A method for identifying wetland boundaries

Abstract

The present application discloses a method for identifying wetland boundaries, comprising obtaining images of survey patches in a preset area, determining the position and length of a baseline; determining the number of sample lines perpendicular to the baseline according to the area of ​​the survey patches and the length of the baseline; determining a plurality of observation points at preset intervals on the sample line, and setting a sample plot with a preset area at each observation point; identifying plants in the sample plot, and when the dominance of wetland plants therein is lower than the dominance of non-wetland plants, determining that the sample plot is not a wetland, and continuing to investigate the next observation point far from the baseline position along the sample line until the dominance of wetland plants in the sample plot is higher than the dominance of non-wetland plants, determining that the sample plot is a wetland, and continuing to set sample plots in the area between the current observation point and the previous observation point until the wetland boundary observation point is determined; and connecting all the obtained wetland boundary observation points along the contour line between the sample lines to obtain the wetland boundary. The method can improve the efficiency and accuracy of wetland boundary identification.

Description

Technical Field

[0001] The invention belongs to the technical field of wetland identification, and in particular relates to a method for identifying wetland boundaries. Background Art

[0002] As an important part of the earth's surface system, wetlands, forests and oceans are known as the world's three major ecosystems. They play an important role in regulating floods, regulating climate, promoting siltation and land reclamation, intercepting pollutants, and providing habitats. Wetlands are closely related to human production and life, and play an important role in supply, regulation, support and cultural functions. There are various types of wetlands in my country, mainly distributed in Greater and Lesser Khingan Mountains, Sanjiang-Songnen Plain, Qinghai-Tibet Plateau and the middle and lower reaches of the Yangtze River Plain. These areas are also the concentrated distribution areas of my country's key ecological functional areas. Mastering the basic characteristics and dynamic changes of wetlands in these areas is of great significance for clarifying the evolution of wetlands under the influence of global climate change, and will also provide reliable information for regional ecological governance.

[0003] Wetland boundary refers to the surface boundary between wetlands and non-wetlands. Boundary demarcation is the basis for obtaining basic wetland attribute information such as wetland area and distribution, and is the primary task in conducting wetland resource and ecological environment surveys. Wetlands are located in the transition zone between aquatic ecosystems and terrestrial ecosystems. They have complex and diverse structures and are relatively sensitive to environmental changes. The determination of wetland boundaries requires strong professional skills, such as the identification of wetland plants, the physiological and ecological characteristics of wetland plants, the characteristics of hydromorphic soils, and so on. In the existing technology, soil organic matter is measured by sampling to determine whether it is wetland soil, but this method is time-consuming. At present, there is a lack of methods for demarcating natural wetland boundaries, which to a certain extent restricts the development of wetland surveys. Summary of the invention

[0004] To solve the above problems, the present invention provides a method for identifying wetland boundaries, which can improve the efficiency and accuracy of wetland boundary identification.

[0005] A method for identifying wetland boundaries provided by the present invention comprises:

[0006] Obtain images of the investigated plaques in a preset area and determine the location and length of the baseline;

[0007] Determine the number of sample lines perpendicular to the baseline according to the area of ​​the survey patch and the length of the baseline;

[0008] Determine a plurality of observation points at preset intervals on the sample line, and set a sample plot with a preset area at each observation point;

[0009] Identify the plants in the sample plot, and when the dominance of the wetland plants therein is lower than the dominance of the non-wetland plants, determine that the sample plot is not a wetland, continue to investigate the next observation point far away from the baseline position along the sample line, until when the dominance of the wetland plants in the sample plot is higher than the dominance of the non-wetland plants, determine that the sample plot is a wetland, and continue to set up sample plots in the area between the current observation point and the previous observation point until the wetland boundary observation point is determined;

[0010] All the wetland boundary observation points obtained are connected along the contour lines between the sample lines to obtain the wetland boundary.

[0011] Preferably, in the above method for identifying wetland boundaries, before acquiring the image of the survey patch in the preset area, the method further includes:

[0012] The information of wetland plants and non-wetland plants in the preset area is obtained.

[0013] Preferably, in the above-mentioned method for identifying wetland boundaries, the image is a remote sensing image.

[0014] Preferably, in the above-mentioned method for identifying wetland boundaries, the identifying of plants in the sample plot, when the dominance of wetland plants therein is lower than that of non-wetland plants, determines that the sample plot is not a wetland, and continues to investigate the next observation point far away from the baseline position along the sample line until the dominance of wetland plants in the sample plot is higher than that of non-wetland plants, and continues to set sample plots in the area between the current observation point and the previous observation point until the wetland boundary observation point is determined, including:

[0015] Identify each plant whose leaves are completely within the sample plot and calculate the cover; when the sum of the wetland plant covers among the top five plants in the sample plot is less than the sum of the non-wetland plant covers, determine that the sample plot is not a wetland, and continue to investigate the next observation point far away from the baseline position along the sample line until the sum of the wetland plant covers among the top five plants in the sample plot is greater than the sum of the non-wetland plant covers; then set up a sample plot in the area where there is a change in vegetation or terrain between the current observation point and the previous observation point until the wetland boundary observation point is determined.

[0016] Preferably, in the above method for identifying wetland boundaries, the baseline is determined as follows:

[0017] The boundary area of ​​the survey patch is used as the baseline and / or the baseline is determined in a direction parallel to the river channel and / or the baseline is determined in a direction perpendicular to the terrain gradient.

[0018] Preferably, in the above method for identifying wetland boundaries, the number of sample lines is no less than four.

[0019] Preferably, in the above-mentioned method for identifying wetland boundaries, one corner of the sample plot is the observation point, and one side is adjacent to the sample line.

[0020] Preferably, in the above-mentioned method for identifying wetland boundaries, the cover of the top five plants is calculated with a grading accuracy of 5%, and when the number of plants in the sample plot is less than 5, the cover of all plants in the sample plot is calculated.

[0021] Preferably, in the above method for identifying wetland boundaries, the preset area of ​​the sample plot is 1 square meter.

[0022] Preferably, in the above method for identifying wetland boundaries, the sample plot is a square with a side length of 1 meter.

[0023] It can be seen from the above description that the method for identifying wetland boundaries provided by the present invention includes obtaining images of survey patches in a preset area to determine the position and length of the baseline; determining the number of sample lines perpendicular to the baseline according to the area of ​​the survey patch and the length of the baseline; determining multiple observation points at preset intervals on the sample line, and setting a sample plot with a preset area at each observation point; identifying plants in the sample plot, and when the dominance of wetland plants therein is lower than the dominance of non-wetland plants, determining that the sample plot is not a wetland, and continuing to investigate the next observation point far away from the baseline position along the sample line until the dominance of wetland plants in the sample plot is higher than the dominance of non-wetland plants, determining that the sample plot is a wetland, and continuing to set sample plots in the area between the current observation point and the previous observation point until the wetland boundary observation point is determined; connecting all the obtained wetland boundary observation points along the contour line between the sample lines to obtain the wetland boundary. It can be seen that this scheme uses the difference in dominance between wetland plants and non-wetland plants to determine the position of the wetland boundary, thereby improving the efficiency and accuracy of wetland boundary identification. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0025] Figure 1 A schematic diagram of an embodiment of a method for identifying wetland boundaries provided by the present invention;

[0026] Figure 2 Provide a schematic diagram of wetland boundary demarcation;

[0027] Figure 3 Schematic diagram for setting up the plant quadrat. DETAILED DESCRIPTION

[0028] The core of the present invention is to provide a method for identifying wetland boundaries, which can improve the efficiency and accuracy of wetland boundary identification.

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] The implementation example of a method for identifying wetland boundaries provided by the present invention is as follows: Figure 1 As shown, Figure 1 A schematic diagram of an embodiment of a method for identifying wetland boundaries provided by the present invention, the method may include the following steps:

[0031] S1: Obtain images of the investigated plaques in the preset area and determine the position and length of the baseline;

[0032] It should be noted that it can be combined with Figure 2 , Figure 2 For the wetland boundary demarcation diagram, the boundary area of ​​the survey patch itself can be used as the baseline, such as roads, farmland and ditches, which are obviously not wetlands. Figure 2 The ellipse boundary 201 is used as the position of the baseline, and the length of the baseline can be measured, which is the basis for determining the number of sample lines later.

[0033] S2: Determine the number of sample lines perpendicular to the baseline according to the area of ​​the survey patch and the length of the baseline;

[0034] It should be noted that the sample line can be set according to the baseline length, uniformity and operability principles, and the sample line is perpendicular to the baseline, such as Figure 2 The hollow triangles in the figure are observation points, all of which are located on the sample lines. Each sample line is perpendicular to the baseline. The number of sample lines should preferably be no less than four, that is, there should be at least one sample line each in the top, bottom, left and right directions, so as to ensure that at least one point of the wetland boundary is determined in four directions. Of course, the number of sample lines can be appropriately increased according to the baseline length and patch area to obtain more wetland boundary observation points and more accurate wetland boundary lines.

[0035] S3: determining a plurality of observation points at preset intervals on the sample line, and setting a sample plot with a preset area at each observation point;

[0036] It should be noted that, combined with Figure 3 , Figure 3A schematic diagram is set for the plant sample plot. A sample plot can be determined at the location of each observation point for observing the plants therein. The area of ​​the sample plot can be set according to actual needs.

[0037] S4: Identify the plants in the sample plot. When the dominance of wetland plants is lower than that of non-wetland plants, the sample plot is determined not to be a wetland. Continue to investigate the next observation point far away from the baseline along the sample line until the dominance of wetland plants in the sample plot is higher than that of non-wetland plants. Then, the sample plot is determined to be a wetland. Continue to set up sample plots in the area between the current observation point and the previous observation point until the wetland boundary observation point is determined.

[0038] Combination Figure 3 To explain this step, first use the naked eye to identify Figure 3 For each plant in this sample plot, when the wetland plant dominance is lower, it is determined that the sample plot is not a wetland, and the next observation point far away from the baseline position is investigated along the sample line, that is, Figure 3 Observe the plants in the plot at the upper hollow triangle observation point in the sample, and so on, until the wetland plant dominance in the sample is higher, the sample is determined to be a wetland, which proves that the wetland boundary is between the observation point and the previous observation point. At this time, continue to set up samples in the area between the current observation point and the previous observation point until the wetland boundary point on the sample line is found, and then continue to find the wetland boundary points on other sample lines in this way. These wetland boundary points can be Figure 2 That is marked as a solid triangle.

[0039] S5: Connect all the wetland boundary observation points obtained along the contour lines between the sample lines to obtain the wetland boundary.

[0040] It should be noted that the reference Figure 2 , connect all wetland boundary observation points obtained by the above steps, that is, the solid triangles along the contour lines between the sample lines, and the figure formed by the enclosed is the wetland boundary.

[0041] It can be seen from the above description that in the embodiment of the above-mentioned method for identifying wetland boundaries provided by the present invention, it includes obtaining images of survey patches in a preset area to determine the position and length of the baseline; determining the number of sample lines perpendicular to the baseline according to the area of ​​the survey patches and the length of the baseline; determining multiple observation points at preset intervals on the sample line, and setting a sample plot with a preset area at each observation point; identifying plants in the sample plot, when the dominance of wetland plants therein is lower than the dominance of non-wetland plants, determining that the sample plot is not a wetland, and continuing to investigate the next observation point far away from the baseline position along the sample line until the dominance of wetland plants in the sample plot is higher than the dominance of non-wetland plants, the sample plot is determined to be a wetland, and sample plots are continued to be set in the area between the current observation point and the previous observation point until the wetland boundary observation point is determined; all the obtained wetland boundary observation points are connected along the contour line between the sample lines to obtain the wetland boundary. It can be seen that this scheme uses the difference in dominance between wetland plants and non-wetland plants to determine the position of the wetland boundary, thereby improving the efficiency and accuracy of wetland boundary identification.

[0042] In a specific embodiment of the above method for identifying wetland boundaries, before obtaining images of survey patches in a preset area, the following steps may also be included:

[0043] Get the information of wetland plants and non-wetland plants in the preset area.

[0044] Specifically, a list of typical wetland plant species in the preset area to be investigated can be obtained by consulting materials or conducting actual investigations. Typical wetland plants refer to plants that only appear in wet environments or in wet and meso environments. In addition, remote sensing images and field surveys can be used to obtain information such as the distribution, shape, and area of ​​the patches to be investigated, providing a basis for subsequent work.

[0045] Moreover, the images used in the above method can preferably be remote sensing images, which are easier to obtain information such as the distribution, shape and area of ​​the patches to be investigated. Of course, other types of images can also be selected according to actual needs, which is not limited here.

[0046] In another specific embodiment of the above method for identifying wetland boundaries, plants in a sample plot are identified. When the dominance of wetland plants therein is lower than that of non-wetland plants, the sample plot is determined to be not a wetland. The next observation point far from the baseline position is continuously investigated along the sample line until the dominance of wetland plants in the sample plot is higher than that of non-wetland plants. Sample plots are continuously set in the area between the current observation point and the previous observation point until the wetland boundary observation point is determined. The specific methods include:

[0047] Identify each plant whose leaves are completely within the sample plot and calculate the cover. When the sum of the wetland plant covers among the top five plants in the sample plot is less than the sum of the non-wetland plant covers, the sample plot is determined to be not a wetland. Continue to investigate the next observation point far away from the baseline along the sample line until the sum of the wetland plant covers among the top five plants in the sample plot is greater than the sum of the non-wetland plant covers. Set up sample plots in areas where there are changes in vegetation or terrain between the current observation point and the previous observation point until the wetland boundary observation point is determined.

[0048] It should be noted that this type of plant cover is easy to identify and can be calculated with the naked eye. Of course, it can also be identified in combination with computer recognition methods. This is not limited here. Furthermore, it is preferred to calculate the cover of the top five plants with a grading accuracy of 5%. When the number of plants in the sample plot is less than 5, calculate the cover of all plants in the sample plot. When the cover is less than 5%, it is recorded as <5%.

[0049] In another specific embodiment of the above method for identifying wetland boundaries, determining the baseline may be specifically: taking the boundary area of ​​the survey patch as the baseline and / or determining the baseline in a direction parallel to the river channel and / or determining the baseline in a direction perpendicular to the terrain gradient.

[0050] In addition, you can continue to refer to Figure 3 , one corner of the sample plot can be set as the observation point, and one side can be adjacent to the sample line. Of course, this can be selected according to actual needs. Moreover, the preset area of ​​the sample plot can be further preferably 1 square meter. Furthermore, the sample plot can be a square with a side length of 1 meter. Such an area is sufficient to ensure that there are enough plants, so as to determine whether the wetland plant or non-wetland plant has a greater dominance, which can help determine whether the sample plot belongs to a wetland.

[0051] In summary, the above method has the following advantages: wetland plants are one of the key elements of swamp ecosystems, and plant adaptation to wetland environments is the result of long-term evolution. Selecting wetland plants as the main indicator for determining wetland boundaries is scientific and reliable; population cover is an indicator that comprehensively reflects the survival and reproduction status of plants, and it is easy to identify. Determining wetland vegetation by the cover of typical wetland plants saves time and effort, and is quick and convenient; the technical links involved in the above method, such as baseline establishment, sample line setting, and cover estimation, are simple to operate and suitable for large-scale promotion and application.

[0052] The above method is explained below with a specific example:

[0053] Zhenlai County, Jilin Province is located in the western part of the Songnen Plain, with a total wetland area of ​​200,000 hectares, accounting for about 46% of the county's area; in addition, the county has 42,000 hectares of grassland and 70,200 hectares of forest land. This example takes the Xipaozi wetland located on the south side of Xilitu Village, Dongping Town, Zhenlai County as an example (45°59′19.54″-45°59′59.69″N, 123°22′40.53″-123°23′55.56″E). It includes the following steps:

[0054] 1. Data acquisition: Through actual investigation, the main wetland plants in Xipaozi include Echinochloa crusgalli, Suaeda salsa, Phragmites australis, and Tripterygium wilfordii. The non-wetland plants mainly include Artemisia annua, Setaria viridis, Chloris virgata, and Kochia scoparia. Affected by the road, the patch is irregular in shape and covers an area of ​​about 1.65 km. 2 .

[0055] 2. Establish a baseline: Select the boundary area of ​​the patch as the baseline, and the extension of the baseline is perpendicular to the terrain gradient; the baseline length is 4930m, and the starting coordinates and their direction are recorded on the base map.

[0056] 3. Sample line setting: 4 sample lines are set according to the principles of uniformity, naturalness and operability. The sample lines are perpendicular to the baseline and the sample line spacing is about 1230m.

[0057] V. Sample plot survey: An observation point was determined every 30m on the sample line, and a 1.0m×1.0m sample plot was laid out, with one corner of the sample plot being the observation point and one side adjacent to the sample line. With a classification accuracy of 5%, each plant with leaves completely within the sample plot was identified, and the cover of the top five species in terms of cover was estimated (when the number of species in the sample plot was less than 5, the cover of all species was recorded). The sample plot record data is shown in Table 1.

[0058] Table 1 Plant sample survey record

[0059]

[0060] 6. Determination of wetland vegetation: Calculate the sum of the covers of typical wetland plant species among the top five plants in terms of coverage within the sample plot, and the sum of the covers of other non-wetland plant species; when the sum of the covers of typical wetland plants is greater than the sum of the covers of other non-wetland plants, it is regarded as wetland vegetation.

[0061] 7. If the sample plot investigated in step 6 is not wetland vegetation, it is necessary to investigate the second observation point along the sample line and repeat steps 5 and 6; and so on, until the vegetation in the sample plot is wetland vegetation, set up sample plots in the area where the vegetation or terrain changes between this observation point and the previous observation point, and finally determine the wetland boundary observation point. The observation point data are shown in Table 2.

[0062] Table 2 Sample data statistics

[0063]

[0064] 8. Boundary delineation: Connect the wetland boundary observation points along the contour lines between the transects to obtain the wetland boundary, with a perimeter of 4066m and a wetland area of ​​approximately 0.98km 2 , accounting for 59.39% of the plaque area.

[0065] In addition, an example is provided here as a comparison. Another method for determining the wetland boundary observation point is to record and obtain the physical and chemical characteristics of the soil at the sample point. It is necessary to use a soil drill or shovel to dig a pit, and immediately record the soil color and redox level below the topsoil layer or 25 cm (whichever is shallower), and collect soil samples and return to the room for processing to determine the organic matter content. Finally, the wetland boundary observation point can also be determined through the soil sample test data, and the wetland boundary observation points are connected along the contour lines between the sample lines to obtain the wetland boundary, perimeter and wetland area. However, compared with the above examples of this application, this comparative example cannot determine the wetland boundary observation point on site, and the steps of air drying, grinding, sieving, and measuring the soil samples in the later stage will take at least 1 month to complete; at least 3 samples are taken from each sample line, and at least 12 samples are collected in total, which requires certain sample transportation fees, processing fees and testing fees; in addition, the observation and recording of soil color and redox reaction also requires personnel with a certain professional background to complete well.

[0066] From the above comparison, it can be seen that the method of using plant sample plot survey data combined with remote sensing technology to determine the wetland boundary on site can be determined on site, saving a lot of time and energy for investigators. Investigators can determine whether it is wetland vegetation after simple calculation based on the dominant plant species and coverage in the sample plot on the ground. There is no need to collect samples and obtain information after a long period of processing and analysis, thus saving costs. Moreover, although wetlands have the characteristics of being changeable with hydrological conditions, for a certain area, the formation and distribution of vegetation are the result of the long-term relationship between plants and hydrology, and are not affected by short-term hydrological fluctuations. Therefore, it is scientific and objective to determine wetland vegetation using the growth characteristics of dominant plants. Moreover, although the determination of plants requires certain professional skills, the number of typical wetland plants in a certain area is limited. Investigators can identify plants well after a little training and through illustrations. In view of the superiority and feasibility of this method, the determination of wetland boundaries in inland areas can be achieved through this method, providing technical support for relevant departments of wetland management.

[0067] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for identifying wetland boundaries, characterized in that: include: Obtain images of the investigated plaques in a preset area and determine the location and length of the baseline; Determine the number of sample lines perpendicular to the baseline according to the area of ​​the survey patch and the length of the baseline; Determine a plurality of observation points at preset intervals on the sample line, and set a sample plot with a preset area at each observation point; Identify the plants in the sample plot, and when the dominance of the wetland plants therein is lower than the dominance of the non-wetland plants, determine that the sample plot is not a wetland, continue to investigate the next observation point far away from the baseline position along the sample line, until when the dominance of the wetland plants in the sample plot is higher than the dominance of the non-wetland plants, determine that the sample plot is a wetland, and continue to set up sample plots in the area between the current observation point and the previous observation point until the wetland boundary observation point is determined; Connecting all the wetland boundary observation points obtained along the contour lines between the sample lines to obtain the wetland boundary; The identifying of plants in the sample plot, when the dominance of wetland plants therein is lower than that of non-wetland plants, determining that the sample plot is not a wetland, continuing to investigate the next observation point far away from the baseline position along the sample line until the dominance of wetland plants in the sample plot is higher than that of non-wetland plants, and continuing to set sample plots in the area between the current observation point and the previous observation point until the wetland boundary observation point is determined, includes: Identify each plant whose leaves are completely within the sample plot and calculate the cover; when the sum of the wetland plant covers among the top five plants in the sample plot is less than the sum of the non-wetland plant covers, determine that the sample plot is not a wetland, and continue to investigate the next observation point far away from the baseline position along the sample line until the sum of the wetland plant covers among the top five plants in the sample plot is greater than the sum of the non-wetland plant covers; then set up a sample plot in the area where there is a change in vegetation or terrain between the current observation point and the previous observation point until the wetland boundary observation point is determined.

2. The method for identifying wetland boundaries according to claim 1, characterized in that: Before obtaining the image of the investigated plaque in the preset area, the method further includes: The information of wetland plants and non-wetland plants in the preset area is obtained.

3. The method for identifying wetland boundaries according to claim 1, characterized in that: The image is a remote sensing image.

4. The method for identifying wetland boundaries according to claim 1, characterized in that: The baseline is determined as follows: The boundary area of ​​the survey patch is used as the baseline and / or the baseline is determined in a direction parallel to the river channel and / or the baseline is determined in a direction perpendicular to the terrain gradient.

5. The method for identifying wetland boundaries according to claim 1, characterized in that: The number of the sample lines is not less than four.

6. The method for identifying wetland boundaries according to claim 1, characterized in that: One corner of the sample plot is the observation point, and one side is adjacent to the sample line.

7. The method for identifying wetland boundaries according to claim 1, characterized in that: The cover of the top five plants in terms of cover was calculated with a classification accuracy of 5%. When the number of plants in the sample plot was less than 5, the cover of all plants in the sample plot was calculated.

8. The method for identifying wetland boundaries according to claim 1, characterized in that: The preset area of ​​the sample plot is 1 square meter.

9. The method for identifying wetland boundaries according to claim 8, characterized in that: The sample plot is a square with a side length of 1 meter.

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