Construction and Optimization of an Ecological Network in Funiu Mountain Area Based on MSPA and MCR Models, China

Abstract

Rapid urbanization has led to a significant expansion of urban space, causing ecological problems such as fragmentation, declining landscape connectivity, and decreasing biodiversity. There is an urgent need to mitigate the conflict between urban expansion and ecological environmental protection by constructing ecological networks to help promote sustainable regional development. This study selected the Funiu Mountain area as the study area. Morphological spatial pattern analysis, the minimal cumulative resistance model, and network index evaluation were used to construct an ecological network in the study area and conduct a comparative analysis with local nature reserves. The results showed: (1) nine ecological source sites were identified, concentrated in the central and northern regions, which had a high spatial overlap with local nature reserves; (2) 34 ecological corridors were extracted, which could effectively connect all ecological source sites as well as most nature reserves; (3) 32 ecological nodes were identified, of which 20 strategic points were scattered along ecological corridors, and 12 artificial environment points were scattered in low-lying areas around nature reserves; (4) the ecological network showed a structure of central concentration and peripheral dispersion. The structural evaluation of the network indicated that it had strong integrity.

1. Introduction

At present, global sustainable development is still challenged by the destruction of ecosystems, inefficient use of land resources, and serious pollution of the natural environment in some areas [1]. Against this backdrop, the International Council for Science (ICSU) released the ”Future Earth”, which emphasizes multidisciplinary exploration and analysis to provide strong support for solving global environmental problems and promoting global sustainable development [2]. In the past two decades, China’s rapid urbanization and industrialization have led to a significant expansion of urban space [3], which has continued to increase the scope and extent of ecological impacts [4], further triggering ecological problems such as fragmentation of ecological source sites, decreased landscape connectivity, and reduced biodiversity [5]. A large number of studies have proposed the construction of ecological networks in multiple disciplines to escape from the limitations of traditional nature reserves, such as small radiation range and insufficient area of biological habitat [6], to alleviate the conflict between urban expansion and ecological environmental protection, and finally to achieve sustainable regional development [7].

Ecological network theory originated from the European natural resource conservation movement in the 1980s. It is based on landscape ecology [8] and integrates biogeography [9], urban planning [10], and other disciplines. It uses land interaction effects to reflect the rules governing ecological elements and functional structure and to determine the spatial pattern required to maintain the stability of ecosystems [11]. In the 1990s, Chinese scholar Yu Kongjian proposed a construction model for the landscape ecological security pattern, the theoretical basis of which covered the essential elements of an ecological network: sources, corridors, and substrates [12]. Since then, the identification of sources, corridors, and nodes around ecological spaces has become the main framework for constructing ecological networks [13]. In terms of source identification, the starting point for research focuses on the Percentage of Importance of Omitted Patches [14], landscape connectivity [15], ecological sensitivity [16], and morphological spatial pattern analysis [17]. In terms of corridor extraction, the minimum cumulative resistance (MCR) model [18], the linkage mapper model [19], and circuit theory [20] have been widely used to identify corridors. Many scholars base their analysis on integrated resistance surfaces [21], while others consider the intersection of ecological corridors as ecological nodes [22] or consider the site type and patch area [23]. Ecological networks are generally studied at small scales, mostly at the county [24,25], city [26,27], and watershed [28] levels. In recent years, a few scholars have explored the construction of ecological networks at the scale of provinces [29,30], and city groups [31], but less attention has been paid to special regions, such as mountainous areas.

The mountainous areas of China account for approximately 65% of the land area [32]. Owing to the large population and ecological fragility of mountainous areas in China, there are currently problems with the development of land and space in these regions, such as changes in soil and water coupling, encroachment onto mountain ecological space, increased stress and risk of mountain disasters, and disorderly urban expansion [33]. Rapid urbanization is intensifying the degree of disturbance to the natural environment by human activities, and China’s mountainous areas face increasingly serious real or potential ecological security problems. However, studies on the construction of ecological networks in mountainous areas of China are still insufficient. The Funiu Mountain area is one of the three major mountain ecological barriers of the Zhongyuan urban agglomeration and a key ecological function area for maintaining biodiversity; however, there is continuing expansion of construction land in the Funiu Mountain area. In the process of the development of more balanced production–living–ecological spaces in the past three decades, many problems have emerged, such as significant changes in the pattern of the three living spaces, continuous reduction of ecological space, and disorderly layout of urban space. Therefore, this study selected the Funiu Mountain area as a representative region, where the conflict between urban expansion and ecological environmental protection continues to intensify. It used the land use data for 2020 to identify ecological source sites through morphological spatial pattern analysis (MSPA), extract ecological corridors and nodes using the MCR model, construct ecological networks, and compare them with nature reserves to provide support for ecological space conservation and optimization. This research will help to promote the sustainable development of the region and the construction of ecological networks while taking into account the study of conservation measures in nature reserves, which can make up for the lack of ecological networks in mountainous areas research methodology.

2. Overview and Data of the Study Area

2.1. Overview of the Study Area

The Funiu Mountains are the transition zone between the Qinling Mountains and the Huanghuai Plain (110°30′–113°30′ E, 32°45′–34°20′ N), with a climate transition from the northern subtropical to the warm temperate zone. The land area is approximately 21,600 km², spanning four prefecture-level cities and containing eight counties (Figure 1). Lushi County, Xixia County, and Neixiang County are included in the national key ecological function areas. Luanchuan County and Song County are included in the key ecological function area of Henan Province. The topography gradually decreases from west to east, transitioning from low and medium mountains and hills to plains and basins. There is a large difference in elevation, ranging from 2171 m to 50 m above sea level. The complex topography supports several nature reserves, and the ecological environment is relatively fragile [34]. As a key ecological barrier for the Zhongyuan urban agglomeration, the Funiu Mountain area is experiencing a series of ecological problems brought about by human activities [35,36]. From 1990 to 2020, the urbanization rate in the Funiu Mountain area increased from 8.20% to 44.32%. The urban space increased by 208.28 km², while the ecological space decreased by a total of 214.03 km². Therefore, it is of practical significance not only for local ecological protection but also for the high-quality development of the Zhongyuan urban agglomeration and even for the ecological security of the north–south transition zone in China to carry out ecological network construction research in the region.

2.2. Data Source and Preprocessing

The data involved in this study included land use, nature reserves, a digital elevation model (DEM), and basic geographic information on the Funiu Mountains, as follows: (1) 30 m spatial resolution land use data in 2020 and data for administrative boundaries such as cities and counties, river network and water system, and transportation road networks were obtained from the Data Center for Resources and Environmental Science Data Center (https://www.resdc.cn/ (accessed on 4 July 2023)); (2) ecological reserve data were obtained from the sharing platform of biological specimen resources of Chinese nature reserves (https://www.papc.cn/ (accessed on 4 July 2023)); and (3) 30 m spatial resolution DEM data were sourced from the Geospatial Data Cloud (https://www.gscloud.cn/ (accessed on 4 July 2023)). The data for the geographic elements involved were uniformly processed with the geographic coordinate system of GCS_Krasovsky_1940 and the projection coordinate system of Krasovsky_1940_Albers.

3. Research Methods

3.1. MSPA Ecological Source Identification

MSPA uses the principle of mathematical morphology [37] and was developed by Vogt and other scholars to measure, select, and segment geographical data according to spatial morphology so as to distinguish different landscape types [38]. Using the ArcGIS reclassification tool, paddy fields with woodland, grassland, and water area were set as foreground files (assigned a value of 1), and other land types were set as background files (assigned a value of 2). Using the Guidos Toolbox3.0 software for MSPA analysis, the foreground connection was set to 4, the edge width to 1, the conversion rate to 1, and the opening to 1, ultimately giving seven different types of landscape source types in the study area. According to previous research [39], small, highly fragmented landscape patches lack the basic conditions for material reserves and energy migration. Therefore, this study first statistically analyzed the patch size within the core area and then extracted the ten largest patches as candidates. On the basis of actual geographical conditions, the patch with the highest area ranking was divided into three parts, giving a total of 12 patches. The 12 patches were used as potential ecological source sites for the next steps in the study.

3.1.1. Landscape Connectivity Evaluation

Landscape connectivity is an important indicator for evaluating landscape patterns and ecological function, and it can indicate the overall balance of ecological patches in the study area [40]. In this paper, the landscape coincidence probability index (LCP), the integral index of connectivity (IIC), and the probability index of connectivity (PC) were selected to evaluate the connectivity between patches. To compare the relative importance among patches, the contribution index (dX) was chosen to evaluate the contribution of a patch to the overall landscape connectivity.

3.1.2. Distance Threshold Calculation

Referring to previous studies [41,42], this study adopted the distance gradient method to select the distance threshold. A total of seven different distance thresholds of 50 m, 100 m, 200 m, 500 m, 1000 m, 1500 m, and 3000 m were selected, the connectivity index that corresponded to a probability of 0.5 was calculated using Conefor2.6 software, and the results were compared to determine the optimal distance threshold (

Table 1. Connectivity indices with different distance thresholds.

Distance Threshold	50 m	100 m	200 m	500 m	1000 m	1500 m	3000 m
dPC	15.27	19.67	19.93	19.87	16.98	16.98	20.91
dIIC	11.85	114.78	15.06	15.09	13.71	14.04	15.99
dLCP	14.91	17.77	18.84	19.44	17.75	17.53	19.93
dPC growth rate	0	28.82%	1.34%	−0.29%	−14.57%	0	23.15%
dIIC growth rate	0	24.77	1.87	0.17	−9.13	2.43	13.85
dLCP growth rate	0	19.18	6.03	3.16	−8.71	−1.19	13.68

). It can be seen that the connectivity indices did not increase after the distance threshold reached 500 m; thus, 500 m was adopted as the optimal distance threshold. On this basis, the landscape connectivity index of potential ecological source areas in 2020 was calculated, and core patches with dPC > 2 were used as ecological source areas.

3.2. Extraction of Ecological Corridors Using MCR

3.2.1. Potential Ecological Corridor Extraction

The MCR model was initially developed to identify the diffusion process of species. Since then, it has been widely used in ecological fields to calculate the cost required for the movement of species from source to destination. In the model, the resistance surface reflects the intensity of spatial resistance to ecological flows moving between ecological source sites, and it is also an important basis for constructing ecological corridors [43]. Referring to previous studies [44,45,46], the cumulative resistance values were set between 1 and 90 in this paper (

Table 2. Table of ecological resistance coefficients.

Resistance Layer	Classification/Grading of Resistance Factors	Cumulative Resistance Value	Resistance Weight	Resistance Layer	Classification/Grading of Resistance Factors	Cumulative Resistance Value	Resistance Weight
MSPA Landscape Factor	Core	10	0.5594	Land type	Paddy field	40	0.2969
	Bridge	10			Dryland	50
	Edge	20			With woodland	10
	Islet	20			Remaining woodland	20
	Branch	30			Grassland	20
	Loop	30			Water area	30
	Perforation Background	40 90			Unused land	50
Elevation(h)/m	h ≤ 373	10	0.0939	Slope(i)/°	i ≤ 8	10	0.0498
	373 < h ≤ 666	30			8° < i ≤ 15	20
	666 < h ≤ 959	50			15° < i ≤ 25	40
	959 < h ≤ 1275	70			25° < i ≤ 40	60
	1275 < h < 2171	90			40 < i	80

), and the resistance layer weights were assigned by SPSSPro software using the hierarchical analysis method. Finally, the four resistance layers were superimposed, and the integrated resistance surface was calculated. Then, the minimum cost path from each ecological source site to the other ecological source sites was calculated to identify the potential ecological corridors.

3.2.2. Gravitational Model

The gravitational model can be used to represent the effectiveness of potential ecological corridors and the importance of connecting patches [47]. In this paper, the gravitational force model was used to calculate the interaction forces between each corridor and to classify ecological corridors according to the magnitude of the gravitational force. The model calculation is as follows:

$$F=\frac{L_{max}^{2}ln{a}_{i}ln{a}_j}{L_{ij}^2{p}_i{p}_j}$$

(1)

In the formula: F represents ecological gravity; a_i and a_j are the patch areas of the source and target points; p_i and p_j are the resistance values of the source and source regions; L_ij is the resistance of the corridor between two source regions; L_max is the maximum resistance value in each corridor.

3.3. Hydrological Analysis to Determine the Ecological Node

In this paper, according to the positive and negative terrain comprising the comprehensive resistance surface, the ecological corridors and artificial environment were integrated, and ecological nodes were divided into strategic points and artificial environment points. First, “ridge lines” were identified from the MCR resistance surface, then the counter-topography of the resistance surface was generated. The same procedure was used to calculate “valley lines”. The intersection points between the ecological corridors and the ridge lines were taken as strategic points, which played a fundamental role in controlling the ecological network. The intersection of the main roads and railroads with the valley lines in the Funiu Mountains were artificial environment points, which combined artificial environment and natural elements and required special consideration in ecological construction.

3.4. Ecological Network Structure Evaluation

This study used network connectivity evaluation indicators to conduct an overall evaluation of the ecological network in the Funiu Mountain area [48]. The evaluation indicators included: network closure (α index), node connectivity (β index), network connectivity (γ index), and cost ratio. The α index was proportional to the network liquidity, and its value was 0–1. The β index was directly proportional to the complexity of network connections. The γ index represented the corridor connection ratio between ecological nodes, and its value was directly proportional to node connectivity [49]. The formulas for calculating the indices are as follows:

$$\mathsf{\alpha }=\frac{L-V+1}{2V-5}$$

(2)

$$\mathsf{\beta }=\frac{L}{V}$$

(3)

$$\mathsf{\gamma }=\frac{L}{3\left(V-2\right)}$$

(4)

$$\mathrm{Cos}\mathrm{tratio}=1-\frac{L}{C}$$

(5)

In the formulas: L is the number of ecological corridors; V is the number of ecological nodes; and C is the corridor length.

4. Results and Analysis

4.1. Identification of Ecological Network Sources

MSPA landscape pattern analysis was carried out using the 2020 land use data of the Funiu Mountain area. The final area of landscape elements obtained was 10,347 km² (

Table 3. The proportion of different types of land components in 2020.

Proportion of MSPA Element Area			Proportion of Land Use Type Area
Type	Area/km²	Area Proportion/%	Type	Area/km²	Area Proportion/%
Edge	1153	11.14	Paddy field	40	0.19
Islet	4	0.04	Dryland	6075	28.07
Core	8649	83.57	With woodland	7922	36.60
Loop	12	0.12	Remaining woodland	4579	21.16
Perforation	285	2.75	Grassland	1896	8.76
Bridge	68	0.66	Water area	490	2.26
Branch	176	1.70	Unused land	641	2.96

), of which the core area was 8649 km². Through the landscape connectivity evaluation, nine core area patches were identified as ecological source sites (Figure 2). These were concentrated in the central and northern regions with higher elevations. The source area covered seven county-level administrative regions in the Funiu Mountain area. Less than 10% of the area was in Lushi, Lushan, Nanzhao, and Zhenping counties. Lushi County is a key national ecological protection area and contains the Lushi Giant Salamander Nature Reserve. The reserve is mostly open woodland with tree height less than 2 m and canopy density less than 30%. Under the source site selection conditions set in this study, most areas of the Lushi Giant Salamander Nature Reserve were not included in the selection of ecological source sites. Lushan, Nanzhao, and Zhenping counties had more dry land and construction land and fewer large woodland patches because of their low topography and intense human activities. These conditions resulted in a smaller area of identified ecological source sites within these three counties.

4.2. Ecological Corridor Extraction

A total of 52 potential ecological corridors were obtained by calculating the minimum cost path. After removing lengthy and repetitive corridors, 26 primary corridors (gravity value greater than 0.01) and 8 secondary corridors were determined by combining the force matrix results of the gravity model (

Table 4. Ecological corridor force matrix.

Number	1	2	3	4	5	6	7	8	9
1		0.0439	0.0274	0.0107	0.0061	0.0033	0.0039	0.0037	0.0036
2			0.0771	0.0265	0.0133	0.0050	0.0062	0.0065	0.0066
3				0.0139	0.0106	0.0084	0.0108	0.0098	0.0077
4					0.0168	0.0264	0.0300	0.0618	0.0452
5						0.0190	0.0654	0.0085	0.0142
6							0.0043	0.0053	0.1930
7								0.0056	0.0092
8									0.0704

). The 34 ecological corridors effectively connected various ecological sources, mostly concentrated in the south-central area of Funiu Mountain, involving Songxian County, Luanchuan County, Xixia County, and Neixiang County (Figure 3). In addition, the 34 ecological corridors connected all nature reserves except Lushi Giant Salamander Nature Reserve and played a significant supporting role in protecting regional energy flow in the Funiu Mountain area.

4.3. Ecological Nodes

The identification of ecological source sites and ecological corridors formed the initial framework of the ecological network. The ecological nodes played the role of “stepping stones” to ensure the smooth operation of ecological flows. On the basis of the spatial density of nodes, a total of 32 ecological nodes were chosen in this paper (Figure 3). Among them, 20 strategic points were concentrated in the central part of the Funiu Mountain area, while 12 artificial environment points were distributed around the eastern and northern parts of the Funiu Mountain area. Most of the nodes were located at higher altitudes and were not completely able to maintain ecological stability and construction of the network. However, the strategic points located in the southwest had geographical advantages and a good ecological foundation; thus, the southwest region was a key area for the construction of ecological nodes. The western, eastern, and southeastern regions with smaller ecological source areas had a certain number of artificial environment points that could provide the necessary support for local ecological construction. In addition, strategic points were distributed around most nature reserves, which had a positive impact on consolidating the ecological network structure and maintaining ecological flows.

4.4. Ecological Network Verification

The ecological network constructed for this paper contained nine ecological source sites, 34 ecological corridors, and 32 ecological nodes with different properties. The spatial distribution showed the characteristics of central concentration and surrounding dispersion. The results of the network structure evaluation (

Table 5. Evaluation results of ecological network structure index.

	Number of Corridors	Number of Nodes	α Index	β Index	γ Index	Cost Ratio
Strategic point	34	20	0.4286	1.7	0.6296	0.9737
Artificial environmental points	34	12	1.2105	2.8333	1.1333	0.9737

) showed that the value ranges for the α index were from 0.42 to 1.21, those for the β index were from 1.7 to 2.84, and those from the γ index were from 0.62 and 1.14. These values indicated that the constructed ecological network had high integrity.

In addition, there was a strong spatial overlap between ecological source areas and nature reserves (72.93%, Figure 4). Among them, the overlapping area between the Xiong’er Mountain Nature Reserve and the ecological source areas in the north reached 105 km². This had a positive impact on improving the ecological connectivity of Xiong’er Mountain and promoting the species richness of the ecological network. The Lushi Giant Salamander Nature Reserve, located in the northwest of the Funiu Mountain area, was only the cluster of potential ecological sources, covering an area of 31.25 km², that was not selected. The effect of the original ecological elements in this range was not significant, but the set of ecological nodes was supplemented in a timely manner. The Nanyang Dinosaur Egg Fossil Group Nature Reserve was mainly covered by dryland and did not belong to the core area of land acquisition; thus, the overlap with the ecological source area was only 41.5 km². However, the other ecological sources around it could provide support for its energy flows. The ecological corridors connecting various ecological sources were relatively simple, without unnecessary duplication.

5. Countermeasures and Recommendations

The construction of the ecological network for this paper aimed to improve the integrity of patches, strengthen the construction and protection of ecological source sites, enhance the connectivity of ecological corridors, cultivate the transition and connection function of ecological nodes, and improve the ecological network structure. Because of the high topographic relief of the Funiu Mountain area and the complexity of the land use composition elements within each county-level administrative area, the recommendations in this paper are divided into the overall Funiu Mountain area and county recommendations. In addition, in the actual eco-construction, not only to take into account the future land use changes in Funiu Mountain under the urbanization process but also the different policies of the local government in different areas need to be adjusted in conjunction with the local planning policies.

The ecological network elements in the Funiu Mountain area are all at high altitudes, which makes the construction slightly more difficult. In the central and northern parts of the Funiu Mountains, where ecological source sites are concentrated, the development scale of construction land should be controlled to reduce the negative impact of human activities on high-value ecological areas. In the south and west, where there are fewer ecological source sites, the local ecosystem service functions should be sustainably used to enhance the overall ecological value system of the region in an orderly manner. Priority should be given to the construction of the proposed 26 primary corridors and to the protection and enhancement of energy flow channels between important ecological regions. For the construction of artificial environment points in the eastern and western fringes of the Funiu Mountain area, attention should be paid to the problems of ecological stress and coordination among ecological elements during human activities. In relation to the construction of strategic points in the central part of the Funiu Mountain area, attention should be paid to the ecological carrying value of the points as the intersection of two corridors.

Likewise, the construction of ecological elements should be considered in combination with nature reserves. Response measures should be taken according to the characteristics of the nature reserves themselves and the environmental elements of the region in which they are located. The Lushi Giant Salamander Nature Reserve lacks an identified ecological source; there is an urgent need to improve the woodland quality and its landscape connectivity. In contrast, for the Nanyang Dinosaur Egg Fossil Group Nature Reserve, it is inappropriate to increase forest land as a means of restoration. The Xiong’er Mountain Nature Reserve, Baotianman Nature Reserve, Funiu Mountain Nature Reserve, and Xixia Giant Salamander Nature Reserve should focus on the conservation of the ecological environment and reduce human activity. The Turtle River Wetland Nature Reserve has a greater focus on protecting the water environment.

6. Discussion and Conclusions

6.1. Discussion

This study used multiple econometric methods to conduct research on the core content, but there were some limitations that are discussed below.

In the foreground settings of MSPA, there are some differences in the basis of site classification in different studies. For example, Xu Feng and other scholars [50] took only woodland landscapes as the foreground in their study of Bazhong Western New District. Cheng Wenqing, while other scholars [51] took only woodland and water as foreground elements in the study in the Su-Xi-Chang Region. In contrast, there were large areas of contiguous woodlands in the Funiu Mountain area, and it was impossible to segment the source sites and conduct subsequent studies without detailed classification. Therefore, to distinguish the relative values in the eco-region, after several experiments, this paper finally selected woodland as the foreground file and the other forested land as the background file, which was more suitable for the geographical characteristics of the Funiu Mountain area.

In the selection of distance thresholds, most studies use the growth rate method to determine the optimal distance thresholds, and there is bound to be a slight difference between the results and the true values. Different methods and purposes of distance threshold selection can produce large differences in the results. For example, Chen Nannan and other scholars set a distance threshold of 380 km from the perspective of species migration in their research in the Qinling Mountains of Shaanxi [52]. In Yao Caiyun’s research [53] on the Three Gorges Reservoir Area, the optimal distance threshold was set at 1 km. The purpose of selecting the distance threshold was to determine whether landscape connectivity meets a specific standard. In this study, after the 500 m threshold interval, the index no longer increased. This indicated that the goal of determining whether the connectivity of the region was feasible had been achieved. Therefore, the 500 m distance threshold determined in this paper had a practical value for the ecological conditions of Funiu Mountain.

On the question of how to reasonably select ecological source sites to cover the nature reserves, some studies [49,54] directly used nature reserves as the ecological source sites of their study area for subsequent analysis. Ecological source sites are selected considering connectivity and internal element composition, while the scope of nature reserves considers complex factors such as biodiversity, soil and water conservation, land importance, and ecological sensitivity. In this paper, the ecological network was constructed using land use data, and then it was compared with local nature reserves for analysis and verification.

This study used 30 m precision land use data, which was satisfactory for the classification of site types. However, if higher precision land use data were used, more accurate results would be obtained for identification. Furthermore, the ecological grid construction using the 2020 land use data in this paper lacked the use of simulated land use data to explore future patterns. In addition, in a future study, the ecological network will be constructed using nature reserves directly as ecological source sites and the ecological network constructed by considering connectivity and internal element composition in this paper will be compared and analyzed in detail to explore the differences and ecological spatial patterns between the two approaches. Future ecological network research needs to consider how to improve the identification of ecological source areas; although different identification methods may lead to different results, for different region, programs need to be adapted to the local conditions; at the same time, the selection of ecological corridors should be considered in conjunction with urban construction.

6.2. Conclusions

In this study, we chose the Funiu Mountain area, where the conflict between urban expansion and ecological environmental protection continues to intensify, as a case study, and constructed MSPA, MCR, and gravity models to spatially identify ecological source sites, ecological corridors, and ecological nodes, respectively, and to structurally evaluate the constituted ecological network using network connectivity. We compared the ecological network with nature reserves and finally proposed corresponding measures to counter the conflict. The research results showed that:

(1)

There were nine ecological source sites in the Funiu Mountain area, most of which were concentrated in the dense woodlands of the central and northern areas and had a high spatial overlap with local nature reserves.

(2)

There were 34 ecological corridors, mostly concentrated in the central and southern parts of the Funiu Mountain area, which could provide basic channels for material circulation among all the ecological source sites and some nature reserves. Among them, 26 primary corridors were wrapped around the periphery of the ecological source areas in the form of a skeleton, while 8 secondary corridors connected the internal areas of the ecological source areas.

(3)

There were 32 ecological nodes, among which 20 strategic points were scattered along the ecological corridors, and 12 artificial environment points were scattered in the low-lying areas around the nature reserves.

(4)

The results of the structural evaluation of the network indicated that the constructed ecological network had strong integrity. The ecological network played an important functional support role in improving regional ecological construction, maintaining the stability of energy flows, and cultivating the carrying capacity of nodes.