A method for quantifying microhabitat spatial heterogeneity of mountain river

Abstract

This invention discloses a method for quantifying the spatial heterogeneity of microhabitats in mountainous rivers, comprising the following steps: Step 1: Setting up sampling sections and sampling points; Step 2: Measuring average water depth, average flow velocity, transparency, turbidity, sediment particle size distribution, and water environment indicators at each sampling point; Step 3: Determining key parameters related to hydrology, water environment indicators, and organisms; Step 4: Statistically analyzing the measurement results of key parameters indoors and calculating the microhabitat heterogeneity index of mountainous rivers; Step 5: Verifying the reliability of the calculated results of the spatial heterogeneity index of microhabitats in mountainous rivers. This invention's method for investigating microhabitats in mountainous rivers combines environmental factor screening with actual field measurements, enabling the quantification of the complexity of spatial habitat structure. Specifically, for the three-dimensional benthic habitat investigation method in mountainous rivers, it calculates the spatial heterogeneity of microhabitats by statistically analyzing river flow patterns and sediment particle size, thus evaluating the living space characteristics and quality of organisms in mountainous rivers.

Description

Technical Field

[0001] This invention belongs to the field of ecological survey and monitoring technology of mountain rivers, specifically involving a quantitative method for the spatial heterogeneity of microhabitats in mountain rivers. Background Technology

[0002] Mountain rivers, mostly located in the upper reaches, directly influence the middle and lower reaches of their basins through their hydrological processes, erosion and sediment production, sediment transport, river geomorphology, and ecological environment. Furthermore, mountain rivers are often important habitats for biological communities and natural and cultural landscapes, and frequently serve as water sources for downstream areas. Therefore, the habitat conditions of mountain rivers not only significantly impact the local ecological environment but also affect the health of the ecosystem in the middle and lower reaches of the basin. Currently, research on mountain rivers is receiving increasing attention from researchers both domestically and internationally.

[0003] Compared to alluvial plain rivers, mountain rivers have more complex sediment particle size distributions and variations in flow velocity and depth; in other words, they possess more complex habitat conditions. They provide algae, microorganisms, and benthic animals with more diverse habitats for inhabitants, predators, hiders, and reproducers. These organisms play a crucial role in nutrient and carbon cycling through various biochemical processes. In recent decades, under the dual impacts of climate change and human activities, the quality of mountain river habitats has significantly declined. For example, dredging has simplified riverbed structures, leading to reduced biodiversity and lower river density. Therefore, conducting habitat surveys and quantitative assessments of heterogeneity in mountain rivers has become an urgent need in the field of mountain river ecology research.

[0004] Currently, there are no quantitative methods for calculating habitat heterogeneity in mountain rivers, either domestically or internationally. The main approaches rely on qualitative or semi-quantitative analyses of the magnitude of habitat heterogeneity. Various studies have analyzed its relationship with river physical heterogeneity and benthic fauna assemblage. Townsend et al. pointed out that widespread species are often associated with unstable sites, while narrowly distributed species tend to be associated with more stable sites. This demonstrates how species adapt to physical heterogeneity to survive disturbance events. Beisel et al. confirmed that the number of species in heterogeneous riverbeds is higher than in homogeneous riverbeds, with homogeneous riverbeds predominantly containing one or two species. However, current research urgently needs quantitative methods for assessing habitat heterogeneity to more accurately evaluate the complexity of mountain river habitats, gain a more precise understanding of the spatial structure characteristics of mountain river habitats, help identify signals of habitat degradation in a timely manner, and reveal the response relationship between biological groups and habitat heterogeneity, providing multifaceted scientific support for the ecological protection of mountain rivers. Summary of the Invention

[0005] In investigating the habitat of mountain rivers, this invention measures the water depth as the average water depth of the sample points, selects three representative locations within the sample points to measure and average the water depth, and similarly measures the flow velocity as the average flow velocity of the sample points. The sediment particle size distribution is obtained by measuring with a ruler and sieving. Through the above methods, the characteristic information of the microhabitat of mountain rivers is obtained, and a quantitative method for the spatial heterogeneity of the microhabitat of mountain rivers is proposed, which aims to make up for the deficiencies of the prior art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for quantifying the spatial heterogeneity of microhabitats in mountainous rivers, comprising the following steps:

[0007] Step 1: Set up the sampling section and sampling points;

[0008] Step 2: Measure the average water depth, average flow velocity, transparency, turbidity, sediment particle size distribution, and water environment indicators at each sampling point;

[0009] Step 3: Determine the key parameters related to hydrology, water environment indicators, and organisms;

[0010] Step 4: Analyze the measurement results of key parameters indoors and calculate the heterogeneity index of microhabitats in mountainous rivers;

[0011] Step 5: Verify the reliability of the spatial heterogeneity index calculation results of the microhabitat spatial heterogeneity index of mountain rivers.

[0012] Preferably, step 1 involves setting up 4-5 sampling sections along the river based on changes in hydrological elements and habitat conditions. Within each section, 5 sampling points are set up based on the principle of objectively reflecting the habitat conditions of that section. The area of ​​each sampling point is 1m². 2 .

[0013] Preferably, the specific operation of step 2 is as follows: the flow regime and sediment particle size distribution of each sample point are measured in the field. The flow regime is determined by the flow velocity and water depth. The average water depth and average flow regime are measured by taking the average of three representative locations within the sample point. The sediment particle size distribution is measured by measuring the large-diameter sediment particles in the riverbed with a ruler and sieving the small-diameter sediment particles in the riverbed. Each sample point is photographed and saved.

[0014] Preferably, step 3 specifically involves: using a bound ordination method to analyze the relationship between biological community distribution and hydrogeomorphology and water environment indicators; using hydrogeomorphology and water environment indicators as environmental data sources, and biological community composition as biological data sources, forming an environmental factor and biological species matrix; and performing logarithmic analysis on the biological community data. 10(x+1) transformation, environmental factors r>0.80 and fluctuation factors>20 were eliminated. The minimum variable combination with important and independent effects on the distribution of biological communities was determined by the pre-selection method and Monte Carlo method. This minimum variable group was used to screen out the key environmental factors that affect organisms in the final canonical correlation analysis, which were flow regime and substrate particle size.

[0015] Preferably, step 4, calculating the habitat heterogeneity index of mountain rivers, specifically includes the following steps:

[0016] Step 41: Calculate the flow regime heterogeneity index of mountain rivers;

[0017] Step 42: Calculate the heterogeneity index of riverbed sediment in mountainous areas;

[0018] The specific calculation process for calculating the flow regime heterogeneity index of mountain rivers in step 41 is as follows:

[0019] In reality, the flow of water in artificial or natural rivers is non-uniform open channel flow; the diversity of water flow patterns is an important component of river habitat heterogeneity. The flow patterns of water are divided into deep pools, slow flow, critical flow and rapid flow (Table 1). In order to distinguish different flow patterns in open channels, the Froude number Fr is used to classify river flow patterns at the microhabitat level.

[0020]

[0021] In equation (1), Fr is a dimensionless number, v is the average flow velocity at the sampling point, h is the average water depth at the sampling point, and g is the gravitational acceleration.

[0022] The heterogeneity of flow regimes in mountainous rivers is defined by the number of flow regime types and the percentage of each type. Shannon's information theory formula is used to describe the uncertainty of habitat types in rivers, and the entropy equation of Shannon's information theory formula has been used to evaluate different indicators. Specifically, Fr is used to calculate the total number and proportion of different flow regimes in each microhabitat unit, and then the Shannon-Wiener index is used to determine the flow regime heterogeneity of the study area. The flow regime heterogeneity index H... f The calculation is based on formula (2):

[0023] A 10-meter stretch of river was selected as a microhabitat unit. Within each microhabitat unit, 20 sampling points were selected, each measuring 1m × 1m. Flow velocity, water depth, and bottom sediment particle size were recorded. Five benthic animal samples were collected from each microhabitat unit, each measuring 1m × 1m. The selected sampling points needed to represent different types of habitats within the microhabitat unit, and the distribution of sampling points in different habitat types was guided by the proportion of area occupied by each type. The layout of the benthic animal sampling points also needed to reflect the overall community status of the microhabitat unit.

[0024] (2) Microhabitat flow heterogeneity index H f for:

[0025]

[0026] In equation (2), s is the number of samples in the microhabitat unit; n i Let N be the number of the i-th type of flow regime in the microhabitat unit, and N be the total number of all flow regimes in the microhabitat unit.

[0027] According to the Shannon-Wiener index, when a microhabitat unit has only one flow regime, i.e., n i / N=1, H'=0; homogeneous flow still contributes to biodiversity in aquatic ecosystems; therefore, regression analysis was used to study the relationship between the number of flow patterns and the flow pattern heterogeneity index; the more flow patterns there are, the greater the flow pattern heterogeneity index; when there is only one flow pattern in a microhabitat unit, H'=0.2( Figure 1 ).

[0028] The derivation process of the specific calculation formula for the heterogeneity index of riverbed sediment in mountainous areas in step 42 is as follows:

[0029] Let d s Let d be the geometric mean particle size of the sediment. The percentage by weight of sediment smaller than a certain particle size in the total sand sample is obtained from the particle size distribution curve. The subscript s to the right of the particle size d indicates the characteristics of the particle size, and is expressed by equations (3) and (4):

[0030]

[0031]

[0032] The sediment particle size exhibits a skewed distribution, while the logarithm of the riverbed sediment particle size can be approximated as a normal distribution. According to the laws of normal distribution, we have:

[0033]

[0034] In equation (5), x is a random variable, x = lnd; Let x be the expected value or mean of x. Since the normal distribution graph is symmetrical, the mean is called the median; σ is the standard deviation of x; p is the mean of the random variable x in the mean value of x. to The probability of them occurring;

[0035] Compared with the considered scenarios, the following should be true:

[0036] lnd 16 =lnd 50 -σ (6)

[0037] lnd 84 =lnd50 +σ (7)

[0038] Adding equations (6) and (7), the expression for the median particle size is:

[0039]

[0040] Subtracting equations (6) and (7), the expression for the root mean square error σ is:

[0041]

[0042] The geometric mean particle size d of the normal distribution curve g It can be represented as:

[0043]

[0044]

[0045] The geometric mean square error σ of the normal distribution curve g The expression is:

[0046]

[0047]

[0048] The degree of heterogeneity in particle size should be selected as σ or σ based on the actual situation. g To express; in the analysis of biological environmental factors, it was found that the average particle size was more correlated with benthic organisms than the median particle size, so the latter σ was selected. g The remaining choices are σ; therefore, the formula for substrate heterogeneity is as follows:

[0049]

[0050] In equation (14), H s is the substrate heterogeneity index, and s is the number of samples in the microhabitat unit;

[0051] In summary, the spatial heterogeneity index H of river microhabitats m =H f ·H s The formula for expressing this is as follows:

[0052]

[0053] Table 1 Classification of Water Flow Patterns

[0054]

[0055]

[0056] Compared with the prior art, the beneficial effects of the present invention are:

[0057] The method for investigating microhabitats in mountain rivers of this invention combines environmental factor screening with actual field measurements, which can quantify the complexity of spatial habitat structure. The method for investigating three-dimensional benthic habitats in mountain rivers calculates the spatial heterogeneity of microhabitats by statistically analyzing river flow patterns and substrate particle size, and evaluates the living space characteristics and quality of organisms in mountain rivers, providing technical support for a more accurate understanding of the ecological status of mountain rivers.

[0058] The equipment and materials required for this invention are readily available and easy to manufacture. The measurement process is simple to operate, requiring no specialized knowledge from the operators, and the underwater work is relatively easy. The survey process involves minimal contact with river organisms, resulting in minimal ecological disturbance and impact. Attached Figure Description

[0059] Figure 1 This invention relates to the relationship between the number of flow regime types and the flow regime heterogeneity index based on regression analysis.

[0060] Figure 2 This serves as a verification of the heterogeneity and rationality of the invention in different mountain and river microhabitats:

[0061] Figure 3 This is a flowchart of the microhabitat spatial heterogeneity index calculation method of the present invention. Detailed Implementation

[0062] Example 1

[0063] like Figure 3 As shown, the inventors selected five debris flow gullies in the Xiaojiang River Basin of Yunnan and five tributaries in the Hanjiang River Basin (all of which are mountain rivers) to conduct a spatial heterogeneity survey and evaluation of microhabitats. The tools used included a 70cm ruler, a 50m measuring tape, a portable Doppler current meter, a turbidity meter, sieves with different apertures, and a YSI multi-parameter water quality analyzer.

[0064] Study area map: (a) Location of the Yangtze River Basin in China; (b) Location of the two sub-basins of the Yangtze River Basin: the Xiaojiang River Basin and the Hanjiang River Basin; (c) Distribution of five debris flow-dominated mountain rivers in the Xiaojiang River Basin (LNP-Lanniping, JJ-Jiangjiagou, QS-Qingshuigou, TJXH-Taojiaxiaohe, DG-Diaogahe); (d) Distribution of five balanced sediment transport mountain rivers in the upper reaches of the Hanjiang River (XS-Xushuihe, JS-Jinshuihe, YH-Yuehe, XH-Xunhe, JQ-Jinqianhe).

[0065] The specific methods for investigating the spatial heterogeneity of microhabitats in mountainous rivers include the following steps:

[0066] (1) Setting up sampling sections and sampling points: Based on the river length and habitat changes, four sections were set up in each debris flow gully in the Xiaojiang River Basin of Yunnan Province, and four sections were set up in each tributary of the Hanjiang River Basin. Five sampling points were set up in each section.

[0067] (2) On-site measurement of hydrological environmental factors at sampling points: the average water depth at different sampling points was measured by ruler, the average flow velocity at different sampling points was measured by portable Doppler current meter, the river flow was measured by tape measure and portable Doppler current meter, the turbidity of the sampling area was determined by turbidity meter, the particle size distribution of the riverbed sediment was measured by ruler and sieves with different apertures, and various water environment indicators were determined by YSI multi-parameter water quality analyzer.

[0068] (3) Based on the field measurement data, the water depth, flow velocity, and sediment particle size distribution (d) of each sampling point were statistically analyzed. 16 d 84 ), and calculate the Froude number Fr to determine the flow regime type.

[0069] (4) Calculation results based on the formula for spatial heterogeneity of microhabitat in mountainous rivers.

[0070] Table 1. Record of Key Environmental Factors in Mountain River Habitats

[0071]

[0072] Taking the Diaoga River in the Xiaojiang River Basin as an example, this paper illustrates the specific process of spatial heterogeneity of microhabitats in the river. The original data are shown in Table 1.

[0073] Taking the Xiaojiang River basin debris flow gully Diaoga River as an example, the percentage of sediment smaller than a certain particle size in the total sand sample is found from the particle distribution curve and marked in the lower right corner of the particle size d to indicate the characteristics of that particle size.

[0074] The spatial heterogeneity of microhabitats in mountainous rivers was calculated based on the data in Table 1. The specific steps are as follows:

[0075] Calculating the flow heterogeneity of mountain rivers: (using cross-section 1 of the Diaoga River as an example of the calculation process)

[0076]

[0077]

[0078] n i N is the number of samples of the i-th flow regime in a microhabitat unit, and N is the total number of all types of flow regimes in a microhabitat unit.

[0079] Calculate the microhabitat flow regime heterogeneity index:

[0080]

[0081] Calculate the sediment heterogeneity index from the data in Table 1:

[0082]

[0083] Calculate the spatial heterogeneity index of microhabitats:

[0084]

[0085] In summary, the spatial heterogeneity of microhabitats at the Diaoga River section 1 is 1.11.

[0086] Verifying the reliability of the spatial heterogeneity index calculation results for mountain river microhabitats in step 5 includes:

[0087] To verify the accuracy and reliability of the proposed RMHI, NMDS analysis was performed on environmental factors (H, V, d16, and d84) from 10 mountain rivers in the Yangtze River Basin. Figure 2 d shows the NMDS analysis results ( Figure 2 b, c) and RMHI values ​​( Figure 2 a) Consistent. In rivers with higher RMHI values, the heterogeneity of the four environmental indices is stronger. Figure 2 b,c).

[0088] Finally, it should be noted that the above-described embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and not to limit it. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments within the technical scope disclosed in the present invention, or make equivalent substitutions for some of the technical features; and these modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of protection described in the claims.

Claims

1. A method for quantifying microhabitat spatial heterogeneity of mountain river, characterized in that, Includes the following steps: Step 1: Set up the sampling section and sampling points; Step 2: Measure the average water depth, average flow velocity, transparency, turbidity, sediment particle size distribution, and water environment indicators at each sampling point; Step 3: Determine the key parameters related to hydrology, water environment indicators, and organisms; Step 4: Analyze the indoor statistical results of key parameter measurements and calculate the microhabitat heterogeneity index of mountain rivers; Step 5: Verify the reliability of the calculated results of the spatial heterogeneity index of microhabitats in mountainous rivers; Step 4, calculating the habitat heterogeneity index of mountain rivers, specifically includes the following steps: Step 41: Calculate the flow regime heterogeneity index of mountain rivers; Step 42: Calculate the heterogeneity index of riverbed sediment in mountainous areas; The specific calculation process for calculating the flow regime heterogeneity index of mountain rivers in step 41 is as follows: In reality, the flow of water in artificial or natural rivers is non-uniform open channel flow; the diversity of water flow patterns is an important component of river habitat heterogeneity. The flow patterns of water are divided into deep pools, slow flow, critical flow and rapid flow. In order to distinguish different flow patterns in open channels, the Froude number Fr is used to classify river flow patterns at the microhabitat level. （1） In formula (1) Fr is a dimensionless number, v is the average flow velocity at the sampling point, h is the average water depth at the sampling point, is the acceleration due to gravity; The heterogeneity of flow regimes in mountainous rivers is defined by the number of flow regime types and the percentage of each type; Shannon's information-theoretic formula is used to describe the uncertainty of habitat types in rivers, and the entropy equation of Shannon's information-theoretic formula has been used to evaluate different indicators; specifically, using... Fr The total number and proportion of different flow regimes in each microhabitat unit were calculated, and then the Shannon-Wiener index was used to determine the flow regime heterogeneity of the study area; the flow regime heterogeneity index The calculation is based on formula (2): A 10-meter stretch of river was selected as a microhabitat unit. Within each microhabitat unit, 20 sampling points were selected, each measuring 1m × 1m. Flow velocity, water depth, and bottom sediment particle size were recorded. Five benthic animal samples were collected from each microhabitat unit, each measuring 1m × 1m. The selected sampling points needed to represent different types of habitats within the microhabitat unit, and the distribution of sampling points in different habitat types was guided by the proportion of area occupied by each type. The layout of the benthic animal sampling points also needed to reflect the overall community status of the microhabitat unit. (1) Microhabitat flow heterogeneity index for: （2） In equation (2), s The number of samples per microhabitat unit; n i The first in the microhabitat unit i The number of flow regimes, where N is the total number of all flow regimes in the microhabitat unit; According to the Shannon-Wiener index, when a microhabitat unit has only one flow regime, that is... H' = 0; homogeneous flow still contributes to biodiversity in aquatic ecosystems; therefore, regression analysis was used to study the relationship between the number of flow patterns and the flow pattern heterogeneity index; the more flow patterns there are, the greater the flow pattern heterogeneity index; when there is only one flow pattern in a microhabitat unit, H' = 0.2; The derivation process of the specific calculation formula for the heterogeneity index of riverbed sediment in mountainous areas in step 42 is as follows: set up Let d be the geometric mean particle size of the sediment. The percentage by weight of sediment smaller than a certain particle size in the total sand sample is obtained from the particle size distribution curve. The subscript s to the right of the particle size d indicates the characteristics of the particle size, and is expressed by equations (3) and (4): （3） （4） The sediment particle size exhibits a skewed distribution, while the logarithm of the riverbed sediment particle size can be approximated as a normal distribution. According to the laws of normal distribution, we have: （5） In equation (5), x is a random variable. ; x is the expected value or mean of x. Since the normal distribution graph is symmetrical, the mean is called the median. Let x be the mean squared error of x; p is the random variable x in... to The probability of them occurring; Compared with the considered scenarios, the following should be true: （6） （7） Adding equations (6) and (7), the expression for the median particle size is: （8） Subtracting equations (6) and (7) yields the mean square error. The expression is: （9） Geometric mean particle diameter of a normal distribution curve may be expressed as: （10） （11） Geometric mean of normal distribution curve The expression is: （12） （13） The degree of heterogeneity in particle size should be selected based on the actual situation, using σ or... To express this; in the analysis of biological environmental factors, it was found that the average particle size was more correlated with benthic organisms than the median particle size, so the latter was selected. The remaining choices are σ; therefore, the formula for substrate heterogeneity is as follows: （14） In formula (14), is the substrate heterogeneity index, s is the number of microhabitat units in the sample; In summary, the spatial heterogeneity index of river micro-habitat of The expression formula is as follows: （15）。 2. The method according to claim 1, wherein, The specific operation of step 1 is as follows: Based on the changes in hydrological elements and habitat conditions along the sampled river, 4-5 sampling sections are set up. On each section, 5 sampling points are set up based on the principle of objectively reflecting the habitat conditions of that section. The area of ​​each sampling point is 1m². 2 .

3. The method of claim 1, wherein the method is characterized by: The specific operation of step 2 is as follows: the flow regime and sediment particle size distribution of each sample point are measured in the field. The flow regime is determined by the flow velocity and water depth. The average water depth and average flow regime are measured by selecting three representative locations within the sample point and then calculating the average. The sediment particle size distribution is measured by measuring the large-diameter sediment particles in the riverbed with a ruler and sieving the small-diameter sediment particles in the riverbed. Each sample point is photographed and saved.

4. The method according to claim 1, wherein, The specific operation of step 3 is as follows: the bound ordination method is used to analyze the relationship between biological community distribution and hydrogeomorphology and water environment indicators; hydrogeomorphology and water environment indicators are used as environmental data sources, and biological community composition is used as biological data sources to form an environmental factor and biological species matrix. In order to optimize the analysis, the biological community data is transformed by log10(x+1). Environmental factors with r>0.80 and fluctuation factors greater than 20 are removed. The pre-selection method and Monte Carlo method are used to determine the minimum variable combination that has an important and independent effect on the distribution of biological community. This minimum variable group is used to screen out the key environmental factors that affect the organisms in the final canonical correlation analysis, namely flow regime and substrate particle size.

Images