in the land-sea transition zone, they have abundant carbon input sources, resulting in a much higher carbon burial rate than terrestrial ecosystems. However, because of the complex composition of their carbon sources, existing carbon source tracing methods and systems can only roughly distinguish the different carbon sources in salt marsh wetlands. The method provided in this invention helps to accurately and meticulously differentiate the carbon sources of salt marsh wetlands.

[0029] A second aspect of the present invention is to provide the application of the method of the first aspect of the present invention in the study of carbon cycle processes in ecosystems.

[0030] The beneficial effects of this invention are:

[0031] Previous methods used n-alkanes / amino sugars alone to indicate a specific type of carbon input in an ecosystem, often tracing carbon sources from a qualitative comparative perspective. However, due to the unique characteristics of salt marsh wetland (and even coastal wetland) ecosystems, which are situated at the land-water interface and receive carbon inputs from both terrestrial and marine sources, simultaneous comparisons of these sources are necessary. Furthermore, due to the complexity of terrestrial carbon inputs, there has been no suitable method for distinguishing and tracing their sources. To comprehensively cover the complex and multi-source carbon input endmembers of coastal wetlands, this invention combines n-alkanes and amino sugars as biomarkers to analyze and compare six biological sources of carbon input in salt marsh wetlands: plant-based (herbaceous, algal, woody, and aquatic) and microbial-based (fungal and bacterial residues). It was found that woody plants can indicate terrestrial organic carbon inputs to some extent, and algae can indicate marine organic carbon inputs to some extent. This achieves the tracing of complex and multi-source carbon inputs from different dimensions.

[0032] The method using stable isotopes can only roughly classify the carbon sources of salt marsh wetlands into marine, plant, and terrestrial organic carbon sources. The method of this invention further refines the subdivision of carbon sources in salt marsh wetlands based on the classification of plant and microbial carbon sources: plant carbon sources are divided into algae, aquatic plants, herbaceous plants, and woody plants, and microbial carbon sources are divided into fungal residue carbon sources and bacterial residue carbon sources.

[0033] The comprehensive source tracing method provided by this invention achieves, for the first time, a quantitative assessment of the contribution of algal-derived carbon input to soil organic carbon in coastal wetland ecosystems. This was previously impossible or prone to significant errors using more detailed and precise methods. Through more detailed and accurate calculations of algal carbon input, this invention provides a theoretical method for monitoring the impacts of abnormal algal activities such as red tides in my country. Simultaneously, it also offers new methods and insights for research on carbon cycle processes in my country's blue carbon ecosystems.

[0034] The method provided by this invention is not only applicable to coastal wetland ecosystems, but theoretically it can also be used for lake, swamp, and even forest and grassland ecosystems to achieve quantitative analysis and further subdivision of different carbon input sources. Attached Figure Description

[0035] Figure 1 A technical roadmap for a comprehensive approach to tracing the sources of organic carbon in salt marshes.

[0036] Figure 2 The results of linear regression analysis were performed on the relevant indicators obtained from the quantification of n-alkanes and the results of stable isotope quantification. Detailed Implementation

[0037] The present invention will now be described in detail with reference to specific embodiments, but this does not limit the scope of the invention.

[0038] Unless otherwise specified, the materials and reagents used in this embodiment are commercially available.

[0039] Example 1

[0040] This study collected soil sediments from two typical salt marsh wetlands in my country—the Yellow River Estuary Salt Marsh Wetland and the Yancheng Salt Marsh Wetland—and brought them back to the laboratory for the determination of biomarkers (n-alkanes + amino sugars). By combining these two biomarkers, the study aimed to determine the carbon origin of salt marsh wetlands from both plant and microbial sources. Figure 1 Quantitative analysis and comparison of the inputs. Simultaneously, the classification method is validated by combining results from stable isotope and end-member mixing effect models. Specifically, the study area is as follows:

[0041] The Yellow River Estuary Salt Marsh Wetland is located in the Yellow River Delta National Nature Reserve (37°45'50″N, 118°59'24″E) in Kenli District, Dongying City, Shandong Province. This area belongs to the warm temperate semi-humid continental monsoon climate zone, with distinct seasons and simultaneous rainfall and heat. The terrain is flat, without natural barriers, and the soil texture is mainly light loam and medium loam, with alluvial soil and saline-alkali soil as the main soil types. The average annual temperature in the study area is 12.9℃, with large annual temperature variations; the frost-free period accounts for about two-thirds of the year. The average annual precipitation is 556.1 mm, with 70% concentrated in the growing season, and the annual evaporation is 1962 mm.

[0042] The Yancheng Salt Marsh Wetland is located in north-central Jiangsu Province, bordering the Yellow Sea to the east. Its geographical coordinates are 32°34′–34°28′N, 119°27′–121°16′E. The area spans Dongtai City, Dafeng City, Tinghu District, Binhai County, and Xiangshui County, with a long coastline and coastal mudflats extending for 445 km. 2 It is the largest continuous intertidal wetland ecosystem in my country. Located in the transition zone between the warm temperate and northern subtropical zones, it is mainly influenced by maritime and continental monsoon climates, with an average annual temperature of 13.8℃ and an average annual rainfall of 1023.8mm.

[0043] Sampling methods

[0044] Soil sediments were collected from two typical salt marsh wetlands—the Yellow River Estuary Salt Marsh Wetland and the Yancheng Salt Marsh Wetland. During sampling, biological burrows were avoided, samples with minimal biological disturbance were selected, and the morphological characteristics of the profiles were recorded. Soil samples from four wetland types—smooth beach, Spartina alterniflora, Suaeda salsa, and Phragmites australis—were collected from both salt marsh wetlands. Repeat sampling was conducted at least 2 meters apart in each type of salt marsh wetland. Collected samples were frozen at -20°C and sealed in polyethylene plastic bags. Specific geographical location information for soil sediment sample collection is shown in Table 1.

[0045] Table 1 Sampling information of different wetland types in the Yellow River Estuary and Yancheng Salt Marsh Wetlands

[0046]

[0047]

[0048] Experimental measurement

[0049] Determination of n-alkanes:

[0050] After air-drying the collected soil sediment samples, 5.0 g of the dried soil sediment sample was weighed into a 50 mL centrifuge tube. A 9:1 mixture of dichloromethane and methanol was added, and ultrasonic extraction was performed for 10 min (32 kHz: 32000 times / min). After extraction, the sample was centrifuged at 3500 rpm for 10 min. The supernatant was poured into a 50 mL glass vial and nitrogen purging was initiated using a nitrogen purging apparatus heated in a 40 °C water bath. The ultrasonic extraction, centrifugation, and nitrogen purging were repeated three times for each sample, with the extracts purified to near dryness in each cycle. The extract mixture was dissolved in 10 mL of hexane; after shaking to homogenize, nitrogen purging was performed again until approximately 2 mL of liquid remained. The remaining liquid was transferred to a 10 mm × 20 cm chromatography column (filled with 100–200 mesh activated silica gel, with 10 mm of activated copper powder added to the top layer), and eluted with n-hexane into a glass vial. Eluent was reduced to approximately 1 mL by nitrogen purging, transferred to a storage bottle, and further purified to approximately 100 μL by nitrogen purging. The solution was stored at -20°C for later use. All n-alkane monomers were determined using gas chromatography / mass spectrometry, with Sigma-Aldrich C7-C64 standards used. 40 The n-alkane monomers were identified based on the retention time of the actual standards, and the concentrations of each n-alkane monomer were calculated based on the standard calibration curves of the corresponding standards.

[0051] As a characterization of the plant parent material source in organic matter, long-chain (C45-C45) alkanes are generally considered to be a significant source of organic matter. 31 +C 33 C is a marker derived from herbaceous plants. 27 +C 29 It is a hallmark indicator derived from terrestrial woody / deciduous plants, medium chain (C) 21 +C 23 +C 25 It is mainly produced by aquatic plants such as mosses, floating plants, and submerged plants, and contains short chains (C). 15 +C 17 +C 19 It mainly comes from phytoplankton, algae, etc.

[0052] Use the following formulas to calculate the proportions of herbaceous plants, woody plants, aquatic plants, and algae in plant-derived carbon inputs:

[0053] The proportion of herbaceous plants in plant-derived carbon input:

[0054] Herbaceous plants = (C 31 +C 33 ) / (C 15 +C 17 +C 19 +C 21 +C 23 +C 25 +C27 +C 29 +C 31 +C 33 );

[0055] The proportion of carbon input from plant sources in woody plants:

[0056] Woody plants = (C 27 +C 29 ) / (C 15 +C 17 +C 19 +C 21 +C 23 +C 25 +C 27 +C 29 +C 31 +C 33 );

[0057] The proportion of carbon input from plant sources:

[0058] Aquatic plants = (C 21 +C 23 +C 25 ) / (C 15 +C 17 +C 19 +C 21 +C 23 +C 25 +C 27 +C 29 +C 31 +C 33 );

[0059] The proportion of carbon input from plant sources in algae:

[0060] Algae = (C 15 +C 17 +C 19 ) / (C 15 +C 17 +C 19 +C 21 +C 23 +C 25 +C 27 +C 29 +C 31 +C 33 ).

[0061] Determination of amino sugars:

[0062] Amino sugars were extracted from the sediment using an acid hydrolysis method, as follows: 0.50 g of air-dried soil (passed through a 0.15 mm sieve) was accurately weighed into a 50 mL PTFE explosion-proof tube. 10 mL of 6 M hydrochloric acid solution was added using a separatory funnel, and the mixture was vortexed until homogeneous. Hydrolysis was carried out at 105 °C for 6 h in an oven. After the hydrolysate cooled to room temperature, the solution was shaken well and allowed to stand for 30 min. 0.5 mL of the supernatant was transferred to a glass test tube and dried under pure nitrogen. Then, 0.5 mL of ultrapure water was added to dissolve the supernatant, and the mixture was vortexed until homogeneous. The solution was then dried again under nitrogen. Finally, 2 mL of ultrapure water was added again to dissolve the supernatant, and the mixture was vortexed until homogeneous. The solution was filtered through a 0.45 μm pore size, 13 mm diameter needle filter. The filtrate was stored in a liquid chromatography vial at 4 °C, and the amino sugar content was determined using high-performance liquid chromatography (HPLC).

[0063] After obtaining the amino sugar content, the amino sugar (F-GluN) derived from fungal microbial residue carbon is calculated using the following formula:

[0064] F-GluN (μg g) -1 = total GluN (μg g) -1 )–2×MurN(μg g -1 )×(179.2 / 251.2).

[0065] Fungal Necromass Carbon (FNC), bacterial Necromass Carbon (BNC), and Total Necromass Carbon (TNC) were calculated using the following formulas after coefficient conversion:

[0066] FNC(μg g -1 ) = F - GluN × 9;

[0067] BNC(μg g -1 ) = MurN × 45;

[0068] TNC(μg g -1 )=FNC(μg g -1 )+BNC(μg g -1 ).

[0069] Validation was performed using a model combining stable isotopes and end-member mixing effects.

[0070] Determination of soil organic carbon and its stable isotopes:

[0071] The determination of stable carbon isotopes in soil was performed as follows: The sample, after inorganic carbon removal, was wrapped in tin foil and analyzed using a Flash EA1112 elemental analyzer (EA) and a MAT253 isotope ratio mass spectrometer (IRMS). The continuous flow interface was ConFloⅢ. All instruments were products of Thermo Finnegan, USA. Carbon in the soil sample was oxidized to CO2 and released. The resulting mixed gas was purified by passing through a halogen absorption tube and a drying tube to remove impurities, yielding pure CO2 gas. The total carbon content in the soil sample was determined by an infrared detector. The instrument configuration was as follows: EA furnace temperature 950℃, column temperature 50℃; ConFloⅢ helium pressure 120 kPa, CO2 pressure 150 kPa; IRMS vacuum degree 2.6 × 10⁻⁶. -8 kPa, emission current 1.5mA; δ 13 At C, the ions (m / z) monitored by IRMS were 44, 45, and 46. The formulas for calculating the isotope results are as follows:

[0072] δ 13 C(‰)=(R 样品 / R 标准 -1)×1000(‰);

[0073] The standard reference material is the international standard reference material PDB (Pee Dee Belemnite).

[0074] To quantitatively calculate carbon inputs from different sources in soil sediments, the inventors used the MixSIAR package in the R programming language to estimate the contributions of endogenous and exogenous carbon inputs. The model is based on the following formula:

[0075] δ 13 C sampl e = f plant ×δ 13 C plant +f terrestrial ×δ 13 C terrestrial +f marine ×δ 13 C marine ;

[0076] N / C sample =f plant ×N / C plant +f terrestrial ×N / C terrestrial +f marine ×N / C marine ;

[0077] f plant +f terrestrial +f marine =1;

[0078] f plant =f autochthonous ;

[0079] f terrestrial +f marine =f allochthonous ;

[0080] The proportions of endogenous, marine, and terrestrial carbon sources calculated by this model, multiplied by the soil organic carbon content, can be converted into quantitative carbon source inputs.

[0081] Results Analysis

[0082] By measuring the content of n-alkanes and amino sugars in soil sediments, the proportion of carbon sources from various plant types and the specific content of carbon sources from various microorganisms were obtained. This allowed for the quantification of carbon sources from each plant type (by subtracting the carbon content of microbial residues, an indicator of amino sugars, from the measured organic carbon content of soil sediments; the remaining organic carbon was considered to be plant-derived carbon input, i.e., the plant carbon input content (g kg) of each part). -1 ) = (Soil sediment organic carbon content - microbial residue carbon content) × the proportion of each plant in the plant-derived carbon input), thus obtaining the carbon content of each plant source and its contribution to soil sediment organic carbon, as well as the carbon content of microbial sources and its contribution to soil sediment organic carbon. Figure 1 ).

[0083] Specifically, for the Yellow River Estuary Salt Marsh Wetland and the Yancheng Salt Marsh Wetland, the measurement and analysis results are as follows: Table 2 shows the proportion of different types of plant carbon input in the plant carbon sources of the Yellow River Estuary Salt Marsh Wetland and the Yancheng Salt Marsh Wetland. The plant carbon in both salt marsh wetlands mainly comes from aquatic plants (accounting for more than 30%), followed by algae and woody plants, with herbaceous plants being relatively less. Table 3 shows the content of different types of microbial carbon sources in the Yellow River Estuary Salt Marsh Wetland and the Yancheng Salt Marsh Wetland. The microbial carbon in both salt marsh wetlands mainly comes from fungal residue carbon. Further calculations yielded the content of different types of plant carbon sources in the Yellow River Estuary Salt Marsh Wetland and the Yancheng Salt Marsh Wetland (Table 4). It is generally believed that in salt marsh wetlands, marine organic carbon input is mainly contributed by marine algae, while terrestrial organic carbon input is mainly contributed by terrestrial woody plants. Therefore, the inventors performed linear regression between the relevant indicators obtained from the quantitative analysis of n-alkanes and the results of stable isotope analysis, and found a significant positive correlation between them. Figure 2 This reflects the scientific validity of combining two biomarkers, n-alkanes and amino sugars, to achieve quantitative analysis of carbon inputs from plant and microbial sources in salt marshes.

[0084] In summary, by combining n-alkanes and amino sugars as biomarkers, we achieved quantitative analysis and comparison of carbon input from plant and microbial sources in salt marsh wetlands. We also found that woody plants can indicate terrestrial organic carbon input to some extent, while algae can indicate marine organic carbon input to some extent. Previous methods using stable isotopes could only roughly classify carbon sources in salt marsh wetlands into marine, plant, and terrestrial organic carbon sources. However, by combining n-alkanes and amino sugars as biomarkers, we further subdivided plant carbon sources into algae, aquatic plants, herbaceous plants, and woody plants, and microbial carbon sources into fungal and bacterial residue carbon sources, building upon the existing classification of plant and microbial carbon sources.

[0085] Table 2. Proportion of different types of plant carbon input in plant carbon sources in the two major regions

[0086]

[0087] Table 3 Microbial carbon source content in the two major regions

[0088]

[0089] Table 4. Plant carbon source content in the two major regions

[0090]

[0091]

[0092] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments, and various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. A method for comprehensive source tracing of wetland organic carbon, comprising the following steps: (1) Collection of sediment samples, wherein the sediment samples are sediments from salt marsh wetlands; (2) Determination of the content of biomarkers in sediment samples, wherein the biomarkers include n-alkanes and amino sugars; (3) Based on the measurement results of step (2), analyze the contribution of plant carbon source and microbial carbon source to sediment organic carbon; The n-alkanes include C7 to C40, and the amino sugars include glucosamine and muramic acid; The analysis of the contribution of plant carbon sources and microbial carbon sources to sediment organic carbon includes calculating the proportion of herbaceous plants, woody plants, aquatic plants, and algae in plant-derived carbon input, the carbon input content of herbaceous plants, the carbon input content of woody plants, the carbon input content of aquatic plants, the carbon input content of algae, as well as the carbon content of fungal residues and bacterial residues. The formula for calculating the proportion of herbaceous plants in plant-derived carbon input is: Herbaceous plants = (C 31 +C 33 ) / (C 15 +C 17 +C 19 +C 21 +C 23 +C 25 +C 27 +C 29 +C 31 +C 33 ); The formula for calculating the proportion of woody plants in plant-derived carbon input is: Woody plants = (C 27 +C 29 ) / (C 15 +C 17 +C 19 +C 21 +C 23 +C 25 +C 27 +C 29 +C 31 +C 33 ); The formula for calculating the proportion of aquatic plants in plant-derived carbon input is: Aquatic plants = (C 21 +C 23 +C 25 ) / (C 15 +C 17 +C 19 +C 21 +C 23 +C 25 +C 27 +C 29 +C 31 +C 33 ); The formula for calculating the proportion of algae in plant-derived carbon input is: Algae = (C 15 +C 17 +C 19 ) / (C 15 +C 17 +C 19 +C 21 +C 23 +C 25 +C 27 +C 29 +C 31 +C 33 ); The carbon content of fungal and bacterial residues is calculated using the following formulas: fungal residue carbon content = F-GluN × 9, bacterial residue carbon content = MurN × 45, where F-GluN is an amino sugar that indicates the carbon content of fungal microbial residues, and MurN is a cell muramic acid. The F-GluN is calculated using the following formula: F-GluN = total GluN – 2 × MurN × (179.2 / 251.2), where GluN is glucosamine; The plant carbon input content is calculated using the following formula: different plant carbon input content = (sediment organic carbon content - microbial residue carbon content) × the proportion of plant in plant-derived carbon input, where microbial residue carbon content = fungal residue carbon content + bacterial residue carbon content; The sediment samples were collected by avoiding biological burrows and selecting soil samples with no obvious biological disturbance.

2. The method according to claim 1, characterized in that, The content of n-alkanes in sediment samples was determined by gas chromatography / mass spectrometry, and the content of amino sugars in sediment samples was determined by high performance liquid chromatography.

3. The application of the method according to any one of claims 1 to 2 in the study of ecosystem carbon cycle processes.

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