Ecological restoration quantification method based on watershed ecological safety complex network

Abstract

The invention discloses an ecological restoration quantification method based on a watershed ecological safety complex network. The method comprises the following steps: S1, obtaining multi-time-sequence watershed multi-source heterogeneous spatial data of a target area; s2, taking the grid as an evaluation unit, establishing a drainage basin ecosystem service function evaluation system, and obtaining spatial-temporal change characteristics of an ecological safety function; s3, analyzing the spatial-temporal change characteristics of the ecological land scale of the watershed; s4, constructing a drainage basin ecological resistance surface; s5, identifying an ecological corridor; s6, constructing an ecological safety complex network model by taking the ecological source as a node, the ecological corridor as an edge, the scale of the ecological source as a point weight and the proportional relation between the connection efficiency of the ecological corridor and the corridor resistance as an edge weight, and extracting spatial-temporal evolution characteristics of an ecological safety structure; s7, a coupling coordination degree model is adopted to simulate and analyze the characteristic relation among the safety function, the safety structure and the land use scale, and the coupling coordination degree is obtained; and S8, guiding and optimizing an ecological restoration implementation strategy. According to the method, ecological security network structure features on the watershed system scale are quantified.

Description

Technical Field

[0001] The present invention relates to the field of surveying and mapping supervision management, and specifically to an ecological restoration quantification method based on a complex network of watershed ecological security. Background Art

[0002] In order to prevent natural disasters, meet water and power supply needs, more and more dam construction projects are being carried out to rationally allocate water resources. After the construction of the dam, the land use and ecological environment within the reservoir basin have received more and more attention, especially the special research on land reclamation and ecological restoration has become a technical problem that urgently needs to be solved in this region.

[0003] Traditional ecological security research mainly uses ecological security evaluation methods to study the functional characteristics of field space, simplifying the interaction between multiple complex elements and ecological security into a weight relationship or fuzzy relationship in regional space. This relationship ignores the complex relationship and dynamic changes within the ecosystem. Therefore, the ecological security network was added later. The existing ecological network is based on the principles of landscape ecology, and the construction method is mainly to identify ecological sources and simulate ecological corridors. However, the existing construction method ignores the resistance of the ecosystem function itself to the construction process of the ecological corridor, and simplifies the structural characteristics of the ecological security network in the flow space. In addition, the existing research methods are mainly carried out from the perspective of ecological functional characteristics or from one of the perspectives of ecological structural characteristics, which cannot fully reveal the systematic relationship between the internal and external benefits of ecological security.

[0004] At the same time, the research area of ​​ecological security issues has gradually extended from the existing regional scale to the watershed scale that breaks the administrative boundaries, and from the research of a single river basin to the common research on the ecological security of key basins and small basins; the research content has evolved from local problem and countermeasure research to more prominent system, overall and comprehensive governance research. Therefore, there is an urgent need for a watershed ecological security network construction method and pattern optimization method based on "function-structure-scale". Summary of the invention

[0005] The purpose of this invention is to provide a quantitative method for ecological restoration based on the complex network of watershed ecological security. Starting from multi-time series and multi-dimensionality, it combines the principles of landscape ecology with complex network models, quantifies the structural characteristics of the ecological security network at the watershed system scale, and optimizes specific countermeasures for watershed ecological restoration.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] A quantitative method for ecological restoration based on a complex network of watershed ecological security includes the following steps:

[0008] S1: Obtain multi-source heterogeneous spatial data of the watershed in the target area in multiple time series;

[0009] S2: Taking kilometer grid as evaluation unit and certain time periods as discontinuity points, establish a watershed ecosystem service function evaluation system, and analyze the spatiotemporal variation characteristics of the ecological security function of the watershed ecosystem field space according to the watershed ecosystem service function evaluation system;

[0010] S3: Extract important ecosystem function areas based on the evaluation results of the ecosystem service function evaluation system, identify regional watershed ecological source areas based on the core areas screened by the landscape connectivity index of the regional ecosystem and the regional ecosystem protection strategy; extract the scale of ecological land based on the regional watershed ecological source areas, and analyze the spatiotemporal variation characteristics of the scale of ecological land in the watershed;

[0011] S4: Based on the principles of landscape ecology, with the purpose of protecting biodiversity and landscape integrity, the organic connection of ecological landscape resource patches is established, and five characteristic indicators, namely, basin topography, surface cover, human disturbance, vegetation status and ecological benefits, are selected to construct the basin ecological resistance surface;

[0012] S5: Identify ecological corridors based on the regional watershed ecological source and the watershed ecological resistance surface, and analyze important ecological pinch points and major ecological obstacle points;

[0013] S6: Taking the ecological source area of ​​the regional watershed as a node, the ecological corridor as an edge, the scale of the ecological source area of ​​the regional watershed as a point weight, and the proportional relationship between the connection efficiency of the ecological corridor and the corridor resistance as an edge weight, an ecological security complex network model is constructed to extract the spatiotemporal evolution characteristics of the ecological security structure of the watershed ecosystem flow space;

[0014] S7: using a coupling coordination degree model to simulate and analyze the characteristic relationship between the spatiotemporal variation characteristics of the ecological security function, the spatiotemporal evolution characteristics of the ecological security structure, and the spatiotemporal variation characteristics of the ecological land scale, and obtain the coupling coordination degree of the three characteristic indexes in time and space;

[0015] S8: Based on the coupling coordination degree, guide and optimize the ecological restoration implementation strategy.

[0016] Furthermore, the S8: guiding and optimizing the ecological restoration implementation strategy according to the coupling coordination degree, specifically includes:

[0017] S801: Use random forest model to build intelligent decision-making model for ecological restoration;

[0018] S802: Analyze the characteristic relationship between the ecological security function, ecological structure and ecological land scale of the watershed based on the coupling coordination degree model, and optimize the ecological security pattern of the watershed from the perspective of "function-structure-scale"; and combine the indicators of ecological restoration engineering projects surveyed on the spot, use the ecological restoration intelligent decision-making model to train and simulate the prediction of ecological restoration strategies under different combination scenarios of the "function-structure-scale" characteristics of watershed ecological security, and obtain the optimal decision;

[0019] S803: At the surface scale, determine whether it is an ecological restoration priority area based on the optimal decision. If it is an ecological restoration priority area, it is recommended to use any of the following modes to zoning the watershed ecological restoration strategy: function priority, structure priority, function-structure priority, scale-function priority, scale-structure priority, or scale-function-structure priority.

[0020] Furthermore, the multi-time series of multi-source heterogeneous spatial data of the watershed includes topographic data, land use data, vegetation and water system data, soil texture data, socio-economic data, remote sensing image data and climate and meteorological data.

[0021] Furthermore, the establishment of a watershed ecosystem service function evaluation system specifically includes:

[0022] From the three types of ecosystem services, namely supply function, regulation function and support function, water conservation service, soil conservation service, climate regulation service and biodiversity maintenance service indicators were selected to evaluate the service function of the watershed ecosystem.

[0023] Water conservation services

[0024] It is mainly related to regional precipitation, evaporation, surface runoff and land cover. Water conservation services are mainly calculated using the total water conservation supply. The water conservation service calculation formula is as follows (1):

[0025] WS tr =P tr -ET tr -R tr (1)

[0026] Among them, WS tr represents the total water conservation supply in grid r in year t, P tr represents the average annual precipitation in grid r in year t, ET tr represents the precipitation evapotranspiration in grid r in year t, R tr represents the cumulative surface runoff in grid r in year t, and the surface runoff is obtained by multiplying precipitation and surface runoff coefficient;

[0027] The soil conservation services

[0028] The soil conservation service reflects whether the reservoir ecosystem can reduce or avoid soil erosion caused by water erosion. Based on the revised universal soil loss equation (RUSLE for The revised universal soil loss equation), the soil conservation service index calculation formula for the region is determined as shown in (2) and (3):

[0029] A tr =RE tr ×SE tr ×LS×(1-CCM tr ×CM tr ) (2)

[0030]

[0031] Among them, A tr represents the soil conservation scale in grid r in year t, RE tr represents the rainfall erosivity factor, p tr The rainfall erosivity is calculated using monthly rainfall data. 2 tri represents the rainfall in the ith month, SE tr represents soil erodibility factor, LS represents slope length and slope factor, CCM tr Represents vegetation cover and management factor, CM tr represents the soil and water conservation measures factor;

[0032] The climate regulation services

[0033] The regional climate regulation service is reflected by calculating carbon storage. Combined with the carbon storage calculation module in the InVEST model, based on the annual land use type data, the carbon storage of aboveground, underground, dead organic matter, and soil organic matter is comprehensively considered. The specific calculation formula is shown as follows (4):

[0034]

[0035] Among them, C tr represents the total carbon sequestration in grid r in year t, C ti1 represents the aboveground carbon density of land cover type i in year t, C ti2 represents the underground carbon density of land cover type i in year t, C ti3 represents the carbon density of dead organic matter in land cover type i in year t, C ti4 represents the soil organic carbon density of land cover type i in year t, Ar tri represents the total area of ​​land cover type i in grid r in year t;

[0036] Biodiversity maintenance services

[0037] Habitat status is an important part of regional biodiversity maintenance. The Habitat Suitability model in the InVest model is used to measure the regional biodiversity maintenance service capacity. This model reflects regional biodiversity by analyzing the threat level of human land use or natural disasters to its biodiversity, combined with the relative sensitivity of each habitat type to each threat.

[0038] Furthermore, the spatiotemporal variation characteristics of the ecological security function of the watershed ecosystem field space are analyzed based on the watershed ecosystem service function evaluation system, including:

[0039] The comprehensive ecosystem service index is used to reflect the comprehensive ecosystem service function of the region, that is, the spatiotemporal variation characteristics of the ecological security function. In order to eliminate the dimension of various ecosystem service function indicators, the indicator types are standardized before calculating the comprehensive ecosystem service index. The processing method is shown in the following formula (5):

[0040]

[0041] In the formula, Sr trj is the standardized index value in the analysis grid r in year t, X trj is the original value of the jth index in the analysis grid r in the tth year, Max(x j ) and Min(X j ) represent the maximum and minimum values ​​of the j index in all years of the study area;

[0042] The Ecosystem Services Composite Index (ESI) tr The accumulation mode is adopted, as shown in the following formula (6):

[0043]

[0044] Further, S3: extracting important ecosystem function areas based on the evaluation results of the ecosystem service function evaluation system, combining the core areas screened by the landscape connectivity index of the regional ecosystem and the nature reserves determined by the regional ecosystem protection strategy, identifying the regional watershed ecological source areas, specifically including:

[0045] S301: Based on the evaluation results of the ecosystem service function evaluation system, the natural breakpoint method classification standard is used to classify the ecosystem service function evaluation results of the basin in each year. The classification results need to be compared and analyzed with the prior results of comprehensive ecological security evaluation in the existing research results of the basin to determine the number of classification levels. On the basis of determining the number of classification levels, the numerical interval of the natural breakpoints of each year is analyzed, and the average value of the breakpoints of the highest level of ecosystem service function is used as the threshold of the importance area of ​​ecosystem service function to classify the important areas of ecosystem service function;

[0046] S302: According to the land use classification standard, extract the forest, grassland and water ecological type land for MSPA ecological connectivity analysis to obtain the core area of ​​habitat patches;

[0047] S303: Nature reserves in the superimposed regional ecosystem protection strategy;

[0048] S304: Determine the minimum area threshold of the ecological source by counting the number of spots of the ecological source under the minimum area threshold, and identify the ecological source of the watershed according to the minimum area threshold.

[0049] Furthermore, S4: based on the principles of landscape ecology, with the purpose of protecting biodiversity and landscape integrity, an organic connection of ecological landscape resource patches is established, and five characteristic indicators, namely, basin topographic conditions, surface cover, human disturbance, vegetation status and ecological benefits, are selected to construct a basin ecological resistance surface, specifically including:

[0050] Based on the principles of landscape ecology, the ecological network is constructed to protect biodiversity and landscape integrity, and to establish an organic connection between ecological landscape resource patches. This connection is a channel to ensure the material circulation, energy flow and information transmission within the ecosystem. This channel needs to comprehensively consider the terrain characteristics, land use type, non-ecological degree, ecological land status and ecological function. Therefore, five characteristic indicators of basin terrain conditions, surface cover, human interference, vegetation status and ecological benefits are selected to construct the basin ecological resistance surface. The basin ecological resistance surface includes the resistance type, resistance factor, ecological resistance value, indicator weight and division standard of each characteristic indicator of the basin ecology;

[0051] The index weight adopts the entropy weight method as the weight assignment method of the resistance factor index, and the information entropy of each spatiotemporal index is calculated by the entropy weight method to determine the influence degree of the resistance factor;

[0052] The entropy value of each spatiotemporal index is calculated using the entropy weight method model, which is shown in the following (7):

[0053]

[0054] In the formula, ω j represents the evaluation weight of spatial index j, k = 1 / lnm (k>0), m is the total number of grids, f rj The ratio of the value of the j-item indicator in the grid number r to the total cumulative value of the spatiotemporal data of the j-item indicator in all years is analyzed, and n is the number of indicators for which weights are sought;

[0055] Calculate the weight of the indicator by using entropy value;

[0056] All characteristic indicators are calculated by weighted summation to calculate the corresponding ecological comprehensive resistance value in each grid in each year, as shown in formula (8):

[0057]

[0058] In the formula, RES tr represents the ecological comprehensive resistance value in the analysis grid number r in the tth year, Es trj Represents the spatial value of a single resistance factor.

[0059] Further, the S5: identifying ecological corridors based on the regional watershed ecological source and the watershed ecological resistance surface, and analyzing important ecological pinch points and major ecological obstacle points, specifically includes:

[0060] Based on circuit theory, the ecological corridor and corridor width of the ecological source area in the regional watershed are simulated through different landscape units with different resistance coefficients to reach another ecological source area, and the Pinchpoint Mapper module is used to identify the ecological pinch point area in the ecological corridor, that is, the cumulative current value of each grid unit is obtained through spatial iterative calculation, and the core area in the watershed that plays an important role in ecological protection is extracted by simulating the current value; the Barrier Mapper module is used to simulate the main obstacle areas that are hindered in the exchange of materials and energy between the ecological sources in the regional watershed.

[0061] Further, S6: taking the regional watershed ecological source as a node, the ecological corridor as an edge, the scale of the regional watershed ecological source as a point weight, and the proportional relationship between the ecological corridor connection efficiency and the corridor resistance as an edge weight, constructing an ecological security complex network model, and extracting the spatiotemporal evolution characteristics of the ecological security structure of the watershed ecosystem flow space, specifically including:

[0062] Based on the complex network model, the spatial center of gravity of the regional watershed ecological source is taken as the node element, the X and Y coordinates of the center of gravity are the node element coordinates, the scale of the regional watershed ecological source is taken as the node element point weight, the ecological corridor is taken as the connecting edge between the node elements, and the connectivity and resistance ratio of the ecological corridor is taken as the edge weight. An ecological security complex network model under dynamic changes in time and space is constructed. The modularity, degree centrality, betweenness centrality, closeness centrality, eigenvector centrality and average path length of the watershed ecological security network are simulated and quantified through the ecological security complex network model, and the ecological complex network structure characteristic index is obtained.

[0063] Furthermore, the coupling coordination model is shown as follows (9):

[0064]

[0065] In the formula, in the formula, CCD tp represents the coupling coordination index in the ecological source area p in the tth year, E tp1 It represents the characteristic index of ecological land scale, representing the area scale of ecological source land p; E tp2 It represents the characteristic index of ecological security function, and represents the average value of the comprehensive index of ecosystem services ESItr in the ecological source area p; E tp3 It represents the ecological security structure characteristic index, which represents the average value of the four ecological complex network structural characteristic indices of degree centrality, betweenness centrality, closeness centrality and eigenvector centrality; w1, w2 and w3 respectively represent the decisive weights of the ecological land scale characteristic index, the ecological security function characteristic index and the ecological security structure characteristic index on ecological security, and the weights are determined by the entropy weight method.

[0066] The spatiotemporal variation characteristics of the ecological security function are referred to as “function”; the spatiotemporal evolution characteristics of the ecological security structure are referred to as “structure”; the spatiotemporal variation characteristics of the ecological land scale are referred to as “scale”.

[0067] Beneficial effects of the present invention:

[0068] 1. It breaks the traditional boundary limitation based on administrative divisions, takes the watershed as the research area, and uses the kilometer grid as the minimum evaluation unit. It can better grasp the integrity and complexity of the ecosystem, avoid the governance fragmentation caused by administrative divisions, and solve the problems of multi-objective balance and coordinated governance of the ecosystem within the watershed.

[0069] 2. Optimization of watershed ecological security network construction based on complex networks

[0070] Combining the principles of landscape ecology and complex network theory, the characteristics of watershed ecological security are analyzed from the two dimensions of "structure-function". The structural characteristics analysis uses a complex network model to construct an ecological security network, and deeply analyzes the systematic structural characteristics of the watershed ecological security network. Compared with the traditional watershed ecological security network construction method, which can only extract the spatial carriers of ecological sources and corridors, the spatial locations of ecological pinch points and obstacles from the structure, this method combines the advantages of traditional methods to further solve the problem that traditional methods cannot quantify the structural characteristics of ecological security networks at the scale of watershed systems.

[0071] 3. New method for quantitative analysis of spatiotemporal characteristics of watershed ecological security

[0072] Collect multi-time series of multi-source heterogeneous spatial data of the watershed, use fixed time periods as discontinuities, evaluate the service functions of the watershed ecosystem, and regularly monitor and analyze the functional characteristics of ecological security at the watershed scale. Based on circuit theory, construct ecological sources and corridors, identify ecological pinch points and obstacles, implement the specific carriers of ecological sources, corridors, pinch points and obstacles in space year by year, and analyze the evolution characteristics of the watershed ecological security pattern in the spatiotemporal structure. Take the spatial center of gravity of the ecological source as the node element, the X and Y coordinates of the center of gravity as the node element coordinates, the source scale as the node element point weight, the ecological corridor as the connecting edge between the node elements, and the ratio of the connectivity and resistance of the ecological corridor as the edge weight, to construct a complex ecological security network under the dynamic changes of time and space. This method can quantify the modularity, degree centrality, betweenness centrality, closeness centrality, and eigenvector centrality of the watershed ecological security network. Based on the quantitative indicators, the spatial community structure of the watershed ecological security network can be structurally divided, and the spatiotemporal organization and function of the watershed ecological security network can be clarified, thereby measuring the degree of connection of each ecological node element in the network, identifying the key nodes connecting different network communities, and the important contact points and the most influential nodes connecting each ecological node element.

[0073] 4. Intelligent decision-making model for ecological restoration based on the correlation characteristics of “function-structure-scale”

[0074] Regularly and continuously track and quantify the ecological functions, ecological structure, and ecological scale characteristics of the watershed's ecological security. Combined with field surveys of indicators such as the implementation time, implementation scale, and project type of ecological restoration projects, the random forest model is used to construct multiple decision trees and aggregate their prediction results for judgment, in order to realize ecological restoration decision-making simulation.

[0075] This method effectively solves the problem of identifying watershed ecological restoration areas and diagnosing strategies. This method enables watershed ecological restoration decisions to not only focus on the selection of priority areas, but also to achieve the optimization of strategies for efficient ecological and security restoration of the watershed from the three dimensions of "function, structure, and scale", and scientifically proposes specific countermeasures for watershed ecological restoration. By demonstrating the spatiotemporal characteristics of the watershed ecological security network, formulating ecological restoration measures for zoning and classification, and proposing strategies to enhance ecological resilience, this method provides technologies and methods for further optimizing the watershed ecological security pattern and enhancing the ecological resilience of the national land space. BRIEF DESCRIPTION OF THE DRAWINGS

[0076] Figure 1 It is a flowchart of a specific embodiment 1 of the present invention;

[0077] Figure 2 This is a flowchart of the ecological source identification process in the specific embodiment 1 of the present invention;

[0078] Figure 3 is the minimum area threshold of the ecological source area in the specific embodiment 1 of the present invention;

[0079] Figure 4 is the minimum area threshold interval of the ecological source area in the specific embodiment 1 of the present invention;

[0080] Figure 5 The spatiotemporal distribution map of the ecological source area of ​​the Three Gorges Reservoir in the specific embodiment 1 of the present invention;

[0081] Figure 6 It is the time-space distribution diagram of the resistance factor and comprehensive resistance surface of the Three Gorges Reservoir area in the specific embodiment 1 of the present invention;

[0082] Figure 7 It is a diagram of spatial identification and change analysis of ecological corridors in the Three Gorges Reservoir area in specific embodiment 1 of the present invention;

[0083] Figure 8 A flowchart of complex network construction in specific embodiment 1 of the present invention;

[0084] Fig. 9 It is a quantitative model of spatiotemporal characteristics of watershed ecological security in a specific embodiment of the present invention;

[0085] Fig.10 It is an ecological security complex network diagram constructed at different time periods in the specific embodiment 1 of the present invention;

[0086] Fig.11 This is a flow chart of the intelligent decision-making model for ecological restoration constructed based on random forest in specific embodiment 1 of the present invention. DETAILED DESCRIPTION

[0087] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Specific embodiment 1:

[0089] See also Figures 1 to 11 As shown in the figure, a quantitative method of ecological restoration based on the complex network of watershed ecological security is taken as an example in a reservoir area in southwest China, which includes the following steps:

[0090] Step S1: Acquire multi-source heterogeneous spatial data of the watershed in the target area in multiple time series; the multi-source heterogeneous spatial data of the watershed in multiple time series includes topographic data, land use data, vegetation and water system data, soil texture data, socio-economic data, remote sensing image data and climate and meteorological data.

[0091] Step S2: Taking kilometer grid as evaluation unit and certain time periods as discontinuity points, a watershed ecosystem service function evaluation system is established, and the spatiotemporal variation characteristics of the ecological security function of the watershed ecosystem field space are analyzed according to the watershed ecosystem service function evaluation system; in this specific embodiment, five years is taken as a time discontinuity point, specifically including:

[0092] This method breaks the traditional boundary limitation based on administrative divisions, takes the watershed as the research area, and uses the kilometer grid as the smallest evaluation unit. It selects four service function indicators, namely, water conservation service, soil conservation service, climate regulation service, and biodiversity maintenance service, from the three types of ecosystem service supply function, regulation function, and support function to evaluate the watershed ecosystem service function; among them, the water conservation service

[0093] The water production service capacity of the ecosystem is an important prerequisite for regional human life and production, a core element for the survival and reproduction of regional organisms, and a limiting indicator for the social and economic development of the reservoir area. Water conservation service is a core indicator that reflects the regional water production service supply capacity. It is mainly related to the regional precipitation, evaporation, surface runoff and land cover. Water conservation service is mainly calculated using the total amount of water conservation supply. The water conservation service calculation formula is shown as follows (1):

[0094] WS tr =P tr -ET tr -R tr (1)

[0095] Among them, WS tr represents the total water conservation supply in grid r in year t, P tr represents the average annual precipitation in grid r in year t, ET tr represents the precipitation evapotranspiration in grid r in year t, Rtr It represents the cumulative surface runoff in grid r in year t. The surface runoff is obtained by multiplying precipitation by surface runoff coefficient. Referring to the existing relevant literature and combining with the actual situation of the reservoir area, it is determined that the surface runoff coefficients of forest and grassland are 4.65% and 3.94% respectively, and the runoff coefficient of other land use types is 0.

[0096] The soil conservation services

[0097] The soil conservation service reflects whether the reservoir ecosystem can reduce or avoid soil erosion caused by water erosion. Based on the revised universal soil loss equation (RUSLE for The revised universal soil loss equation), the soil conservation service index calculation formula for the region is determined as shown in (2) and (3):

[0098] A tr =RE tr ×SE tr ×LS×(1-CCM tr ×CM tr ) (2)

[0099]

[0100] Among them, A tr represents the soil conservation scale in grid r in year t, RE tr represents the rainfall erosivity factor, p tr The rainfall erosivity is calculated using monthly rainfall data. 2 tri represents the rainfall in the ith month, SE tr represents soil erodibility factor, LS represents slope length and slope factor, CCM tr Represents vegetation cover and management factor, CM tr Represents the soil and water conservation measures factor.

[0101] The climate regulation services

[0102] The regional climate regulation service is reflected by calculating carbon storage. Combined with the carbon storage calculation module in the InVEST model, based on the annual land use type data, the carbon storage of aboveground, underground, dead organic matter, and soil organic matter is comprehensively considered. The specific calculation formula is shown as follows (4):

[0103]

[0104] Among them, C tr represents the total carbon sequestration in grid r in year t, C ti1 represents the aboveground carbon density of land cover type i in year t, Cti2 represents the underground carbon density of land cover type i in year t, C ti3 represents the carbon density of dead organic matter in land cover type i in year t, C ti4 represents the soil organic carbon density of land cover type i in year t, Ar tri It represents the total area of ​​land cover type i in grid r in year t.

[0105] Biodiversity maintenance services

[0106] Habitat status is an important part of regional biodiversity maintenance. The Habitat Suitability model in the InVest model is used to measure the regional biodiversity maintenance service capacity. This model reflects regional biodiversity by analyzing the threat level of human land use or natural disasters to its biodiversity, combined with the relative sensitivity of each habitat type to each threat.

[0107] According to the evaluation system of watershed ecosystem service function, the spatiotemporal variation characteristics of the ecological security function of the watershed ecosystem field space are obtained. The comprehensive ecosystem service index is used to reflect the comprehensive ecosystem service function of the region, that is, the spatiotemporal variation characteristics of the ecological security function. In order to eliminate the dimension of various ecosystem service function indicators, the indicator type is standardized before calculating the comprehensive ecosystem service index. The processing method is shown in the following formula (5):

[0108]

[0109] In the formula, Sr trj is the standardized index value in the analysis grid r in year t, X trj is the original value of the jth index in the analysis grid r in the tth year, Max(x j ) and Min(X j ) represent the maximum and minimum values ​​of the j index in all years of the study area;

[0110] The Ecosystem Services Composite Index (ESI) tr The accumulation mode is adopted, as shown in the following formula (6):

[0111]

[0112] Step S3: extracting important ecosystem function areas based on the evaluation results of the ecosystem service function evaluation system, combining the core areas screened by the landscape connectivity index of the regional ecosystem and the regional ecosystem protection strategy to identify the regional watershed ecological source areas; based on the watershed ecological source areas, extracting the scale of ecological land, using Moran's I and hot and cold spot pattern analysis spatial correlation analysis model to analyze and obtain the spatiotemporal variation characteristics of the scale of watershed ecological land.

[0113] Based on the evaluation of the service function of the watershed ecosystem, the important areas of ecosystem function are extracted, and the core areas with close connections and prominent interactions in the ecological process are screened out in combination with the ecological land landscape connectivity index. The natural reserves determined by the local strategic guidance in ecosystem protection are comprehensively considered, and the identification of regional ecological sources is optimized with strategic ecological land. Specifically, Figure 2 As shown:

[0114] S301: Based on the evaluation results of the ecosystem service function evaluation system of multiple time series, the natural breakpoint method classification standard is used to classify the ecosystem service function evaluation results of the basin in each year, and the classification results are compared and analyzed with the prior results of comprehensive ecological security evaluation in the existing research results of the basin to determine the number of divided levels. On the basis of determining the number of divided levels, the numerical interval of the natural breakpoint division of each year is analyzed, and the average value of the breakpoint of the highest level of ecosystem service function is used as the threshold of the importance area of ​​ecosystem service function to divide the important areas of ecosystem service function. In this specific embodiment: the ecosystem service function evaluation results of the basin in each year are divided into five levels, and the effect is optimal.

[0115] S302: According to the land use classification standard, extract the forest, grassland and water ecological type land for MSPA ecological connectivity analysis to obtain the core area of ​​habitat patches;

[0116] S303: Nature reserves in the superimposed regional ecosystem protection strategy;

[0117] S304: Determine the minimum area threshold of the ecological source by counting the number of spots of the ecological source under the minimum area threshold, and identify the ecological source of the watershed according to the minimum area threshold. Figure 3 and Figure 4 As shown, the minimum area threshold is 3KM 2 The number of spots in the ecological source area tends to be stable, and the minimum area threshold is 3KM 2 After each additional 1KM 2 The area of ​​ecological source map spots is low and the fluctuation is very small. Therefore, the minimum area threshold of ecological source spots is determined to be 3 km. 2 .like Figure 5 As shown, the spatial and temporal distribution map of the ecological source area of ​​a reservoir area from 2000 to 2020 was obtained.

[0118] Step S4: Based on the principles of landscape ecology, with the purpose of protecting biodiversity and landscape integrity, an organic connection of ecological landscape resource patches is established, and five characteristic indicators, namely, basin topography, surface cover, human disturbance, vegetation status and ecological benefits, are selected to construct the basin ecological resistance surface; specifically, the following are included:

[0119] Based on the construction of ecological network based on the principles of landscape ecology, with the purpose of protecting biodiversity and landscape integrity, the organic connection of ecological landscape resource patches is established. This connection is a channel to ensure the material circulation, energy flow and information transmission within the ecosystem. This channel needs to comprehensively consider the terrain characteristics, land use type, non-ecological degree, ecological land use status and ecological function. Therefore, five characteristic indicators of basin terrain conditions, surface cover, human interference, vegetation status and ecological benefits are selected to construct the basin ecological resistance surface. The basin ecological resistance surface includes the resistance type, resistance factor, ecological resistance value, indicator weight and division standard of each characteristic indicator of basin ecology. Among them, the determination of the spatial value of the resistance factor of surface cover and vegetation status refers to the existing division standard and assignment method of resistance factor by Fu Mengdi et al. The ecological benefit division standard is divided according to the ecosystem service function level determined in the study. The terrain conditions and human interference resistance factors are processed by standardization of the original data, and the standard division is carried out on the basis of comparing the role of factors and analyzing the characteristics of basin factors, as shown in the following table:

[0120]

[0121] The methods for determining the index weights mainly include subjective and objective forms. This method selects the more objective and scientific entropy weight method as the method for assigning the weights of the resistance factor indexes. The index weights adopt the entropy weight method as the method for assigning the weights of the resistance factor indexes. The information entropy of each spatiotemporal index is calculated by the entropy weight method to determine the influence of the resistance factor.

[0122] The entropy value of each spatiotemporal index is calculated using the entropy weight method model, and the index weight is calculated using the entropy value. The entropy weight method model is shown as follows (7):

[0123]

[0124] In the formula, ω j represents the evaluation weight value of spatial index j, k = 1 / lnm (k>0), m is the total number of grids, n is the number of indexes to obtain weights, here n = 5, f rj The proportion of the j-item index value in the analysis grid number r in the total cumulative spatial and temporal data of the entire j-item index in all years;

[0125] All characteristic indicators are calculated by weighted summation to calculate the corresponding ecological comprehensive resistance value in each grid in each year, as shown in formula (8):

[0126]

[0127] In the formula, RES tr represents the ecological comprehensive resistance value in the analysis grid number r in the tth year, Est rj Represents the spatial value of a single resistance factor. Figure 6 As shown in Figure 2, the spatiotemporal distribution of ecological resistance factors and ecological comprehensive resistance surface in a reservoir area from 2000 to 2020. Figure 7 As shown, the spatial identification and change analysis of ecological corridors in the Three Gorges Reservoir area from 2000 to 2020.

[0128] Step S5: Identify ecological corridors based on the regional watershed ecological source and the watershed ecological resistance surface, and analyze important ecological pinch points and major ecological obstacle points; specifically including:

[0129] Based on circuit theory, the ecological corridor and corridor width of the ecological source area in the regional watershed are simulated through different landscape units with different resistance coefficients to reach another ecological source area, and the Pinchpoint Mapper module is used to identify the ecological pinch point area in the ecological corridor, that is, the cumulative current value of each grid unit is obtained through spatial iterative calculation, and the core area in the watershed that plays an important role in ecological protection is extracted by simulating the current value; the Barrier Mapper module is used to simulate the main obstacle areas that are hindered in the exchange of materials and energy between the ecological sources in the regional watershed.

[0130] S6: extracting the connection relationship between the ecological source areas in the regional watershed and the ecological corridor simulation data, taking the regional watershed ecological source areas as nodes, the ecological corridors as edges, the scale of the regional watershed ecological source areas as point weights, and the proportional relationship between the connection efficiency of the ecological corridors and the corridor resistance as edge weights, constructing an ecological security complex network model, and extracting the spatiotemporal evolution characteristics of the ecological security structure of the watershed ecosystem flow space; specifically including:

[0131] Based on the complex network model, the spatial center of gravity of the ecological source of the regional watershed is taken as the node element, the X and Y coordinates of the center of gravity are the node element coordinates, the scale of the ecological source of the regional watershed is taken as the node element point weight, the ecological corridor is taken as the connecting edge between the node elements, and the connectivity and resistance ratio of the ecological corridor is taken as the edge weight. The ecological security complex network model under the dynamic change of time and space is constructed. The modularity, degree centrality, betweenness centrality, closeness centrality, eigenvector centrality and average path length of the watershed ecological security network are simulated and quantified through the ecological security complex network model, and the ecological complex network structure characteristic index is obtained. Figure 8 The method of constructing ecological security complex network is shown in the figure. Fig. 9 The quantitative model of spatiotemporal characteristics of watershed ecological security is shown in the figure. Fig.10Shown is the ecological security complex network constructed from 2010 to 2020.

[0132] Step S7: using a coupling coordination degree model to simulate and analyze the characteristic relationship between the spatiotemporal variation characteristics of the ecological security function, the spatiotemporal evolution characteristics of the ecological security structure, and the spatiotemporal variation characteristics of the ecological land scale, and obtaining the spatiotemporal coupling coordination degree of the three characteristic indexes; the coupling coordination degree model is shown below (9):

[0133]

[0134] In the formula, in the formula, CCD tp represents the coupling coordination index in the ecological source area p in the tth year, E tp1 It represents the characteristic index of ecological land scale, representing the area scale of ecological source land p; E tp2 Represents the ecological security function characteristic index, representing the comprehensive ecosystem service index ESI in the ecological source area p tr The average value of E tp3 It represents the ecological security structure characteristic index, which represents the average value of the four ecological complex network structural characteristic indices of degree centrality, betweenness centrality, closeness centrality and eigenvector centrality; w1, w2 and w3 respectively represent the decisive weights of the ecological land scale characteristic index, the ecological security function characteristic index and the ecological security structure characteristic index on ecological security, and the weights are determined by the entropy weight method.

[0135] By adopting the coupling coordination model, the coordinated development level of the three major characteristic indexes of the basin's ecological function, ecological structure and ecological scale in time and space is simulated. The larger the coupling coordination value, the better the coordination between the three major characteristics of ecological function, ecological structure and ecological scale that affect ecological security. This method considers multiple time series and multiple dimensions, and the quantitative index obtained is more accurate.

[0136] Step S8: Based on the coupling coordination degree, guiding and optimizing the ecological restoration implementation strategy.

[0137] Specifically, see Fig.11 As shown:

[0138] S801: Use random forest model to build intelligent decision-making model for ecological restoration;

[0139] S802: Analyze the characteristic relationship between the ecological security function, ecological structure and ecological land scale of the watershed based on the coupling coordination degree model, and optimize the ecological security pattern of the watershed from the perspective of "function-structure-scale"; and combine the indicators of ecological restoration engineering projects surveyed on the spot, use the ecological restoration intelligent decision-making model to train and simulate the prediction of ecological restoration strategies under different combination scenarios of the "function-structure-scale" characteristics of watershed ecological security, and obtain the optimal decision;

[0140] S803: At the surface scale, determine whether it is an ecological restoration priority area based on the optimal decision. If it is an ecological restoration priority area, recommend function priority, structure priority, function-structure priority, scale-function priority, scale-structure priority, or scale-function-structure priority to implement the watershed ecological restoration strategy. This method aims to improve the resilience of watershed ecological security, optimizes the watershed ecological security pattern from the perspective of multi-time series "function-structure-scale" characteristic relationship demonstration, identifies priority areas for watershed ecological restoration implementation at the surface scale, and proposes priority strategies for watershed ecological restoration implementation at the point scale.

[0141] The technical solution provided by the present invention is described in detail above. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. It should be pointed out that for ordinary technicians in this technical field, without departing from the principle of the present invention, the present invention can also be improved and modified in a number of ways, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A quantitative method for ecological restoration based on a complex network of watershed ecological security, characterized in that: The steps include: S1: Obtain multi-source heterogeneous spatial data of the watershed in the target area in multiple time series; S2: Using the grid as the evaluation unit, establish a watershed ecosystem service function evaluation system, and analyze the spatiotemporal variation characteristics of the ecological security function of the watershed ecosystem field space based on the watershed ecosystem service function evaluation system; S3: Extracting important ecosystem function areas based on the evaluation results of the ecosystem service function evaluation system, combining the core areas screened by the landscape connectivity index of the regional ecosystem and the regional ecosystem protection strategy, and identifying the regional watershed ecological source areas; Based on the ecological source area of ​​the watershed in the region, the scale of ecological land is extracted, and the spatiotemporal variation characteristics of the scale of ecological land in the watershed are analyzed; S4: Based on the principles of landscape ecology, with the purpose of protecting biodiversity and landscape integrity, the organic connection of ecological landscape resource patches is established, and five characteristic indicators, namely, basin topography, surface cover, human disturbance, vegetation status and ecological benefits, are selected to construct the basin ecological resistance surface; S5: Identify ecological corridors based on the regional watershed ecological source and the watershed ecological resistance surface, and analyze important ecological pinch points and major ecological obstacle points; S6: Taking the ecological source area of ​​the regional watershed as a node, the ecological corridor as an edge, the scale of the ecological source area of ​​the regional watershed as a point weight, and the proportional relationship between the connection efficiency of the ecological corridor and the corridor resistance as an edge weight, an ecological security complex network model is constructed to extract the spatiotemporal evolution characteristics of the ecological security structure of the watershed ecosystem flow space; S7: using a coupling coordination degree model to simulate and analyze the characteristic relationship between the spatiotemporal variation characteristics of the ecological security function, the spatiotemporal evolution characteristics of the ecological security structure, and the spatiotemporal variation characteristics of the ecological land scale, and obtain the spatiotemporal coupling coordination degree of the three characteristic indexes; S8: Based on the coupling coordination degree, guide and optimize the ecological restoration implementation strategy.

2. The method for quantifying ecological restoration based on a complex network of watershed ecological security according to claim 1 is characterized by: S8: Based on the coupling coordination degree, guiding and optimizing the ecological restoration implementation strategy, specifically including: S801: Use random forest model to build intelligent decision-making model for ecological restoration; S802: Analyze the characteristic relationship between the ecological security function, ecological structure and ecological land scale of the watershed based on the coupling coordination degree model, and optimize the ecological security pattern of the watershed from the perspective of "function-structure-scale". Combined with the indicators of ecological restoration engineering projects investigated on the spot, use the ecological restoration intelligent decision-making model to train and simulate the prediction of ecological restoration strategies under different combination scenarios of the "function-structure-scale" characteristics of watershed ecological security, and obtain the optimal decision. S803: At the surface scale, determine whether it is an ecological restoration priority area based on the optimal decision. If it is an ecological restoration priority area, it is recommended to use any of the following modes to zoning the watershed ecological restoration strategy: function priority, structure priority, function-structure priority, scale-function priority, scale-structure priority, or scale-function-structure priority.

3. The method for quantifying ecological restoration based on a complex network of watershed ecological security according to claim 1 is characterized by: The multi-time series of multi-source heterogeneous spatial data of the watershed includes topographic data, land use data, vegetation and water system data, soil texture data, socio-economic data, remote sensing image data and climate and meteorological data.

4. The method for quantifying ecological restoration based on a complex network of watershed ecological security according to claim 1 is characterized by: The establishment of a watershed ecosystem service function evaluation system specifically includes: From the three types of ecosystem services, namely supply function, regulation function and support function, water conservation service, soil conservation service, climate regulation service and biodiversity maintenance service indicators were selected to evaluate the service function of the watershed ecosystem. Water conservation services It is mainly related to regional precipitation, evaporation, surface runoff and land cover. Water conservation services are mainly calculated using the total water conservation supply. The water conservation service calculation formula is as follows: WS tr =P tr -AND tr -R tr Among them, WS tr represents the total water conservation supply in grid r in year t, P tr represents the average annual precipitation in grid r in year t, ET tr represents the precipitation evapotranspiration in grid r in year t, R tr represents the cumulative surface runoff in grid r in year t; The soil conservation services The soil conservation service reflects whether the reservoir ecosystem can reduce or avoid soil erosion caused by water erosion. Based on the modified universal soil loss equation, the calculation formula for the soil conservation service index in the region is as follows: A tr =RE tr ×SE tr ×LS×(1-CCM tr ×CM tr ) Among them, A tr represents the soil conservation scale in grid r in year t, RE tr represents the rainfall erosivity factor, p tr The rainfall erosivity is calculated using monthly rainfall data. 2 tri represents the rainfall in the ith month, SE tr represents soil erodibility factor, LS represents slope length and slope factor, CCM tr Represents vegetation cover and management factor, CM tr represents the soil and water conservation measures factor; The climate regulation services The regional climate regulation service is reflected by calculating carbon storage. Combined with the carbon storage calculation module in the InVEST model, based on the annual land use type data, the carbon storage of aboveground, underground, dead organic matter, and soil organic matter is comprehensively considered. The specific calculation formula is as follows: Among them, C tr represents the total carbon sequestration in grid r in year t, C ti1 represents the aboveground carbon density of land cover type i in year t, C ti2 represents the underground carbon density of land cover type i in year t, C ti3 represents the carbon density of dead organic matter in land cover type i in year t, C ti4 represents the soil organic carbon density of land cover type i in year t, Ar tri represents the total area of ​​land cover type i in grid r in year t; Biodiversity maintenance services Habitat status is an important part of regional biodiversity maintenance. The habitat suitability model in the InVest model is used to measure the regional biodiversity maintenance service capacity. This model reflects regional biodiversity by analyzing the threat level of human land use or natural disasters to its biodiversity, combined with the relative sensitivity of each habitat type to each threat.

5. The method for quantifying ecological restoration based on a complex network of watershed ecological security according to claim 1 is characterized by: According to the evaluation system of watershed ecosystem service function, the spatiotemporal variation characteristics of the ecological security function of the watershed ecosystem field space are analyzed, including: The comprehensive ecosystem service index is used to reflect the comprehensive ecosystem service function of the region, that is, the spatiotemporal variation characteristics of the ecological security function. In order to eliminate the dimensions of various ecosystem service function indicators, the indicator types are standardized before calculating the comprehensive ecosystem service index. The processing method is shown in the following formula: In the formula, Sr trj is the standardized index value in the analysis grid r in year t, X trj is the original value of the jth index in the analysis grid r in the tth year, Max(x j ) and Min(X j ) represent the maximum and minimum values ​​of the j-item index in all years of the study area; The Ecosystem Services Composite Index (ESI) tr Adopt the accumulation mode, as shown in the following formula:

6. The method for quantifying ecological restoration based on a complex network of watershed ecological security according to claim 1 is characterized by: S3: Extracting important ecosystem function areas based on the evaluation results of the ecosystem service function evaluation system, combining the core areas screened by the landscape connectivity index of the regional ecosystem and the determination of the regional ecosystem protection strategy, and identifying the regional watershed ecological source areas, specifically including: S301: Based on the evaluation results of the ecosystem service function evaluation system, the natural breakpoint method classification standard is used to classify the ecosystem service function evaluation results of the basin in each year. The classification results are compared and analyzed with the prior results of comprehensive ecological security evaluation in the existing research results of the basin to determine the number of classification levels. On the basis of determining the number of classification levels, the numerical interval of the natural breakpoints of each year is analyzed, and the average value of the breakpoints of the highest level of ecosystem service function is used as the threshold of the importance area of ​​ecosystem service function to classify the important areas of ecosystem service function; S302: According to the land use classification standard, extract the forest, grassland and water ecological type land for MSPA ecological connectivity analysis to obtain the core area of ​​habitat patches; S303: Nature reserves in the superimposed regional ecosystem protection strategy; S304: Determine the minimum area threshold of the ecological source by counting the number of spots of the ecological source under the minimum area threshold, and identify the ecological source of the watershed according to the minimum area threshold.

7. The method for quantifying ecological restoration based on a complex network of watershed ecological security according to claim 1 is characterized by: S4: Based on the principles of landscape ecology, with the purpose of protecting biodiversity and landscape integrity, an organic connection of ecological landscape resource patches is established, and five characteristic indicators, namely, basin topography, surface cover, human disturbance, vegetation status and ecological benefits, are selected to construct the basin ecological resistance surface, including: Based on the principles of landscape ecology, the ecological network is constructed to protect biodiversity and landscape integrity, and to establish an organic connection between ecological landscape resource patches. This connection is a channel to ensure the material circulation, energy flow and information transmission within the ecosystem. This channel needs to comprehensively consider the terrain characteristics, land use type, non-ecological degree, ecological land status and ecological function. Therefore, five characteristic indicators of basin terrain conditions, surface cover, human interference, vegetation status and ecological benefits are selected to construct the basin ecological resistance surface. The basin ecological resistance surface includes the resistance type, resistance factor, ecological resistance value, indicator weight and division standard of each characteristic indicator of basin ecology. The index weight adopts the entropy weight method as the weight assignment method of the resistance factor index, and the information entropy of each spatiotemporal index is calculated by the entropy weight method to determine the influence degree of the resistance factor; The entropy weight method model is used to calculate the entropy value of each spatiotemporal indicator, and the indicator weight is calculated by the entropy value; the entropy weight method model is as follows: In the formula, ω j represents the evaluation weight of spatial index j, k = 1 / lnm (k>0), m is the total number of grids, f rj The ratio of the value of the j-item indicator in the grid number r to the total cumulative value of the spatiotemporal data of the j-item indicator in all years is analyzed, and n is the number of indicators for which weights are sought; All characteristic indicators are calculated by weighted summation to calculate the corresponding ecological comprehensive resistance value in each grid in each year, as shown in the following formula: In the formula, RES tr represents the ecological comprehensive resistance value in the analysis grid number r in the tth year, Es trj Represents the spatial value of a single resistance factor.

8. The method for quantifying ecological restoration based on a complex network of watershed ecological security according to claim 1 is characterized by: S5: Identify ecological corridors based on the regional watershed ecological source and the watershed ecological resistance surface, and analyze important ecological pinch points and major ecological obstacle points, specifically including: Based on circuit theory, the ecological corridor and corridor width of the ecological source area in the regional watershed are simulated through different landscape units with different resistance coefficients to reach another ecological source area, and the Pinchpoint Mapper module is used to identify the ecological pinch point area in the ecological corridor, that is, the cumulative current value of each grid unit is obtained through spatial iterative calculation, and the core area in the watershed that plays an important role in ecological protection is extracted by simulating the current value; the Barrier Mapper module is used to simulate the main obstacle areas that are hindered in the exchange of materials and energy between the ecological sources in the regional watershed.

9. The method for quantifying ecological restoration based on a complex network of watershed ecological security according to claim 1 is characterized by: S6: Taking the regional watershed ecological source as a node, the ecological corridor as an edge, the scale of the regional watershed ecological source as a point weight, and the proportional relationship between the ecological corridor connection efficiency and the corridor resistance as an edge weight, construct an ecological security complex network model to extract the spatiotemporal evolution characteristics of the ecological security structure of the watershed ecosystem flow space, specifically including: Based on the complex network model, the spatial center of gravity of the regional watershed ecological source is taken as the node element, the X and Y coordinates of the center of gravity are the node element coordinates, the scale of the regional watershed ecological source is taken as the node element point weight, the ecological corridor is taken as the connecting edge between the node elements, and the connectivity and resistance ratio of the ecological corridor is taken as the edge weight. An ecological security complex network model under dynamic changes in time and space is constructed. The modularity, degree centrality, betweenness centrality, closeness centrality, eigenvector centrality and average path length of the watershed ecological security network are simulated and quantified through the ecological security complex network model, and the ecological complex network structure characteristic index is obtained.

10. The method for quantifying ecological restoration based on a complex network of watershed ecological security according to claim 1, characterized in that: The coupling coordination model is shown below (9): Where, CCD tp represents the coupling coordination index in the ecological source area p in the tth year, E tp1 It represents the characteristic index of ecological land scale, representing the area scale of ecological source land p; E tp2 Represents the ecological security function characteristic index, representing the comprehensive ecosystem service index ESI in the ecological source area p tr The average value of E tp3 It represents the ecological security structure characteristic index, which represents the average value of the four ecological complex network structural characteristic indices of degree centrality, betweenness centrality, closeness centrality and eigenvector centrality; w1, w2 and w3 respectively represent the decisive weights of the ecological land scale characteristic index, the ecological security function characteristic index and the ecological security structure characteristic index on ecological security, and the weights are determined by the entropy weight method.

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