An ecological restoration quantification method based on a complex network of basin ecological safety

Abstract

The application discloses a kind of ecological restoration quantification method based on complex network of watershed ecological security, comprising: S1: obtaining the multi-source heterogeneous spatial data of target area multi-time sequence watershed;S2: with grid as evaluation unit, establish the evaluation system of watershed ecosystem service function, obtain the spatial-temporal variation characteristics of ecological security function;S3: analyze the spatial-temporal variation characteristics of watershed ecological land scale;S4: construct watershed ecological resistance surface;S5: identify ecological corridor;S6: with ecological source as node, ecological corridor as edge, the scale of ecological source is regarded as point weight, the proportional relationship of ecological corridor connection efficiency and corridor resistance is regarded as edge weight, construct ecological security complex network model, extract the spatial-temporal evolution characteristics of ecological security structure;S7: using coupling coordination degree model simulates and analyzes the characteristic relationship between security function, security structure and land scale, obtains coupling coordination degree;S8: guide optimization ecological restoration implementation strategy.The application quantifies the ecological security network structure characteristics on watershed system scale.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of surveying and mapping supervision and management, and particularly relates to an ecological restoration quantification method based on a complex network of basin ecological safety. BACKGROUND

[0002] In order to prevent natural disasters, water and power needs, more and more dams are built to reasonably distribute water resources. After the dam is built, the land use and ecological environment within the reservoir basin have been increasingly concerned, and in particular, the special research on land reclamation and ecological restoration has become a technical problem to be solved urgently in this region.

[0003] Traditional ecological safety research mainly uses ecological safety evaluation methods to study the functional characteristics of the space. The relationship between multiple complex elements and ecological safety is simplified as a weight relationship or a fuzzy relationship under the regional space. This relationship ignores the complex relationship and dynamic changes within the ecological system. Therefore, ecological safety networks are added later. The existing ecological network is based on the principles of landscape ecology. The construction method mainly identifies ecological sources and simulates ecological corridors. However, the existing construction method ignores the resistance of the ecological system function itself to the construction process of the ecological corridor, and simplifies the structural characteristics of the ecological safety network in the flow space. Moreover, the existing research method mainly starts from one of the perspectives of ecological function characteristics or ecological structure characteristics, and cannot fully reveal the systematic relationship between internal and external benefits of ecological safety.

[0004] At the same time, the research region of ecological safety problems gradually extends from the present concerned regional scale to the basin scale which breaks the administrative boundaries, and expands from the single river basin research to the common research of key basin and small basin ecological safety. The research content is from the local problem and countermeasure type research to the more prominent system, whole and comprehensive management research, so a basin ecological safety network construction method, pattern optimization method based on "function-structure-scale" is urgently needed. SUMMARY

[0005] The purpose of the present application is to provide an ecological restoration quantification method based on a complex network of basin ecological safety, which combines the principles of landscape ecology and complex network models from multiple time sequences and multiple dimensions, quantifies the structural characteristics of the ecological safety network at the basin system scale, and optimizes the specific countermeasures for basin ecological restoration.

[0006] In order to achieve the above purpose, the present application adopts the following technical scheme:

[0007] An ecological restoration quantification method based on a complex network of basin ecological safety, comprising the following steps:

[0008] S1: obtaining multi-source heterogeneous spatial data of a target region in multiple time sequences;

[0009] S2: Taking a kilometer grid as an evaluation unit and a certain time period as an interval point, a basin ecosystem service function evaluation system is established, and the spatial and temporal variation characteristics of the ecological security function of the basin ecosystem field are analyzed according to the basin ecosystem service function evaluation system;

[0010] S3: Extracting an important area of ecosystem function based on the evaluation results of the ecosystem service function evaluation system, screening a core area combined with a landscape connectivity index of a regional ecosystem and a regional ecosystem protection strategy, and identifying a regional basin ecological source; based on the regional basin ecological source, the scale of ecological land is extracted, and the spatial and temporal variation characteristics of the basin ecological land scale are analyzed;

[0011] S4: Based on the principle of landscape ecology, the organic connection of ecological landscape resource patches is established for the purpose of protecting biodiversity and landscape integrity, five characteristic indexes of basin terrain conditions, land cover, human disturbance, vegetation state and ecological benefit are selected to construct a basin ecological resistance surface;

[0012] S5: Based on the regional basin ecological source and the basin ecological resistance surface, an ecological corridor is identified, and important ecological pinch points and main ecological obstacle points are analyzed;

[0013] S6: Taking the regional basin ecological source as a node and the ecological corridor as an edge, the scale of the regional basin ecological source is taken as a point weight, and the proportional relationship between the connection efficiency of the ecological corridor and the resistance of the corridor is taken as an edge weight, an ecological security complex network model is constructed, and the spatial and temporal evolution characteristics of the ecological security structure of the basin ecosystem flow space are extracted;

[0014] S7: The coupling coordination degree of the spatial and temporal variation characteristics of the ecological security function, the spatial and temporal evolution characteristics of the ecological security structure, and the spatial and temporal variation characteristics of the ecological land scale are obtained by simulating and analyzing the feature relationship between the three characteristics indexes on the space-time coupling coordination degree model;

[0015] S8: According to the coupling coordination degree, the implementation strategy of ecological restoration is optimized.

[0016] Further, the S8: According to the coupling coordination degree, the implementation strategy of ecological restoration is optimized, specifically including:

[0017] S801: An intelligent decision-making model for ecological restoration is constructed by using a random forest model;

[0018] S802: Based on the coupling coordination degree model, the characteristic relationship among the ecological security function, the ecological structure and the ecological land scale of the basin is analyzed, the basin ecological security pattern is optimized from the perspective of "function-structure-scale", and the ecological restoration intelligent decision model is trained to simulate and predict the ecological restoration strategy of the basin ecological security "function-structure-scale" characteristics under different combination scenarios combined with the ecological restoration engineering project index of the field investigation, and the optimal decision is obtained.

[0019] S803: At the basin scale, according to the optimal decision, it is judged whether it is an ecological restoration priority area, if it is an ecological restoration priority area, any one of the function priority, or the structure priority, or the function-structure priority, or the scale-function priority, or the scale-structure priority, or the scale-function-structure priority is recommended for the basin ecological restoration strategy partition.

[0020] Further, the multi-time sequence basin multi-source heterogeneous spatial data includes topographic data, land use data, vegetation water system data, soil texture data, social and economic data, remote sensing image data and climate data.

[0021] Further, the establishment of the basin ecosystem service function evaluation system specifically includes:

[0022] From the supply function, the regulation function and the support function of the ecosystem service, the water conservation service, the soil conservation service, the climate regulation service and the biodiversity maintenance service index are selected for the basin ecosystem service function evaluation, wherein,

[0023] The water conservation service

[0024] The water conservation service is mainly related to the precipitation, evaporation, surface runoff and land cover of the region, and the water conservation service is mainly calculated by the total water conservation supply, and the water conservation service calculation formula is shown as the following formula (1):

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

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

[0027] The soil conservation service

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

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

[0030]

[0031] Wherein, A tr represents the soil conservation scale in grid r in the t year, RE tr represents the rainfall erosion factor, p tr represents the rainfall erosion factor calculated by using monthly rainfall data, P 2 tri represents the rainfall of the i month, SE tr represents the soil erodibility factor, LS represents the slope length and slope factor, CCM tr represents the vegetation cover and management factor, CM tr represents the water and soil conservation measure factor;

[0032] The climate regulation service

[0033] The carbon storage is calculated to reflect the climate regulation service of the region. In combination with the carbon storage calculation module in the InVEST model, the carbon storage of aboveground, underground, dead organic matter and soil organic matter is comprehensively considered on the basis of annual land use type data, and the specific calculation formula is shown in the following (4):

[0034]

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

[0036] The biodiversity maintenance service

[0037] The habitat status is an important part of regional biodiversity maintenance, and the habitat suitability model in the InVest model is used to calculate the regional biodiversity maintenance service capacity.

[0038] Further, the spatial and temporal variation characteristics of the ecological security function of the basin ecosystem field space are analyzed according to the basin ecosystem service function evaluation system, and specifically include:

[0039] The ecological system service comprehensive index is used to reflect the comprehensive service function of the regional ecological system, i.e., the spatial and temporal variation characteristics of the ecological security function, in order to eliminate the dimensions of various ecological system service function indexes, the index types are standardized before the ecological system service comprehensive index is calculated, and the processing mode is shown in the following formula (5):

[0040]

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

[0042] The ecological system service comprehensive index ESI tr is in an accumulation mode, as shown in the following formula (6):

[0043]

[0044] Further, the S3: extracting the ecological system function important area based on the evaluation result of the ecological system service function evaluation system, combining the core area screened by the landscape connectivity index of the regional ecological system and the nature reserve determined by the regional ecological system protection strategy, and identifying the regional basin ecological source, specifically includes:

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

[0046] S302: According to the land use division standard, the MSPA ecological connectivity analysis is carried out on the ecological type land of forest land, grassland and water area to obtain the habitat patch core area;

[0047] S303: Superimpose the nature reserves in the regional ecosystem protection strategy;

[0048] S304: Determine the minimum patch area threshold of the ecological source by counting the number of patch of the ecological source under the minimum area threshold. The minimum patch area threshold is used to identify the ecological source of the basin.

[0049] Further, the S4: based on the principle of landscape ecology, the organic connection of ecological landscape resource patches is established for the purpose of protecting biodiversity and landscape integrity. Five characteristic indexes including basin terrain condition, land cover, human disturbance, vegetation state and ecological benefit are selected to construct the basin ecological resistance surface, which specifically includes:

[0050] Based on the principle of landscape ecology, the ecological network is constructed for the purpose of protecting biodiversity and landscape integrity, and the organic connection of ecological landscape resource patches is established. This connection is a channel to protect the material circulation, energy flow and information transmission within the ecological system. This channel needs to comprehensively consider the terrain characteristics, land use type, non-ecological degree, ecological land state and ecological function. Therefore, five characteristic indexes including basin terrain condition, land cover, human disturbance, vegetation state and ecological benefit are selected to construct the basin ecological resistance surface. The basin ecological resistance surface includes the resistance type, resistance factor, ecological resistance value, index weight and division standard of each characteristic index of the basin;

[0051] The index weight adopts the entropy weight method as the resistance factor index weight assignment method. The information entropy of each time and space index is measured by the entropy weight method to determine the influence degree of the resistance factor;

[0052] The entropy value of each time and space index is measured by the entropy weight method model. The entropy weight method model is shown in the following (7):

[0053]

[0054] In the formula, ω j represents the evaluation weight value of the spatial index j, k = 1 / lnm (k > 0), m is the total number of the grid, f rj is the proportion of the j index value in the analysis grid number r in the total sum of the spatial and temporal data of all years of the j index value, n is the number of indexes for weight calculation;

[0055] The index weight is measured by entropy value;

[0056] All feature indexes are measured 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 t year, Es trj represents the spatial value of the single resistance factor.

[0059] Further, the S5: based on the regional basin ecological source and the basin ecological resistance surface, the ecological corridor is identified, the important ecological pinch point and the main ecological obstacle point are analyzed, which specifically includes:

[0060] Based on the circuit theory, the ecological corridor and the corridor width of the regional basin ecological source through different landscape units under different resistance coefficients to another ecological source are simulated, 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 by spatial iteration operation, and the core area with important role in ecological protection in the basin is extracted by simulating the current value; the Barrier Mapper module is used to simulate the main obstacle area hindered by the material and energy exchange between the regional basin ecological sources.

[0061] Further, the S6: taking the regional basin ecological source as a node and the ecological corridor as an edge, taking the size of the regional basin ecological source as a point weight, and taking 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, and the spatial and temporal evolution characteristics of the ecological security structure of the basin ecosystem flow space are extracted, which specifically includes:

[0062] Based on the complex network model, the spatial gravity point of the regional basin ecological source is taken as the node element, the gravity X and Y coordinates are taken as the node element coordinates, the scale of the regional basin ecological source is taken as the node element point weight, and the ecological corridor is taken as the connection edge between the node elements, and the connectivity and resistance ratio of the ecological corridor is taken as the edge weight, to construct the ecological security complex network model under the dynamic change of space and time, and the modularity, degree centrality, betweenness centrality, closeness centrality, eigenvector centrality and average path length of the basin ecological security network are simulated and quantified through the ecological security complex network model, and the structural characteristic index of the ecological complex network is obtained.

[0063] Further, the coupling coordination degree model is as shown in the following (9):

[0064]

[0065] In the formula, in the formula, CCD tp Indicates the coupling coordination degree index in the ecological source p in the t year, E tp1 Indicates the ecological land scale characteristic index, represents the area scale of the ecological source p; E tp2 Indicates the ecological security function characteristic index, represents the average value of the ecological system service comprehensive index ESItr in the ecological source p; E tp3 Indicates the ecological security structure characteristic index, represents the average value of the four ecological complex network structural characteristic indexes of degree centrality, betweenness centrality, closeness centrality and eigenvector centrality; w1, w2 and w3 respectively represent the decisive weight of the ecological land scale characteristic index, the ecological security function characteristic index and the ecological security structure characteristic index to the ecological security, and the weight is determined by using the entropy weight method.

[0066] The spatial and temporal variation characteristics of the ecological security function are abbreviated as "function"; the spatial and temporal evolution characteristics of the ecological security structure are abbreviated as "structure"; and the spatial and temporal variation characteristics of the ecological land scale are abbreviated as "scale".

[0067] The beneficial effects of the present application are:

[0068] 1. The traditional boundary limitation according to administrative region is broken, the basin is taken as the research region object, and the kilometer grid is taken as the minimum evaluation unit, so that the integrity and complexity of the ecological system can be better grasped, the governance fragmentation problem caused by the administrative division is avoided, and the multi-objective balance and ecological system collaborative governance problem in the basin are solved.

[0069] 2. The basin ecological security network construction optimization based on complex network

[0070] The principles of landscape ecology and complex network theory are combined to analyze the characteristics of basin ecological security from the "structure-function" two dimensions. The structural characteristics analysis uses the complex network model to construct the ecological security network, and deeply analyzes the systematic structural characteristics of the basin ecological security network. Compared with the traditional method of constructing basin ecological security network, which can only extract the spatial carrier of ecological source and corridor, the spatial location of ecological pinch point and obstacle point from the structure, this method combines the advantages of traditional methods to further solve the problem of quantifying the structural characteristics of ecological security network at the scale of basin system.

[0071] 3. New method for quantitative analysis of spatial and temporal characteristics of basin ecological security

[0072] Multi-temporal and multi-source heterogeneous spatial data of the basin are collected, and the basin ecosystem service function is evaluated with fixed time intervals. Based on circuit theory, ecological sources and corridors are constructed, and ecological pinch points and obstacle points are identified. The specific carriers of ecological sources, corridors, and pinch points and obstacle points in space are implemented year by year, and the evolution characteristics of the spatial and temporal structure of the basin ecological security pattern are analyzed. Taking the spatial gravity point of the ecological source as the node element, the gravity X and Y coordinates as the node element coordinates, and the source size as the node point weight, the ecological corridor is taken as the connection 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 under the condition of dynamic change of space and time is constructed. This method can quantify the modularity, degree centrality, betweenness centrality, closeness centrality, and eigenvector centrality of the basin ecological security network. Based on the quantitative indicators, the spatial community structure of the basin ecological security network is divided from the structure, and the spatial and temporal organization and function of the basin ecological security network are clarified, so as to measure the connection degree of each ecological node element in the network, identify the key nodes connecting different network communities, and identify the important contact points and most influential nodes connecting each ecological node element.

[0073] 4. Intelligent decision-making model for ecological restoration under the correlation characteristics of "function-structure-scale"

[0074] The ecological function, ecological structure, and ecological scale characteristics of basin ecological security are quantified regularly and continuously, combined with the indicators of ecological restoration engineering implementation time, implementation scale, and engineering type obtained through field investigation, and the random forest model is used to construct multiple decision trees and integrate their prediction results for judgment, so as to realize the simulation of ecological restoration decision-making.

[0075] The problems of basin ecological restoration region identification and strategy diagnosis are effectively solved, the method makes the basin ecological restoration decision not only stay in the selection of priority area, but also can realize the strategy optimization of basin efficient ecological safety recovery from the three dimensions of "function, structure and scale", and scientifically proposes the specific countermeasures of basin ecological restoration. Through the demonstration of the spatial and temporal characteristics of the basin ecological safety network, the partitioned and classified ecological restoration measures are formulated, and the ecological resilience improvement strategy is proposed, which provides technology and method for further optimizing the basin ecological safety pattern and improving the ecological resilience of national space. BRIEF DESCRIPTION OF DRAWINGS

[0076] Figure 1 The flowchart of embodiment 1 of the present application is for the flowchart of ecological source identification in embodiment 1 of the present application;

[0077] Figure 2 The flowchart of embodiment 1 of the present application is for the flowchart of ecological source identification in embodiment 1 of the present application;

[0078] Figure 3 The minimum plot area threshold of the ecological source in embodiment 1 of the present application is for the minimum plot area threshold of the ecological source in embodiment 1 of the present application;

[0079] Figure 4 The minimum plot area threshold interval of the ecological source in embodiment 1 of the present application is for the minimum plot area threshold interval of the ecological source in embodiment 1 of the present application;

[0080] Figure 5 The spatial and temporal distribution map of the ecological source in the Three Gorges Reservoir area in embodiment 1 of the present application is for the spatial and temporal distribution map of the ecological source in the Three Gorges Reservoir area in embodiment 1 of the present application;

[0081] Figure 6 The spatial and temporal distribution map of the ecological source in the Three Gorges Reservoir area in embodiment 1 of the present application is for the spatial and temporal distribution map of the ecological source in the Three Gorges Reservoir area in embodiment 1 of the present application;

[0082] Figure 7 The spatial and temporal distribution map of the ecological source in the Three Gorges Reservoir area in embodiment 1 of the present application is for the spatial and temporal distribution map of the ecological source in the Three Gorges Reservoir area in embodiment 1 of the present application;

[0083] Figure 8 The flowchart of complex network construction in embodiment 1 of the present application is for the flowchart of complex network construction in embodiment 1 of the present application;

[0084] Figure 9 The spatial and temporal characteristic quantity model of the basin ecological safety in the embodiment of the present application is for the spatial and temporal characteristic quantity model of the basin ecological safety in the embodiment of the present application;

[0085] Figure 10 The ecological safety complex network map constructed at different time periods in embodiment 1 of the present application is for the ecological safety complex network map constructed at different time periods in embodiment 1 of the present application;

[0086] Figure 11 The flowchart of the ecological restoration intelligent decision model constructed based on the random forest in embodiment 1 of the present application is for the flowchart of the ecological restoration intelligent decision model constructed based on the random forest in embodiment 1 of the present application. DETAILED DESCRIPTION

[0087] With reference to the accompanying drawings on the basis of the embodiments of the present application, the technical solutions in the embodiments of the present application will be described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Specific embodiment 1:

[0089] With reference to the accompanying drawings on the basis of the embodiments of the present application, the technical solutions in the embodiments of the present application will be described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Figures 1 to 11 As shown in the drawings, a quantitative method of ecological restoration based on a complex network of watershed ecological safety, taking a reservoir area in the southwest region as an example, includes the following steps:

[0090] Step S1: Obtain multi-temporal watershed multi-source heterogeneous spatial data of a target region; the multi-temporal watershed multi-source heterogeneous spatial data includes topographic data, land use data, vegetation water system data, soil texture data, social and economic data, remote sensing image data, and climate data.

[0091] Step S2: Take a kilometer grid as an evaluation unit, and take a certain period as an interval point to establish a watershed ecosystem service function evaluation system, and obtain the spatial and temporal variation characteristics of the ecological safety function of the watershed ecosystem field according to the watershed ecosystem service function evaluation system; in this specific embodiment, five years are taken as a time interval, which specifically includes:

[0092] This method breaks the traditional boundary limitation according to administrative regions, takes a watershed as a research region object, and takes a kilometer grid as the smallest evaluation unit, selects four service function indexes of water conservation service, soil conservation service, climate regulation service and biodiversity maintenance service from three types of supply function, regulation function and support function of the ecological system to evaluate the watershed ecosystem service function; wherein, the water conservation service

[0093] The water production service capacity of the ecological system is an important prerequisite for regional human life and production, a core element for regional biological survival and reproduction, and a limiting index for the social and economic development of the reservoir area. Water conservation service is a core index reflecting the supply capacity of regional water production service, mainly related to regional precipitation, evaporation, surface runoff and land cover, and the water conservation service is mainly calculated by using the total water conservation supply, and the water conservation service calculation formula is shown as formula (1) below:

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

[0095] Wherein, WS tr represents the total water supply in grid r in the t year, P tr represents the average annual precipitation in grid r in the t year, ET tr represents the precipitation evaporation in grid r in the t year, and Rtr represents the cumulative surface runoff in the grid r in the t year, which is obtained by multiplying the precipitation and the surface runoff coefficient. According to the existing related literature and combined with the actual situation of the reservoir area, the surface runoff coefficients of forest land and grassland are determined to be 4.65% and 3.94% respectively, and the runoff coefficients of other land use types are 0.

[0096] The soil conservation service

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

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

[0099]

[0100] Wherein, A tr represents the soil conservation scale in the grid r in the t year, RE tr represents the rainfall erosivity factor, p tr represents the rainfall erosivity calculation, P 2 tri represents the rainfall in the i month, SE tr represents the soil erodibility factor, LS represents the slope length and slope factor, CCM tr represents the vegetation cover and management factor, CM tr represents the water and soil conservation measure factor.

[0101] The climate regulation service

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

[0103]

[0104] Wherein, C tr represents the total carbon storage in the grid r in the t year, C ti1 represents the aboveground carbon density of the i type of land cover in the t year, Cti2 Ct,i represents the below-ground carbon density of the i-th land cover in the t-th year, C ti3 Ct,i represents the dead organic matter carbon density of the i-th land cover in the t-th year, C ti4 Ct,i represents the soil organic matter carbon density of the i-th land cover in the t-th year, Ar tri Ct,i represents the total area of the i-th land cover in the t-th year in the grid r.

[0105] The biodiversity maintenance service

[0106] The habitat status is an important part of the regional biodiversity maintenance, and the habitat suitability model in the InVest model is used to calculate the regional biodiversity maintenance service capacity. The model reflects the regional biodiversity by analyzing the threat degree of human land use or natural disasters to the biodiversity and combining the relative sensitivity of each habitat type to each threat.

[0107] According to the analysis of the watershed ecosystem service function evaluation system, the spatial and temporal variation characteristics of the ecological security function of the watershed ecosystem field space are obtained, and the comprehensive index of the ecosystem service is used to reflect the comprehensive service function of the regional ecosystem, i.e., the spatial and temporal variation characteristics of the ecological security function. In order to eliminate the dimensions of various ecosystem service function indexes, the index type is standardized before calculating the comprehensive index of the ecosystem service, and the processing method is shown in the following formula (5):

[0108]

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

[0110] The comprehensive index of the ecosystem service ESI tr is obtained by using the cumulative mode, as shown in the following formula (6):

[0111]

[0112] Step S3: Based on the evaluation results of the ecosystem service function evaluation system, the important area of the ecosystem function is extracted, the core area is screened in combination with the landscape connectivity index of the regional ecosystem, and the regional watershed ecological source is identified. Based on the watershed ecological source, the ecological land scale is extracted, and the spatial correlation analysis model is analyzed by using Moran's I and hot and cold spot pattern analysis to obtain the spatial and temporal variation characteristics of the watershed ecological land scale.

[0113] On the basis of the evaluation of the watershed ecosystem service function, the important areas of the ecosystem function are extracted, and the core areas that are closely connected and interacted in the ecological process are screened out by combining the landscape connectivity index of the ecological land, and the nature reserves determined by the local strategic guidance in the ecological system protection are comprehensively considered to optimize the identification of the regional ecological source land. Specifically, as shown in Figure 2 , the following is included:

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

[0115] S302: According to the land use division standard, the MSPA ecological connectivity analysis is performed on the ecological type land of forest land, grassland and water area to obtain the habitat patch core area;

[0116] S303: Superimpose the nature reserves in the regional ecosystem protection strategy;

[0117] S304: The number of ecological source land patches under the minimum area threshold value is counted to determine the minimum patch area threshold value of the ecological source land, and the watershed ecological source land is identified according to the minimum patch area threshold value. In this specific embodiment: as shown in Figure 3 and Figure 4 , the number of ecological source land patches tends to be stable after 3KM 2 , and the number of ecological source land patches changes by 1KM 2 after 3KM 2 , and the number of ecological source land patches changes by 1KM 2 , and the number of ecological source land patches changes by 1KM 2 . As shown in Figure 5 , the time and space distribution diagram of the ecological source land of a reservoir area from 2000 to 2020 is obtained.

[0118] Step S4: Based on the principle of landscape ecology, the organic connection of ecological landscape resource patches is established for the purpose of protecting biodiversity and landscape integrity, five characteristic indexes including topographic conditions, land cover, human disturbance, vegetation state and ecological benefit are selected to construct the ecological resistance surface of the basin; specifically including:

[0119] Based on the principle of landscape ecology, the organic connection of ecological landscape resource patches is established for the purpose of protecting biodiversity and landscape integrity, the connection is the channel to protect the material circulation, energy flow and information transmission within the ecological system, the channel needs to comprehensively consider the topographic characteristics, land use type, non-ecological degree, ecological land state and ecological function, therefore, five characteristic indexes including topographic conditions, land cover, human disturbance, vegetation state and ecological benefit are selected to construct the ecological resistance surface of the basin, the ecological resistance surface of the basin includes the resistance type, resistance factor, ecological resistance value, index weight and division standard of each characteristic index of the basin. Among them, the determination of the spatial numerical value of the land cover and vegetation state resistance factor refers to the existing division standard and valuation method of the resistance factor by Fu Mengdi et al., the ecological benefit division standard is divided according to the service function level of the ecological system determined in the research, the topographic conditions and human disturbance resistance factor are standardized by processing the original data, and the standard division is carried out on the basis of comparing the factor effect and analyzing the characteristics of the basin, as shown in the following table:

[0120]

[0121] The determination method of the index weight mainly includes subjective and objective forms, this method selects the more objective and scientific entropy weight method as the index weight valuation method of the resistance factor, the index weight adopts the entropy weight method as the index weight valuation method of the resistance factor, and the influence degree of the resistance factor is determined by measuring the information entropy of each space-time index through the entropy weight method;

[0122] The entropy value of each space-time index is measured by using the entropy weight method model, the index weight is measured through the entropy value, and the entropy weight method model is shown in the following formula (7):

[0123]

[0124] In the formula, ω j represents the evaluation weight value of the space index j, k = 1 / lnm (k > 0), m is the total number of grids, n is the number of indexes for which the weight is calculated, here n = 5, f rj is the proportion of the j index value in the grid number r in the proportion of the j index value in the entire j index space-time data cumulative value sum in all years;

[0125] The corresponding ecological comprehensive resistance value in each grid of each year is measured by using the weighted summation of all characteristic indexes, as shown in the following formula (8):

[0126]

[0127] In the formula, RES tr represents the ecological comprehensive resistance value in the analysis grid number r in the t year, Est rj represents the spatial value of a single resistance factor. As shown in the formula, the spatial value of a single resistance factor is calculated by the formula: Est Figure 6 The ecological resistance factor and the ecological comprehensive resistance surface of a certain reservoir area from 2000 to 2020 are shown in the figure. Figure 7 The spatial identification and change analysis diagram of the ecological corridor in the Three Gorges Reservoir Area from 2000 to 2020 is shown in the figure.

[0128] Step S5: Based on the regional basin ecological source and the basin ecological resistance surface, an ecological corridor is identified, important ecological pinch points and main ecological barrier points are analyzed; specifically including:

[0129] Based on the circuit theory, the ecological corridor and the corridor width of the regional basin ecological source through different landscape units under different resistance coefficients to reach another ecological source are simulated, and the ecological pinch point area in the ecological corridor is identified by using the Pinchpoint Mapper module, that is, the cumulative current value of each grid unit is obtained by spatial iterative operation, and the core area with important role in ecological protection in the basin is extracted by simulating the current value; the main barrier area hindered by the material and energy exchange between the regional basin ecological sources is simulated by using the Barrier Mapper module.

[0130] S6: In the regional basin ecological source and the ecological corridor simulation data, the connection relationship between the ecological sources is extracted, the regional basin ecological source is taken as a node, the ecological corridor is taken as an edge, the scale of the regional basin ecological source is taken as a point weight, and the proportional relationship between the connection efficiency and the corridor resistance of the ecological corridor is taken as an edge weight, to construct an ecological security complex network model, and extract the spatio-temporal evolution characteristics of the ecological security structure of the basin ecosystem flow space; specifically including:

[0131] Based on the complex network model, the spatial gravity point of the regional basin ecological source is taken as a node element, the gravity X and Y coordinates are taken as node element coordinates, the scale of the regional basin ecological source is taken as a node element point weight, the ecological corridor is taken as a connection edge between node elements, and the connectivity and resistance ratio of the ecological corridor are taken as edge weights, to construct an ecological security complex network model under the spatio-temporal dynamic change, and the modularity, degree centrality, betweenness centrality, closeness centrality, eigenvector centrality and average path length of the basin ecological security network are simulated and quantified by the ecological security complex network model, to obtain the structural characteristic index of the ecological complex network. Referring to the ecological security complex network construction method shown in Figure 8 the flow space of the basin ecological security spatio-temporal characteristic quantification model shown in Figure 9 Figure 10 ​The ecological safety complex network constructed in 2010-2020 is shown.

[0132] Step S7: Simulate and analyze the characteristic relationship between the spatio-temporal variation characteristics of the ecological safety function, the spatio-temporal evolution characteristics of the ecological safety structure, and the spatio-temporal variation characteristics of the ecological land scale by using the coupling coordination degree model, and obtain the coupling coordination degree of the three characteristic indexes in space and time; the coupling coordination degree model is shown in the following formula (9):

[0133]

[0134] In the formula, CCD tp represents the coupling coordination degree index in the ecological source land p in the t year, E tp1 represents the ecological land scale characteristic index, and represents the area scale of the ecological source land p; E tp2 represents the ecological safety function characteristic index, and represents the average value of the ecosystem service comprehensive index ESI tr in the ecological source land p; E tp3 represents the ecological safety structure characteristic index, and represents the average value of the four ecological complex network structural characteristic indexes 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 safety function characteristic index, and the ecological safety structure characteristic index on ecological safety, and the weights are determined by using the entropy weight method.

[0135] By using the coupling coordination degree model to simulate the coordinated development level of the three types of characteristic indexes of basin ecological function, ecological structure, and ecological scale in space and time, the greater the coupling coordination degree value, the better the coordination between the three characteristics of ecological function, ecological structure, and ecological scale affecting ecological safety. The method considers multiple time sequences and multiple dimensions, and the obtained quantitative index is more accurate.

[0136] Step S8: According to the coupling coordination degree, guide the optimization of ecological restoration implementation strategy.

[0137] Specifically, referring to Figure 11 shown in the formula:

[0138] S801: Construct an ecological restoration intelligent decision-making model by using a random forest model;

[0139] S802: Analyze the characteristic relationship between the basin ecological safety function, ecological structure, and ecological land scale based on the coupling coordination degree model, optimize the basin ecological safety pattern from the perspective of “function-structure-scale”, and combine the ecological restoration engineering project indexes obtained by field investigation, train and simulate the ecological restoration strategy of the basin ecological safety “function-structure-scale” characteristics in different combination scenarios by using the ecological restoration intelligent decision-making model, and obtain the optimal decision.

[0140] S803: At the surface domain scale, it is determined again whether it is an ecological restoration priority area according to the optimal decision, if it is an ecological restoration priority area, any one of the modes of function priority, or structure priority, or function-structure priority, or scale-function priority, or scale-structure priority, or scale-function-structure priority is recommended for the watershed ecological restoration strategy. The method aims to improve the ecological security resilience of the watershed, optimizes the ecological security pattern of the watershed from the perspective of the multi-time sequence "function-structure-scale" characteristic relationship, identifies the watershed ecological restoration implementation priority area at the surface domain scale, and proposes the watershed ecological restoration implementation priority strategy at the point scale.

[0141] The technical solutions provided by the present application are described in detail above. The principles and implementation modes of the present application are described by applying specific examples in this paper, and the above examples are only used to help understand the method and core idea of the present application. It should be pointed out that, for ordinary skilled persons in the technical field, some improvements and modifications can be made to the present application without departing from the principles of the present application, and these improvements and modifications also fall within the protection scope of the claims of the present application.

Claims

1. An ecological restoration quantification method based on a complex network of watershed ecological safety, characterized in that, The method comprises the following steps: S1: acquiring multi-temporal and multi-source heterogeneous spatial data of a target region; S2: taking a grid as an evaluation unit, establishing an evaluation system for the ecosystem service function of the basin, and analyzing the spatial and temporal variation characteristics of the ecological security function of the basin ecosystem field based on the evaluation system; S3: extracting the important area of the ecosystem function based on the evaluation results of the ecosystem service function evaluation system, screening the core area and the regional ecosystem protection strategy based on the landscape connectivity index of the regional ecosystem, and identifying the regional basin ecological source; Based on the regional basin ecological source, the scale of the ecological land is extracted, and the spatial and temporal variation characteristics of the basin ecological land scale are analyzed; S4: based on the principle of landscape ecology, the organic connection of ecological landscape resource patches is established for the purpose of protecting biodiversity and landscape integrity, five characteristic indexes including basin terrain condition, land cover, human disturbance, vegetation state and ecological benefit are selected to construct the basin ecological resistance surface; S5: based on the regional basin ecological source and the basin ecological resistance surface, the ecological corridor is identified, and the important ecological pinch point and the main ecological obstacle point are analyzed; S6: taking the regional basin ecological source as a node and the ecological corridor as an edge, taking the scale of the regional basin ecological source as a point weight, and taking the proportional relationship between the connection efficiency and the corridor resistance of the ecological corridor as an edge weight, a complex network model of ecological security is constructed, and the spatial and temporal evolution characteristics of the ecological security structure of the basin ecosystem flow space are extracted; S7: the characteristic relationship between the spatial and temporal variation characteristics of the ecological security function, the spatial and temporal evolution characteristics of the ecological security structure and the spatial and temporal variation characteristics of the ecological land scale is simulated and analyzed by using the coupling coordination degree model, and the coupling coordination degree of the three characteristic indexes in space and time is obtained; S8: according to the coupling coordination degree, the implementation strategy of ecological restoration is optimized.

2. The method of claim 1, wherein the method is characterized by: The S8: according to the coupling coordination degree, the implementation strategy of ecological restoration is optimized, which specifically comprises: S801: an intelligent decision model of ecological restoration is constructed by using a random forest model; S802: based on the coupling coordination degree model, the characteristic relationship between the basin ecological security function, the ecological structure and the ecological land scale is analyzed, the basin ecological security pattern is optimized from the perspective of "function-structure-scale", and the ecological restoration strategy of the basin ecological security "function-structure-scale" characteristics in different combination scenarios is simulated and predicted by using the intelligent decision model of ecological restoration combined with the ecological restoration engineering project index obtained by field investigation, and the optimal decision is obtained; S803: on the plane scale, whether it is an ecological restoration priority area is judged according to the optimal decision, if it is an ecological restoration priority area, any one of the following modes is recommended for the basin ecological restoration strategy zoning: function priority, or structure priority, or function-structure priority, or scale-function priority, or scale-structure priority, or scale-function-structure priority.

3. The method of claim 1, wherein the method is characterized by: The multi-temporal and multi-source heterogeneous spatial data of the basin includes terrain data, land use data, vegetation data, soil texture data, social and economic data, remote sensing image data and climate data.

4. The method of claim 1, wherein the method is characterized by: The establishment of the watershed ecosystem service function evaluation system specifically includes: From the supply function, regulation function and support function of the ecosystem service, the water conservation service, soil conservation service, climate regulation service and biodiversity maintenance service indicators are selected for the watershed ecosystem service function evaluation, wherein, The water conservation service The water conservation service is mainly related to the precipitation, evaporation, surface runoff and land cover of the region, and the water conservation service is mainly calculated by the total amount of water conservation supply, and the water conservation service calculation formula is as follows: WS tr = P tr - ET tr - R tr Wherein, WS tr represents the total amount of water supply in the grid r in the t year, P tr represents the average annual precipitation in the grid r in the t year, ET tr represents the precipitation evapotranspiration in the grid r in the t year, R tr represents the cumulative surface runoff in the grid r in the t year; The soil conservation service The soil conservation service reflects whether the reservoir area ecosystem can reduce or avoid the soil erosion effect caused by water erosion, and based on the modified universal soil loss equation, the soil conservation service index calculation formula of the region is determined as follows: A tr = RE tr × SE tr × LS × (1 - CCM tr × CM tr ) wherein, A tr represents the soil conservation scale in the grid r in the t year, RE tr represents the rainfall erosivity factor, p tr represents that the rainfall erosivity is calculated by using the monthly rainfall data, P 2 tri represents the rainfall in the i month, SE tr represents the soil erodibility factor, LS represents the slope length and slope gradient factor, CCM tr represents the vegetation cover and management factor, CM tr represents the soil and water conservation measure factor; The climate regulation service The climate regulation service of the region is reflected by calculating the carbon storage, and based on the carbon storage calculation module in the InVEST model, on the basis of annual land use type data, the carbon storage of aboveground, underground, dead organic matter and soil organic matter is comprehensively considered, and the specific calculation formula is as follows: wherein C tr represents the total amount of carbon sequestration in grid r in the tth year, C ti1 represents the aboveground carbon density of the i-type land cover in the tth year, C ti2 represents the belowground carbon density of the i-type land cover in the tth year, C ti3 represents the dead organic matter carbon density of the i-type land cover in the tth year, C ti4 represents the soil organic matter carbon density of the i-type land cover in the tth year, Ar tri represents the total area of the i-type land cover in grid r in the tth year; The biodiversity maintenance service The habitat state is an important content of regional biodiversity maintenance, and the InVest model is used to calculate the regional biodiversity maintenance service capacity, which is a model that analyzes the threat degree of human land use or natural disasters to its biodiversity, and combines the relative sensitivity of each habitat type to each threat to reflect the regional biodiversity.

5. The method of claim 1, wherein the method is characterized by: According to the watershed ecosystem service function evaluation system, the spatial and temporal variation characteristics of the ecological security function of the watershed ecosystem field are analyzed, specifically including: The ecological system service comprehensive index is used to reflect the comprehensive service function of the regional ecological system, that is, the ecological security function space-time variation characteristics, in order to eliminate the dimension of various ecological system service function indicators, the index type is standardized before calculating the ecological system service comprehensive index, and the processing method is shown in the following formula: In the formula, Sr trj is the standardized index value in the grid r in the tth year, X trj is the original value of the jth index in the grid r in the tth year, Max(X j ) and Min(X j ) represent the maximum and minimum values of the jth index in all years in the study area, respectively. The ecosystem service comprehensive index ESI tr In an accumulative mode, as shown in the following formula:

6. The method of claim 1, wherein the method is characterized by: S3: Based on the evaluation results of the ecological system service function evaluation system, the important area of the ecological system function is extracted, the core area is screened combined with the landscape connectivity index of the regional ecological system, and the regional ecological system protection strategy is determined, and the regional watershed ecological source is identified, specifically including: S301: Based on the evaluation results of the ecological system service function evaluation system, the natural breakpoint method classification standard is used to classify the ecological system service function evaluation results of the watershed in each year, the classification results are compared and analyzed with the prior results of the ecological security comprehensive evaluation in the existing research results of the watershed, to determine the number of classification levels, and based on the determination of the classification level number, the natural breakpoint division value interval of each year is analyzed, the average value of the breakpoint of the highest level of the ecological system service function is taken as the threshold value of the important area of the ecological system service function, and the important area of the ecological system service function is divided; S302: According to the land use division standard, the MSPA ecological connectivity analysis is carried out on the ecological types of forest land, grassland and water area, and the habitat patch core area is obtained; S303: superimpose the nature reserves in the regional ecosystem protection strategy; S304: determine the minimum patch area threshold of the ecological source area by counting the number of patch areas of the ecological source area under the minimum area threshold, and identify the ecological source area of the watershed according to the minimum patch area threshold.

7. The method of claim 1, wherein the method is characterized by: S4: Based on the principle of landscape ecology, the organic connection of ecological landscape resource patches is established for the purpose of protecting biodiversity and landscape integrity. Five characteristic indexes including watershed topographic conditions, land cover, human disturbance, vegetation status and ecological benefit are selected to construct the watershed ecological resistance surface, which specifically includes: Based on the principle of landscape ecology, the organic connection of ecological landscape resource patches is established for the purpose of protecting biodiversity and landscape integrity. This connection is a channel to protect the material circulation, energy flow and information transmission within the ecological system. This channel needs to comprehensively consider the topographic characteristics, land use types, non-ecological degree, ecological land status and ecological function. Therefore, five characteristic indexes including watershed topographic conditions, land cover, human disturbance, vegetation status and ecological benefit are selected to construct the watershed ecological resistance surface. The watershed ecological resistance surface includes the resistance type, resistance factor, ecological resistance value, index weight and division standard of each characteristic index of the watershed ecology; The index weight adopts entropy weight method as the resistance factor index weight assignment method, and the influence degree of the resistance factor is determined by measuring the information entropy of each spatio-temporal index by entropy weight method; The entropy value of each spatio-temporal index is measured by entropy weight method model, and the index weight is measured by entropy value; the entropy weight method model is as follows: In the formula, ωj represents the evaluation weight value of the spatial index j, k = 1 / lnm (k > 0), m is the total number of grids, f j rj is the proportion of the jth index value in the grid number r in the total sum of the spatial and temporal data of the jth index in all years, and n is the number of indexes for which the weight is calculated.​ The corresponding ecological comprehensive resistance value in each grid of each year is measured by using the weighted summation of all characteristic indexes, as shown in the following formula: where RES tr Es represents the ecological resistance value in the analysis grid number r in the tth year trj represents the spatial value of the single resistance factor.

8. The method of claim 1, wherein the method is characterized by: S5: Based on the regional watershed ecological source area and the watershed ecological resistance surface, the ecological corridor is identified, and the important ecological pinch point and the main ecological obstacle point are analyzed, which specifically includes: Based on the circuit theory, the ecological corridor and the corridor width of the regional watershed ecological source area reaching another ecological source area under different resistance coefficients through different landscape units are simulated, and the ecological pinch point area in the ecological corridor is identified by using Pinchpoint Mapper module, that is, the cumulative current value of each grid unit is obtained by spatial iteration operation, and the core area with important role in ecological protection in the watershed is extracted by simulating the current value; the main obstacle area of the regional watershed ecological source area is simulated by using Barrier Mapper module when the material and energy exchange is hindered.

9. The method of claim 1, wherein the method is characterized by: S6: Taking the regional watershed ecological source area as a node and the ecological corridor as an edge, taking the size of the regional watershed ecological source area as a point weight, and taking 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 spatio-temporal evolution characteristics of the ecological security structure of the watershed ecosystem flow space, which specifically includes: Based on the complex network model, taking the spatial gravity point of the regional basin ecological source as the node element, the X and Y coordinates of the gravity point as the node element coordinates, the scale of the regional basin ecological source as the node element point weight, and the ecological corridor as the connection edge between the node elements, the connectivity and resistance ratio of the ecological corridor are the edge weight, the ecological security complex network model under the dynamic change of space and time is constructed, the modularity, degree centrality, betweenness centrality, closeness centrality, eigenvector centrality and average path length of the basin ecological security network are simulated and quantified through the ecological security complex network model, and the structural characteristic index of the ecological complex network is obtained.

10. The method of claim 1, wherein the method is characterized by: The coupling coordination degree model is as shown in the following formula (9): In the formula, CCD tp E represents the coupling and coordination index in ecological source area p in year t. tp1 E represents the ecological land use scale characteristic index, which indicates the area size of the ecological source area p; tp2 The Ecosystem Security Function Characteristic Index (ESI) represents the comprehensive ecosystem service index (ESI) of the ecological source area p. tr The average value of E; tp3 The ecological security structural characteristic index represents the average value of four structural characteristic indices of ecological complex networks: degree centrality, betweenness centrality, proximity centrality, and eigenvector centrality. w1, w2, and w3 represent the decisive weights of the ecological land use scale characteristic index, the ecological security function characteristic index, and the ecological security structural characteristic index on ecological security, respectively, and the weights are determined by the entropy weight method.

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