Introduction

Rapid urbanization has resulted in profound environmental and social challenges globally, particularly within densely populated urban areas1. Urban green spaces (UGSs) play a crucial role in addressing these challenges by providing diverse ecological services and enhancing the quality of urban life through social benefits2. Consequently, increasing attention has been devoted to planning and improving UGSs, especially through government-led initiatives aimed at mitigating public health issues and fostering sustainable urban environments3.

UGSs deliver dual ecological and social benefits, reinforcing their importance in urban development agendas4. Ecologically, UGSs provide significant services, including carbon sequestration, pollutant absorption, biodiversity conservation, and mitigation of urban heat islands5,6,7. Simultaneously, they offer essential social functions such as recreation, aesthetic appreciation, cultural engagement, and health improvement8. Despite these benefits, harmonizing ecological and social objectives often poses substantial challenges9. For instance, recreational activities, while socially beneficial, may adversely impact vegetation and soil integrity. Conversely, conservation measures aiming at ecological preservation may limit recreational accessibility and social engagement opportunities10,11. Achieving a balanced integration of ecological and social functionalities within UGSs is thus essential for enhancing urban sustainability and residents’ quality of life12.

To effectively manage the increasing conflicts between urban expansion and UGS conservation, accurately assessing both ecological and social values of these spaces is crucial. Research on ecological values of UGSs typically emphasizes quantification of ecosystem services such as climate regulation, air quality enhancement, and biodiversity conservation13,14,15,16,17,18. However, the lack of standardized indicators continues to limit comprehensive ecological assessments15,19.

In comparison, the social value of UGSs is frequently assessed as intangible, non-market benefits reflecting residents’ perceptions, including cultural, aesthetic, and recreational services20. Tools such as Public Participation GIS (PPGIS) and the Social Values for Ecosystem Services (SolVES) model have emerged as effective methods for capturing spatial variations in these intangible benefits8,21,22,23. Despite their significance, studies examining both ecological and social dimensions simultaneously are scarce, especially those addressing comprehensive UGS systems rather than focusing narrowly on large parks or scenic areas24,25. This gap reduces the potential for precise, site-specific planning and management interventions.

To overcome these limitations, biotope mapping provides a systematic approach for classifying urban ecosystems, integrating land cover and biological components such as flora and fauna26. While widely applied in urban conservation and planning contexts27, traditional biotope classifications frequently neglect vegetation structure, a key determinant of both ecological functions and social perceptions28,29. Vegetation density and vertical structure significantly influence microclimatic variations between green and non-green urban areas, impacting ecological services and public comfort30. Furthermore, specific vegetation structures, such as tree-shrub-herb layers, critically affect atmospheric particulate matter regulation and negative ion production31. Large, open spaces also significantly enhance residents’ recreational experiences and perceptions32. However, few studies have explored biotopes as the fundamental units for comprehensively analyzing multidimensional values within UGSs.

Addressing the pressing need for sustainable urban development, this study incorporates vegetation structure into a biotope classification system and systematically investigates the coupling coordination between ecological and social values of UGSs in urban historical areas of Xi’an. The objectives of this research are to: (1) develop an integrated biotope classification system through field surveys and cartographic analysis to generate detailed biotope maps; (2) evaluate ecological and social values of different biotopes within UGSs using 12 ecological indicators (including biodiversity, green quantity, air quality regulation, and carbon storage among others) and 6 social indicators (including aesthetics, recreation, spiritual, and culture among others); (3) assess the coupling coordination relationship between these values and identify key influencing factors. Ultimately, the research aims to offer tailored strategies for optimizing UGSs, guiding urban planning, policy-making, and sustainable green infrastructure development.

Study area and data

Study area

The study area encompasses the historical areas of Xi’an (Fig. 1), situated between 108°55′-108°59′E and 34°15′-34°17′N, covering a total area of 11.07 km2. As the earliest urban center of Xi’an, this region is celebrated for its vibrant commercial activity and rich historical and cultural heritage, which present substantial potential for development33. However, the UGSs in this area face more severe challenges. On one hand, this region is the core area of Xi’an with a large population, leading to a higher demand for the ecological and social value of UGSs. On the other hand, the region needs to balance the protection of historical heritage with the fulfillment of modern urban demands, while being constrained by planning and development limitations. Therefore, how to enhance the ecological and social value of UGSs through conservation and restoration methods within the existing layout of this area is an important task.

Fig. 1
figure 1

Study area.Satellite imagery obtained from Xingqiuditu (https://datacloud.geovisearth.com/) and map created using ArcGIS software (v10.5, Esri, https://www.esri.com/).

Since 2001, various UGSs protection policies have been implemented34, including the establishment of relevant regulations by the government, the definition of indicators for UGSs, the initiation of co-construction and sharing initiatives for UGSs, and the formulation of an UGSs system. The total area of UGSs in the region has expanded to 3.64 km2. This includes prominent parks such as City Ring Park, Revolution Park, Lianhu Park, Children’s Park, and Wuji Park, along with residential land affiliated green space and road and transportation facilities land affiliated green space. These UGSs are primarily characterized as public open spaces, fulfilling essential roles in recreation and therapeutic activities. Studies on Xi’an indicate that UGSs effectively counter urban heat threats through their cooling effects, helping to prevent health risks for residents35. At the same time, UGSs also have an impact on the mental health of the youth population36.

Data sources

Remote sensing imagery data were obtained from the USGS Landsat 8–9 C2 L2SP datasets (https://www.usgs.gov/). Key environmental indicators, including temperature, humidity, normalized difference vegetation index (NDVI), and fractional vegetation cover (FVC), were derived from the processed remote sensing data. Additionally, digital Elevation Model (DEM) data were sourced from the Geospatial Data Cloud (https://www.gscloud.cn/).

Point of Interest (POI) data, which include information on transportation and public facilities, were acquired from Map Lab (https://lbs.amap.com). Road data were downloaded from the OpenStreetMap (https://download.geofabrik.de/) and the 91wemap website (https://www.91wemap.com/). Furthermore, annual average rainfall and temperature data were obtained from the 2022 Statistical Yearbook published by the Xi’an Municipal Bureau of Statistics (http://tjj.xa.gov.cn/). All data utilized in this study pertain to the year 2022, with specific monthly data collected for July and August.

Methods

Urban green space biotope classification

This study commenced with the preliminary processing of 0.5-m resolution remote sensing imagery of Xi’an city, supplemented by field surveys to collect data on the characteristics of UGSs. Based on classification criteria proposed by Qiu et al.37, a biotope classification system that integrates various factors related to vegetation structure was developed, including both horizontal and vertical aspects, as well as tree types (Table 1).

Table1 Classification criteria for biotope.

The classification process began by categorizing the study area into gray, green, and blue spaces based on land cover types. Green spaces were further divided into four hierarchical categories: Horizontal Vegetation Structure classifies areas according to the proportion of tree and shrub canopy cover, with categories set at < 10%, 10–30%, 30–70%, and > 70%; Surface Cover Types distinguishes spaces based on their primary cover, which can be either groundcover or hardscape; Vertical Vegetation Structure differentiates areas into one-layer (containing only tree or sub-tree layers) and multi-layer (featuring double tree layers or combinations of trees and shrubs), with open and partly open green spaces further classified by their dominant vegetation type as either herbaceous (including low shrubs < 1 m) or shrubby (shrubs > 1 m); and finally, Species Composition classifies areas according to the tree species present, distinguishing between coniferous, broadleaf, and mixed forests.

Gray spaces were classified according to the percentage of abiotic coverage (60–75%, 75–90%, 90–100%), dominant vegetation (trees, shrubs, herbaceous), species composition (coniferous, broadleaf, or mixed forests), and the type of hard surface. Blue spaces were classified based on waterbody types, such as rivers or ponds.

Once the biotope classification system was established, all biotopes in the study area were surveyed in the field. Data collected from these surveys, along with aerial imagery, were utilized to refine and enhance the preliminary classifications. The data were processed, edited, and analyzed using ArcGIS software (v10.5; ESRI, Redlands, CA), resulting in the creation of a comprehensive biotope map that incorporates various vegetation structure factors. According to relevant studies38,39, the minimum mapping unit for this classification was set at 500 m2.

Ecological value

Existing studies have identified several factors that contribute to the ecological value of UGSs, including plant growth, air regulation, climate regulation, hydrological regulation, carbon sequestration, and carbon storage5,40,41,42,6,43,7,44. Based on the specific conditions of the study area and relevant research, twelve ecological value indicators were identified: vegetation growth condition, green quantity, arbor layer species diversity, dust retention, sulfur dioxide (SO₂) absorption, carbon sequestration, oxygen release, hydrological regulation capacity, temperature regulation capacity, humidity regulation capacity, carbon storage, and noise reduction capacity. The calculation methods for these indicators are detailed below:

Vegetation growth condition

NDVI serves as an effective measure of vegetation growth status and coverage, obtainable through remote sensing image processing45.

Green quantity

The three-dimensional green quantity (3D green biomass) accurately reflects the canopy structure and vegetation density, enhancing the reliability of UGS planning15. It is calculated using the green volume ratio (GVR)46:

$$GVR_{i} = e^{{1.804 - 0.784/N_{i} }}$$
(1)
$$GQ_{i} = GVR_{i} \times S_{i}$$
(2)

where, GVRi is the green volume ratio of biotope I, Ni is the NDVI of biotope I, GQi is the green quantity in cubic meters (m3), and Si is the area of biotope I in square meters (m2).

Arbor layer species diversity

A diverse arbor layer provides habitats for various species and influence herbaceous diversity47. Biodiversity in UGSs is represented by the following formula48:

$${\text{B}}_{{\text{i}}} = - 0.096{\text{N}}_{{\text{i}}} + 0.131{\text{TC}}_{{2{\text{i}}}} + 0.143{\text{TC}}_{{3{\text{i}}}} + 1.673$$
(3)

where, Bi represents arbor layer species diversity, Ni is NDVI, and TC2i and TC3i represent greenness and humidity value of biotope I, respectively.

Dust retention, SO2 absorption, carbon sequestration, oxygen release

UGSs act as natural filters that effectively reduce dust pollution and improve air quality49. The capacities for gas regulation are estimated using the three-dimensional green quantity and established formulas from prior research15,50.

Hydrological regulation capacity

UGSs help regulate stormwater runoff and prevent urban flooding51. The hydrological regulation capacity is estimated by the ratio of impervious surface area to the total area of each biotope, reflecting the capacity of rainwater infiltration.

Temperature regulation capacity, humidity regulation capacity

UGSs provide cooling and humidifying effects52,53. These capacities are represented by the absolute differences in temperature and humidity within each biotope.

Carbon storage

UGSs play a crucial role in carbon accumulation54,55. Carbon density data are calculated based on national averages, adjusted for the study area’s annual rainfall and temperature56,57, see Supplementary Material 1 for details. Total carbon storage is determined by summing the carbon densities for each land use type:

$$\begin{array}{c}{C}_{totali}={C}_{abovei}+{C}_{belowi}+{C}_{soili}=\left({CD}_{abovei}+{CD}_{belowi}+{CD}_{soili}\right)\times {S}_{i}\end{array}$$
(4)

where Ctotali is the total carbon storage of land cover type I, Cabovei, Cbelowi, and Csoili represent aboveground, underground, and soil carbon storage of land cover type i, respectively.CDabovei, CDbelowi, and CDsoili represent the aboveground, underground, and soil carbon densities of land cover type i, respectively. Si is the area of land cover type i in square meters (m2). The carbon content of dead organic matter is not considered due to its negligible contribution58.

Noise reduction capacity

Vegetation barriers are effective in mitigating urban noise pollution59,60. This study employs the area-absorption capacity method, correlating different vegetation types with their respective noise reduction capabilities. Noise reduction capacity is calculated based on the area of each biotope, referencing relevant formulas from Chen et al.61.

To reflect the relationship between biotope types and ecological value, and eliminate the influence of area, the above indicators were calculated using methods such as zonal statistics and other approaches, with the average value of each grid within each biotope taken as its ability to provide ecological value. Subsequently, all ecological value indicators were normalized and combined with equal weights to obtain the overall ecological value of the study area. Similarly, the overall social value of the study area was calculated in the same way as the ecological value.

Social value

The Social Values for Ecosystem Services (SolVES) model provides a framework for assessing the social value of UGSs. This model primarily relies on raster datasets of environmental elements, vector boundary data for the study area, and field survey point data. At its core, the model employs weighted kernel density analysis based on the distribution of respondents’ perceptions regarding the social value of each biotope62,63,64. By analyzing the kernel density surface values of the social value indices, the model explores the relationship between social values and environmental factors, facilitating the visualization of the spatial distribution of social value65.

The reliability of the SolVES model is evaluated using the Area Under the Receiver Operating Characteristic Curve (AUC), where an AUC value closer to 1 indicates a more accurate and reliable assessment. Conversely, an AUC value of ≤ 0.70 suggests that the model’s performance is suboptimal24,66.

This study aims to synergistically enhance both ecological and social functions to improve human well-being. Accordingly, the social value of UGSs is defined as the experiential functional value related to human use, intentionally excluding considerations such as social equity. Drawing from existing research and the specific characteristics of the study area, six relevant types of social values were identified for evaluation by respondents67,68. To ensure clarity, the definitions of these social values were tailored for better understanding by the respondents (Table 2).

Table 2 Definition of social values.

Field survey point data were collected through a questionnaire (see Supplementary Material 2 for details) that comprised the following main components: (1) Personal information of the respondents, including age, gender, education level, and whether they are local residents. (2) The selection of 1–3 points on a map that respondents believe best represent locations exhibiting each type of social value. All participants provided written informed consent to participate in this study, and they were informed about the purpose of the study, the procedures involved, and their right to withdraw at any time. All experiments in this study were conducted in accordance with relevant guidelines and regulations and were approved by the Ethics Committee of the College of Landscape Architecture and Arts, Northwest A&F University.

After completing the field survey, it is essential to filter the objective environmental factors. Previous studies have identified several commonly used environmental variables, including digital elevation model (DEM), slope, distance to roads, distance to water bodies, and land cover67,69,70,71,72,73.

In this study, given the focus on UGSs, traditional land cover classifications alone are insufficient to effectively represent the distinctions between biotopes. Consequently, additional factors that better reflect the characteristics of UGSs, such as fractional vegetation cover (FVC) were incorporated. Additionally, considering the socio-economic context, distances to transportation facilities and public amenities were included. Among the newly integrated environmental factors, FVC serves as a crucial indicator of vegetation cover and growth status, while the distances to transportation and public facilities provide insights into location accessibility and usage preferences.

The final selection of environmental factors comprises: DEM, FVC, slope, distance to roads, distance to water bodies, distance to transportation facilities, and distance to public amenities.

Spatial layout and coupling coordination analysis of ecological and social values

This study employs the coupling coordination degree model to illustrate the interdependence and mutual constraints between ecological and social values74,75. This model serves as a valuable tool for assessing the overall level of balanced development within the study area76.

After calculating the ecological and social values, the coupling coordination degree was calculated for each biotope using the following formulas:

$$D = \sqrt {C \times T}$$
(5)
$$C = 2\sqrt {\frac{{X_{e} \times X_{s} }}{{\left({X_{e} + X_{s} } \right)^{2} }}}$$
(6)
$$T = \alpha X_{e} + \beta X_{s}$$
(7)

where, D represents the coupling coordination degree of ecological and social values, C is the coupling degree, Xe and Xs are the calculated results of ecological and social value, respectively, T is the comprehensive coordination index, \(\alpha\) and \(\beta\) are undetermined weights. Given the equal importance of ecological and social values in UGSs, we set \(\alpha\)=\(\beta\)=0.5.

Subsequently, spatial layout analyses will be conducted for the obtained ecological values, social values, and coupling coordination degrees. First, Moran’s I will be employed to assess spatial autocorrelation, determining whether spatial clustering exists77. Next, the Getis-Ord Gi* index will be utilized for hotspot analysis to identify areas of high-value clusters (hot spots) and low-value clusters (cold spots), thereby clarifying the locations of spatial clustering78. During hotspot analysis, confidence intervals of 90%, 95%, and 99% are used to define meaningful clusters.

Influencing factors of coupling coordination relationship between ecological and social Values

This study employs the Geodetector model to explore the factors influencing the spatial heterogeneity of the coupling coordination relationship between ecological and social values of UGSs. The Geodetector is a well-established statistical method79,80 that detects the consistency between the spatial distribution patterns of the dependent variable and independent variables. It measures the explanatory power of independent variables on the dependent variable81.

The factor detector within the Geodetector framework determines the explanatory degree of each influencing factor, measured by the q-value. A higher q-value indicates a greater impact of the influencing factor on the spatial distribution of the coupling coordination relationship. The calculation formula is given as follows:

$$q = 1 - \frac{{\mathop \sum \nolimits_{h = 1}^{L} N_{h} \sigma_{h}^{2} }}{{N\sigma^{2} }}$$
(8)

where, q represents the explanatory power of each influencing factor, L is the number of samples for the influencing factor, h denotes the classification of the variable or influencing factor, Nh and N represent the number of units in classification h and the total area, respectively; \({\sigma }_{h}^{2}\) and \({\sigma }^{2}\) are the variance of classification h and the total area, respectively.

In selecting influencing factors, secondary processed factors—such as noise reduction capacity, carbon storage, and oxygen release (calculated based on biotope categories and canopy density)—were excluded. Based on relevant literature, a total of 11 influencing factors were ultimately selected for analysis, including:

  1. (1)

    Ecological Factors: NDVI, arbor layer species diversity, canopy density, distance to water, and biotope category.

  2. (2)

    Physical Attribute Factors: DEM, slope, and abiotic coverage rate.

  3. (3)

    Socio-Economic Factors: Distance to roads, distance to public facilities, and distance to transportation facilities.

Each influencing factor was discretized using the natural breaks method. At the same time, the Variance Inflation Factor (VIF) index was calculated. When the VIF is less than 5, it indicates that there is no multicollinearity or high correlation issue among the factors82,83.

Framework overview

The framework for evaluating the coordination relationship between ecological and social values of UGSs is illustrated in Fig. 2. This study is organized into five stages:

  1. (1)

    Biotope Mapping: Identification and classification of various biotopes within the study area based on vegetation structure and land cover.

  2. (2)

    Ecological Value Assessment: Evaluation of the ecological value of UGSs, considering factors such as plant growth, carbon sequestration, and hydrological regulation.

  3. (3)

    Social Value Assessment: Analysis of the social values associated with UGSs, focusing on human experiences and preferences as gathered through surveys.

  4. (4)

    Analysis of the Coupled Coordination Relationship: Examination of the interactions between ecological and social values to assess their mutual influence and overall coordination.

  5. (5)

    Analysis of Influencing Factors: Investigation of the factors affecting the coupling coordination degree between ecological and social values, utilizing statistical models to identify significant influences.

Fig. 2
figure 2

Framework of study.

Result

Biotope mapping

A biotope map of urban green spaces (UGSs) in Xi’an was developed using field survey data and high-resolution remote sensing imagery (Fig. 3). The study identified 28 distinct biotope types. Green spaces accounted for 2.89 km2 (79.97% of the study area) across 1,027 patches. Closed green spaces, mainly those with hardscape surfaces, comprised the largest proportion, occupying 1.59 km2 across 606 patches. Grey and blue spaces covered 0.41 km2 (11.31%) and 0.32 km2 (8.72%), respectively (Table 3).

Fig. 3
figure 3

Biotope map of UGSs in Xi’an. The map created using ArcGIS software (v10.5, Esri, https://www.esri.com/).

Table 3 Metrics of Biotope Categories.

Blue spaces were predominantly concentrated around the moat of City Ring Park, while large green patches were primarily found in City Ring Park, Lianhu Park, and Revolution Park. Grey spaces were typically embedded within green areas, such as plazas.

Ecological value of biotopes

The ecological value of UGSs in Xi’an was classified into five levels: extremly low (1.945%), low (26.525%), intermediate (43.018%), high (22.693%), and extremly high (5.819%) (Fig. 4). The overall ecological value score of the UGSs in historical core was 0.509, indicating it’s a intermediate level of ecological function. Spatially, a “high periphery, low center” pattern emerged, with high-value zones located mainly in City Ring Park. In contrast, low-value areas were found near roadsides and in the Bell Tower vicinity, often corresponding to closed green spaces with high hardscapes proportions. Medium-value areas were scattered across street greenery and residential green patches.

Fig. 4
figure 4

Ecological value of biotopes.The map created using ArcGIS software (v10.5, Esri, https://www.esri.com/).

Spatial autocorrelation analysis revealed significant clustering (Moran’s I = 0.137, Z = 8.208), with ecological hotspots around City Ring Park, Revolution Park, Lianhu Park, and the provincial government compound. Cold spots were concentrated near the Bell Tower and Hanguang Gate (Fig. 5).

Fig. 5
figure 5

Ecological value hotspot analysis. The map created using ArcGIS software (v10.5, Esri, https://www.esri.com/).

Biotope-level analysis (excluding types with fewer than 20 samples) revealed significant differences in ecological value (H = 557.107, p < 0.001). Pairwise comparisons with Bonferroni correction (Fig. 6) showed that green spaces had significantly higher ecological value than grey and blue spaces, while the difference between grey and blue spaces was not statistically significant. Biotopes such as partly closed multi-layer mixed forest primarily covered by ground cover (G PC He B & Co L-2), the closed one-layer broad-leaved forest primarily covered by ground cover (G C He B L-1), the closed one-layer mixed forest primarily covered by ground cover (G C He B & Co L-1), the closed multi-layer broad-leaved forest primarily covered by ground cover (G C He B L-2), and the closed multi-layer mixed forest primarily covered by ground cover (G C He B & Co L-2) showed the highest ecological values. In contrast, grey spaces dominated by broad-leaved trees with an abiotic coverage ratio of 75%-90% (H H2 T B), squares (H H3 S), and rivers (W R) were identified as having low ecological value.

Fig. 6
figure 6

The differences in ecological value among different biotopes.

Social value of biotopes

Out of 210 distributed questionnaires, 202 valid responses were collected (response rate: 96.19%). Demographically, respondents were slightly male-dominant (59.41%). Age distribution was relatively balanced across youth (18.81%), middle-aged (22.28%), older adults (29.21%), and elderly (29.70%). Educational levels ranged from secondary to postgraduate degrees. (Fig. 7).

Fig. 7
figure 7

Demographic data.

Model validation indicated high reliability, with AUC values exceeding 0.85 across all six social value dimensions. Nearest neighbor analysis confirmed spatial clustering for all social values (R < 1, Z highly negative), see Supplementary Material 1 for details.

The spatial distribution of composite social value (Fig. 8) showed that 66.092% of the area had extremly low values, followed by low (15.000%), intermediate (16.500%), high (2.376%), and extremly high (0.036%) levels. The overall average social value score was 0.186, indicating an extremly low level. Social value followed a clearer "high periphery, low center" trend, with elevated values in City Ring Park and four other major parks.

Fig. 8
figure 8

Social value of biotopes. The map created using ArcGIS software (v10.5, Esri, https://www.esri.com/).

Significant clustering of social value was observed (Moran’s I = 0.598, Z = 35.605), with hot spots in City Ring Park and other key parks, and cold spots around the Shaanxi Provincial Government and street tree areas (Fig. 9).

Fig. 9
figure 9

Social value hotspot analysis. The map created using ArcGIS software (v10.5, Esri, https://www.esri.com/).

Further analysis (H = 279.133, p < 0.001) and Bonferroni pairwise comparisons (Fig. 10) showed that open green spaces with herbaceous vegetation (G O He) had the highest social value. Conversely, the closed multi-layer broad-leaved forests primarily covered by hardscape (G C Ha B L-2) had significantly lower values.

Fig. 10
figure 10

Differences in social values among various biotopes.

Coupling Coordination of Ecological and Social Values

The coupling coordination model revealed five categories: extreme disorder (11.764%), primary disorder (25.229%), on the verge of disorder (34.968%), primary coordination (21.685%), and excellent coordination (6.355%). The overall coupling coordination degree was 0.467, suggesting the system is on the verge of disorder and requires improvement.

The spatial pattern also followed a "high periphery, low center" structure (Fig. 11). Extreme disorder areas were concentrated in the east and southwest, particularly in street tree belts and residential green spaces. Primary coordination was seen in City Ring Park, while Revolution and Lianhu Parks achieved excellent coordination. Clustering was statistically significant (Moran’s I = 0.581, Z = 34.560), with hot spots in City Ring Park and cold spots in the southeastern and southwestern sectors (Fig. 12).

Fig. 11
figure 11

Coupling coordination degree of biotopes. The map created using ArcGIS software (v10.5, Esri, https://www.esri.com/).

Fig. 12
figure 12

Coupling coordination degree hotspot analysis. The map created using ArcGIS software (v10.5, Esri, https://www.esri.com/).

Statistical tests confirmed significant differences in coordination levels among biotopes (H = 250.394, p < 0.001). Open green spaces with herbaceous vegetation (G O He) exhibited significantly higher coordination (classified as primary coordination), while closed one-layer broad-leaved forests primarily covered by hardscape (G C Ha B L-1) and closed multi-layer broad-leaved forests primarily covered by hardscape (G C Ha B L-2) showed significantly lower coordination, falling into the primary disorder category (Fig. 13).

Fig. 13
figure 13

The differences in the coupling coordination degree of different biotopes.

Influencing factors of coupling coordination degree

Using the factor detector of the Geodetector, 11 variables were found to significantly influence the coupling coordination degree (p < 0.05), with all VIF values below 5, confirming no multicollinearity (Table 4). Arbor layer species diversity and distance to water were the most influential, followed by FVC, distance to roads, biotope category, NDVI, abiotic coverage rate, DEM, distance to transportation facilities, distance to public facilities and slope. This indicates that ecological factors are the primary drivers, while spatial accessibility variables also contribute.

Table 4 Analysis of influencing factors on coupling coordination degree.

Interaction detection further revealed that all two-factor combinations increased explanatory power compared to individual factors. The interaction between FVC and distance to water had the highest explanatory strength, followed closely by the combination of arbor layer species diversity and distance to water (Fig. 14). These findings underscore the dominant role of vegetation structure and spatial layout in determining eco-social coordination.

Fig. 14
figure 14

Interaction of influencing factors on the coupling coordination degree.

Discussion

Using biotopes as research units

This study advances previous research by integrating biotope mapping theory into the classification and assessment of urban green spaces (UGSs), incorporating vegetation structure to distinguish biotope types. Two key rationales support this approach.

First, while biotope mapping has traditionally been applied in biodiversity conservation38,37, its utility for assessing ecological and social values and their coupling coordination has been underexplored. Since different vegetation structures yield varied ecological and social benefits, an in-depth understanding of specific biotope contributions is essential.

Second, most existing research focuses on large parks or scenic zones, which limits actionable insights. In contrast, this study demonstrates that different biotopes exhibit unique characteristics and distinct value patterns, greatly influencing eco-social coordination. By integrating biotope theory with value assessment models, our framework enables targeted identification of UGSs requiring renovation.

As more countries develop ecological base maps through biotic surveys27,84, this study bridges biotope mapping with urban planning strategies. This integration provides scientific support and practical recommendations for UGS classification, policy formulation, and site-specific improvements, promoting sustainable planning and community well-being.

In conclusion, the use of biotope mapping as a framework for assessing UGSs represents a significant advancement in understanding the ecological and social dynamics of UGSs. This approach has far-reaching implications for promoting sustainable urban development, enhancing community resilience, and optimizing the ecological and social contributions of urban environments. Future research should continue to explore and refine this framework, deepening our insights into the complex interactions between ecological and social values across diverse urban contexts.

Differences between biotope categories

The analysis reveals distinct differences in ecological and social values among various biotope categories within the study area. Overall, green spaces significantly outperform grey and blue spaces in terms of ecological value, with blue spaces slightly exceeding grey spaces. Notably, the social value of grey spaces has increased substantially, nearly matching that of green spaces. This underscores the indispensable roles that grey spaces play in urban transportation, social interactions, environmental management, and aesthetic enhancement.

However, it is essential to highlight that closed green spaces primarily composed of hardscape exhibit the lowest social value among green spaces. This limitation likely arises from their predominant use of street trees, which have traditionally been selected based on ecological criteria85,86 without sufficient consideration of public preferences87. Consequently, these spaces demonstrate poor coupling coordination due to their low social value relative to their ecological value. In contrast, these green spaces and certain grey spaces show no significant differences in coupling coordination, suggesting that while closed green spaces primarily covered by hardscape may lack social engagement, they nonetheless play a vital role as street tree spaces88,89. Therefore, strategies aimed at optimizing these biotopes are essential.

Focusing on other types of green spaces, the ecological value across different biotope categories shows only minor variations. While a few closed green spaces with one-layer mixed forests primarily covered by ground cover (G C He B & Co L-1) demonstrate exceptionally high ecological value, this highlights the untapped ecological potential of such biotopes. Conversely, open green spaces with herbaceous vegetation (G O He) provide the highest social value, indicating a community preference for spaces that offer moderate openness. This preference likely stems from the restrictive nature of highly enclosed spaces. Relevant studies90 have also shown that urban green open spaces play a crucial role in promoting physical activity, especially among women and the elderly, thereby enhancing public health in China.

For the grey spaces in the urban green areas of Xi’an, there are no significant differences in the ecological value, social value, and coupling coordination degree between squares (H H3 S) and the grey spaces of broad-leaved trees with an abiotic coverage rate of 75%-90% (H H2 T B). This indicates that when the abiotic area is too high, a small number of broad-leaved trees cannot significantly enhance the ecological value of the space. From the perspective of social value, squares (H H3 S) outperform the grey spaces of broad-leaved trees with an abiotic coverage rate of 75%-90% (H H2 T B). This may be closely related to the functional attributes of the squares in the study area. The squares in the study area mainly include public sports venues in park green spaces, such as badminton courts, table tennis courts, and children’s playgrounds, which can more effectively meet the social and recreational needs of the citizens, thereby enhancing their social value. This, in turn, indirectly leads to the ecological-social value coupling coordination degree of the squares being superior to that of the grey spaces of broad-leaved trees with an abiotic coverage rate of 75%-90%.

From the perspective of spatial distribution, biotopes in urban park green spaces, due to their excellent vegetation cover and ecological environment, are often able to provide higher ecological and social values. Additionally, biotopes with a coupling coordination degree of “primary coordination” or above are typically concentrated in well-planned and well-maintained park green spaces, such as Ring City Park, Revolution Park and Lian Hu Park. This result is consistent with previous studies. Chen et al.91 found that the carbon density in the tree layer of park green spaces is significantly higher than that in affiliated green spaces and square green spaces.

In summary, the variations in ecological value, social value, and coupling coordination degree among different biotope categories highlight the necessity of studying specific biotopes. This emphasizes the importance of biotope classification for informed urban planning. Consequently, targeted improvements or transformations of UGSs can be effectively approached through the enhancement or modification of biotope categories.

Recommendations for UGSs planning and development

As urbanization accelerates, UGSs face increasing challenges related to ecological protection and the fulfillment of resident needs92. Addressing how to foster ecological civilization and enhance public well-being through planning and transformation of UGSs is a pressing issue for cities. This study proposes several strategic recommendations from both urban management and localized renovation perspectives:

Participatory approach to UGS planning

The findings indicate that socioeconomic factors, such as the geographical positioning of UGSs (e.g., proximity to water and transport routes) and their connections to surrounding facilities, significantly influence the coupling of ecological and social values. National territorial spatial planning serves as a critical framework for urban development, facilitating rational spatial layouts and regional planning that align with the functional characteristics of various spaces93. Clear guidance on the structure, function, and spatial arrangement of UGSs should be embedded within territorial spatial planning. Structurally, biotope theory should guide the establishment of classification standards for UGS structures. Functionally, decisions regarding the construction, renovation, or removal of UGSs should be informed by their designated functions and corresponding biotope categories. Spatially, it is vital to integrate UGS planning with housing and infrastructure developments, ensuring the construction and enhancement of UGSs in newly developed residential areas, regions with rising housing densities, and core urban renewal zones.

Regional balance of functional values

From a regional perspective, existing developed areas should aim to enhance their ecological or social value based on specific local contexts. In urban ecological residential zones, the ecological value of green spaces should take precedence, primarily addressing essential social needs. Conversely, in densely populated core residential areas, green spaces should not only provide ecological and cultural services8,94 but also maximize social value. Specific types of green spaces should be prioritized based on their intended functional roles. Efforts must also be made to achieve an even distribution of ecological and social values, thereby maximizing the functional potential of UGSs. This approach will create a spatial layout characterized by “balanced regional ecological coverage and conveniently accessible social functions,” promoting the coordinated development of ecological and social values.

Targeted strategies for biotope development

Enhancing Ecological Value: Green spaces can significantly improve biodiversity by diversifying plant species and increasing the complexity of vegetation structures, thereby bolstering their ecological value95. Upgrading closed green spaces dominated by hardscapes can be achieved without altering their designated functions through two strategies: (1) introducing permeable pavements or connecting existing tree pits to form strip grasslands, enhancing hydrological regulation96; and (2) planting understory trees or shrubs to enrich vegetation complexity and ecological value95. In instances where planting is challenging, initiatives like the “ForestaMi” project can serve as references, utilizing mobile forests to increase biodiversity in such areas.

Enhancing Social Value: Closed green spaces primarily covered by hardscapes often exhibit low social value. However, studies suggest that modifications addressing residents’ emotional and practical needs can enhance social value97. This may include adding seating along pedestrian pathways, establishing rest facilities, or planting aesthetically pleasing species such as cherry blossoms or ginkgo trees to create scenic routes98. For other biotopes, a wider variety of activities and amenities should be provided, including fitness equipment, running tracks, public art installations, and educational plant signage.

These strategies are broadly applicable to UGSs. By instituting specialized planning aimed at optimizing the ecological and social values of UGSs through territorial spatial planning and employing urban residential divisions as a framework, the structure and geographical layout of UGSs can be improved. This method will guide the construction and renewal of UGSs, enhance the coupling between ecological and social values, and ultimately foster ecological civilization while improving public well-being.

Using Xi’an as a case study, the following adjustments should be made to urban land use in the city: Align with the latest territorial spatial planning and the specific UGS and open space strategies released by the Xi’an Municipal People’s Government99. Establish classification standards for UGSs and set development goals that prioritize ecological quality while enriching social and cultural experiences. Spatially, efforts should focus on enhancing ecological value in the southern and southeastern regions within the city walls and the northeastern areas of the City Ring Park. Concurrently, social value should be bolstered in the southern, eastern, and southeastern regions inside the city walls, with specific renovation plans aligned with the strategies outlined above.

Conversely, the trade-off between enhancing eco-social values is also a key issue in urban planning. On one hand, prioritizing ecological value by increasing vegetation cover to improve air quality and thermal comfort brings environmental and public health benefits. However, this may reduce the open space available for recreation, activities, social gatherings, or sports. On the other hand, prioritizing social functions by creating large open areas for activities or recreation may limit the ability of UGSs to serve ecological functions.

To address this trade-off, a biotope perspective can be used for optimization. Based on biotope mapping, large UGSs can be finely divided into different zones. This allows UGSs to create multiple spatial types within limited areas, meeting both ecological and social needs. Meanwhile, the detailed division system of biotope enables decision-makers to carry out targeted improvements in smaller areas, enhancing the flexibility of the space.

Additionally, participatory planning can be applied to address the trade-off. Involving local community residents in the design of UGSs ensures that both eco-social values are considered. Furthermore, adaptive management strategies can help monitor, adjust and optimize the use and management of UGSs, continuously improving and adapting to changing needs.

Limitations and future prospects

This study assessed the social value of UGSs using the SolVES model, but certain limitations must be acknowledged. Although the SolVES model provides quantitative and spatially explicit indicators that reflect stakeholders’ preferences, addressing some of the shortcomings associated with economic methods challenges remain69. Despite using smart electronic devices to assess remote sensing images and record spatial coordinate information, which enhances the accuracy of our findings, difficulties persist. In large study areas, residents may struggle to recall all UGSs within a short time frame, leading them to record only the most memorable spaces, which may not accurately represent their overall valuation. This limitation can potentially distort our experimental results.

Additionally, our analysis focused solely on the ecological and social values of UGSs within the city of Xi’an. However, perceptions of UGSs may vary significantly between residents in urban centers and those in suburban areas100. This suggests the necessity for more comprehensive studies that encompass a broader range of contexts.

Most importantly, this research emphasizes the current state of UGSs. However, the spatiotemporal evolution of land use and regional vegetation can lead to fluctuations in the ecological and social values of these ecosystems101,102,103. Therefore, future research should investigate the changes in ecological and social values of UGSs and their coupling coordination relationships over time. Such studies will provide more accurate recommendations for the maintenance and renovation of UGSs, ensuring they meet the evolving needs of urban communities.

Conclusion

This study developed an assessment system for evaluating the coupling and coordination relationship between the ecological and social values of UGSs using biotope mapping theory. By incorporating vegetation structure to classify UGS types, this approach provides valuable insights into the relationship between ecological and social values across different biotope categories.

The study identified 28 biotope types in the old city of Xi’an, covering 2.89 km2 of green spaces, 0.41 km2 of grey spaces, and 0.32 km2 of blue spaces. A consistent pattern of “high outside, low inside” was observed for ecological value, social value, and coupling coordination in spatial distribution, with an overall coordination degree of 0.467, indicating being on the verge of disorder .

Among the biotopes, the ecological value of the partly closed multi-layer mixed forest primarily covered by ground cover (G PC He B & Co L-2), the closed one-layer broad-leaved forest primarily covered by ground cover (G C He B L-1), the closed one-layer mixed forest primarily covered by ground cover (G C He B & Co L-1), the closed multi-layer broad-leaved forest primarily covered by ground cover (G C He B L-2), and the closed multi-layer mixed forest primarily covered by ground cover (G C He B & Co L-2) is significantly higher than that of other biotope types. Besides that, open green spaces dominated by grass (G O He) exhibit significantly higher social value and coupling coordination than the other biotope types.These findings underscore the significant influence of ecological factors on the coupling coordination of biotopes.This study systematically evaluates the relationship between ecological and social values in UGSs, identifies areas needing renovation, and provides targeted improvement plans. The insights gained can guide the construction and renewal of UGSs, promoting ecological sustainability and enhancing public well-being.

The study provides a practical reference for UGS transformation and planning, enabling targeted enhancements based on biotope categories. Future work should focus on tracking temporal dynamics to improve long-term adaptability and planning precision.