A method for evaluating the health of small and medium-sized rivers based on niche suitability analysis

Abstract

The present invention provides a method for evaluating the health of small and medium-sized rivers based on niche suitability analysis, including screening a set of indicator species for small and medium-sized rivers, constructing a set of initial environmental elements for small and medium-sized rivers, extracting important niche dimensions using data dimensionality reduction technology, constructing niche suitability curves for each dimension, solving the hypervolume of a multidimensional hyperrectangle in an ideal state of an optimal niche, proposing a niche suitability evaluation method based on the fit between the actual and optimal niche hypervolumes, and constructing a new system for evaluating the health of small and medium-sized rivers based on the niche suitability of indicator species; by quantifying the concept of niche, a new method for evaluating the health of small and medium-sized rivers is proposed from an ecological perspective, providing technical support for better achieving the goal of ecological environmental recovery of rivers and lakes.

Description

Technical Field

[0001] The present invention relates to the field of water ecological environment evaluation, and in particular to a method for evaluating the health of small and medium-sized rivers based on niche suitability analysis. Background Art

[0002] With the rapid development of modern society, economy, and science and technology, explosive population growth and increasing material needs have led to the predatory exploitation and utilization of water resources. Overexploitation, waste, and water pollution have damaged the ecological "immune system" of rivers and lakes, preventing them from self-regulating and restoring their health. This has led to problems such as water pollution, deteriorating hydrological conditions, damage to morphological structures, loss of species diversity, and degradation of river and lake functions.

[0003] Current river and lake health assessment methods often employ multi-level, multi-indicator approaches. These indicators encompass multiple areas, including hydrology and water resources, river physical structure, water quality, and aquatic biological characteristics, providing a comprehensive picture of river health. However, evaluating the health of small and medium-sized rivers presents two challenges. First, these methods require a wide variety of data, which is often relatively scarce for small and medium-sized rivers, making practical applications potentially challenging. Second, due to the relatively small spatial scale of small and medium-sized rivers, their ecosystems exhibit strong feedback loops between biological communities and the environment. Current river health assessment methods are relatively broad, making it difficult to highlight the unique structural and interconnected features of small and medium-sized river ecosystems.

[0004] The ecological niche is a crucial concept in modern ecology, representing the needs of a species for its external environment and reflecting the mutual influence and interaction between species and their environment. The study and application of the ecological niche is a core concept in modern ecology. Historically, many scholars have attempted to define the niche, but the rich and diverse nature of the concept has made practical application difficult.

[0005] The present invention quantifies the niche distribution in each dimension, solves the ideal niche super volume, and uses the method of comparing the actual niche super volume fit to evaluate the species niche suitability, and then assess the health status of small and medium-sized rivers. Summary of the Invention

[0006] The purpose of the present invention is to address the deficiencies of the above-mentioned prior art and provide a small and medium-sized river health assessment method based on niche suitability analysis, which can evaluate the health status of small and medium-sized rivers.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] The present invention provides a method for evaluating the health of small and medium-sized rivers based on ecological niche suitability analysis, comprising the following steps:

[0009] S1. Screening of indicator species sets for small and medium-sized rivers ;

[0010] S2. Constructing the initial environmental element set for small and medium-sized rivers ;

[0011] S3, data dimensionality reduction method to extract niche dimensions;

[0012] S4. Calculate the niche suitability curves of each dimension;

[0013] S5. Solve the ideal state in the most suitable ecological niche dimensional hyperrectangular hypervolume;

[0014] S6. Analyze the ecological niche under actual and ideal conditions Dimensional supervolume fit to evaluate actual niche suitability;

[0015] S7. Evaluate the health status of small and medium-sized rivers based on the niche suitability of each indicator species.

[0016] Furthermore, the S1 is specifically:

[0017] According to the geographical location, climate conditions, species distribution and composition of small and medium-sized rivers, select indicator species that reflect the characteristics of small and medium-sized rivers , thus forming a small and medium-sized river indicator species set for river health assessment :

[0018] ;

[0019] in, is the serial number of the indicator species; is the total number of indicator species used for river health assessment.

[0020] Furthermore, the S2 is specifically:

[0021] According to the characteristics of small and medium-sized rivers and the composition of indicator species sets, the environmental factors that affect indicator species are determined to form the initial environmental factor set of small and medium-sized rivers. :

[0022] ;

[0023] ;

[0024] ;

[0025] ;

[0026] ;

[0027] in, is the initial physical element set; To initialize the chemical element set; is the initial spatiotemporal distribution element set; is the initial water flow feature set; For the bottom of small and medium-sized rivers; for illumination; is the water temperature; For small and medium rivers value; is the dissolved oxygen content in water; is the total phosphorus in water; is the river length position; For water depth; For the time period; For traffic; is the flow rate; Water level fluctuations.

[0028] Furthermore, the S3 is specifically:

[0029] Since the initial environmental element set of small and medium-sized rivers There are many dimensions in the calculation, so some linearly related dimensions and indicator species sets of small and medium rivers need to be eliminated in actual calculation. The dimensions with less impact can reduce the space occupied by data, improve the computing speed, and reduce the space and time complexity of the algorithm.

[0030] The initial environmental element set of small and medium-sized rivers Considered as a OK Column matrix :

[0031] ;

[0032] in, is the number of environmental element types, i.e., dimension; is the sample size, and there is a sample size Number of environmental factors ; For the Environmental factor samples vector.

[0033] In theory, the matrix Column vectors of environmental factors in Should be linearly independent, that is, the matrix Rank In actual analysis, some environmental factors are correlated, that is, environmental column vectors can represent each other. Therefore, it is necessary to use correlation analysis, principal component analysis, and feature analysis to eliminate redundant factors. Assume that after eliminating linearly correlated factors, the remaining environmental factors are , then after reducing the dimension, the environmental factor matrix becomes , abbreviated as ,in ;

[0034] In addition, after reducing the dimension, the environmental factor matrix The degree of influence of each environmental factor on the characteristics of indicator species is also different. When calculating, the environmental factors with greater influence should be retained, while the environmental factors with smaller influence should be eliminated. By adopting the canonical correspondence method or redundant algorithm, the number of environmental factors can be further reduced to dimensional, and finally extract the matrix that has the greatest impact on each indicator species , abbreviated as ,in, . This is the number of dimensions used for niche analysis after data dimensionality reduction.

[0035] Furthermore, the S4 is specifically:

[0036] Since the matrix with greater influence on each indicator species after data dimensionality reduction If the dimensions in the matrix are linearly independent, the sample data can be used to deduce the matrix that has the greatest impact on each indicator species. Niche fitness function of each dimension in , and draw the niche suitability curves of each dimension. Polynomial fitting, generalized additive algorithm, and machine learning algorithm were used for calculation.

[0037] Furthermore, S5 is specifically:

[0038] Solve the niche fitness function of each dimension The corresponding optimal ecological niche , the optimal ecological niche The optimal ecological niche is a theoretical solution. In actual work, there is no optimal ecological niche with a unique optimal solution. , and from the data format requirements of subsequent similarity evaluation, the most suitable ecological niche needs to be There is a certain spatial extensibility in the dimensional Euclidean space, that is, it is necessary to find the value range of the optimal ecological niche in each dimension. According to the actual work needs, the corresponding allowable error value needs to be set. , and combined with the niche fitness function and optimal niche , solve for the neighborhood value , the calculation formula is:

[0039] ;

[0040] Since the niche fitness function The distribution form of the neighborhood value There are two solutions, respectively denoted as the previous neighborhood values and the subsequent neighborhood values , and there are , then the value range of the optimal niche in each dimension is expressed as , and then The value range of the optimal ecological niche is converted into the Euclidean space dimensional hyperrectangle , specifically:

[0041] ;

[0042] but dimensional hypervolume The calculation formula is:

[0043] .

[0044] Furthermore, the S6 is specifically as follows:

[0045] According to the actual environment element set , for the indicator species set in For each indicator species, the following method should be used for calculation:

[0046] That is: use the data dimensionality reduction method in S3 to extract the actual important environmental factor matrix , and use the method in S5 to calculate the actual dimensional hyperrectangle ,but:

[0047] ;

[0048] in, The actual ecological niche The value range of the dimension, the lower boundary is The upper boundary is represented by express;

[0049] According to the calculation method in S5, we can deduce Hypervolume of actual ecological niche for:

[0050] .

[0051] Furthermore, the optimal ecological niche dimensional hyperrectangle and actual niche dimensional hyperrectangle The position relationship in space is divided into: separation, intersection, optimal inclusion, and actual inclusion. The niche suitability index of each position relationship is expressed as follows:

[0052] ;

[0053] in, is the total set of niche suitability indices under each position relationship; The most suitable ecological niche dimensional hyperrectangle and actual niche dimensional hyperrectangle The niche suitability index when the spatial position is separated is referred to as the separated niche suitability index; The most suitable ecological niche dimensional hyperrectangle and actual niche dimensional hyperrectangle The niche suitability index when the spatial position is intersecting is referred to as the intersection niche suitability index; The most suitable ecological niche dimensional hyperrectangle Completely encompasses the actual niche dimensional hyperrectangle The niche suitability index at that time is referred to as the most inclusive niche suitability index; Actual ecological niche dimensional hyperrectangle Completely encompasses the optimal niche dimensional hyperrectangle The niche suitability index at that time is referred to as the actual niche suitability index;

[0054] If the optimal ecological niche dimensional hyperrectangle and actual niche dimensional hyperrectangle The spatial positions of are separated, that is, there is no intersection between the two, and the mathematical expression is , then the niche suitability index is ;

[0055] If the optimal ecological niche dimensional hyperrectangle and actual niche dimensional hyperrectangle The spatial position of is intersecting, and the mathematical relationship expression is , then the niche fitness index is calculated by the ratio of the hypervolume of the intersection of the two hyperrectangles to the hypervolume of the union of the two hyperrectangles, then the intersection niche fitness index is The calculation method is as follows:

[0056] ;

[0057] ;

[0058] ;

[0059] in, Indicates the The posterior neighborhood value of the dimensional niche.

[0060] If the optimal ecological niche dimensional hyperrectangle Contains actual ecological niche dimensional hyperrectangle , that is, the optimal package is actually, the mathematical expression is , then the most inclusive niche suitability index ;

[0061] If the actual niche dimensional hyperrectangle Completely encompasses the optimal niche dimensional hyperrectangle , that is, the actual package is optimal, and the mathematical expression is , then the actual niche suitability index The calculation formula is:

[0062] .

[0063] Further, the S7 is specifically:

[0064] Indicator species collection for small and medium-sized rivers in Repeat S3 to S6 for each indicator species and calculate the niche suitability index of each indicator species. The resulting set is:

[0065] ;

[0066] According to the number, type and preciousness of each indicator species, the algorithm average method, hierarchical analysis method and entropy weight method are used to assign weights to each indicator species, and then the comprehensive niche suitability index of indicator species in small and medium-sized rivers is calculated. , the calculation formula is:

[0067] ;

[0068] in, The weights of each indicator species matrix.

[0069] According to the comprehensive habitat suitability index , combined with setting an appropriate threshold , the health status of small and medium-sized rivers can be evaluated and analyzed.

[0070] The beneficial effects of this invention are as follows: currently, conventional river health assessment methods all focus solely on the water environment or aquatic species. By introducing the concept of ecological niche, this method achieves a river health assessment based on an ecological perspective, focusing on the relationship between species and habitats. Furthermore, by combining numerical and geometric concepts, the method transforms the niche matrix into a hyperrectangle in Euclidean space, transforming the complex algebraic problem into a more intuitive geometric one. A similarity calculation method based on the hyperrectangle fit is proposed, which quantitatively analyzes the niche suitability method. This provides a new method for more accurately assessing river health, thereby promoting the healthy recovery of rivers and lakes.

[0071] The beneficial effects of this invention are as follows: currently, conventional river health assessment methods all focus solely on the water environment or aquatic species. By introducing the concept of ecological niche, this method achieves a river health assessment based on an ecological perspective, focusing on the relationship between species and habitats. Furthermore, by combining numerical and geometric concepts, the method transforms the niche matrix into a hyperrectangle in Euclidean space, transforming the complex algebraic problem into a more intuitive geometric one. A similarity calculation method based on the hyperrectangle fit is proposed, which quantitatively analyzes the niche suitability method. This provides a new method for more accurately assessing river health, thereby promoting the healthy recovery of rivers and lakes. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] Figure 1 This is a flowchart of a method for evaluating the health of small and medium-sized rivers based on niche suitability analysis;

[0073] Figure 2 For indicator species About the environmental dimension Niche fitness curve of ;

[0074] Figure 3 For indicator species Niche suitability curve for the environmental dimension water temperature;

[0075] Figure 4 For indicator species About the environmental dimension Niche suitability curve of

[0076] Figure 5 For indicator species Niche suitability curve for the environmental dimension water temperature;

[0077] Figure 6 For indicator species of , the relationship diagram between the two-dimensional optimum of water temperature and the actual ecological niche hyperrectangular spatial position;

[0078] Figure 7 For indicator species of , the relationship diagram between the two-dimensional optimum of water temperature and the actual ecological niche hyper-rectangular spatial position. DETAILED DESCRIPTION

[0079] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0080] See also Figure 1 , a method for evaluating the health of small and medium-sized rivers based on niche suitability analysis, including the following steps:

[0081] S1. Screening of indicator species collections for small and medium-sized rivers ;

[0082] Select a small or medium-sized river As the study area of this embodiment, according to the small and medium rivers Based on the geographical location, climate conditions, species distribution and composition, two indicator species reflecting the characteristics of small and medium-sized rivers were selected. and , recorded as and , thus forming the indicator species set used for river health assessment in this embodiment. :

[0083] ;

[0084] S2. Constructing the initial environmental element set for small and medium-sized rivers ;

[0085] S3, data dimensionality reduction method to extract niche dimensions;

[0086] S4. Calculate the niche suitability curves of each dimension;

[0087] S5. Solve the ideal state in the most suitable ecological niche dimensional hyperrectangular hypervolume;

[0088] S6. Analyze the ecological niche under actual and ideal conditions Dimensional supervolume fit to evaluate actual niche suitability;

[0089] S7. Evaluate the health status of small and medium-sized rivers based on the niche suitability of each indicator species.

[0090] S2. Constructing the initial environmental element set for small and medium-sized rivers :

[0091] According to small and medium rivers Characteristic and indicator species collection composition, determine the indicator species and Environmental factors that have an impact, after analysis, affect indicator species and indicator species The main physical factors are light and water temperature The main chemical factors are and total nitrogen The main spatial and temporal distribution elements are water depth , the main flow element is flow velocity , thus forming small and medium-sized rivers Initial environment feature set .

[0092] S3. Extracting niche dimensions using data dimensionality reduction:

[0093] First, small and medium-sized rivers Initial environment feature set Treated as a 6-row matrix , according to the calculation, the rank of the matrix , which shows that the matrix The rank is not full, so the correlation analysis method is used to eliminate the linearly related environmental factors to ensure that the remaining environmental factors are linearly independent vectors. and water temperature , water depth and light , the correlation is high.

[0094] Therefore, water depth is excluded and light After removing the relevant factors, four linearly independent environmental factors are retained, which is consistent with the matrix analysis. The conclusion is consistent.

[0095] This example uses the canonical correspondence method to analyze the effects of various environmental factors on indicator species. and indicator species The results showed that for indicator species and indicator species For example, total nitrogen and flow rate The degree of influence on ecological niche characteristics is relatively low. For the convenience of calculation, the total nitrogen is excluded. and flow rate Two environmental factors, only water temperature is retained and Two dimensions were used for subsequent niche analysis.

[0096] S4. Derivation of niche suitability curves for each dimension:

[0097] Using the generalized additive algorithm to deduce indicator species and indicator species In water temperature The two-dimensional niche fitness function and the corresponding niche fitness curve are plotted. Figure 2 and Figure 3 ;

[0098] S5. Solve the ideal state in the most suitable ecological niche The hypervolume of a dimensional hyperrectangle:

[0099] Depend on Figures 3 to 7 , we can find the indicator species and indicator species The upper and lower neighborhood values of the two dimensions of , and the indicator species are obtained based on this A two-dimensional hyperrectangle and indicator species A two-dimensional hyperrectangle , specifically:

[0100] ;

[0101] ;

[0102] Calculate indicator species based on the hypervolume expression A two-dimensional hyperrectangle and indicator species A two-dimensional hyperrectangle Specifically in this embodiment, the hypervolume of a two-dimensional hyperrectangle is the projection of the hyperrectangle on the two-dimensional plane, that is, the area of the rectangle, and the calculation formula is:

[0103] ;

[0104] ;

[0105] S6. Analyze the ecological niche under actual and ideal conditions Dimensional supervolume fit to evaluate actual niche suitability;

[0106] According to the actual environment element set , using the data dimensionality reduction method in S3 to extract the actual important environmental factor matrix , and the indicator species were calculated using the method in S5 The actual ecological niche dimensional hyperrectangle and indicator species The actual ecological niche dimensional hyperrectangle , the expression is:

[0107] ;

[0108] ;

[0109] in, For indicator species The first dimension of the actual niche The value range of is [7.8, 8.3]; For indicator species The second dimension of the actual ecological niche: water temperature The value range of is [20.1, 22.5]; For indicator species The first dimension of the actual niche The value range of is [8.0, 8.4]; For indicator species The second dimension of the actual ecological niche: water temperature The value range is [20.0, 23.6].

[0110] S5. Determine indicator species based on the calculation method in S5 2-dimensional hypervolume of actual ecological niche and indicator species 2-dimensional hypervolume of actual ecological niche for:

[0111] ;

[0112] ;

[0113] Depend on Figure 7 It is known that indicator species and indicator species The two-dimensional optimal and actual ecological niche hyperrectangles are intersecting in space and do not contain each other, which is consistent with The discriminant conditions, therefore, indicate species and indicator species The niche suitability is calculated as:

[0114] ;

[0115] ;

[0116] S7. Evaluate the health of small and medium-sized rivers based on the niche suitability of each indicator species;

[0117] According to the indicator species collection of small and medium-sized rivers Two indicator species in and indicator species , the niche suitability set is constructed as:

[0118] ;

[0119] The arithmetic mean method is used to calculate the small and medium rivers Comprehensive habitat suitability index of indicator species , the calculation formula is:

[0120] ;

[0121] Set the threshold for health assessment of small and medium-sized rivers to , respectively 0~0.25, 0.25~0.5, 0.5~0.7, >0.75, characterizing the health of the river as unhealthy, sub-healthy, healthy and strong health, based on which the small and medium-sized rivers in this embodiment are evaluated. Unhealthy rivers.

[0122] The above-described embodiments merely illustrate the implementation methods of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A method for evaluating the health of small and medium-sized rivers based on niche suitability analysis, characterized in that: The following steps are involved: S1. Screening of indicator species collections for small and medium-sized rivers ; S2. Constructing the initial environmental element set for small and medium-sized rivers ; The S2 is specifically: According to the characteristics of small and medium-sized rivers and the composition of indicator species sets, the environmental factors that affect indicator species are determined to form the initial environmental factor set of small and medium-sized rivers. : S3, data dimensionality reduction method to extract niche dimensions; The S3 is specifically: The initial environmental element set of small and medium-sized rivers Considered as a OK Column matrix : ； in, is the number of environmental element types, i.e., dimension; is the sample size, and there is a sample size Number of environmental factors ; For the Environmental factor samples vector; S4. Calculate the niche suitability curves for each dimension; use the generalized additive algorithm to derive indicator species and indicator species In water temperature The two-dimensional niche fitness function and the corresponding niche fitness curve are drawn; S5. Solve the ideal state in the most suitable ecological niche dimensional hyperrectangular hypervolume; S5 is specifically: Solve the niche fitness function of each dimension The corresponding optimal ecological niche , and according to the set allowable error value Calculate neighborhood values , the calculation formula is: ； Since the niche fitness function The distribution form of the neighborhood value There are two solutions, respectively denoted as the previous neighborhood values and the subsequent neighborhood values , and there are , then the value range of the optimal niche in each dimension is expressed as , and then The value range of the optimal ecological niche is converted into the Euclidean space dimensional hyperrectangle , specifically: ； but dimensional hypervolume The calculation formula is: ； S6. Analyze the ecological niche under actual and ideal conditions Dimensional supervolume fit to evaluate actual niche suitability; The S6 is specifically: According to the actual environment element set , using the data dimensionality reduction method in S3, extract the actual important environmental factor matrix , and use the method in S5 to calculate the actual dimensional hyperrectangle ,but: ； in, The actual ecological niche The value range of the dimension, the lower boundary is The upper boundary is represented by express; According to the calculation method in S5, we can deduce Hypervolume of actual ecological niche for: ； S7. Evaluate the health status of small and medium-sized rivers based on the niche suitability of each indicator species.

2. A method for evaluating the health of small and medium-sized rivers based on niche suitability analysis according to claim 1, characterized in that: The S1 is specifically: According to the geographical location, climate conditions, species distribution and composition of small and medium-sized rivers, select indicator species that reflect the characteristics of small and medium-sized rivers , thus forming a small and medium-sized river indicator species set for river health assessment : ； in, is the serial number of the indicator species; is the total number of indicator species used for river health assessment.

3. The method for evaluating the health of small and medium-sized rivers based on niche suitability analysis according to claim 2 is characterized by: The initial environmental element set of small and medium-sized rivers : ； ； ； ； ； in, is the initial physical element set; To initialize the chemical element set; is the initial spatiotemporal distribution element set; is the initial water flow feature set; For the bottom of small and medium-sized rivers; for illumination; is the water temperature; For small and medium rivers value; is the dissolved oxygen content in water; is the total phosphorus in water; is the river length position; For water depth; For the time period; For traffic; is the flow rate; Water level fluctuations.

4. A method for evaluating the health of small and medium-sized rivers based on niche suitability analysis according to claim 3, characterized in that: Optimal ecological niche dimensional hyperrectangle and actual niche dimensional hyperrectangle The position relationship in space is divided into: separation, intersection, optimal inclusion, and actual inclusion. The niche suitability index of each position relationship is expressed as follows: ； in, is the total set of niche suitability indices under each position relationship; The most suitable ecological niche dimensional hyperrectangle and actual niche dimensional hyperrectangle The niche suitability index when the spatial position is separated is referred to as the separated niche suitability index; The most suitable ecological niche dimensional hyperrectangle and actual niche dimensional hyperrectangle The niche suitability index when the spatial position is intersecting is referred to as the intersection niche suitability index; The most suitable ecological niche dimensional hyperrectangle Completely encompasses the actual niche dimensional hyperrectangle The niche suitability index at that time is referred to as the most inclusive niche suitability index; Actual ecological niche dimensional hyperrectangle Completely encompasses the optimal niche dimensional hyperrectangle The niche suitability index at that time is referred to as the actual niche suitability index; If the optimal ecological niche dimensional hyperrectangle and actual niche dimensional hyperrectangle The spatial positions of are separated, that is, there is no intersection between the two, and the mathematical expression is , then the niche suitability index is ; If the optimal ecological niche dimensional hyperrectangle and actual niche dimensional hyperrectangle The spatial position of is intersecting, and the mathematical expression is ; The niche fitness index is calculated by the ratio of the hypervolume of the intersection of two hyperrectangles to the hypervolume of the union of two hyperrectangles, so the intersection niche fitness index is The calculation method is: ； ； ； ； in, Indicates the The posterior neighborhood value of the dimensional niche; If the optimal ecological niche dimensional hyperrectangle Contains actual ecological niche dimensional hyperrectangle , that is, the optimal package is actually, the mathematical expression is , then the most inclusive niche suitability index ; If the actual niche dimensional hyperrectangle Completely encompasses the optimal niche dimensional hyperrectangle , that is, the actual package is optimal, and the mathematical expression is , then the actual niche suitability index The calculation formula is: 。 5. A method for evaluating the health of small and medium-sized rivers based on niche suitability analysis according to claim 4, characterized in that: The S7 is specifically: Indicator species collection for small and medium-sized rivers in Repeat S3 to S6 for each indicator species and calculate the niche suitability index of each indicator species. The resulting set is: ； According to the number, type and preciousness of each indicator species, the algorithm average method, hierarchical analysis method and entropy weight method are used to assign weights to each indicator species, and then the comprehensive niche suitability index of indicator species in small and medium-sized rivers is calculated. , the calculation formula is: ； in, The weights of each indicator species matrix.

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