Spatiotemporal assessment of recreation ecosystem service flow from green spaces in Zhengzhou’s main urban area

Spatiotemporal assessment of recreation ecosystem service flow from green spaces in Zhengzhou’s main urban area

Recreation ecosystem services (RES) supply, demand, and supply-demand relationship

RES supply assessment

From 2010 to 2020, the distribution of RPS in the main urban area of Zhengzhou City showed a gradual increase in high values (0.20–0.40) and a gradual decrease in low values (0.20–0.40), with the distribution of high-value areas tending to cluster. The distribution of ROS high values gradually increases, while the low values (0–0.20) gradually decrease. The distribution of high values becomes more concentrated in the city center, and the differences in opportunity supply between different regions in the main urban area gradually decrease.

In 2010, the total supply of RES in the main urban areas of Zhengzhou ranged from 0 to 0.80, with a main range of 0.20 to 0.60 (Fig. 4). The low values were mainly distributed in the west, south, and at edge of the main urban area, while the high values were scattered in different locations. In 2015, the total supply of RES in the main urban area increased compared to that in 2010 (Fig. 5). The distribution of low values was concentrated in the west and south. The regions with a total supply value between 0.40 and 0.60 increased more than in 2010, and the growth mainly took place in the northeast and southwest. In 2020, the total supply of RES in the main urban area as a whole was between 0 and 0.80, mainly ranging from 0.40 to 0.60. This represented an increase in supply capacity compared to 2015 (Fig. 6). The low values were concentrated in the northeast region. The regions with a total supply value between 0.40 and 0.60 increased more than in 2015, and the growth mainly occurred in the northwest, northeast, and south regions. The regions having a total supply value ranging from 0.40 to 0.60 have witnessed significant growth compared to 2015, with the growth predominantly taking place in the northwest, northeast, and south.

Fig. 4: Recreational ecosystem services supply in 2010.
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a RPS; b ROS; c total supply.

Fig. 5: Recreational ecosystem services supply in 2015.
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a RPS; b ROS; c total supply.

Fig. 6: Recreational ecosystem services supply in 2020.
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a RPS; b ROS; c total supply.

Over the past decade, urbanization has advanced rapidly, accompanied by an augmented effort in ecological civilization construction. The green infrastructure in the main urban area has continuously increased, the area of ecological land has expanded, and the construction of green space has become more systematic. However, owing to the functions of the economic, political, and cultural center in the main urban area, the blue-green spaces in the city exhibit block-like and belt-like forms and are distributed in a scattered fashion, thereby resulting in a scattered distribution of recreational service supply areas.

RES demand assessment

The development of recreational activities is inseparable from human beings and society. The evaluation of RES demand based on residential area density is shown in Fig. 7. From 2010 to 2020, the demand for RES in urban centers increased, and the scope of demand expanded, presenting a spatial mismatch with the supply of RES. The demand for RES was concentrated in the urban center, especially in the northeast, northwest, southwest, and southeast of the main urban area. Conversely, the demand was less in the urban fringe.

Fig. 7: Recreational ecosystem services demand.
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In 2010, the demand for RES was mainly between 0 and 0.15. The high value of demand (0.60 to 1) was relatively low, and the distribution was scattered. In 2015, the demand for RES was mainly between 0 and 0.40. The high demand value (0.60 to 1) increased, and the distribution was more concentrated than in 2010. In 2020, the demand for RES was mainly between 0 and 0.40. The high demand value (0.60 to 1) increased compared with 2010 but had only a small increase compared with 2015. The main urban area of Zhengzhou is dominated by plains, with the north side adjacent to the Yellow River and a small amount of hilly areas in the northwest and southwest. The natural environmental conditions have laid the foundation for the rapid urban expansion of the main urban area of Zhengzhou. The land use in the main urban area has become saturated, and the demand for RES is constantly increasing.

Recreation ecosystem service supply-demand relationship assessment

(1) Analysis of the supply-demand difference in RES

In the main urban areas of Zhengzhou in 2010, 2015, and 2020, there was a significant between supply and demand. The surplus areas gradually expanded, and the deficit areas were more concentrated in the urban center (Fig. 8). The surplus areas of RES were larger than the deficit areas. The supply-demand difference was greater in the surplus areas and smaller in the deficit areas. In the deficit areas, the supply-demand difference was mainly distributed between −0.60 and 0. While in the surplus areas, the supply-demand difference was mainly distributed between 0 and 0.79.

Fig. 8: Recreational services supply and demand.
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(2) Analysis of the supply-demand regions of RES

From 2010 to 2020, the distribution of RES hot spots in the main urban area of Zhengzhou expanded from east to west, and some hot spots in the northeast gradually disappeared. In addition to the city center, the distribution of cold spots also appears at the edge of the main urban area, and the cold spots in the west gradually disappear. In order to present the flow of RES more intuitively, the main urban area of Zhengzhou was divided based on the analysis of hot and cold spots. The hot spots in 2010, 2015, and 2020 were divided into g1-g4 zones, the cold spots were divided into d1-d6 zones, and the insignificant zones were divided into n1-n5 zones (Fig. 9).

Fig. 9: Hot and cold spot zone.
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Evaluation of the flow process of recreation ecosystem service flow (RESF)

RESF quantity and direction assessment

(1) Probability of beneficiary arrival

From 2010 to 2020, in the main urban area of Zhengzhou city, RES beneficiaries had the highest probability of reaching the hot-spot area with the largest RES, followed by the non- significant area with the largest size.

In 2010, the arrival probability of the beneficiaries of RES was between 0 and 5% (Fig. 10a). For the beneficiaries of RES, the G4 area had the highest arrival probability (the probability of all areas reaching G4 was more than 3%). The arrival probability of the beneficiaries of RES in the d5 and n3 areas was less than 0.03%. The arrival probability of beneficiaries in the D6 area was 0. This was because the D6 area was located at the edge of the main urban area. It was small in size, and its land use type did not contain ecological land.

Fig. 10: The arrival probability of beneficiaries by areas.
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In 2015, the arrival probability of the beneficiaries of RES was between 0 and 7.30% (Fig. 10b). The arrival probability of recreation service beneficiaries in the g3 area was the highest (the probability of all areas reaching g3 was more than 4.90%). The arrival probability of the beneficiaries of the RES in g1, g2 and d1 areas was less than 0.02%.

The probability of the arrival of the beneficiaries of RES in 2020 was between 0 and 8.10% (Fig. 10c). The arrival probability of recreation service beneficiaries in the g1 area was the highest (the probability of all areas reaching g1 was more than 5%). The probability of the beneficiaries of RES in the n1 area was less than 0.02%. The arrival probability of beneficiaries in the n3 area was 0. This was because the n3 area was located at the edge of the main urban area, the area was small, and the land use type did not contain ecological land.

(2) RESF quantity and direction

The RESF is bidirectional, and the flow of RES in each supply and demand area is divided into two directions: inflow and outflow. Red represents inflow, and blue represents outflow. From 2010 to 2020, the number of areas with a two-way flow of RES decreased, and the areas with the largest inflow were usually the cold spot area and hot-spot area, while the areas with the largest outflow were usually the hot-spot areas (Fig. 11).

Fig. 11: Quantity and direction of recreational ecosystem services flow.
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Inflow (ac); outflow (df).

In 2010, except for d5-g2, g3-d5, g1-d5, and g2-g1, the flow of RES was a two-way flow between two areas (Fig. 11a, d). The area with more inflow was d3. The area with more outflow was g4. The flow of d3 and n1 areas, d3 and g4 areas, d3 and n2 areas, and d3 and d4 areas had great changes with the change of direction. The inflow (n1-d3) quantity was 61,684 people, while the outflow (d3-n1) quantity was 7318 people. The inflow (g4-d3) quantity was 110,842 people, while the outflow (d3-g4) quantity was 47 people. The inflow (n2-d3) quantity was 12,018 people, while the outflow (d3-n2) quantity was 18 people. The inflow (d4-d3) quantity was 7832 people, while the outflow (d3-d4) quantity was 357 people.

In 2015, except for d2-g1, d4-n2, d1-n2, d1-d5, and d2-n2, the flow of RES was a two-way flow between two areas (Fig. 11b, e). The areas with more inflow were d3 and g3, and the area with more outflow was g3. The flow of d3 and g3 areas, d3 and n1 areas, and d3 and n2 areas had great changes with the change of direction. The inflow (g3-d3) quantity was 218,346 people, while the outflow (d3-g3) quantity was 12,611 people. The inflow (n1-d3) quantity was 120,356 people, while the outflow (d3-n1) quantity was 12077 people. The inflow (n2-d3) quantity was 2444 people, while the outflow (d3-n2) quantity was 13 people.

In 2020, except for n3-g1, n3-d2, n3-n2, n3-n5, d3-d1, n1-d1, n1-n2, the flow of RES was a two-way flow between two areas (Fig. 11c, f). The areas with large inflow were d2 and g1. The area with a large outflow was g1. The flow in the d2 and n4 areas, g1 and n2 areas, d2 and n2 areas, and d2 and d3 areas had great changes with the change of direction. The inflow quantity from n4 to d2 was 24,440 people, while the outflow quantity from d2 to n4 was 616 people. The inflow (n2-g1) quantity was 7159 people, while the outflow (g1-n2) was 293 people. The inflow (n2-d2) quantity was 21,277 people, while the outflow (d2-n2) quantity was 1 person. The inflow (d3-d2) quantity was 3852 people, while the outflow (d2-d3) quantity was 122 people.

RESF supply and boundary

As can be observed from Fig. 12a–c in 2010, the boundaries of the areas accessible by walking at a speed of 4 km/h were predominantly located in the center and north of the main urban area, along with areas such as d1, n2, n3, d4, and d6 in the east and south. The flow speed of RES after a 60 min walk was still zero. The boundary of the area is reachable by cycling at a speed of 15 km/h and nearly covers the entire main urban area, with only the edge areas of g1, d1, and d5 having zero flow velocity. The boundary of the area reachable at a speed of 45 km/h nearly covers the entire main urban area. In 2010, the urban construction of Zhengzhou was relatively incomplete. Green spaces are mainly distributed in the city center and northern areas, which can be reached within a 30 min walk.

Fig. 12: Speed and boundary of recreational ecosystem services flow.
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a 2010 walking, b 2010 cycling, c 2010 driving, d 2015 walking, e 2015 cycling, f 2015 driving, g 2020 walking, h 2020 cycling, j 2020 driving.

As can be observed from Fig. 12d–f in 2015, the boundaries of areas accessible at a walking speed of 4 km/h expanded compared to 2010, with additional locations not only at the city’s periphery but also in the city center. Particularly in the eastern and southern parts of the main urban area, there are more areas that can be reached within 60 min on foot. The boundary of the area is reachable by cycling at a speed of 1 km/h nearly covers the entire main urban area, with only a few areas on the periphery of the main urban area, such as n2 and d6, having zero flow velocity. Compared to 2010, the number of areas reachable within 30 min by cycling has increased. The boundary of the area reachable at a speed of 45 km/h nearly covers the entire main urban area. Compared to 2010, the number of areas reachable within 15 min by car has increased.

As can be observed from Fig. 12g, h, j in 2020, the boundaries of the areas accessible by walking at a speed of 4 km/h have expanded compared to 2015, with more locations situated in the eastern part of the main urban area. The area reachable within 15 and 30 min on foot has increased significantly. The boundary of the area is reachable by cycling at a speed of 15 km/h nearly covers the entire main urban area. Compared to 2015, there are more areas reachable within 15 min by cycling. The boundary of the area reachable at a speed of 45 km/h essentially covers the entire main urban area.

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