A multi-layer vertical spatial structural diversity description method for wetland vegetation

Abstract

This invention provides a method for describing the multi-layer vertical spatial structural diversity of wetland vegetation, belonging to the field of ecology. The method comprises the following steps: dividing wetland vegetation into canopy, middle, and bottom layers by height; and collecting vegetation parameters at different layers to construct corresponding models to describe the structural diversity at each layer. This method can describe the structural diversity of wetland vegetation at all levels and multiple angles at all vertical levels, including the bottom, middle, and canopy layers, as well as wetland tree and herbaceous vegetation. This method enables a comprehensive, multifaceted, and multi-dimensional assessment of vegetation structural diversity, providing a more comprehensive and accurate reflection of wetland vegetation structural characteristics.

Description

Technical Field

[0001] The invention belongs to the field of ecology, and in particular relates to a method for describing the diversity of multi-layer vertical spatial structures of wetland vegetation. Background Art

[0002] The strength of an ecosystem's functioning is not only related to its scale, vegetation, and type, but also to its distribution within it. The individual size and physical arrangement of species within an ecosystem, particularly its vegetation, influence the flow and utilization of energy and resources such as heat and nutrients. Therefore, accurately and quantitatively describing vegetation structural diversity and understanding its current status and changes are crucial for studying ecosystem function.

[0003] Currently, a wide range of research and calculation methods have been developed for the study and quantification of diversity at various levels, such as alpha, beta, and gamma diversity, distribution pattern indices, and separation indices. However, these indices focus on describing the abundance and number of communities, or the horizontal spatial distribution of stands, from a single perspective. Furthermore, these indices cannot directly visualize the three-dimensional structural morphology of stands. Furthermore, for wetland vegetation, the distribution of aerial roots and herbaceous vegetation together form a complex stand understory. For mangrove wetlands, which have high ecosystem productivity and complex stand structures, specific methods for describing and quantifying structural diversity are needed. Summary of the Invention

[0004] The purpose of this invention is to describe the structural diversity of wetland vegetation from three vertical levels: bottom layer, middle layer and canopy layer, based on the complex root system and stem and leaf structure of wetland vegetation, and calculate the structural diversity index of each level.

[0005] The technical solution of the present invention is:

[0006] A method for describing the multi-layer vertical spatial structural diversity of wetland vegetation includes the following steps:

[0007] Wetland vegetation is divided into canopy, middle layer and bottom layer by height;

[0008] The parameters of vegetation at different levels are collected to construct corresponding models to describe the structural diversity of each level.

[0009] Furthermore, it is characterized in that the parameters of vegetation at different levels are collected to construct corresponding models to describe the structural diversity of each level, specifically:

[0010] The location and height data of mangrove trees in the wetland are collected to construct a three-dimensional tree height fold model, and the tree height structure diversity of the wetland vegetation canopy is obtained based on the three-dimensional tree height fold model;

[0011] The base diameter and breast diameter data of vegetation in the wetland sample plot are collected to construct a three-dimensional main stem frustum model, and the main stem structure diversity of the middle layer of the wetland vegetation is obtained based on the three-dimensional main stem frustum model;

[0012] The height of aerial roots of mangrove plants above the ground and their distance from the main trunk were collected in the wetland sample plots to construct a three-dimensional root radiation model. Based on the three-dimensional root radiation model, the structural diversity of the above-ground root systems of wetland vegetation was obtained.

[0013] Collecting the height and distribution boundary position data of herbaceous plants in the wetland sample plot to construct a three-dimensional model of herbaceous plants, and obtaining the three-dimensional diversity of the herbaceous layer of wetland vegetation based on the three-dimensional model of herbaceous plants;

[0014] The bottom layer structural diversity of wetland vegetation is obtained based on the above-ground root structure diversity of wetland vegetation and the herb layer structural diversity of wetland vegetation.

[0015] Furthermore, the location and tree height data of mangrove trees in the wetland are collected to construct a three-dimensional tree height fold model. Based on the three-dimensional tree height fold model, the tree height structure diversity of the wetland vegetation canopy is obtained as follows:

[0016] The triangulated network map is constructed with the horizontal coordinate of the tree position in the plot as x, the vertical coordinate as y, and the height of the crown vertex as z;

[0017] The tree height diversity index is obtained by calculating the three-dimensional fold model of tree height based on the area of each triangle in the triangulated network diagram. The formula is:

[0018] ,

[0019] Where, is the area of any triangular grid in the triangulated network diagram, A is the area of the wetland plot, n is the total number of triangles in the grid, and l is the lth triangle.

[0020] Furthermore, the base diameter and breast diameter data of vegetation in the wetland sample plot were collected to construct a three-dimensional main stem frustum model. Based on the three-dimensional main stem frustum model, the structural diversity of the middle-layer main stems of wetland vegetation was obtained as follows:

[0021] With the tree position in the plot as the x-coordinate and the y-coordinate, the main stem diameter distribution map of vegetation was drawn based on the vegetation base diameter and breast diameter data;

[0022] Based on the vegetation main stem diameter distribution map, the three-dimensional main stem frustum model is calculated to obtain the main stem structure diversity index of the middle layer of trees at any height in the sample plot. The formula is:

[0023] ,

[0024] Where S R is the cross-sectional area at the base diameter of any vegetation in the grid, S ris the cross-sectional area at the height of the crown base of any vegetation in the grid, A is the area of the wetland plot, m is the total number of frustum sections in the plot, and j is the jth frustum section.

[0025] Furthermore, data on the height of aerial roots of mangrove plants above the ground and their distance from the trunk were collected in the wetland sample plots to construct a three-dimensional root system radiation model. Based on the three-dimensional root system radiation model, the structural diversity of the above-ground root systems of wetland vegetation was obtained as follows:

[0026] The vegetation root system radial network diagram was drawn with the tree position in the plot as x, the vertical coordinate as y, the aerial root height as z, the aerial root distribution radius as r, and the aerial root fan arc length as l.

[0027] The root system three-dimensional radiation model is calculated based on the vegetation root system radiation network diagram to obtain the root system three-dimensional structural diversity index, and the formula is:

[0028] ,

[0029] Where, is the area of any sector grid in the vegetation root radial network diagram, A is the area of the wetland plot, p is the total number of sectors in the grid, and k is the kth sector.

[0030] Furthermore, the height and distribution boundary position data of the herbaceous plants in the wetland sample plot were collected to construct a three-dimensional model of the herbaceous plants. Based on the three-dimensional model of the herbaceous plants, the three-dimensional diversity of the herbaceous layer of the wetland vegetation was obtained as follows:

[0031] Draw a three-dimensional vegetation distribution structure map based on the x, y edge position of herbaceous plants in each area of the sample plot and the height h of herbaceous vegetation;

[0032] The three-dimensional model of herbaceous plants is calculated based on the three-dimensional vegetation distribution structure map to obtain the three-dimensional diversity index of the herbaceous layer. The formula is:

[0033] ,

[0034] Where, is the area of any triangular grid in each top surface grid in the three-dimensional distribution structure diagram, A is the area of the wetland plot, is the height of each vegetation, is the height of the tallest herbaceous vegetation in the plot, is the order of herbaceous plants sorted from small to large in height, and n is the total number of herbaceous plant individuals.

[0035] Furthermore, based on the wetland vegetation aboveground root structure diversity and the wetland vegetation herb layer structure diversity, the wetland vegetation bottom layer structure diversity is specifically:

[0036] ,

[0037] in, is the root three-dimensional structural diversity index, is the three-dimensional diversity index of the herb layer.

[0038] Compared with the prior art, the present invention has the following advantages:

[0039] The present invention establishes a diversity description method at the vegetation structure level, which can describe the structural diversity of the bottom layer, middle layer and canopy layer of wetland vegetation, as well as wetland tree vegetation and herbaceous vegetation at all levels and multiple angles at vertical height, thereby realizing a comprehensive, multi-faceted and multi-dimensional evaluation of vegetation structural diversity, and reflecting the structural characteristics of wetland vegetation more comprehensively and accurately.

[0040] The present invention comprehensively considers the impact of the size distribution and physical arrangement of the roots, stems, and leaves of wetland vegetation on the overall habitat vegetation structure. The aerial roots growing in the bottom layer of wetland vegetation are the main feature that distinguishes it from other vegetation types. This method takes the structural diversity of various types of aerial roots as an important part and comprehensively considers the structural diversity of wetland vegetation. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The accompanying drawings illustrate various embodiments generally by way of example and not limitation, and together with the description and claims, serve to explain embodiments of the invention. Where appropriate, the same reference numerals are used throughout the drawings to refer to the same or similar parts. Such embodiments are illustrative and are not intended to be exhaustive or exclusive of the embodiments of the present apparatus or method.

[0042] Figure 1 Shown is a schematic flow chart of the method of the present invention;

[0043] Figure 2 A schematic diagram of a tree canopy height triangulated network diagram of the present invention is shown;

[0044] Figure 3 A schematic diagram of an arbitrary triangle ΔABC in the triangular mesh of the present invention is shown;

[0045] Figure 4 A schematic diagram of a three-dimensional main stem cone model of a tree according to the present invention is shown;

[0046] Figure 5 A schematic diagram showing the calculation of stem diameter distribution at plant height H based on a three-dimensional main stem frustum model of the present invention is shown;

[0047] Figure 6 A schematic diagram of a vegetation root system radial network diagram of the present invention is shown;

[0048] Figure 7A schematic diagram showing a three-dimensional distribution structure diagram of wetland herbaceous vegetation according to the present invention is shown;

[0049] Figure 8 A schematic diagram showing the vertical three-dimensional structure of the herbaceous vegetation canopy density of the present invention is shown. DETAILED DESCRIPTION

[0050] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0051] like Figure 1 As shown, the present invention discloses a multi-layer vertical spatial structure diversity description method for wetland vegetation, comprising the following steps:

[0052] S1 collects the location and tree height data of wetland vegetation (tall mangrove trees), establishes a three-dimensional tree height fold model based on the formula, determines the morphology of the three-dimensional tree height fold layer, calculates the tree height structural diversity, and describes the tree height structural diversity of the wetland vegetation canopy;

[0053] S2 collects the basal diameter and diameter at breast height data of wetland vegetation, establishes a three-dimensional main stem cone model based on the formula, determines the three-dimensional morphology of the stem, calculates the main stem structural diversity, and describes the main stem structural diversity of the middle layer of wetland vegetation;

[0054] S3 collects data on the height and distance of aerial roots from the main trunk of wetland vegetation (mangrove plants) in the sample plot, establishes a three-dimensional radial model of the root system based on the formula, determines the three-dimensional radial morphology of the root system, calculates the root system structure diversity, and describes the above-ground root system structure diversity of wetland vegetation;

[0055] S4 herb modeling collects data on the height of herbs (mainly Acanthus paniculatus) in wetland sample plots and the distribution boundary position data of herb plants in the sample plots, establishes a three-dimensional model of herb plants based on the formula, determines the three-dimensional morphology of herb plants, calculates the structural diversity of herb plants, and describes the structural diversity of the herb layer of wetland vegetation.

[0056] S5 Determine the diversity of the bottom layer structure of wetland vegetation based on the diversity of the aboveground root system structure and the diversity of the herb layer structure.

[0057] See Figure 2 The top of any tree canopy in the quadrat is connected to the tops of the two nearest trees to form a triangle. The tops of all tree canopies in the quadrat are connected in this way to form a three-dimensional fold triangular network, forming a tree canopy top height triangular network. Figure 3 , the area of the triangle can be calculated according to the definition of the vector product of two vectors:

[0058] .

[0059] Based on the location and height data collected from wetland mangrove trees, a three-dimensional tree height model was constructed based on the crown height within the sample plot. The horizontal coordinate of the tree position within the sample plot was x, the vertical coordinate was y, and the crown vertex height was z. A triangulated network diagram of each sample plot was drawn based on the sample data. The three-dimensional wrinkle index FS,I of the tree crown height is calculated as follows:

[0060] ,

[0061] Where, is the area of any triangular grid in the triangulated network diagram, A is the area of the wetland plot, n is the total number of triangles in the grid, and l is the lth triangle.

[0062] The three-dimensional fold index of the tree canopy height of the sample can be calculated based on the area of each triangle in the triangulated network within the sample. The three-dimensional fold index of the tree canopy height of the sample canopy is the tree height diversity index of the sample canopy. A higher tree height diversity index indicates a more complex vegetation height structure within the sample canopy.

[0063] Below the tree canopy is the main stem. Since most tree stem branches are concentrated in the middle and upper parts, and the branching stems overlap with the canopy after branching, only the main stem below the branching stem is considered for modeling and simulation. Based on the tree location data and base diameter at breast height data collected from the wetland plots, a three-dimensional main stem cone model of vegetation was constructed. The trunk radius gradually decreases from base to top, and the main stem of a tree can be roughly understood as a cone with the base diameter as the cone base circumference and the crown base height as the height. Figure 4 .

[0064] With the tree position in the plot as the horizontal coordinate x and the vertical coordinate y, the main stem diameter distribution map of vegetation at any height of each plot is drawn based on the plot data. Figure 5 Taking the frustum shown in the figure as an example, the calculation formula for the stem diameter DR and cross-sectional area S at the plant height H is:

[0065] ,

[0066] Where R is the base diameter of the tree, H is any height on the main stem of the tree, r1.3 is the radius at the tree's diameter at breast height (1.3m), and R is the radius at the base diameter of the tree.

[0067] The diversity index F of the main stem structure of trees in the middle layer at any height of the plot S，2 , the calculation formula is:

[0068] ,

[0069] Where S R is the cross-sectional area at the base diameter of any vegetation in the grid, S ris the cross-sectional area at the height of the crown base of any vegetation in the grid, A is the area of the wetland plot, m is the total number of frustum sections in the plot, and j is the jth frustum section.

[0070] The lower layer of wetland vegetation is mainly composed of various plant roots and herbaceous plants. The method of the present invention is divided into two parts for separate calculations. The biggest difference between wetland vegetation and vegetation in other ecosystems is the widespread growth of various types of aerial roots, such as shoot roots, knee roots, plate roots, etc., which have a certain height and are fan-shaped and radially distributed around the tree position as the midpoint. Based on the collected data on the height of aerial roots above the ground and the distance from the trunk of wetland plot vegetation (mangrove plants), a three-dimensional radiation model of the root system is established. The horizontal coordinate of the tree position in the plot is x, the vertical coordinate is y, the height of the aerial root is z, the distribution radius of the aerial root is r, and the fan-shaped arc length of the aerial root is l. A root system radiation network diagram of each plot vegetation is drawn, as shown below: Figure 6 The calculation formula of root three-dimensional structure diversity index F is:

[0071] ,

[0072] Where, is the area of any sector grid in the vegetation root radial network diagram, A is the area of the wetland plot, p is the total number of sectors in the grid, and k is the kth sector.

[0073] like Figure 6 For any sector in the sector grid, the sector area can be calculated based on the aerial root distribution radius r and the sector arc length l. Due to the different heights of the sector grids, there may be overlapping parts. The area of the overlapping part is calculated separately for each sector grid:

[0074] ,

[0075] The root structure diversity index of the sample plot can be calculated based on the area of each sector of the fan-shaped network within the sample plot.

[0076] The main herbaceous vegetation in the mangroves is Acanthus truncatus. In some areas, Acanthus truncatus grows vigorously, with a height of more than 1 meter, and there are intersections with the main stem and roots. Based on the herb height and distribution boundary data of the wetland sample plot, a three-dimensional model of wetland herbaceous plants is constructed. Wetland herbaceous plants are distributed in sheets. The vegetation at the edge of the distribution area is relatively low, and the middle is relatively high. The entire area forms a three-dimensional spatial structure with an irregular top triangular grid and the herbaceous plant distribution area as the base. The top surface is similar to the three-dimensional fold model of the tree height. The height of herbaceous vegetation can be obtained by combining Lidar laser radar scanning with field measurement. Based on the edge position (x, y) of the herbaceous plant distribution in each area of the sample plot and the height h of the herbaceous vegetation in each area, a three-dimensional distribution structure diagram of the herbaceous vegetation in each sample plot is drawn, as shown below: Figure 7 .

[0077] Divide the vertical space into three layers according to the height of the herbaceous plants in the sample plot. For example, if the maximum height of the herbaceous plants is 1.5m, set up three layers: 0cm-50cm, 50cm-100cm, and 100cm-150cm. Use a leaf area index meter to operate at the top of the canopy and the bottom of each layer, measure the leaf area index at the top and the bottom of each layer, and obtain the non-intercepted scattering of each vertical layer of the canopy. The light transmittance of each layer of the canopy can be obtained according to the formula:

[0078] ,

[0079] Where, is the zenith angle, L is the leaf area index of the layer, is the optical fiber transmittance at a certain zenith angle.

[0080] For the top canopy layer, the light transmittance can be directly calculated by the leaf area index. For the canopy layer below, the light transmittance can be calculated by the formula:

[0081] ,

[0082] Where, T up is the light transmittance of all upper layers of a vertical canopy, T un is the light transmittance of the lower layer of a vertical canopy.

[0083] The canopy density of each layer of herbaceous vegetation is determined by this method, and the vertical three-dimensional structure of the canopy density of herbaceous vegetation is established by combining the three-dimensional fold model of herbaceous vegetation, such as Figure 8 shown.

[0084] The complexity of the three-dimensional structure of herbaceous vegetation is composed of two aspects: the degree of grid wrinkles on the top surface and the degree of height difference. Therefore, the three-dimensional diversity index is composed of two parts. The height difference of herbaceous vegetation in the sample site is represented by the Gini index of herbaceous vegetation height. The formula for calculating the three-dimensional diversity index of herbaceous vegetation F is:

[0085] ,

[0086] Where Si is the area of each triangle in the top surface grid, A is the area of the plot, hi is the height of each vegetation, h is the height of the highest herbaceous vegetation in the plot, i is the order of herbaceous plants in ascending order of height, and n is the total number of herbaceous plant individuals.

[0087] The calculation method of the three-dimensional wrinkle index of the triangular mesh of the herb top surface is the same as that of the tree height.

[0088] The herbaceous plant structural diversity index was calculated based on the height of herbs (mainly Acanthus truncatus) in the wetland sample plots and the location data of the herbaceous plant distribution boundaries within the sample plots.

[0089] The underlying structure of vegetation is mainly composed of aerial roots and herbaceous plants. Therefore, the diversity index of the underlying structure of vegetation is based on the diversity of the above-ground root structure of vegetation and the diversity of the herbaceous layer structure, so as to determine the diversity of the underlying structure of wetland vegetation.

[0090] ,

[0091] in, is the root three-dimensional structural diversity index, The above is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art who, within the technical scope disclosed by the present invention, makes equivalent substitutions or changes based on the technical solution and inventive concept of the present invention shall be covered by the scope of protection of the present invention.

Claims

1. A method for describing the multi-layer vertical spatial structural diversity of wetland vegetation, characterized in that: The following steps are involved: Wetland vegetation is divided into canopy, middle layer and bottom layer by height; Collect the parameters of vegetation in different layers and build corresponding models to describe the structural diversity of each layer; The parameters of vegetation at different levels are collected to construct corresponding models to describe the structural diversity of each level. Specifically: The location and height data of mangrove trees in the wetland are collected to construct a three-dimensional tree height fold model, and the tree height structure diversity of the wetland vegetation canopy is obtained based on the three-dimensional tree height fold model; The base diameter and breast diameter data of vegetation in the wetland sample plot are collected to construct a three-dimensional main stem frustum model, and the main stem structure diversity of the middle layer of the wetland vegetation is obtained based on the three-dimensional main stem frustum model; The height of aerial roots of mangrove plants above the ground and their distance from the main trunk were collected in the wetland sample plots to construct a three-dimensional root radiation model. Based on the three-dimensional root radiation model, the structural diversity of the above-ground root systems of wetland vegetation was obtained. Collecting the height and distribution boundary position data of herbaceous plants in the wetland sample plot to construct a three-dimensional model of herbaceous plants, and obtaining the three-dimensional diversity of the herbaceous layer of wetland vegetation based on the three-dimensional model of herbaceous plants; The bottom layer structure diversity of wetland vegetation is obtained based on the above-ground root structure diversity of wetland vegetation and the herb layer structure diversity of wetland vegetation; The height of aerial roots and their distance from the main trunk of mangrove plants in wetland plots were collected to construct a three-dimensional root radiation model. Based on the three-dimensional root radiation model, the structural diversity of the aboveground root systems of wetland vegetation was obtained as follows: The vegetation root system radial network diagram was drawn with the tree position in the plot as x, the vertical coordinate as y, the aerial root height as z, the aerial root distribution radius as r, and the aerial root fan arc length as l. The root system three-dimensional radiation model is calculated based on the vegetation root system radiation network diagram to obtain the root system three-dimensional structural diversity index, and the formula is: ， Where, is the area of any fan-shaped grid in the vegetation root radial network diagram, A is the area of the wetland plot, is the total number of sectors in the grid, and k is the kth sector.

2. The method for describing the multi-layer vertical spatial structure diversity of wetland vegetation according to claim 1, characterized in that: The location and height data of mangrove trees in the wetland are collected to construct a three-dimensional tree height fold model. The tree height structure diversity of the wetland vegetation canopy is obtained based on the three-dimensional tree height fold model. Specifically: The triangulated network map is constructed with the horizontal coordinate of the tree position in the plot as x, the vertical coordinate as y, and the height of the crown vertex as z; The tree height diversity index is obtained by calculating the three-dimensional fold model of tree height based on the area of each triangle in the triangulated network diagram. The formula is: ， Where, is the area of any triangle grid in the triangulated network diagram, A is the area of the wetland plot, is the total number of triangles in the mesh, and l is the lth triangle.

3. The method for describing the multi-layer vertical spatial structure diversity of wetland vegetation according to claim 1, characterized in that: The base diameter and diameter at breast height data of vegetation in the wetland sample plot were collected to construct a three-dimensional main stem frustum model. Based on the three-dimensional main stem frustum model, the structural diversity of the main stems of the wetland vegetation in the middle layer was obtained as follows: With the tree position in the plot as the x-coordinate and the y-coordinate, the main stem diameter distribution map of vegetation was drawn based on the vegetation base diameter and breast diameter data; Based on the vegetation main stem diameter distribution map, the three-dimensional main stem frustum model is calculated to obtain the main stem structure diversity index of the middle layer of trees at any height in the sample plot. The formula is: ， Where S R is the cross-sectional area at the base diameter of any vegetation in the grid, S r is the cross-sectional area at the height of any vegetation crown in the grid, A is the area of the wetland plot, is the total number of frustum sections in the plot, and j is the jth frustum section.

4. The method for describing the multi-layer vertical spatial structure diversity of wetland vegetation according to claim 1, characterized in that: The height and distribution boundary position data of herbaceous plants in the wetland sample plot were collected to construct a three-dimensional model of herbaceous plants. Based on the three-dimensional model of herbaceous plants, the three-dimensional diversity of the herbaceous layer of wetland vegetation was obtained as follows: Draw a three-dimensional vegetation distribution structure map based on the x, y edge position of herbaceous plants in each area of the sample plot and the height h of herbaceous vegetation; The three-dimensional model of herbaceous plants is calculated based on the three-dimensional vegetation distribution structure map to obtain the three-dimensional diversity index of the herbaceous layer. The formula is: ， Where, is the area of any triangular grid in each top surface grid in the three-dimensional distribution structure diagram, A is the area of the wetland plot, is the height of each vegetation, is the height of the tallest herbaceous vegetation in the plot, To sort the herbs in ascending order of height, is the total number of herbaceous plant individuals.

5. The method for describing the multi-layer vertical spatial structure diversity of wetland vegetation according to claim 1, characterized in that: Based on the diversity of the wetland vegetation's aboveground root system structure and the diversity of the wetland vegetation's herbaceous layer structure, the diversity of the wetland vegetation's underlying structure is specifically as follows: ， in, is the root three-dimensional structural diversity index, is the three-dimensional diversity index of the herb layer.

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