A method for early warning of spartina invasion

Abstract

The present application relates to a kind of early warning methods of Spartina alterniflora invasion, including sample collection, sample stable carbon, nitrogen isotope ratio determination, mixed model analysis and spartina alterniflora invasion prediction etc. 13 C and δ 15 N value, in combination with stable isotope end member mixing model, can identify the signal of spartina alterniflora, and early warning can be carried out according to its change characteristics to its possible recurrence, which can realize the early warning of spartina alterniflora invasion, and achieve the purpose of early prevention and control.

Description

Technical Field

[0001] This invention relates to the field of environmental monitoring technology, and in particular to an early warning method for the invasion of Spartina alterniflora. Background Technology

[0002] Coastal wetland ecosystems possess extremely high carbon sequestration and storage capabilities, making their carbon sink function particularly important in the context of global warming. The invasion of Spartina alterniflora is one of the major problems facing coastal wetland ecosystems, causing degradation of native vegetation and reduced biodiversity.

[0003] Currently, the removal and ecological restoration of damaged Spartina alterniflora in wetlands are widely underway. Due to its extremely strong vitality and dispersibility, long-term ecological and environmental monitoring is necessary after its removal to prevent its re-invasion on a large scale. Existing monitoring technologies are mainly based on ground vegetation surveys. Because this method relies primarily on visual observation, seeds and seedlings partially hidden in the soil are easily overlooked. Furthermore, due to high labor costs and complex operations, surveys are typically conducted only 2-4 times per year, making it difficult to detect existing Spartina alterniflora in a timely manner, let alone predict future invasions. In short, existing methods often have a certain lag in early warning of Spartina alterniflora invasions. Summary of the Invention

[0004] The purpose of this invention is to overcome the lag in existing Spartina alterniflora monitoring technologies and to provide an early warning method for Spartina alterniflora invasion.

[0005] The technical principles and solutions adopted in this invention are as follows: Stable isotope ratio (δ) refers to the relative thousandths difference between the ratios of two isotopes in a sample and their corresponding ratios in a standard. The differences in stable carbon and nitrogen isotope characteristic values ​​of organic matter from different sources are currently used to identify the origin of organic matter in a large number of nearshore and estuarine sediments. 13 C and δ 15 This study was completed based on the analysis of N. The inventors discovered that *Spartina alterniflora* is a significant source of soil organic matter in coastal wetlands, and changes in its contribution to soil organic matter can serve as a signal for assessing its clearance, residue, and recurrence. Based on an investigation of potential sources of soil organic matter in the project site, the δ¹⁸O value of its contribution to organic matter was obtained. 13 C and δ 15 By combining the N value with a stable isotope end-member mixing model, the signal of Spartina alterniflora can be identified, and its change characteristics can be used to provide early warning of possible recurrence.

[0006] The specific plan is as follows:

[0007] An early warning method for Spartina alterniflora invasion includes the following steps:

[0008] (1) Sample collection: Collect soil samples from the area to be tested and the area where Spartina alterniflora has just been cleared, and select soil organic matter source samples, including at least one of plant samples and particulate organic matter samples from the outer water body;

[0009] (2) Sample pretreatment: The sample is pretreated to obtain a sample to be tested that meets the requirements of elemental analyzer and stable isotope ratio mass spectrometry.

[0010] (3) The sample to be tested is sent to the oxidation furnace and reduction furnace of the elemental analyzer to form CO2 and / or N2, respectively. After separation and purification by chromatographic column, it is sent to a stable isotope ratio mass spectrometer to determine the organic matter content and δ¹⁴ ppm. 13 C and δ 15 N-value determination;

[0011] (4) Calculate according to formula (I), where δ i and δ M These are the stable isotope values ​​of the source and the mixture, respectively, f i γ is the contribution ratio of the i-th source to the mixture. i It represents the stable isotope value of the i-th source and its fractionation value with the mixture, where n is a positive integer representing the n-th source; M represents the mixture, corresponding to the soil sample.

[0012] δ M =f1(δ1+γ1)+f2(δ2+γ2)+...f i (δ i +γ i )…+f n (δ n +γ n (I)

[0013] The sample δ measured in step (3) 13 C and δ 15 Substituting the N value into formula (I), the contribution ratio f of Spartina alterniflora in the area to be detected and the area where Spartina alterniflora has just been cleared are calculated respectively. 待测互花米草 f 基准互花米草 ;

[0014] (5) Spartina alterniflora invasion prediction: based on the contribution ratio f of Spartina alterniflora in areas that have just been cleared of Spartina alterniflora. 基准互花米草 As the baseline value, when the detection area f 待测互花米草 A value more than three times the baseline indicates that Spartina alterniflora will re-invade; otherwise, it is determined that there is no Spartina alterniflora invasion.

[0015] Further, the plant samples mentioned in step (1) include Spartina alterniflora and mangrove plants, wherein the whole plant sample of Spartina alterniflora is taken, and the roots, stems and leaves of the mangrove plants are collected and combined into one sample;

[0016] The sample of particulate organic matter in the outer water body was obtained by filtering the outer seawater through a filter membrane with a pore size of 0.1-10 μm and collecting the solid phase.

[0017] Furthermore, the soil organic matter source samples mentioned in step (1) also include benthic algae, freshwater, and sewage, and the δ of the organic matter contributed by these samples is... 13 C and δ 15 The N value is determined based on reported values ​​from similar areas, or by on-site measurement.

[0018] Further, the pretreatment in step (2) includes: drying the plant sample at 50-70℃ and then grinding it; removing plant residues larger than 1cm from the soil sample, drying it at 50-70℃, grinding it, and sieving it; acidifying all the above samples with concentrated hydrochloric acid for more than 48 hours to remove inorganic components; and then drying all the samples again at 50-70℃.

[0019] Furthermore, the temperature of the oxidation furnace in step (3) is 900-1000℃, preferably 950℃; the temperature of the reduction furnace is 600-700℃, preferably 650℃. Different temperatures do not affect the detection results; as long as the temperature is within the above range, the detection of carbon isotope and nitrogen isotope content can be achieved.

[0020] Furthermore, in step (4), the isotope tracing model software IsoSource is used. When the source is greater than n+1, all possible combinations of each source are calculated by superposition according to the given increment. The weighted average value of each combination is compared with the measured value of the target mixture. If it is within the set tolerance, it is considered a possible solution. In this way, the contribution ratio of different sources to the mixture is obtained.

[0021] Furthermore, f 基准互花米草 =0.1-10%.

[0022] Furthermore, the method provides early warning of impending Spartina alterniflora invasion 3-6 months in advance.

[0023] Furthermore, when the area to be detected f 待测互花米草 If the value remains above the baseline for more than 3 months, it indicates that recurrent Spartina alterniflora plants will be visually observed within 3-6 months after the last test.

[0024] Beneficial effects: This invention can fill the gap in the monitoring of underground seeds and seedlings in traditional methods. At the same time, due to its simple operation, it can increase the monitoring frequency and coverage, so as to achieve the purpose of early warning and prevention of Spartina alterniflora invasion. Attached Figure Description

[0025] To more clearly illustrate the technical solution of the present invention, the accompanying drawings will be briefly described below. Obviously, the drawings described below only relate to some embodiments of the present invention and are not intended to limit the present invention.

[0026] Figure 1 This is a flowchart provided in one embodiment 1 of the present invention. Detailed Implementation

[0027] Preferred embodiments of the present invention will now be described in more detail. While preferred embodiments of the present invention are described below, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Where specific techniques or conditions are not specified in the embodiments, they are performed in accordance with techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products. In the following embodiments, unless otherwise specified, "%" refers to weight percentage.

[0028] Example 1

[0029] The Quanzhou Bay Estuary Wetland Nature Reserve, located in southeastern Fujian Province, faces a major ecological problem caused by the invasion of Spartina alterniflora, which has led to the degradation of native mangrove vegetation and a decrease in biodiversity. Since the second half of 2022, Fujian Province has launched a comprehensive campaign to remove Spartina alterniflora and has been restoring damaged wetlands by replanting mangrove plants.

[0030] To test the usability of this invention, it was tested on an ecologically restored mudflat within the Quanzhou Estuary Wetland Nature Reserve from September 2022 to June 2023. For details, please refer to [link to relevant documentation]. Figure 1 The operation steps are as follows:

[0031] (1) Preliminary Investigation: Preliminary investigation revealed that the main sources of soil organic matter at the project site include Spartina alterniflora, mangrove plants (after replanting), benthic algae, and external water sources (seawater, freshwater, and wastewater). To determine the contribution ratio of each source to the soil organic matter at the project site, it is necessary to obtain the stable carbon and nitrogen isotope ratios (δ¹⁸O) of the organic matter from the aforementioned sources. 13 C and δ 15 N). During the test, the δ¹⁸O⁻ of organic matter contributed by benthic algae, freshwater, and wastewater was measured. 13 C and δ 15 The N value is derived from reported values ​​in similar regions, while the carbon and nitrogen isotope ratios of Spartina alterniflora, mangrove plants, and marine organic matter are derived from field measurements.

[0032] (2) Sample collection: Sample collection included plant sample collection, marine particulate organic matter sample collection, and soil sample collection. For Spartina alterniflora, whole plant samples were collected and frozen at -20℃. For mangrove plants, roots, stems, and leaves were collected separately and combined into one sample, which was then frozen at -20℃. Marine particulate matter was collected by filtering 2L of outer seawater through a glass fiber filter membrane with a pore size of 0.3μm (pre-burned at 450℃ for 4h), and the resulting membrane sample was stored at -20℃ for analysis. Surface soil samples were collected using soil sampling tubes with an inner diameter of 5cm and stored at -20℃ for analysis.

[0033] (3) Sample pretreatment: After drying the plant samples in an oven at 60℃, grind them thoroughly and mix them evenly; after removing large pieces of plant debris from the soil samples, dry them in an oven at 60℃, grind them thoroughly and sieve them; thaw the membrane samples in the laboratory; acidify all of the above samples with concentrated hydrochloric acid, and control the acid fumigation time to more than 48 hours to fully remove the inorganic components; then, place the samples in an oven at 60℃ again to dry them thoroughly before testing.

[0034] (4) Sample determination: Take 0.1g each of fully dried and ground plant and soil samples, wrap them in a tin cup for testing; take one-quarter of the dried membrane sample, wrap it in a tin cup for testing; the organic matter content and δ in the samples... 13 C and δ 15 The nitrogen value was determined using an elemental analyzer and stable isotope ratio mass spectrometry (Thermo Delta). plus The analysis was performed using a combination of X-ray diffraction (XPD) and carbon dioxide (XDC) spectrometry. The sample was processed in the oxidation furnace (950℃) and reduction furnace (650℃) of the elemental analyzer to form CO2 or N2. After separation and purification by chromatographic column, the CO2 or N2 was sent to a stable isotope ratio mass spectrometer via a ConFlo II interface for analysis. The relative deviations of the isotope ratios were all less than 0.2‰.

[0035] (5) Spartina alterniflora signal identification:

[0036] The main principle for identifying Spartina alterniflora is the law of conservation of stable isotope mass:

[0037] δ M =f1(δ1+γ1)+f2(δ2+γ2)+...f i (δ i +γ i )…+f n (δ n +γ n )

[0038] Where δ i and δ M These are the stable isotope values ​​of the source and the mixture, respectively, f i γ is the contribution ratio of the i-th source to the mixture.i It is the fractional value of the stable isotope ratio of the i-th source and its mixture, i.e., the quotient of the two. In the formula, n is a positive integer, representing the n-th source; M represents the mixture, which is the soil sample.

[0039] In this invention, the identification of Spartina alterniflora was accomplished using IsoSource, a mainstream isotope tracing modeling software, and the δ¹⁸O values ​​of various obtained samples were measured. i Values ​​(including carbon and nitrogen isotopes), input into the model software, γ i It uses the software's built-in settings; when the number of sources is greater than n+1, it calculates all possible combinations of sources by superposition according to a given increment (usually set at 1% or 2%), compares the weighted average of each combination with the measured value of the target mixture, and if it is within the set tolerance, it is considered a possible solution. This is used to obtain the contribution ratio of different sources to the mixture, i.e., f. i .

[0040] (6) Trial results: From September 2022 to June 2023, the main sources and contribution ratio of organic carbon in the soil of an ecological restoration tidal flat in the Quanzhou Bay Estuary Wetland Nature Reserve were monitored. The sampling times were September 2022 (before the removal of Spartina alterniflora), October 2022 (after the removal of Spartina alterniflora), December 2022 (after the replanting of mangrove plants), March 2023 and June 2023.

[0041] Table 1 shows the main sources and contributions of soil organic matter at each station during the survey period. After Spartina alterniflora was cleared, its signal weakened rapidly but was still detectable, possibly due to the presence of small-particle Spartina alterniflora residues in the soil. In December 2022, except for station 5, the signal values ​​of Spartina alterniflora at the other stations increased significantly, with signal intensities reaching 3 to 27 times that of October. This indicates that Spartina alterniflora is likely to recur, but is currently still in the germination stage, and no Spartina alterniflora plants were found at the project site. From December 2022 to March 2023, the Spartina alterniflora signal at each station remained stable. The signal intensity continued to increase until March 2023, when the signal values ​​of Spartina alterniflora at stations 1 to 4 were 3 to 137 times that of October, but no Spartina alterniflora plants were observed at this time. In June 2023, the signal values ​​of Spartina alterniflora at stations 1 to 4 remained at a high level, 3 to 131 times that of October, and Spartina alterniflora plants could be observed at all of the above stations. In contrast, the signal value of Spartina alterniflora at station 5 was lower, only 1.5 times that of October 2023, and no Spartina alterniflora plants were observed at this station.

[0042] Therefore, the contribution ratio of Spartina alterniflora measured immediately after its eradication can be used as a baseline value. By comparing the difference between this value and the subsequent measured value, an early warning of Spartina alterniflora re-invasion can be issued. When the observed value increases to three times the baseline value, it indicates a possible re-invasion of Spartina alterniflora; when the high signal value persists for more than three months, it indicates that re-invaded Spartina alterniflora plants may be observed within the next three months.

[0043] The above experiments show that there is a mechanism for δ in soil. 13 C and δ 15 Monitoring and analyzing N-values, and identifying signals from Spartina alterniflora, can efficiently determine the removal, residue, and recurrence of Spartina alterniflora, and provide timely warnings of potential recurrences, thus compensating for the shortcomings of visual observation in vegetation surveys and improving the efficiency of ecological early warning.

[0044] Table 1. Contribution ratio of Spartina alterniflora to soil organic matter

[0045]

[0046]

[0047] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0048] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0049] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. An early warning method for Spartina alterniflora invasion, characterized in that: Includes the following steps: (1) Sample collection: Collect soil samples from the area to be tested and the area where Spartina alterniflora has just been cleared, and select soil organic matter source samples, including at least one of plant samples and particulate organic matter samples from the outer water body; (2) Sample pretreatment: The sample is pretreated to obtain a sample to be tested that meets the requirements of elemental analyzer and stable isotope ratio mass spectrometry. (3) The sample to be tested is sent to the oxidation furnace and reduction furnace of the elemental analyzer to form CO2 and / or N2, respectively. After separation and purification by chromatographic column, it is sent to a stable isotope ratio mass spectrometer to determine the organic matter content and δ¹⁴ ppm. 13 C and δ 15 N-value determination; (4) Calculate according to formula (I), where δ i and δ M These are the stable isotope values ​​of the source and the mixture, respectively, f i γ is the contribution ratio of the i-th source to the mixture. i It represents the stable isotope value of the i-th source and its fractionation value with the mixture, where n is a positive integer representing the n-th source; M represents the mixture, corresponding to the soil sample. d M =f1(δ1+γ1)+f2(δ2+γ2)+...f i (d i +g i )…+f n (d n +g n ) (I) The sample δ measured in step (3) 13 C and δ 15 Substituting the N value into formula (I), the contribution ratio f of Spartina alterniflora in the area to be detected and the area where Spartina alterniflora has just been cleared are calculated respectively. 待测互花米草 f 基准互花米草 ; (5) Spartina alterniflora invasion prediction: based on the contribution ratio f of Spartina alterniflora in areas that have just been cleared of Spartina alterniflora. 基准互花米草 As the baseline value, when the detection area f 待测互花米草 A value more than three times the baseline indicates that Spartina alterniflora will re-invade; otherwise, it is determined that there is no Spartina alterniflora invasion.

2. The early warning method for Spartina alterniflora invasion according to claim 1, characterized in that: The plant samples mentioned in step (1) include Spartina alterniflora and mangrove plants, wherein the whole plant sample of Spartina alterniflora is taken, and the roots, stems and leaves of the mangrove plants are collected and combined into one sample; The sample of particulate organic matter in the outer water body was obtained by filtering the outer seawater through a filter membrane with a pore size of 0.1-10 μm and collecting the solid phase.

3. The early warning method for Spartina alterniflora invasion according to claim 2, characterized in that: The soil organic matter source samples mentioned in step (1) also include benthic algae, freshwater, and sewage, and the δ of organic matter contributed by these samples is... 13 C and δ 15 The N value is determined based on reported values ​​from similar areas, or by on-site measurement.

4. The early warning method for Spartina alterniflora invasion according to claim 2, characterized in that: The pretreatment in step (2) includes: drying the plant sample at 50-70℃ and then grinding it; removing plant debris larger than 1cm from the soil sample, drying it at 50-70℃, grinding it, and sieving it; acidifying all the above samples with concentrated hydrochloric acid for more than 48 hours to remove inorganic components; and then drying all the samples again at 50-70℃.

5. The early warning method for Spartina alterniflora invasion according to any one of claims 1-4, characterized in that: The temperature of the oxidation furnace in step (3) is 900-1000℃; the temperature of the reduction furnace is 600-700℃.

6. The early warning method for Spartina alterniflora invasion according to any one of claims 1-4, characterized in that: In step (4), the isotope tracing model software IsoSource is used. When the source is greater than n+1, all possible combinations of each source are calculated by superposition according to the given increment. The weighted average value of each combination is compared with the measured value of the target mixture. If it is within the set tolerance, it is considered a possible solution. In this way, the contribution ratio of different sources to the mixture is obtained.

7. The early warning method for Spartina alterniflora invasion according to claim 6, characterized in that: f 基准互花米草 ＝0.1-10％。 8. The early warning method for Spartina alterniflora invasion according to claim 1, characterized in that: The method provides early warning of impending Spartina alterniflora invasion 3-6 months in advance.

9. The early warning method for Spartina alterniflora invasion according to claim 8, characterized in that: When the area to be detected is f 待测互花米草 If the value remains above the baseline for more than 3 months, it indicates that recurrent Spartina alterniflora plants will be visually observed within 3-6 months after the last test.

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