Method for in-situ monitoring of gas fluxes of different components in wetland ecosystem

Abstract

The invention belongs to the technical field of gas measurement, and particularly provides a method for in-situ monitoring of gas fluxes of different components in a wetland ecosystem. The method comprises the following steps: firstly, before in-situ monitoring, completely removing plant root systems and benthic organisms in bottom mud of a to-be-monitored sample plot; respectively fixing the flux rings A, B, C, D and E in a to-be-detected sample plot according to the method provided by the invention; and finally, monitoring and evaluating the gas fluxes of five components including bottom mud, root systems, plants, water microorganisms and water planktons in the wetland ecosystem only through simple calculation. The invention provides a new technology for ecology field long-term positioning monitoring. According to the method, the defect that the gas flux of specific components cannot be measured through macroscopic monitoring is overcome, and a scientific basis is provided for formulating protection and management strategies for the components such as plants, soil, water, atmosphere, water microorganisms and planktons in a wetland ecosystem.

Description

Technical Field

[0001] The invention belongs to the technical field of gas measurement, and in particular relates to a method for in-situ monitoring of gas fluxes of different components in a wetland ecosystem. Background Art

[0002] Wetlands are the transition zone between land and water. Wetland ecosystems are a special transitional ecosystem between terrestrial ecosystems and aquatic ecosystems. Therefore, they have rich resources of both terrestrial and aquatic ecosystems, such as plants, soil, water, atmosphere, aquatic microorganisms and plankton. They have a variety of functions and play an irreplaceable role in both humans and the natural environment.

[0003] The organic carbon pool stored in wetland ecosystems accounts for 20%-30% of the total carbon pool in the surface layer of the terrestrial ecosystem, and the carbon storage per unit area is three times that of forests. 2 and CH 4 Gas flux is particularly important for monitoring wetland carbon sources and sinks.

[0004] Currently, wetland ecosystem greenhouse gases (CO 2 , CH 4 The flux measurement and evaluation of wetland ecosystems mainly adopts macroscopic methods, such as using a portable trace gas analyzer (LI-COR, USA, Li-7810) to measure the greenhouse gas flux at the water-air interface or using a vortex tower analysis system platform (LI-COR, USA, Li-7700) to evaluate the flux of greenhouse gases in the wetland atmosphere. This method measures the gas flux of wetland ecosystems from a macroscopic perspective and cannot grasp the CO2 content of specific components of wetland ecosystems such as plants, soil, water, atmosphere, aquatic microorganisms and plankton. 2 and CH 4 However, the gas flux in the wetland ecosystem is composed of multi-component gas flux (including sediment components (microorganism respiration in the sediment), root components (plant root respiration in the sediment), plant components (submerged plant respiration), water body microorganism components (microorganism respiration in the water body) and water body plankton components (plankton and plant respiration in the water body)). The components such as plants, soil, water, atmosphere, water body microorganisms and plankton are not isolated things, but are interconnected and interact with each other. If it is impossible to measure the CO2 of specific components such as plants, soil, water, atmosphere, water body microorganisms and plankton in the wetland ecosystem, it is difficult to determine the CO2 of specific components such as plants, soil, water, atmosphere, water body microorganisms and plankton in the wetland ecosystem. 2 and CH 4If the flux is not measured, the relationship between environmental variables and greenhouse gas flux and their influencing factors cannot be further analyzed. Therefore, providing a method for measuring the gas flux of each component of wetland ecosystem is of great significance for the protection and management of wetland ecosystem. Summary of the invention

[0005] The purpose of the present invention is to provide a method for in-situ monitoring of gas fluxes of different components in a wetland ecosystem, so as to overcome the defect that macroscopic monitoring cannot measure the gas fluxes of specific components in a wetland ecosystem.

[0006] To achieve the above object, the present invention adopts the following technical solutions: A method for in situ monitoring of gas fluxes of different components in a wetland ecosystem comprises the following steps: (1) A square with uniform species diversity was selected in the wetland to be monitored as the sample site to be tested. One year before the in-situ monitoring, the water in the sample site to be tested was drained, all the bottom mud with plant roots was dug out, and the plant roots and benthic organisms in the bottom mud were removed; in the spring of the year of in-situ monitoring, the excavated bottom mud was backfilled into the sample site to be tested, and water with a depth of ≥ 0.5 m was injected into it; Preferably, the bottom mud is dug out in the winter of the year before the in-situ monitoring; plant roots and benthic organisms in the bottom mud can be removed by successively drying, air-drying, crushing, and sieving; (2) Fix flux rings A, B, C, D, and E in the sample plot to be tested according to the following method, wherein the flux rings A, B, C, D, and E are all long round tubes with the same radius and wall thickness and an open top, and are all provided with two holes on the opposite side walls at the same height between the bottom mud and the water surface. The two holes on each flux ring are of the same size and opposite positions, so that the water can flow normally in the ring and keep consistent with the external water level: ① Check and remove the above-ground parts and all roots of submerged plants germinated in the bottom mud seed bank at the location of the flux ring A, and insert the flux ring A into the bottom mud; the depth of the flux ring A inserted into the bottom mud is greater than the maximum growth length of the roots of the submerged plants in the sample plot to be tested (to block the roots of the submerged plants in the sample plot to be tested from entering); ② Check and remove the above-ground parts of submerged plants germinated in the bottom mud seed bank where the flux ring B is located, and insert the flux ring B into the bottom mud; the depth of the flux ring B inserted into the bottom mud is preferably such that the lateral root system of the submerged plants is not blocked from growing and entering; ③ Insert the flux ring C into the bottom mud, and the depth of the flux ring C into the bottom mud should not block the lateral root growth of submerged plants; ④ Seal the bottom ends of flux ring D and flux ring E, place them on the bottom mud surface respectively, and seal the two holes on the side wall of flux ring E with a plankton net; (3) 24 hours before the start of in situ monitoring, the water in flux ring E was filtered through a plankton net and then added; (4) Use a gas flux measuring instrument to measure the gas flux in flux rings A, B, C, D, and E respectively, and calculate the gas flux of different components in the wetland ecosystem to be measured according to the following formula: Gas flux of sediment components = gas flux of flux loop A - gas flux of flux loop D; Root component gas flux = flux loop B gas flux - flux loop A gas flux; Plant component gas flux = flux loop C gas flux - flux loop B gas flux; Gas flux of water microbial components = gas flux of flux loop E; Gas flux of plankton component in water body = gas flux of flux loop D - gas flux of flux loop E.

[0007] The specific wetland ecosystem composition and gas flux loop settings are as follows: Figure 1 As shown, the specific gas flux composition of each flux ring is as follows: The gas flux in flux loop A is composed of three gas fluxes: sediment component, water microbial component and water plankton component; The gas flux in flux loop B is composed of four gas fluxes: sediment component, root component, water body microbial component and water body plankton component; The gas flux in flux loop C is composed of five gas flux components: sediment component, root component, plant component, water body microbial component and water body plankton component; The gas flux in flux loop D is composed of two gas fluxes: the water microbial component and the water plankton component; The gas flux in flux loop E is composed only of the gas flux of the water microbial components.

[0008] Furthermore, flux rings A, B, C, D, and E are all made of highly transparent acrylic material to eliminate the influence of light on the gas flux measurement.

[0009] Furthermore, the flux rings A, B, C, D, and E are each provided with two holes on the opposite side walls at 1 / 2 of the water depth.

[0010] Furthermore, the flux rings A, B, C, D, and E are all above the water surface, and the heights above the water surface are the same or different.

[0011] Furthermore, before using the gas flux measuring instrument to measure the gas flux in the flux rings A, B, C, D, and E, a wooden stick is used to move along the outer wall of each flux ring to remove the plants that have entered the ring through the side wall opening, and the side wall opening is sealed. Preferably, a rubber band is used to cover the flux ring opening to make it sealed.

[0012] Furthermore, in step (2), the fixing time of flux loop A is before the sludge is backfilled, and the fixing time of flux loops B, C, D, and E is after the sludge is backfilled.

[0013] Furthermore, in step (2), the depth of the insertion of flux ring B and flux ring C into the bottom mud is 5-10 cm.

[0014] Furthermore, in step (2), the intervals between the flux rings A, B, C, D, and E are fixed at 10-20 cm.

[0015] Furthermore, the pore size of the plankton net is mainly to be able to intercept plankton, preferably 0.064 mm.

[0016] Furthermore, during experimental measurements, the instrument can only be operated around the sample site to be measured, and the water body must not be disturbed. Keep quiet during the entire measurement process to reduce interference with the environment around the gas flux ring, which will affect the measured data values ​​of the gas flux of each ring, and ensure that the obtained measurement data is true and reliable.

[0017] The beneficial effects of the present invention are: The present invention provides a method for in-situ monitoring of gas fluxes of different components in a wetland ecosystem. According to the method of the present invention, five flux rings are fixed respectively, and the gas fluxes of five components of the wetland ecosystem, namely, sediment, root system, plant, water microorganisms and water plankton, can be monitored and evaluated respectively with simple calculations. The flux data of different components in the wetland ecosystem will help us to carry out accurate CO2 analysis for each component of the wetland ecosystem. 2 and CH 4 The flux of gases such as nitrogen and nitrogen can be evaluated, and the understanding of wetlands can be deepened, providing a scientific basis for the formulation of protection and management strategies for components such as plants, soil, water, atmosphere, aquatic microorganisms and plankton in wetland ecosystems. The present invention will provide a new technology for long-term positioning monitoring in the field of ecology. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of the wetland ecosystem composition and gas flux loops.

[0019] Figure 2 Schematic diagram of in situ monitoring of gas fluxes of different components in wetland ecosystems. DETAILED DESCRIPTION

[0020] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0021] The method for in-situ monitoring of gas fluxes of different components in a wetland ecosystem using the present invention comprises the following steps: (1) Setting up fixed sample plots and fixed plots A 4×4 m square with uniform species diversity was selected in the wetland to be tested as the test site. A 0.5×2 m fixed sample plot was set up in the test site to fix flux rings A, B, C, D, and E. The interval between each gas flux ring was 20 cm.

[0022] (2) Sample plot processing A fence with a height of 1.5 m was set up around the 4×4 m plot to be tested. In the winter of the year before the in-situ monitoring, the water in the fence was pumped out, and the bottom mud in the fence was dug 2 m underground and cleared out. After drying, air drying, and crushing, it was passed through a 4 mm pore sieve to remove plant roots and benthic organisms in the bottom mud. The sieved soil was mixed evenly and set aside.

[0023] The soil in the sample plot to be tested is not sown with submerged plants, and the germplasm resources in the self-generated soil seed bank of the bottom mud are relied on for germination.

[0024] (3) Backfilling of sample plots and setting of gas flux rings.

[0025] In the spring of the year of in situ monitoring, the soil from step (2) was backfilled into the enclosure of the 4×4 m plot to be tested, and the water level in the enclosure was controlled at 0.5 m using an automatic water inlet. Five flux rings were fixed as follows: ① Check and remove the submerged plants germinated in the bottom mud seed bank at the location of flux ring A, and use a small iron rake to remove the above-ground parts and all roots of the submerged plants; before backfilling the bottom mud, insert the flux ring A into the bottom mud to a depth of 90 cm (i.e. the bottom end of the flux ring A is 90 cm from the bottom mud surface); ② Check and remove the submerged plants germinated in the bottom mud seed bank at the location of flux ring B, and use a small iron rake to remove the above-ground parts of the submerged plants; after the bottom mud is backfilled, insert the flux ring B into the bottom mud by 10 cm (so as not to block the lateral root growth of the submerged plants); ③ After the bottom mud is backfilled, the flux ring C is inserted into the bottom mud by 10 cm (so as not to block the lateral root growth of submerged plants); ④ After the bottom mud is backfilled, the bottom ends of flux ring D and flux ring E are sealed and placed on the bottom mud surface respectively; and the two holes on the side wall of flux ring E are sealed with a plankton net; Among them, the flux rings A, B, C, D, and E are all long round tubes made of transparent acrylic material, with an outer diameter of 20 cm, a wall thickness of 0.3 cm, and an inner diameter of 19.4 cm. When fixed, they all leak 10 cm above the water surface (the flux ring A is 150 cm high, the flux rings B and C are 70 cm high, and the flux rings D and E are 60 cm high). At a water depth of 25 cm, two holes are opened on the opposite side walls of each ring to allow water to flow normally in the ring body and keep consistent with the external water level.

[0026] (4) 24 hours before the measurement, the water in flux ring E was filtered through a plankton net and then added; (5) Numerical determination of gas flux in each ring (specifically, the schematic diagram of in-situ monitoring at the sample site to be tested is as follows Figure 2 shown) Before measuring the gas flux data, use a wooden stick to move along the outer wall of the gas flux ring to remove the plants that have entered the ring through the opening, and use a 10 cm wide rubber band to cover the opening of the flux ring to make it sealed; The CO of each flux loop was measured monthly using a Li-7810 (LI-COR, Lincoln, Nebraska, USA) instrument. 2 and CH 4 The flux was measured three times (usually around the 5th, 15th and 25th), each time between 9:00 and 11:00 in the morning on a clear day; During the experimental measurement, the instrument can only be operated around the sample site to be measured, and the water body must not be disturbed. Keep quiet during the whole measurement process to reduce the interference with the surrounding environment of the gas flux ring, which will affect the measured data value of the gas flux of each ring, and ensure that the obtained measurement data is true and reliable; step: a. Preheat the Li-7810 host and Smart Chamber for 30 minutes to ensure the stability of the measured values; b. Set the measurement parameters, pipeline length 200 cm, gas flux ring cross-sectional area 295.59 cm 2 , the gas flux ring is 10 cm above the water surface. The measurement time is 60 s, and the interval ventilation time is 15 s; c. Gently place the modified gas chamber on the top of the gas flux ring (to avoid vibration affecting the measurement data), click Start to start the measurement; d. Set labels and save data; e. After the measurement is completed, remove the 10 cm wide rubber band ring to make the environment inside and outside the ring the same.

[0027] (6) Gas flux data processing The monthly mean is the average of multiple gas flux measurements of each flux ring in the same month, the annual mean is the average of 9 months in the same year (water bodies freeze in winter in northern my country, and can be measured for 12 months a year in the south), and the seasonal value is the average of the corresponding monthly mean values. The spring value is the average of March to May, the summer value is the average of June to August, and the autumn value is the average of September to November. The specific gas flux measurement results are shown in Tables 1 and 2.

[0028] Table 1. CO of each flux ring 2 Seasonal mean of flux Table 2. CH of each flux ring 4 Seasonal mean of flux Among them, the gas flux in flux loop A is composed of three parts of gas flux, namely, sediment component, water body microorganism component and water body plankton component; the gas flux in flux loop B is composed of four parts of gas flux, namely, sediment component, root component, water body microorganism component and water body plankton component; the gas flux in flux loop C is composed of five parts of gas flux, namely, sediment component, root component, plant component, water body microorganism component and water body plankton component; the gas flux in flux loop D is composed of two parts of gas flux, namely, water body microorganism component and water body plankton component; the gas flux in flux loop E is composed only of the gas flux of water body microorganism component.

[0029] The gas fluxes of different components in the wetland ecosystem to be tested were calculated according to the following formulas, and the results are shown in Tables 3 and 4: Gas flux of sediment components = gas flux of flux loop A - gas flux of flux loop D; Root component gas flux = flux loop B gas flux - flux loop A gas flux; Plant component gas flux = flux loop C gas flux - flux loop B gas flux; Gas flux of water microbial components = gas flux of flux loop E; Gas flux of plankton component in water body = gas flux of flux loop D - gas flux of flux loop E.

[0030] Table 3. CO of each component 2 Seasonal mean of flux Table 4. CH of each component 4 Seasonal mean of flux From the results in Tables 1 and 3, it can be found that in wetland ecosystems, sediment components, root components and water microbial components emit CO 2 , as a carbon source; plant components and water body plankton components absorb CO 2 , which is a carbon sink; the entire wetland ecosystem CO 2 When the amount absorbed is greater than the amount emitted, it is a carbon sink.

[0031] From the results in Tables 2 and 4, it can be found that in wetland ecosystems, sediment components, plant components, root components, water body plankton components and water body microbial components all emit CH 4 , as a carbon source, wetland ecosystem CH 4 Emissions mainly come from sediment components and root components, and plant components promote CH 4emission.

[0032] The above embodiments are only used to illustrate the present invention, and any equivalent changes and improvements made on the basis of the technical solution of the present invention should not be excluded from the protection scope of the present invention.

Claims

1. A method for in situ monitoring of gas fluxes of different components in a wetland ecosystem, characterized in that: The following steps are involved: (1) A square with uniform species diversity was selected in the wetland to be monitored as the sample site to be tested. One year before the in-situ monitoring, the water in the sample site to be tested was drained, all the bottom mud with plant roots was dug out, and the plant roots and benthic organisms in the bottom mud were removed; in the spring of the year of in-situ monitoring, the excavated bottom mud was backfilled into the sample site to be tested, and water with a depth of ≥ 0.5 m was injected into it; (2) Fix flux rings A, B, C, D, and E in the sample plot to be tested according to the following method, wherein the flux rings A, B, C, D, and E are all long round tubes with the same radius and wall thickness and an open top, and are all provided with two holes on the opposite side walls at the same height between the bottom mud and the water surface. The two holes on each flux ring are of the same size and are located relative to each other: ① Check and remove the above-ground parts and all roots of submerged plants germinated in the bottom mud seed bank at the location of the flux ring A, and insert the flux ring A into the bottom mud; the depth of the flux ring A inserted into the bottom mud is greater than the maximum growth length of the roots of the submerged plants in the sample plot to be tested; ② Check and remove the above-ground parts of submerged plants germinated in the bottom mud seed bank at the location of the flux ring B, and insert the flux ring B into the bottom mud; the depth of the flux ring B inserted into the bottom mud does not block the lateral root growth of the submerged plants; ③ Insert the flux ring C into the bottom mud, the depth of the flux ring C into the bottom mud does not block the lateral root growth of submerged plants; ④ Seal the bottom ends of flux ring D and flux ring E, place them on the bottom mud surface respectively, and seal the two holes on the side wall of flux ring E with a plankton net; (3) 24 hours before the start of in situ monitoring, the water in flux ring E was filtered through a plankton net and then added; (4) Use a gas flux measuring instrument to measure the gas flux in flux rings A, B, C, D, and E respectively, and calculate the gas flux of different components in the wetland ecosystem to be measured according to the following formula: Gas flux of sediment components = gas flux of flux loop A - gas flux of flux loop D; Root component gas flux = flux loop B gas flux - flux loop A gas flux; Plant component gas flux = flux loop C gas flux - flux loop B gas flux; Gas flux of water microbial components = gas flux of flux loop E; Gas flux of plankton component in water body = gas flux of flux loop D - gas flux of flux loop E.

2. The method for in-situ monitoring of gas fluxes of different components in a wetland ecosystem according to claim 1, characterized in that: Flux rings A, B, C, D, and E are all made of highly transparent acrylic.

3. The method for in-situ monitoring of gas fluxes of different components in a wetland ecosystem according to claim 1, characterized in that: Flux rings A, B, C, D, and E all have two holes on the opposite side walls at 1 / 2 the water depth.

4. The method for in-situ monitoring of gas fluxes of different components in a wetland ecosystem according to claim 1, characterized in that: Flux rings A, B, C, D, and E are all above the water surface, and their heights above the water surface may be the same or different.

5. The method for in-situ monitoring of gas fluxes of different components in a wetland ecosystem according to claim 1, characterized in that: Before using the gas flux measuring instrument to measure the gas flux in flux rings A, B, C, D, and E, use a wooden stick to move along the outer wall of each flux ring to push out the plants that have entered the ring through the side wall openings, and then seal the side wall openings.

6. The method for in-situ monitoring of gas fluxes of different components in a wetland ecosystem according to claim 1, characterized in that: In step (2), the fixing time of flux loop A is before the sludge is backfilled, and the fixing time of flux loops B, C, D, and E is after the sludge is backfilled.

7. The method for in-situ monitoring of gas fluxes of different components in a wetland ecosystem according to claim 1, characterized in that: In step (2), the depth of flux ring B and flux ring C inserted into the bottom mud is 5-10 cm.

8. The method for in-situ monitoring of gas fluxes of different components in a wetland ecosystem according to claim 1, characterized in that: In step (2), the intervals between flux rings A, B, C, D, and E are fixed at 10-20 cm.

9. The method for in-situ monitoring of gas fluxes of different components in a wetland ecosystem according to claim 1, characterized in that: The aperture size of the plankton net is mainly to be able to intercept plankton.

10. The method for in-situ monitoring of gas fluxes of different components in a wetland ecosystem according to claim 9, characterized in that: The pore size of the plankton net is 0.064 mm.

Images