Intertidal zone wetland lateral hydrological communication structure index construction method

Abstract

The invention discloses an intertidal zone wetland lateral hydrological communication structure index construction method, and relates to the technical field of wetland ecological hydrological communication, and the intertidal zone wetland lateral hydrological communication structure index construction method comprises the following steps: arranging uniform sampling points in an intertidal zone, and collecting structure index data; performing Z score centralization processing on the structure index data; and acquiring coefficients of the structure index on the first two axes by using a principal component analysis method, constructing a comprehensive hydrological connectivity index, and determining the hydrological connectivity. According to the method, the structure indexes playing an important role in tidal water movement are screened, the comprehensive hydrological connectivity index based on the tidal flat structure indexes is constructed, the hydrological connectivity of different positions of the surface of the intertidal wetland is quantified, and a grasp is provided for repairing, protecting and managing the coastal wetland.

Description

Technical Field

[0001] This invention relates to the field of wetland eco-hydrological connectivity technology, and more specifically to a method for constructing a lateral hydrological connectivity structure index for intertidal wetlands. Background Technology

[0002] Hydrological connectivity refers to the process of transport of matter, energy, and organisms within or between various elements of the wetland hydrological cycle, using water as a medium, thereby influencing the distribution patterns of organisms. Hydrological connectivity can serve as a crucial tool for wetland management, regulation, and restoration. Hydrological connectivity indices are important methods for characterizing hydrological connectivity and can be categorized into structural connectivity indices, process connectivity indices, and functional connectivity indices. From a directional perspective, they can be classified as longitudinal, lateral, and vertical hydrological connectivity indices. Currently, various indices are selected for calculating hydrological connectivity in different ecosystems, including process indices based on indicators such as flow and water level, and structural indices based on indicators such as elevation and slope. Compared to hydrological process and functional connectivity indices, hydrological structural connectivity indices are fundamental, determining the potential magnitude of hydrological process and functional connectivity. Furthermore, structural indicators are easier to obtain and can be directly acquired through remote sensing imagery, field surveys, and map measurements.

[0003] Current hydrological connectivity indices focus more on river systems and less on coastal wetland systems. Coastal wetland systems are relatively flat, and the tidal currents cause the tidal flats to be intermittently submerged and exposed. The topography and distance characteristics of intertidal wetlands largely determine their lateral hydrological connectivity, and thus the migration and distribution of tidal water and its carried sediment, nutrients, and seeds on the intertidal surface.

[0004] Therefore, in view of the shortcomings of the existing technology, how to provide a method for constructing the lateral hydrological connectivity structure index of intertidal wetlands is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, the present invention provides a method for constructing a lateral hydrological connectivity structure index for intertidal wetlands. This method screens structural indicators that play an important role in tidal movement, constructs a comprehensive hydrological connectivity index based on tidal flat structural indicators, quantifies the hydrological connectivity at different locations on the surface of intertidal wetlands, and provides a tool for the restoration, protection and management of coastal wetlands.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a method for constructing the lateral hydrological connectivity structure index of intertidal wetlands, comprising: Sampling points were evenly distributed in the intertidal zone to collect structural index data; The structural index data are subjected to Z-score centering. Principal component analysis was used to obtain the coefficients of the structural index on the first two axes, and a comprehensive hydrological connectivity index was constructed to determine the degree of hydrological connectivity.

[0007] Preferably, the structural index data includes: tidal channel level, tidal channel length, tidal channel cross-sectional area, lateral distance, and elevation.

[0008] Preferably, principal component analysis is used to obtain the coefficients of the structural indices on the first two axes, including: PCA first axis score: y1 = a1x1 + ... + a n x n ; PCA second axis score: y2 = b1x1 + ... + b n x n ; Where, x n This represents structural indicator data, where n represents the number of structural indicators; a n and b n These are the principal component coefficients of each indicator on the first and second axes of the principal components. The principal component coefficients can be obtained directly from factor analysis using SPSS software.

[0009] Preferably, a comprehensive hydrological connectivity index is constructed, including: Hydrological connectivity structure index H Cs =(C1y1+C2y2) / Cc; Where C1 is the cumulative contribution rate of the first axis, C2 is the cumulative contribution rate of the second axis, and Cc is the cumulative contribution rate of the first two axes. The cumulative contribution rates are directly calculated by factor analysis using SPSS software.

[0010] Preferably, the obtained comprehensive hydrological connectivity index is normalized using the maximum-minimum method to determine the hydrological connectivity. The final comprehensive hydrological connectivity index value is between 0 and 1. The larger the value, the greater the hydrological connectivity.

[0011] Preferably, the length of the tidal channel is the length of the tidal channel from the tidal channel section corresponding to a certain point on the tidal flat to the tidal channel estuary section. The tidal channel level is the classification of the tidal channel at a certain point on the tidal flat. The cross-sectional area of ​​a tidal channel is the product of the width and depth of the tidal channel at a certain point on the tidal flat. Lateral distance is the vertical distance from a point on the tidal flat to the nearest tidal channel; The tidal flat elevation is the elevation of a specific point on the tidal flat.

[0012] Preferably, ArcGIS is used to analyze and obtain data on tidal channel length and lateral distance; The cross-sectional area of ​​the tidal channel was obtained by using field surveys to acquire data on the width and depth of the cross-section. Elevation data of points can be obtained through RTK field measurements or spectral analysis.

[0013] Preferably, the tidal channel levels are assigned according to the reverse Strahler classification to divide the entire intertidal zone into tidal channel levels.

[0014] As can be seen from the above technical solution, compared with the prior art, this invention discloses a method for constructing a lateral hydrological connectivity structure index for intertidal wetlands, including: distributing uniform sampling points in the intertidal zone to collect structural index data; performing Z-score centering processing on the structural index data; and using principal component analysis to obtain the coefficients of the structural index on the first two axes to construct a comprehensive hydrological connectivity index. This invention selects structural indicators that play an important role in tidal movement, constructs a comprehensive hydrological connectivity index based on tidal flat structural indicators, quantifies the hydrological connectivity at different locations on the surface of intertidal wetlands, and provides a tool for the restoration, protection, and management of coastal wetlands. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of the hydrological connectivity process on the surface of a salt marsh, provided in an embodiment of the present invention.

[0017] Figure 2 This is a schematic diagram illustrating the division of tidal channels according to an embodiment of the present invention.

[0018] Figure 3 This is a schematic diagram of the implementation area of ​​the lateral hydrological connectivity structure index provided in an embodiment of the present invention (the sampling points are within the red box).

[0019] Figure 4 This is a schematic diagram showing the distribution of each variable on the principal component axis, provided for an embodiment of the present invention.

[0020] Figure 5 This is a schematic diagram illustrating the distribution characteristics of the structural hydrological connectivity intensity in areas A and B, provided for an embodiment of the present invention.

[0021] Figure 6 This is a schematic diagram illustrating the relationship between flooding frequency and hydrological connectivity, provided for an embodiment of the present invention.

[0022] Figure 7 This is a schematic diagram illustrating the relationship between the hydrological connectivity structure index and tidal flat sedimentation volume, provided as an embodiment of the present invention. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] This invention discloses a method for constructing the lateral hydrological connectivity structure index of intertidal wetlands, comprising: Sampling points were evenly distributed in the intertidal zone to collect structural index data; The structural index data are subjected to Z-score centering. Principal component analysis was used to obtain the coefficients of the structural index on the first two axes, and a comprehensive hydrological connectivity index was constructed to determine the degree of hydrological connectivity.

[0025] Specifically, structural indicators sensitive to intertidal wetland water flow movement are selected, including tidal channel morphology and tidal flat landform characteristics. Based on the movement trajectory of the tide on the tidal flat surface, the hydrological connectivity between a certain point on the tidal flat surface and the ocean depends on the following structural indicators: tidal channel level, tidal channel length, tidal channel cross-sectional area, lateral distance, and elevation.

[0026] Specifically, the collection of structural index data requires determining the scope of the study area, evenly distributing sample points, and making sure that the sample points cover the complete land-sea gradient as much as possible. The number of sampling points should be more than 30.

[0027] Specifically, ArcGIS was used to analyze and obtain data on tidal channel length and lateral distance. The cross-sectional area of ​​the tidal channel was obtained by using field surveys to acquire data on the width and depth of the cross-section. Elevation data of points can be obtained through RTK field measurements or spectral analysis.

[0028] Specifically, it is necessary to determine the correlation between structural indicator data and the direction of changes in hydrological connectivity. Indicators positively correlated with hydrological connectivity include tidal channel level and tidal channel cross-sectional area, while indicators negatively correlated include tidal channel length, lateral distance, and elevation. Based on the correlation direction between structural indicators and hydrological connectivity, positive values ​​are assigned to structural indicators (tidal channel level and tidal channel cross-sectional area) that are positively correlated with hydrological connectivity, and negative values ​​are assigned to structural indicators (tidal channel length, lateral distance, and elevation) that are negatively correlated with hydrological connectivity, ensuring that the input data is consistent with the direction of changes in hydrological connectivity.

[0029] Specifically, principal component analysis is used to obtain the coefficients of the structural indices on the first two axes, including: PCA first axis score: y1 = a1x1 + ... + a n x n; PCA second axis score: y2 = b1x1 + ... + b n x n ; Where, x n This represents structural indicator data, where n represents the number of structural indicators, n=5; a n and b n These are the principal component coefficients of each indicator on the first and second axes of the principal components. The principal component coefficients can be obtained directly from factor analysis using SPSS software.

[0030] Specifically, a comprehensive hydrological connectivity index is constructed, including: Hydrological connectivity structure index H Cs =(C1y1+C2y2) / Cc; Where C1 is the cumulative contribution rate of the first axis, C2 is the cumulative contribution rate of the second axis, and Cc is the cumulative contribution rate of the first two axes. The cumulative contribution rates are directly calculated by factor analysis using SPSS software.

[0031] Specifically, the obtained comprehensive hydrological connectivity index is normalized using the maximum-minimum method to determine the hydrological connectivity. The final comprehensive hydrological connectivity index value is between 0 and 1. The larger the value, the greater the hydrological connectivity.

[0032] Specifically, the input data is centered, the Z-score of each structural index is calculated in SPSS, and the Z-score is then used as input data for PCA analysis to obtain the coefficients of the principal components of each structural index. The principal component scores of the structural index on the first and second axes are calculated, and the comprehensive hydrological connectivity index is obtained.

[0033] Specifically, the length of a tidal channel is the length of the tidal channel from a certain point on the tidal flat to the tidal channel estuary. A tidal channel level is the classification of a tidal channel at a specific point on a tidal flat. In this embodiment of the invention, the tidal channel levels are assigned according to the reverse Strahler classification: a tidal channel directly connected to the ocean is a Class 1 tidal channel, a Class 1 tidal channel directly connected to a Class 1 tidal channel is a Class 2 tidal channel, a Class 2 tidal channel directly connected to a Class 2 tidal channel is a Class 3 tidal channel, and so on, thus classifying the tidal channel levels of the entire intertidal zone. Figure 2 As shown; The cross-sectional area of ​​a tidal channel is the product of the width and depth of the tidal channel at a certain point on the tidal flat. Lateral distance is the vertical distance from a point on the tidal flat to the nearest tidal channel; The tidal flat elevation is the elevation of a specific point on the tidal flat.

[0034] Specifically, the tidal channel levels are assigned values ​​according to the reverse Strahler classification to divide the entire intertidal zone into tidal channel levels.

[0035] Specifically, step two requires determining the correlation between structural indicators and the direction of changes in hydrological connectivity. Indicators positively correlated with hydrological connectivity include tidal channel level and tidal channel cross-sectional area, while indicators negatively correlated include tidal channel length, lateral distance, and elevation. Based on the correlation direction between structural indicators and hydrological connectivity, positive values ​​are assigned to structural indicators (tidal channel level and tidal channel cross-sectional area) that are positively correlated with hydrological connectivity, and negative values ​​are assigned to structural indicators (tidal channel length, lateral distance, and elevation) that are negatively correlated with hydrological connectivity, ensuring that the input data is consistent with the direction of changes in hydrological connectivity.

[0036] This invention proposes a framework for assessing hydrological connectivity in salt marshes based on tidal channel systems. The framework uses the hydrological connections between points on the tidal flats and the ocean, resulting from the movement of tidal water on the salt marsh surface, as the core of hydrological connectivity. Figure 1 As shown, the movement trajectory of seawater along the tidal channel on the surface of the salt marsh is illustrated. A composite structural connectivity index based on the tidal channel morphology and geomorphological features and a multi-time process connectivity index based on the movement of water on the salt marsh surface are established. All points on the salt marsh surface are incorporated into a complete hydrological connectivity gradient, which facilitates the analysis and comparison of hydrological elements, habitat elements and vegetation characteristics on the salt marsh surface.

[0037] Tidal channels, as transport channels for tidal water, determine the potential pathways of tidal movement. Therefore, the morphology and topographic features of tidal channels constitute structural connectivity, while the spatiotemporal variations in water volume and its carried fluxes (such as seed flux, deposition flux, and nutrient flux) constitute process connectivity, or functional connectivity. Structural connectivity is a simplified form of process or functional connectivity. Compared to process connectivity, quantitative data for structural connectivity is easier to obtain, requiring only measurements of the tidal channel's morphological and topographic features.

[0038] In one specific embodiment of the present invention, such as Figure 3 As shown, the relationship between the hydrological connectivity structure index and structural indicators and their distribution characteristics are investigated: two tidal channel systems in the wetlands on the north bank of the Yellow River Estuary are selected to calculate the lateral hydrological connectivity structure index and verify its effectiveness.

[0039] PCA analysis shows that, Figure 4 As shown, the first two axes of the principal component analysis (PCA) of the five variables explained 85.25% of the total variability. The variables showed the highest correlation with the first axis (60.84% ​​of the total variability) and roughly the same correlation with the second axis (24.41% of the total variability). The PCA loadings for tidal channel morphology variables (tidal channel class, length, and cross-sectional area) exceeded 0.8 on the first axis, while the PCA loadings for lateral distance and elevation exceeded 0.6 on both the first and second axes (Table 1).

[0040] Table 1. Principal Components and Component Coefficient Matrix

[0041] Spatial distribution characteristics of structural hydrological connectivity intensity are shown in Figure 5 From the perspective of longitudinal connectivity of tidal channels, the connectivity intensity of the tidal flats corresponding to the main tidal channel is higher than that of the secondary tidal channels. Furthermore, as the tidal channel extends further from the sea, the hydrological connectivity intensity gradually decreases. This is consistent with the characteristics of water flow and velocity in the tidal channel: high flow and velocity result in high connectivity intensity, while low flow and velocity result in low connectivity intensity. Analyzing a single branch of the tidal channel reveals that as the channel extends, its cross-sectional area decreases, its water volume gradually diminishes, its flow velocity slows, and its hydrological connectivity intensity gradually decreases until the water disappears. From the perspective of lateral connectivity of tidal channels, as the lateral distance of the channel increases, the elevation of the tidal flats gradually increases. The frequency of flooding gradually decreases with increasing elevation and distance, resulting in high-frequency and low-frequency flooding zones, i.e., the wet-dry boundary. The hydrological connectivity intensity also gradually weakens with increasing lateral distance. Generally speaking, high hydrological connectivity zones are located near the main tidal channel; medium hydrological connectivity zones are located in areas at a moderate distance from the main tidal channel and near the secondary tidal channel; and low hydrological connectivity zones are located in areas far from the main tidal channel and far from the secondary tidal channel.

[0042] In one specific embodiment of the present invention, such as Figure 6 As shown, the lateral hydrological connectivity index indicates the frequency of flooding: The lateral hydrological connectivity index shows a high correlation with the measured flooding frequency. The flooding frequency increases with the increase of hydrological connectivity intensity, which can effectively indicate the flooding intensity characteristics at various points on the tidal flat. This is consistent with the connotation of the hydrological connectivity intensity index established in the embodiments of the present invention. Areas with higher hydrological connectivity intensity have greater tidal flux; and a high flooding frequency is a manifestation of high tide flux.

[0043] In one specific embodiment of the present invention, such as Figure 7 As shown, the lateral hydrological connectivity index indicates the amount of sediment deposited in tidal flats: The lateral hydrological connectivity index shows a high correlation with the measured sedimentary amount in tidal flats. After log processing of the measured sedimentary data, the goodness of fit between the two is 0.8408. The sedimentary amount in tidal flats increases with the increase of hydrological connectivity intensity, which can effectively indicate the sedimentary intensity characteristics at various points in the tidal flat. This is consistent with the connotation of the hydrological connectivity intensity index established in the embodiments of the present invention. In areas with higher hydrological connectivity intensity, the tidal sedimentary flux is also greater, indicating that the lateral hydrological connectivity index has a good indicative effect on the sedimentary characteristics of tidal flats.

[0044] The hydrological connectivity assessment framework for salt marshes based on tidal channel systems proposed in this invention uses the hydrological connections between various points on the tidal flats and the ocean, generated by the movement of tidal water on the salt marsh surface, as the connotation of hydrological connectivity. Figure 1 We established a composite structural connectivity index based on tidal creek morphology and geomorphological features, and a multi-period process connectivity index based on water movement on the surface of the salt marsh. This incorporated all points on the salt marsh surface into a complete hydrological connectivity gradient, facilitating the analysis and comparison of hydrological elements, habitat elements, and vegetation characteristics on the salt marsh surface.

[0045] Tidal channels, as transport channels for tidal water, determine the potential pathways of tidal movement. Therefore, the morphology and topographic features of tidal channels constitute structural connectivity, while the spatiotemporal variations in water volume and its carried fluxes (such as seed flux, deposition flux, and nutrient flux) constitute process connectivity or functional connectivity. Structural connectivity is a simplified form of process or functional connectivity; compared to process connectivity, quantitative data for structural connectivity is easier to obtain, requiring only measurements of the tidal channel's morphological and topographic features.

[0046] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0047] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those 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 invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for constructing the lateral hydrological connectivity structure index of intertidal wetlands, characterized in that, include: Sampling points were evenly distributed in the intertidal zone to collect structural index data; The structural index data are subjected to Z-score centering. Principal component analysis was used to obtain the coefficients of the structural index on the first two axes, and a comprehensive hydrological connectivity index was constructed to determine the degree of hydrological connectivity.

2. The method for constructing the lateral hydrological connectivity structure index of intertidal wetlands according to claim 1, characterized in that, Structural data include: tidal channel level, tidal channel length, tidal channel cross-sectional area, lateral distance, and elevation.

3. The method for constructing the lateral hydrological connectivity structure index of intertidal wetlands according to claim 1, characterized in that, Principal component analysis is used to obtain the coefficients of structural indices on the first two axes, including: PCA first axis score: y1 = a1x1 + ... + a n x n ; PCA second axis score: y2 = b1x1 + ... + b n x n ; Where, x n This represents structural indicator data, where n represents the number of structural indicators; a n and b n These are the principal component coefficients of each index on the first and second axes of the principal components, respectively.

4. The method for constructing the lateral hydrological connectivity structure index of intertidal wetlands according to claim 3, characterized in that, Construct a comprehensive hydrological connectivity index, including: Hydrological connectivity structure index H Cs =(C1y1+C2y2) / Cc; Where C1 is the cumulative contribution rate of the first axis, C2 is the cumulative contribution rate of the second axis, and Cc is the cumulative contribution rate of the first two axes.

5. The method for constructing the lateral hydrological connectivity structure index of intertidal wetlands according to claim 1, characterized in that, The obtained comprehensive hydrological connectivity index is normalized using the maximum-minimum method to determine the hydrological connectivity. The final comprehensive hydrological connectivity index value is between 0 and 1. The larger the value, the greater the hydrological connectivity.

6. The method for constructing the lateral hydrological connectivity structure index of intertidal wetlands according to claim 2, characterized in that, The length of a tidal channel is the length of the tidal channel from a certain point on the tidal flat to the tidal channel estuary. The tidal channel level is the classification of the tidal channel at a certain point on the tidal flat. The cross-sectional area of ​​a tidal channel is the product of the width and depth of the tidal channel at a certain point on the tidal flat. Lateral distance is the vertical distance from a point on the tidal flat to the nearest tidal channel; The tidal flat elevation is the elevation of a specific point on the tidal flat.

7. The method for constructing the lateral hydrological connectivity structure index of intertidal wetlands according to claim 2, characterized in that, ArcGIS was used to analyze and obtain data on tidal channel length and lateral distance. The cross-sectional area of ​​the tidal channel was obtained by using field surveys to acquire data on the width and depth of the cross-section. Elevation data of points can be obtained through RTK field measurements or spectral analysis.

8. The method for constructing the lateral hydrological connectivity structure index of intertidal wetlands according to claim 2, characterized in that, The tidal channel levels are assigned values ​​according to the Strahler classification in reverse order to divide the entire intertidal zone into tidal channel levels.

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