Zoning and Management of Ecological Restoration from the Perspective of Ecosystem Service Supply and Demand: A Case Study of Yuzhong County in Longzhong Loess Hilly Region, China

Abstract

The loess hilly region is a typical ecologically fragile and sensitive area. It is of great significance when measuring the balance between supply and demand of ecosystem services and clarify the relationship between supply and demand of ecosystem services for scientific ecological restoration zoning and realizing regional ecological security and social and economic sustainable development. We take Yuzhong County in the loess hilly region of Longzhong, China as an example; by constructing the matching and coordinating relationship between ecosystem service supply and demand and following the idea of “problem diagnosis—strategic orientation—key optimization”, this paper delimits the ecological restoration zones and proposes corresponding governance strategies. The results show that: (1) The supply and demand of ecosystem services were mainly at a low and medium level, with significant spatial heterogeneity. Overall, the spatial pattern of ecosystem services showed high supply and low demand in the southwest mountainous areas and showed low supply and high demand in the urban gully areas of Yuzhong. (2) There were four types of spatial matching of ecosystem service supply and demand: HH type, LH type, LL type, and HL type. The local spatial autocorrelation of supply and demand was dominated by high-low or low-high spatial misadjustment. The average degree of coordination between supply and demand of ecosystem services was 0.629, indicating that supply and demand were basically coordinated. (3) The ecological restoration zones in Yuzhong County can be divided into six categories: the ecological core protection area, ecological potential restoration area, key ecological restoration area, soil and water conservation restoration area, ecological agriculture development area, and ecological innovation promotion area. The results of this study can provide ideas for the refined management and targeted restoration practice of regional ecosystem services. It provides a strong guarantee for ecosystem management and decision-making in the loess hilly region.

1. Introduction

Ecological and environmental issues are one of the hot topics in the world [1,2]. Since the Industrial Revolution, human activities have greatly interfered with the natural ecological environment, resulting in changes to the relationship between man and the land. In particular, unreasonable human activities have led to the continuous deterioration of the ecological environment, which has limited the sustainable utilization of natural resources and the sustainable development of economic society to a certain extent [3,4]. It is necessary to understand and deal with the relationship between human activities and natural ecosystems to solve the increasingly serious ecological and environmental problems and gradually achieve the goal of sustainable development. To carry out ecological restoration and protection through natural or human intervention, managers at all levels should actively identify key areas of ecological restoration and protection [5], restore damaged and degraded ecosystems, and protect high-quality ecological spaces [6,7].

Ecological restoration zoning is an important prerequisite for the implementation of spatial regulation of various ecological restoration projects and the implementation of differentiated spatial management in practice [8,9,10]. A scientific and reasonable zoning scheme can improve the pertinence and targeting of ecological restoration [11]. The aim of national land ecological restoration is to realize the benign and healthy development of the ecosystem and the ecological security of the regional landscape through the adjustment and optimization of land elements and their spatial structure, the restoration and improvement of ecological functions, or the self-regulation and restoration of the ecosystem on a regional or national scale [12]. In recent years, scholars have carried out a series of ecological restoration research studies and practices on a single element such as forest, grassland, mine, and farmland [13,14]. The most frequently restored elements are forest, shrubland, and grassland. The quality of a forest, shrub, or grassland area is characterized by the quality of the ecosystem [15,16,17]. Some scholars have focused on a single function, such as biodiversity and ecological sensitivity [18,19,20], and carried out restoration of the natural reserve system, habitat degradation, soil erosion, and land desertification [21,22]. However, the existing literature does not take into account the systematization and completeness of the ecological restoration of a land space, which leads to an insignificant improvement in the quality and services of the overall ecosystem in a region. On the basis of scientifically analyzing the regional ecological environment and systematically identifying regional ecological problems, scholars have constructed a multi-element and multi-function evaluation index system [23,24], and have proposed combining ecosystem service functions with ecological restoration [23,25,26]. This shows the systematization and completeness of ecological restoration, and has achieved good results, laying an important foundation for identifying and solving existing ecological problems in a region and guiding the implementation of restoration projects [27,28].

Ecological restoration is the key to the improvement of ecosystem services, and the improvement of ecosystem services is one of the goals of ecological restoration [29,30]. Ecological restoration involves the ecological conservation, cultivation, restoration, management, and reconstruction of national land space through protection, improvement, guidance, optimization, reshaping, etc. [31,32,33]. Ecological restoration not only changes the elements (such as vegetation, soil, water, microclimate, etc.), structure, land use combination, and spatial pattern of an ecosystem, but also affects the gains and losses of a regional ecosystem service and the sustainability of value supply [34,35]. As a link connecting the structure, process, function, service of the ecosystem and the demand and well-being of the social system, the ecosystem service is considered to be an important tool to measure the relationship between human activities and ecosystem functions, and to support the optimal management of ecosystems [26,36]. Changes in the gain and loss of ecosystem services and the supply–demand balance cause different stakeholders in land management to make trade-offs, assessments, adjustments, and controls [37,38,39]. In the process of obtaining various ecosystem services, scholars weigh and optimize ecosystem services according to the social demand, the goal of land consolidation and restoration, and the supply–demand of ecosystem services, thereby subtly affecting the direction, goal, planning and design, and zoning layout of ecological land restoration [40,41].

It is necessary to carry out this case study on the spatial zoning of ecological land restoration in typical regions based on the supply and demand of ecosystem services and spatial matching. Yuzhong County is located in the hilly region of the Loess Plateau in China. It is a typical ecologically sensitive and fragile region in the northwest inland area of China with a fragile ecological environment and a unique landform type of the Loess Plateau. This has caused a series of ecological and environmental problems, such as drought and fragmentation of the land surface, serious degradation of land ecosystems, and significant regional differences in ecosystem services. It has seriously affected the quality of the ecological environment and the function of ecosystem services. Most of the existing literature considers ecological zoning restoration in terms of administrative units. However, there are very few studies conducted on a finer grid scale. Therefore, this paper uses a grid as the evaluation unit to measure and analyze the spatial differentiation characteristics, matching types, and the degree of correlation of ecosystem service supply and demand, coupling the ecosystem and the economic system in Yuzhong County in 2020. Based on the supply and demand balance of ecosystem services, we carried out ecological restoration zoning and proposed differentiated governance strategies. This aims to provide a theoretical basis for the differentiated and refined management and practice of ecological restoration in loess hilly regions in China.

2. Study Area and Data Sources

2.1. Study Area

Yuzhong County is located between 103°49′15″ E~104°34′4″ E and 35°34′2″ N~36°26′3″ N, which is the intersection of the Loess Plateau and the Qinghai-Tibet Plateau and three natural areas in China. It is located in the eastern suburb of Lanzhou, the provincial capital in the central part of Gansu Province and is the eastern gateway of Lanzhou. The county is about 37 km away from the main urban area of Lanzhou; the railway runs between the cities in the county and expressways cross from city to city, with a well-developed traffic system (Figure 1). At the end of 2020, Yuzhong County had jurisdiction over 20 towns and 268 administrative villages. The elevation of the county is between 1480 m and 3670 m, and the total area of the county is 3302 km².

As a representative region of the Longzhong loess hilly region, Yuzhong County is a typical area with a fragile ecological environment. The county terrain is broken, hilly and rugged, and the geographical environment is very special. The southern rocky mountain area is an eastward extension of the Qilian mountain range. Along the county boundary, there are two mountain ranges, the Maxian mountains and the Xinglong mountains. This area is the main forest and grassland area of the county with abundant precipitation and dense vegetation. It is also an important ecological barrier, undertaking multiple ecological functions, such as water conservation and biodiversity protection within the city. The central gully is an area of urban, industrial, and agricultural development. It is an interleaved area of complex systems and diverse ecology, and it is also a key area for the optimization and development of the ecosystem. In the loess plateau region of northern Longzhong, precipitation is scarce, vegetation cover is low, and the ecological environment is fragile, which is the main difficulty when it comes to ecological restoration in the region. The fragile ecological environment and the unique landform type of the Loess Plateau have resulted in a series of ecological and environmental problems, such as arid and broken surfaces, serious degradation of the land ecosystem, and great differences between ecosystem service regions, which have seriously affected the quality of the ecological environment and the play of ecosystem service functions. For such ecologically fragile areas, more attention should be paid to ecological security construction and ecological restoration.

2.2. Data Sources

The data of this study mainly come from the following four aspects. (1) Natural geographic data: digital elevation model (DEM) data was taken from the geospatial data cloud platform (http://www.gscloud.cn/, accessed on 22 September 2022); land use data was taken from the Resource and Environment Science and Data Center of the Chinese Academy of Sciences (https://www.resdc.cn/, accessed on 20 August 2022); soil data was taken from the China Soil Dataset (http://westdc.westgis.ac.cn/, accessed on 25 August 2022); precipitation and temperature data were taken from Gansu Provincial Meteorological Bureau; potential evapotranspiration data was taken from the National Earth System Science Data Center (http://www.geodata.cn, accessed on 16 September 2022). (2) Night light data was taken from the National Qinghai-Tibet Plateau Scientific Data Center (http://data.tpdc.ac.cn/zh-hans/, accessed on 8 August 2022). (3) Socioeconomic data: population, GDP, and other data were taken from the Resource and Environment Science and Data Center of the Chinese Academy of Sciences (http://www.resdc.cn/, accessed on 20 September 2022). (4) Basic base map data: the vector administrative boundary of Yuzhong County (1:250,000) was taken from the Gansu Provincial Bureau of Surveying and Mapping; road data was taken from the website of the National Basic Geographic Information Center.

Due to the multi-precision, multi-source, and multi-scale characteristics of the acquired data, different data sources and different data acquisition methods have different mathematical foundations and precision of the same elements. Therefore, to ensure the unity and precision of the data, we processed the data with coordinate unification, projection transformation, geometric correction, and standardization using ArcGIS10.5. Then, all the data were processed at a resolution of 100 m × 100 m. According to the natural environment of Yuzhong County, we constructed 500 m × 500 m, 1 km × 1 km, 2 km × 2 km grids as pre-selected evaluation units based on the existing literature. We finally determined 13,153 grids with a size of 500 m × 500 m as the evaluation unit using analysis tools, such as ArcGIS 10.5 software, Create Fishnet, Dissolve, Clip, Merge, etc. Then, we used this as the research unit to study the zoning and governance path of ecosystem restoration in Yuzhong County.

3. Methods

3.1. Research Concept

Ecosystem service supply refers to the ability of ecosystems to provide related products and services for human and social development within a certain time and region [42]. Ecosystem service supply is one of the goals of ecological land restoration and zoning and is also the ecological basis for ensuring regional social and economic development. Ecosystem service demand refers to the demand area of the ecosystem service flow from which human beings benefit from ecosystem services. In other words, the ecosystem services provided by the supply area depend on some medium and are transmitted along a certain direction and path by human society, which is consumed, used, or desired [27,43,44], and is the potential driving force and direction of social development and land consolidation. The formation of ecosystem services is very complex, and the differences in the definition of service entities are largely due to different understandings of the process. The ecosystem is the starting point of service formation. The inherent components and structures of an ecosystem, as well as the processes and functions formed by their interactions (biological, physical, and chemical) [45], are the basis for an ecosystem to provide a variety of services. Ecosystem processes and functions are often regarded as synonyms [46,47], but compared with ecosystem processes, ecosystem functions imply certain purposes [48], such as atmospheric regulation, flood regulation, pest control, etc., which are often mentioned. Ecosystem processes and functions form services after adding human value orientation. Services are the intermediary between ecosystems and human well-being. Their existence depends on the supply of nature, but also reflects human value orientation, which is the basis of realizing human benefits. The benefits generated by the combination of ecosystem services and human inputs constitute human well-being [49]. Ecosystems provide products and services to humans, and human beings have demand and consumption for the products and services of the ecosystem. This forms the supply and demand relationship of ecosystem services. Suppliers and demanders jointly form a dynamic process in which ecosystem services flow from natural ecosystems to human social systems [43,44]. The relationship between supply and demand is an important indicator that reflects the balance (the matching of supply and demand—carrying capacity) and the coordination (the coordination degree of supply and demand—sustainability) of the regional “ecological system” and “socioeconomic system”.

However, there are obvious differences and dislocations in the supply and demand of ecosystem services in regional spaces [39,50,51]. This mainly includes the imbalance between total supply and demand and space allocation. This will lead to a decline in the sustainable supply capacity of ecosystem services, the waste and unfair distribution of green resources, and will affect human well-being [52]. Spatial differentiation, supply–demand matching, and the zoning of ecosystem services are the basis for constructing models and approaches for regional ecological land restoration [53,54,55], and are prerequisites for the sustainable use of land resources. Based on the concept of building a live community of “mountains, rivers, forests, fields, lakes, grass and sand” [56], we evaluated the supply and demand of ecosystem services in Yuzhong County in 2020. Then, we analyzed the correlation and coupling mechanism of these two elements and clarified the balance between supply and demand and spatial features [31,57]. This indicates the interaction mechanism between the ecological restoration of a land space and ecosystem services. We put forward an ecological restoration model for the national land and implementation strategies and measures based on ecosystem services. These can adjust the imbalance between supply and demand, build a safe spatial pattern of the national land, and improve ecosystem services and sustainable regional development (Figure 2).

3.2. Calculation of Ecosystem Service Supply and Demand

3.2.1. Calculation of Ecosystem Service Supply

The Common International Classification of Ecosystem Services (CICES) divides ecosystem products and services into three categories, namely: supply services (materials, energy, etc.); regulation and maintenance services (restoration and regulation of the biophysical environment, regulation of the physical and chemical environment, etc.); and cultural services (physical or experiential utilization of ecosystems, etc.) [58]. Due to the special geographical environment—such as the arid climate, serious soil erosion, sparse vegetation, and broken surface in the Longzhong loess hilly region, which is greatly affected by precipitation, landform, climate change, and biodiversity—we finally selected water yield service, soil conservation service, carbon storage service, and habitat quality as the guidance for the assessment of the current status of ecosystem service supply in Yuzhong County. Based on the InVEST model, we selected four types of ecosystem services: water yield service, soil conservation service, carbon storage service, and habitat quality service, using the Water Yield module, Sediment Delivery Rate module, Carbon Storage module, and Habitat Quality module to assess the ecosystem health status of Yuzhong County (

Table 1. The calculation of ecosystem services based on the InVEST model.

Ecosystem Services	Formula	Variables
Water yield	$Y_{xj}=(1-\frac{{AET}_{xj}}{P_x})\times P_x$	Yxj represents the water yield of the xth grid of land use type j (m3·hm−2); AETxj represents the annual actual evapotranspiration of the xth grid of land use type j (mm); Px represents the average annual precipitation of the xth grid (mm); Rxj represents the aridity index of the xth grid of land use type j; wx represents the available water content of vegetation.
	$\frac{AET\left(x\right)}{P\left(x\right)}=\frac{1+w_x{R}_{xj}}{1+w_x{R}_{xj}+\frac{1}{R_{xj}}}$
Soil conservation	${SC}_i={RKLS}_i-{USLE}_i$	SCi is the soil holding capacity; RKLSi is the potential erosion; USLEi is the actual erosion; Ri is the rainfall erosivity factor; Ki is the soil erodibility factor; LSi is the slope length factor; Ci is the vegetation cover management factor; Pi is the soil and water conservation measure factor.
	${RKLS}_i=R_i\times K_i\times {LS}_i$
	${USLE}_i=R_i\times K_i\times {LS}_i\times C_i\times P_i$
Carbon storage	$C_{total}=C_{above}+C_{below}+C_{soil}+C_{dead}$	Ctotal is the total carbon storage; Cabove is the aboveground carbon storage; Cbelow is the underground carbon storage; Csoil is the soil carbon storage; Cdead is the carbon storage of dead organic matter. The unit is t·hm−2.
Habitat quality	$Q_{xj}=H_j[1-(\frac{D_{xj}^2}{D_{xj}^2+K^2}\left)\right]$	Qx represents the habitat quality of the xth patch of land use type j; $D_{xj}^2$ represents the habitat stress degree of the xth patch of land use type j; Hj represents the suitability of the habitat; K2 is the half-saturation constant.

). The parameters of the biophysical properties of the model were taken from existing studies of the loess hilly region [59] and Yuzhong and its surrounding regions [60]. The results of the four ecosystem services were normalized and superimposed with equal weights to obtain the evaluation index of ecosystem service supply in Yuzhong.

3.2.2. Calculation of Ecosystem Services Demand

Four types of indicators, including population density, per area GDP, nighttime light brightness, and land-use intensity, were selected to indicate the state of economic and social activities in the region and represent the ecosystem services demand [61]. The greater the value of the four types of indicators, the lower the ecosystem service supply, and the greater the ecosystem service demand. Due to significant differences in the spatial distribution of population, economy, and nighttime light brightness, we used the natural logarithm method to eliminate its local violent fluctuation.

$$Y_i=X_1+lg{X}_2+{lgX}_3+lg{X}_4$$

(1)

where Y_i represents the total ecosystem services demand of unit i; X₁ represents the intensity of land use and development; X₂ represents the population density (people·km⁻²); X₃ represents the per area GDP (yuan·km⁻²); and X₄ represents the average nighttime light brightness of units (nW·cm⁻²·sr⁻¹). If the nighttime light and per area GDP were 0, their values were directly taken as 0 without logarithm.

3.3. The Relationship between Ecosystem Services Supply and Demand

3.3.1. Matching the Relationship between Supply and Demand for Ecosystem Services

We standardized the supply and demand of ecosystem services using the z-score of the variance and conducted a corresponding analysis of supply and demand to indicate the carrying capacity of regional ecosystems [54]. The x-axis represents the standardized supply of ecosystem services. The y-axis represents the standardized demand of ecosystem services [8]. The supply–demand matching relationship was divided into four state quadrants: high supply–high demand (HH, quadrant I); low supply–high demand (LH, quadrant II); low supply–low demand (LL, quadrant III); high supply–low demand (HL, IV quadrant) [62] (Figure 3).

$$x=\frac{x_i-\stackrel{-}{x}}{S}$$

(2)

$$\stackrel{-}{x}=\frac{1}{n}{\sum }_{i=1}^n{x}_i$$

(3)

$$S=\sqrt{\frac{1}{n}{\sum }_{i=1}^n(x_i-\stackrel{-}{x})}$$

(4)

where x is the standardized value of the supply and demand of the four ecosystem services; x_i is the actual supply or demand of the ith grid; $\stackrel{-}{x}$ is the average value of the actual supply or demand of the whole county; S is the standard deviation; and n is the number of units.

The bivariate Local Indicators of Spatial Association (LISA) can reflect the degree of correlation and spatial aggregation between the attribute value of a spatial unit and the same attribute value of its adjacent spatial unit [63]. We can reveal the spatial matching patterns of supply and demand for various ecosystem services through visual LISA diagrams.

$${LISA}_i=\frac{1}{n}\frac{(x_i-\stackrel{-}{x})}{\sum _i{(x_i-\stackrel{-}{x})}^2}\sum _j{w}_{ij}(x_j-\stackrel{-}{x})$$

(5)

where LISA_i is the bivariate local spatial autocorrelation index; w_ij is the spatial weight matrix between unit i and unit j; i represents the ith unit; j represents the adjacent jth unit; x_i and x_j are the values (attributes) of adjacent paired spatial units; $\stackrel{-}{x}$ is the average attribute value; and n is the total number of units. If LISA > 0, the service balance degree of the spatial unit is a spatial aggregation of high–high or low–low. If LISA < 0, the service balance degree of the spatial unit is a spatial aggregation of high–low or low–high.

3.3.2. Coordination Relationship between Supply and Demand of Ecosystem Services

We constructed a coordination index for ecosystem service supply and demand to evaluate the ecosystem sustainability. According to the physical and geographical characteristics, socio-economic status, and spatial planning of Yuzhong County, we discussed the spatial zoning of ecological restoration and the proposed restoration and governance strategies for different areas [64].

$$D=\sqrt{C\times T}$$

(6)

$$C=\sqrt{\frac{P_s{\times P}_d}{{\left[(P_s+P_d)/2\right]}^2}}$$

(7)

$$T=\alpha P_s+\beta P_d$$

(8)

where D is the degree of coordination, D ∈ [0, 1]. The greater the D, the better the coordination between the supply and demand of ecosystem services in the region; C is the degree of coupling; T is the comprehensive index. We separately normalized the supply and demand of unit ecosystem services to eliminate the impact of dimensions. P_s represents normalized supply; P_d represents normalized demand; $\alpha$ and $\beta$ are the weight coefficients of supply and demand, respectively. Supply and demand for ecosystem services are equally important in restoration zoning, and we set α = β = 0.5. Then, we determined the degree of coordination according to the natural breakpoint method (high misadjustment, mid misadjustment, basic coordination, moderate coordination, high coordination).

To sum up, we analyzed and discussed the degree of spatial aggregation, matching characteristics, and coordination correlation of regional ecosystem services supply and demand through LISA, as well as the degree of coordination between ecosystem services supply and demand [60].

3.4. Logical Framework for Ecological Restoration Zoning and Strategies

Based on the analysis of the relationship between supply and demand of ecosystem services in Yuzhong County, the regional spatial development strategy was summarized according to the spatial distribution characteristics, matching types, and coordination degree of supply and demand of ecosystem services, and the regional status quo, according to the Master Plan of Territorial Space of Yuzhong County (2021–2035) and other relevant documents. In combination with the geographical environment, land use status, and ecological function regionalization of Yuzhong County, the status quo of natural resources and industries in the region was identified and diagnosed. Following the idea and method of “problem diagnosis—strategic orientation—key optimization”, GIS spatial analysis technology was used to view ecological restoration, governance, and regional development. The ecological restoration area in Yuzhong County was divided into six types: an ecological core protection area, ecological potential restoration area, key ecological restoration area, soil and water conservation restoration area, ecological agriculture development area, and ecological innovation promotion area. The corresponding management strategies are proposed according to the different ecological restoration zones (Figure 4).

4. Results

4.1. Analysis of the Pattern of Ecosystem Service Supply

The status of ecosystem services supply in Yuzhong County was classified into five levels using the quantile method. There were significant spatial pattern differences in the supply of different types of ecosystem services (Figure 5). Among them, the water yield service gradually decreased from south to north. The overall level was low, and the average value was 65.187 mm. The proportion of grids with values greater than the average was 35.6%. The high-value areas were mainly distributed in the south of Yuzhong, and the low-value areas were mainly distributed in the north of Yuzhong (Figure 5a). The carbon storage service showed a spatial pattern which was low in the center and high in the surrounding area. The overall level was high with an average value of 64.513 t. The proportion of grids with values greater than the average was 67.0%. High-value areas were mainly distributed in the southwest of Yuzhong County and other surrounding areas. Low-value areas were mainly distributed in densely populated areas, such as central urban areas (Figure 5b). The soil conversation service showed a spatial pattern which was high in the southwest and low in the center. The overall level was low with an average value of 101.118 t. The proportion of grids with values greater than the average was 30.0%. The high-value areas were mainly distributed in the southwest of Yuzhong. The low-value areas were mainly concentrated in Chengguan Town, etc. (Figure 5c). The spatial pattern of habitat quality was similar to that of carbon storage services. The overall level was medium-high with an average value of 0.547. The proportion of grids with values greater than the average was 54.5%. The high-value areas were mainly distributed in the southwest, central and northeast of Yuzhong. Low-value areas were mainly distributed in densely populated areas, such as central urban areas (Figure 5d). The supply of integrated ecosystem services in Yuzhong County showed a spatial pattern that was high in the southwest and low in the center. The overall level was mainly low-medium. The average value of the ecosystem service supply was 0.349. The proportion of grids with values greater than the average was 48.9%. The high-value areas were mainly distributed in the rocky mountain area in the southwest of Yuzhong. The low-value areas were mainly distributed in the alluvial plain area in the central part and the loess hilly and gully areas in the northeast. The ecosystem service supply in the northeast region was weak (Figure 5e).

4.2. Analysis of the Pattern of Ecosystem Service Demand

Both population density and per area GDP showed a spatial pattern which was high in the south and low in the north. The high-value areas were mainly distributed in the southwest, especially the area around Chengguan Town. The low-value areas were mainly distributed in the northeast (Figure 6a,d). The nighttime light brightness and the land-use intensity showed a spatial pattern which was high in the center and low in the north and south. The high-value areas were mainly distributed in Chengguan Town in the central urban area and towns near the urban area of Lanzhou. The low-value areas were mainly distributed in the southwest and northeast (Figure 6b,c). The comprehensive ecosystem services demand showed a spatial pattern which was high in the central area and low in the north. The overall level was mainly low and medium with an average value of 2.365. The proportion of grids with values greater than the average was 37.9%. It showed a “center–periphery” circle distribution pattern, that is, a decreasing trend from the center to the periphery(Figure 6e).

4.3. Correlation Analysis of the Matching of Ecosystem Service Supply and Demand

4.3.1. Matching Relationship between Supply and Demand of Ecosystem Services

There are certain quantitative and spatial differences in the matching relationship between the supply and demand of ecosystem services in Yuzhong County based on quadrant distribution (Figure 7a,b). In terms of quantity, it can be roughly classified into four matching types: the spatial matching type of high supply-high demand (HH, 2119 grids); the spatial misadjustment type of low supply-high demand (LH, 2866 grids); the spatial matching type of low supply-low demand (LL, 3898 grids); and the spatial misadjustment type of high supply-low demand (HL, 4270 grids) (Figure 7a). Spatially, the supply and demand of ecosystem services was negatively correlated in a Pearson correlation coefficient analysis. In addition, the bivariate local spatial autocorrelation of ecosystem service supply and demand was performed using Geoda software. Moran’s I value was −0.337. At a 95% confidence level, 8080 grid units represented significant spatial agglomeration, and 5073 grid units was non-significant. There was a significant aggregation between the supply and demand of ecosystem services in most grid units. Except for insignificant regions, LH agglomeration and HL agglomeration accounted for 28.2% and 27.0%, respectively. HH agglomeration and LL agglomeration accounted for 8.9% and 35.3%, respectively. The spatial autocorrelation of the matching of ecosystem service supply and demand was dominated by the spatial agglomeration of LL or LH. The proportion of spatial misadjustment was greater than that of spatial matching (Figure 7b,c).

4.3.2. Coordination Degree of Supply and Demand of Ecosystem Services

According to the natural breakpoint method, the degree of coordination between supply and demand for ecosystem services was classified into five types (Figure 8). The average index of the coordination degree of ecosystem services supply and demand in Yuzhong County was 0.629. This indicated that the relationship between the ecosystem services supply and human demands was coordinated, and ecosystem services were sustainable. The coordination degree of supply and demand for ecosystem services showed a spatial distribution pattern which was high in the southwest and low in the northeast. Among them, the proportion of highly coordinated areas accounted for 16.0%, the proportion of moderately coordinated areas accounted for 26.7%, the proportion of basic coordinated areas accounted for 31.2%, the proportion of mid misadjusted areas accounted for 29.3%, and the proportion of high misadjusted areas accounted for 1.8%.

4.4. Ecological Restoration Zoning Results and Governance Strategies

According to “problem diagnosis—strategic orientation—key optimization”, GIS spatial analysis technology (overlay analysis) was used to divide the ecological restoration areas of Yuzhong County into six types: an ecological core protection area, an ecological potential restoration area, a key ecological restoration area, a water and soil conservation restoration area, an ecological agriculture development area, and an ecological innovation promotion area (

Table 2. Ecological restoration zoning in Yuzhong County based on “problem diagnosis—strategic orientation—key optimization”.

Status Quo Features	Strategic Orientation	Supply and Demand Matching /Coordination Relationship	Restoration Zoning	Proportion
The proportion of ecological protection red lines is high; there were many nature reserves including the Xinglong Mountain National Nature Reserve; the proportion of the planting industry and tourism industry was high.	The strategy should be guided by ecological priorities and green development, promote the ecological restoration of the Nanshan water conservation ecological area in the south, the rural ecological function area in the central area, the comprehensive management of the Wanchuan River Basin, and water and soil conservation management in the Beishan water and soil conservation ecological function area in the north.	HL/HC + HL/MC	Ecological core protection area	10.3%
The terrain was flat and the urbanization process was fast; the proportion of construction land is high; the population density is high; the vegetable, transportation, and logistics industries are developed.		LH/HC +LH/MC + LH/BC	Ecological potential restoration area	20.2%
Some areas were adjacent to downtown Lanzhou, had a high population density and developed secondary and tertiary industries. Some areas are located in the Wanchuan River Basin in the center and in the Yellow River flows in Qingcheng Town in the north.		LH/HM + LH/MM	Key ecological restoration areas	1.6%
The overall altitude is high; the proportion of areas prone to geological disasters is high; the loess hilly and gully areas have serious water and soil erosion; the proportion of cultivated land is high, but the quality is poor.	The strategy should take the water and soil erosion area in the northern mountainous area as the key area for sloping farmland improvement, combining this with water and soil erosion control, improving the quality of the ecological environment, and guiding the adjustment of agricultural structures.	HL/HM + HL/MM + LL/HM + LL/MM	Soil and water conservation restoration area	25.3%
With traditional agriculture as the leading industry, the proportion of cultivated land is high, the geological conditions are good.	The strategy should propose high-standard farmland construction and guidelines for land consolidation projects, improve the quality of cultivated land, and develop modern ecological and efficient agriculture practices.	HL/BC + LL/BC	Ecological agriculture development areas	26.5%
The proportion of ecological land is high; the population density and economic development are at the upper-middle level of Yuzhong County; the industry was dominated by breeding.	The strategy should develop modern urban service-oriented agriculture practices, and accelerate the construction of characteristic economic forests in the central mountain region.	HH/HC + HH/MC	Ecological innovation promotion areas	16.1%

and Figure 9). Then, we proposed different governance and optimization strategies for the different areas.

4.4.1. Ecological Core Protection Area

Ecosystem services showed a spatial distribution pattern of “high supply-low demand” with “supply and demand coordination”. This area is mainly distributed in the southwest of Yuzhong County, accounting for 10.3% of the total area. This area should focus on conservation and the maintenance of ecosystem service functions, take its resource advantages to moderately develop ecological industries and improve the demand side, and adopt the strategy of “constraints on ecological protection red lines + tourism-based ecological economy”. The ecological protection red line area should prohibit development and construction, and focus on strengthening the protection and restoration of water conservation forests, the construction and management of forest nature reserves, and the construction of biological corridors, thereby strengthening habitat connectivity and improving forest quality. The general ecological area can develop an underforest economy and ecotourism by formulating regional access conditions.

4.4.2. Ecological Potential Restoration Area

Ecosystem services showed a spatial distribution pattern of “low supply-high demand” with “supply and demand coordination”. This area is mainly distributed in the towns of Heping, Dingyuan, Lianta, Chengguan in the center of Yuzhong, and Qingcheng in the north, accounting for 20.2% of the total area. The area should focus on ecological improvement, ecological restoration and the improvement of ecosystem service functions, improve the supply side, strictly control the demand side, and adopt the strategy of “urban development boundary constraints + ecological improvement projects + dynamic monitoring of land use growth”. First, by building an urban ecological network, we should improve the urban green infrastructure and corridor landscapes in urban areas, increase the area of parks and green leisure spaces, increase vegetation coverage, expand ecological land space (such as green leisure spaces and parks), and improve the soil conservation service, carbon stroage service, and habitat quality. Second, we should save land and develop it intensively, strictly control the disorderly growth of urban space, and regularly and dynamically monitor the scale and shape of construction land. We should avoid the encroachment of ecological space by the expansion of construction land, and the decrease in the supply capacity of ecosystem services, leading to an imbalance between supply and demand. Then, a comprehensive balance between ecological civilization construction and economic development in the region can be reached.

4.4.3. Key Ecological Restoration Area

The key ecological restoration area showed a spatial distribution pattern of “low supply-high demand” and “imbalance between supply and demand”. This area was mainly distributed in Heping Town and the Wanchuan River Basin in the central area, and the area where the Yellow River flows through Qingcheng Town in the north, accounting for 1.6% of the total area. This area should focus on improving ecosystem service functions and comprehensive watershed management, and adopt the strategy of “ecological improvement + ecosystem service function improvement + comprehensive watershed management”. First, we should carry out comprehensive river basin management, in situ protection, afforestation, etc. to restore the natural ecological revetment, so that the ecosystems in the Yuzhong section of the upper reaches of the Yellow River and the Wanchuan River Basin will develop in a virtuous cycle. This can maximize the various functions and benefits of the ecosystem and realize the sustainable use of resources. Second, according to the construction plan of the ecological innovation city, we should implement the water ecological restoration of the Wanchuan River Basin, use the ecological water diversion project to supplement the ecological water volume of the river course, and ensure the water demand for the ecological environment of the Yellow River Basin and the Wanchuan River Basin. We should develop the water circulation system in the urban area to form a green ecological river corridor of the Wanchuan River to meet the ecological water volume of the river. We should effectively control pollutants entering the river through pollution control and land-use adjustment, thereby improving the water environment of the river and its ecological function, and restoring the ecosystem on both sides of the river.

4.4.4. Soil and Water Conservation Restoration Area

The soil and water conservation restoration area is dominated by the relationships of “high supply-low demand”, “low supply-low demand”, and “imblance between supply and demand”. This area is mainly distributed in the central and northern part of Yuzhong, accounting for 25.3% of the total area. This area should carry out ecological renovation and reconstruction and adopt the strategy of “ecological compensation + ecological reconstruction project + supervision and management”. First, through the establishment of an ecological compensation mechanism, we should guide farmers to carry out ecological migration, participate in ecological protection and restoration practices, and encourage social capital to finance ecological compensation. Second, this area should improve its soil water storage and moisture conservation capacity through terrace construction. We should take the soil erosion area as the key area for sloping farmland consolidation, combining soil erosion control, improving the quality of the ecological environment, and guiding the adjustment of the agricultural structure. This area should focus on the construction of terraced fields, taking precious soil, water storage, and water conservation as the main measures, strengthening the construction of small-scale farmland water conservancy, building an effective comprehensive prevention and control system of soil erosion, and improving agricultural production conditions. In addition, in the process of carrying out ecological restoration projects in the region, we should use satellite remote sensing monitoring and other information-based means to supervise, manage, and conduct timely ecological benefit evaluations before, during, and after restoration to ensure scientific and effective restoration practices are being maintained.

4.4.5. Ecological Agriculture Development Area

Ecosystem services showed a spatial distribution pattern of “high supply-high demand”, “low supply-low demand”, and “basic coordination”. This area is mainly distributed in the southeast of Yuzhong, accounting for 26.5% of the total area. We should reconstruct and improve the ecological environment in areas with a low supply of ecosystem services and adopt the strategy of “ecological improvement and restoration project + modern agricultural development”. First, we should carry out the transformation of low- and medium-yield fields through improving the quality of cultivated land by leveling the land, improving the water storage and fertilizer retention capacity of cultivated land. In addition, we should build high-standard farmland, carry out land consolidation projects, improve agricultural production conditions, and improve the ecological environment of the land. Second, we should improve the level of agricultural land intensification, strengthen the protection and construction of basic farmland, and build high-standard farmland demonstration areas. We should promote large-scale operations through comprehensive improvement, develop modern ecological and efficient agriculture, build cooperatives to carry out the large-scale planting of scattered farmland, and develop ecological and economic industries, such as plateau summer vegetables, Chinese herbal medicines, lilies, and other special agricultural products.

4.4.6. Ecological Innovation Promotion Area

The ecological innovation promotion area showed a spatial distribution pattern of “high supply-high demand” and “coordination between supply and demand”. This area was mainly distributed on the periphery of urban construction areas in central Yuzhong, accounting for 16.1% of the total area. This area should protect and maintain the current ecosystem and its supply and demand situation, strengthen agricultural land use control, ecological innovation, and adopt the strategy of “ecosystem maintenance + agricultural land use control + ecological innovation and development”. First, the southern agricultural area should highlight the ecological protection of the Xinglong Mountain scenic area, emphasize the development of forestry, accelerate the conversion of farmland to forests, protect forest resources, and appropriately develop a small amount of crops, such as Chinese medicinal materials and lilies. Second, we should coordinate the development of agricultural space, prevent urban sprawl, and promote the improvement of ecological functions and the development of urban agriculture. The overall structure and landscape pattern of agricultural production space should be constructed in this area, and the comprehensive functions of production, ecology, landscape, and intervals of farmland should be brought into play. The central agricultural area should focus on the cultivation of plateau summer vegetables, the development of modern urban service agriculture, and the cultivation of facility agriculture and sightseeing agriculture, such as fruit picking and flower growing. We should encourage ecological innovation models, such as the combination of rural revitalization strategies and the development of pastoral complexes.

5. Discussion

5.1. The Relationship between Supply and Demand of Ecosystem Services

The relationship between the supply and demand of ecosystem services is an important representation of the balance and coordination between the regional “ecological system” and “socio-economic system”. The balance between the supply and demand of ecosystem services indicates that these two are consistent in quantity. The coordination between the supply and demand of ecosystem services indicates that these two are coordinated in quality. When the supply and demand of ecosystem services are balanced and coordinated, regional development should maintain a better status quo or be adjusted towards a high-quality direction. When the supply and demand of ecosystem services are imbalanced or misadjusted, the regional ecology, production, and living spaces are under greater pressure or have ample space for development. This requires the effective use and management of ecology, production, and living spaces, and the adoption of corresponding governance strategies for different supply and demand models. There was a common misadjustment and incoordination between the supply and demand of ecosystem services in the mountains in the southwest of Yuzhong County and in the central part of Yuzhong. This indicated that there was a serious spatial imbalance in the supply and demand of ecosystem services in Yuzhong County.

The spatial differentiation of the supply and demand of ecosystem services in Yuzhong County indicated that the supply and demand of ecosystem services showed high supply and low demand of ecosystem services in the southwest mountainous areas. However, in urban areas of the central part of Yuzhong, the spatial pattern of ecosystem service showed low supply and high demand because of the difference in resource endowment. According to statistics, in 2020 the forest area of Yuzhong County was 560.8 km², accounting for 17.1% of the county, but more than 3/4 of the forest resources were concentrated in the southwestern mountainous area, and the average population density in the southwestern mountainous area was less than 200 people/km². The construction land area of Yuzhong County is 145.4 km², accounting for 4.4% of the whole county, 2/3 of which is concentrated in Chengguan, Heping, Dingyuan and other towns and townships in the middle of Yuzhong County. The population density of these areas is more than 2000 people/km², up to 12,780 people/km², and the average area GDP is as high as 138,000 yuan/km². The southwestern part of Yuzhong has a better ecology, water yield, carbon storage, and soil and water conservation, as well as a small population. Therefore, it represented a state of ecosystem service surplus. The central part of Yuzhong was densely populated and its own ecological resources were limited, coupled with the interference of human activities on the ecosystem, resulting in a state of loss of ecosystem services. Second, the spatial layout of the economy may have a certain impact on the spatial imbalance between the supply and demand of ecosystem services. The construction of the ecological innovation city and Heping-Dingyuan comprehensive urban area in the national land space development and the protection pattern of “one vein, three areas, one axis and two cores” will effectively promote the development of Yuzhong county towns. In addition, from the perspective of the development of the provincial capital, Yuzhong Basin, as one of the three major basins in Lanzhou, is suitable for construction with sufficient space and is close to the densely populated area of Chengguan District. The Yuzhong Basin has the land-use conditions to undertake the functional release of the central urban area of Lanzhou. In addition, with the construction of the Eco-Innovation City, the urban population growth of Yuzhong County mainly comes from the large number of new people attracted by the construction of the Eco-Innovation City and the relocation of the population in the central urban area of Lanzhou further undertaken by the Peace Group and the Dinglian Group. From the perspective of regional ecological vulnerability, there are many ecologically fragile areas in Gansu Province. Population dispersal and ecological relocation in these areas are under great pressure, and it is necessary to further coordinate and optimize the urban and rural population distribution from the regional population structure. The comprehensive carrying capacity of Lanzhou in all aspects has a comparative advantage over Gansu. Yuzhong is the optimal area to host the population concentration of Lanzhou, and it should host a more provincial ecological transfer population. The above factors have lead to the high supply and low demand of ecosystem services in the southwestern mountainous area of Yuzhong County, while the supply of ecosystem services in the central gully area is low and the demand of ecosystem services is high.

5.2. The Advantages and Limitations of the Study

As a typical ecologically fragile and sensitive area in China, the loess hilly area has natural socio-economic characteristics such as an arid climate, broken terrain, serious soil erosion, and an underdeveloped economy. We comprehensively considered the supply and demand of ecosystem services in this area and carried out ecological restoration zoning. This helped to scientifically understand the differentiation rules of regional ecological functions and promote the overall protection and coordinated management of regional ecosystems. The selection of the research area, the grasp of the research scale, and the innovation of the research process in this paper are typical and representative and can provide scientific reference for the realization of differentiated and refined ecological restoration zoning management in the loess hilly region of Longzhong, China. This is also a useful exploration of integrating the concept of ecosystem service supply and demand into practical applications. First, most of the existing literature focuses on the analysis of the supply and demand of ecosystem services in independent administrative units (such as cities, counties, townships, etc.). Such large-scale studies do not show the differences within regions. This paper conducts research on a finer grid scale. This can solve the regional characteristics of the ecosystem service supply and demand, and it is also easy to spatialize the supply and demand relationship within the region. Second, this paper delimits the ecological restoration area by developing the relationship between the supply and demand of ecosystem services and puts forward management measures according to the regional conditions in combination with the current situation of the region and its strategic orientation. This has novelty and practical significance. The restoration zoning results of this study can provide valuable information for government and planning decision-makers to assist policy makers in maintaining specific ecosystem services or improving human well-being. There are also some limitations. First, this paper does not quantify the demand for each ecosystem service. It roughly characterizes the demand of ecosystem services based on population density, land use intensity, nighttime lighting, and per area GDP. Second, from the perspective of time, due to data limitations, this paper only selected a single year of 2020 in the research process and did not explain the changes in the supply and demand of ecosystem services from the time series. In the future, researchers can enrich a number of indicators to evaluate the supply of ecosystem services and represent the demand of ecosystem services with the actual consumption or willingness preference of various services. Meanwhile, it is necessary to analyze and explore the relationship between the supply and demand of ecosystem services in the loess hilly area and its changing characteristics in multi-scale and cross-time dimensions.

6. Conclusions

In this paper, Yuzhong County of Gansu Province, a typical region of the loess hilly region in China, is taken as an example. Based on grid scale, multi-source data, and the InVEST model, ArcGIS and GeoDA software were used to quantitatively evaluate the supply and demand of regional ecosystem services, as well as the matching and coordination relationship between supply and demand. The ecological restoration zones were delimited according to the idea of “problem diagnosis—strategic orientation—key optimization”. In addition, differentiated governance strategies for the different zones were put forward. The main conclusions are as follows:

(1) The spatial distribution difference of ecosystem service supply and demand in Yuzhong County was obvious. Ecosystem service supply and demand was mainly at a medium and low level. The areas with a low supply of and high demand for ecosystem services are mainly the central urban areas with high socio-economic development level and rapid urbanization process, while the areas with high supply and low demand are mainly the mountainous areas with a high altitude, poor geological conditions, and a sparse population.

(2) The matching relationship of ecosystem services supply and demand in Yuzhong County can be divided into four types: high supply-high demand, low supply-low demand, low supply-high demand, and high supply-low demand. The spatial mismatch of low supply-high demand and high supply-low demand is the dominant matching type. The coordination degree of ecosystem service supply and demand showed a spatial pattern which was high in the southwest and low in the northeast, and the overall coordination degree index of supply and demand was 0.629, indicating that ecosystem service supply and demand were basically coordinated.

(3) We combined the supply and demand relationship of ecosystem services with the current situation and strategic orientation of Yuzhong. According to the idea of “problem diagnosis—strategic orientation—key optimization”, Yuzhong County was divided into six ecological restoration zones: an ecological core restoration area, an ecological potential restoration area, a key ecological restoration area, a soil and water conservation restoration area, an ecological agriculture development area, and an ecological innovation promotion area. Different management strategies were adopted for the different ecological restoration zones.