Hot spots and trends in recreational landscape research since the 21st century: A CiteSpace-based visual analysis

Abstract The purpose of this paper is to analyze the article publication volume, keyword co-occurrence, keyword clustering, and keyword mutation of recreational landscape using CiteSpace visual analysis software and to put forward the research hotspots and similarities and differences between Chinese and international recreational landscape since the 21st century. In this paper, 583 articles from the China Knowledge Network Database (CNKI) and 3227 articles from the Scopus Database are used as samples for comparative analyses to provide a scientific basis and valuable theoretical references for the research on the recreational landscape. The study shows that: 1. China is relatively lagging in recreational landscape research, with few core journals. Although international recreational landscape research started relatively early, the number of articles at the beginning stage is also relatively small. 2. The hotspots of international journals are biodiversity, urban parks, forest recreation, and the planning and management of recreational landscapes. Chinese journals focus on the theory of recreational landscape, forest recreation, and recreational landscape design of nursing institutions and hospitals. 3. With the more comprehensive coverage of recreational landscape design, future research on recreational landscapes will be more diversified and standardized, with more emphasis on the specific needs of recreational landscapes of a particular group of people as the object of research.


Introduction
On 26 August 2016, the Political Bureau of the Central Committee of the Communist Party of China (CPC) considered and adopted the "Health China 2030" Planning Outline, which is an important step for China to actively participate in global health governance and fulfill its commitment to the UN "2030 Agenda for Sustainable Development".The establishment of the Professional Committee of Horticultural Therapy and Landscape Recreation of the Chinese Society of Landscape Architecture in 2020 has led to scholars' increasing emphasis on recreational landscapes and an overall upward trend in research on recreational landscapes.
According to a survey conducted by the World Health Organization, only 5 % of the population is healthy, 20 % is diagnosed with various diseases, and 75 % is in a state of sub-health between health and disease.Sub-healthy people are directly related to the fast pace of modern life and the high level of competitive stress.The World Health Organization has included stress-related diseases as a priority for health prevention.Recreational landscapes indirectly address human health problems and can improve physical, mental, and social health, which are economically viable and effective measures (Li et al., 2019).Research has shown that the natural environment is an essential public health resource for stress recovery (Bell et al., 2014;Helbich et al., 2019;Li et al., 2021).
Recreational landscapes are mainly concerned with leisure, entertainment, health, happiness, and other aspects (Hansen, 2021), and this paper focuses on the beneficial effects of recreational landscapes on people's health and physical rehabilitation.The shift in health awareness has led researchers and designers to focus not only on the design and application of nursing homes, prisons, hospitals, and other notable institutions in the study of rehabilitation landscapes but also on parks and green spaces, green spaces in residential areas, and public green spaces in urban areas, etc.Most people who seem healthy may be in a sub-healthy state (World Health Organization, 2010), and they also need the assisted rehabilitation of recreational landscapes.Therefore, the status, trends, and hotspots of research on recreational landscapes are significant to researchers.This paper is a literature review article, and from the literature search, it is known that there have been two literature review articles on recreational landscape, one on conceptual definition (Hansen, 2021) and the other on recreational landscape accessibility (Koppen et al., 2014).There is a gap in the literature review of hotspots and trend prediction of recreation landscapes.Given this, the article visualizes and compares articles on recreational landscapes in two significant databases, SCOPUS and CNKI, to accurately analyze the trends and hotspots of recreational landscape research.From the article search, there is no existing literature comparing the similarities and differences between Chinese and international publications on recreational landscapes, so this study focuses on comparing the similarities and differences between Chinese and international recreational landscapes regarding hotspots, trends, and frontiers.Meanwhile, the international literature can provide valuable insights for the design and further improvement of China's theoretical system of recreational landscapes.

Methodology
CiteSpace, which can quickly target key information and core themes that need attention, is an excellent bibliometric software that can visualize the relationship between the literature in the form of a scientific knowledge graph, helping to make sense of past and present developments and to derive the currently active research frontiers and future development trends.In this paper, with the help of CiteSpace version 5.7.R5 software for visual analysis (Chen et al., 2015), the literature related to recreational landscapes published between 1 January 2000 and 31 December 2022 was used as a research sample, and through the detection of the number of literature, keyword co-occurrence, clustering, and the emergence rate (Xiao et al., 2011), we obtained hotspots of recreational landscapes themes, similarities and differences in development trends, indicating the development direction of recreational landscape research.

Data sources
To ensure the collected data's breadth, depth, and accuracy, the SCOPUS database is selected for international literature, and the China Knowledge Network (CNKI) database is selected for Chinese literature.SCOPUS is the world's largest abstract and citation database, which contains more than 25,000 scientific journals in science, technology, medicine, and social sciences from over 5,000 publishers from over 150 countries and over 40 languages.CNKI is China's most significant academic paper database, containing more than 7,000 academic journals of natural and social sciences.Therefore, the relevant literature in SCOPUS and CNKI databases is very representative of international and Chinese literature, and analyzing the articles in these two databases can grasp the current research hotspots and trends in recreational landscapes.

Data retrieval
To ensure the quality and operability of the research data, corresponding exclusion and inclusion criteria were set in the literature search, as shown in Table 1.The literature search method is as follows: in the SCOPUS database, using the search formula (TITLE-ABS-KEY (recreation*AND landscape)) AND PUBYEAR > 1999 AND PUBYEAR < 2023 AND (LIMIT-TO (DOCTYPE, "ar")) AND (LIMIT-TO (LANGUAGE, "English") AND (LIMIT-TO (SRCTYPE, "j")), retrieved 3227 articles related to recreational landscapes from 1 January 2000 to 31 December 2022 included.Using the professional search method, in the CNKI database, the subject search formula SU%=Recreational Landscape was set up, and a total of 124 documents were retrieved.Synonym replacement was used to expand the search scope due to the low data resources.Using the search formula (SU%=Leisure Landscape, OR SU%=Recreation Landscape, OR SU%=Health Landscape, OR SU%=Rehabilitation Landscape), 583 journal articles related to recreational landscapes included from 1 January 2000 to − 31 December 2022 were retrieved.The above-collected data resources were used as the base data for this visualization analysis for mapping.Since the article focuses on high-frequency keywords, keyword emergence, and clustering in the direction of recreational landscapes, the article will no longer use the systematic literature review method to read the articles one by one in an acceptable way.It will only use the Figure 1 method to screen the data.

Data processing
To ensure the accuracy of the results, the literature was screened again to ensure that no papers were duplicated before pre-processing the text data from SCOPUS, CNKI, using Citespace5.7.R5's inbuilt data converter.The data were imported into CiteSpace 5.7.R5 for analysis and were restricted to January 2000 to December 2022; the time slice was set to 1 year, and the threshold was set to "TOP N = 50".The visual options were selected as "Cluster view-static" and "Show merged networks".

Differences in the number of publications and time distribution
The number of publications reflects the attention of the academic community to the field, and the higher the number of documents indicates, the more active the relevant research is.The more attention the country and relevant research institutions pay to the research in this direction (Wu et al., 2019b).Before the visualization analysis, the data statistics analysis of the number of annual publications in the SCOPUS, CNKI database was carried out using EXCEL.As shown in Figure 2, the research on recreational landscapes shows a phase change, and there is a large gap between the number of articles published in Chinese and international journals.
Figure 2 shows that between 2000 and 2009, the research on recreational landscapes was in the beginning stage (Li, 2000), the overall number of publications was relatively small, and the annual literature volume of international journals was less than 100 articles, which was a slow growth.The number of Chinese journal publications was less than ten, and fewer scholars researched this direction.After 2010, the heat of recreational landscape research increased yearly, and the number of international publications showed an overall upward trend with a relatively fast development rate.In China, from 2010 to 2018, although the overall number of publications increased, the annual number of publications was less than 50, the growth was slow, and the overall number of publications lagged behind the number of international publications.However, from 2021 onwards, Chinese research enters a rapid development phase, with more than 100 documents and an overall upward trend in Chinese and international journal publications.This is directly related to the worldwide outbreak of COVID-19 and people's increased health awareness, and the United Nations General Assembly declared 2021 to 2030 as the decade of healthy aging, making health a shared global concern.

Research hotspot differences
The researcher can access the core connotation of the paper, and its discourse focus with the help of examining keywords.Given this, this paper is based on CiteSpace 5.7.R5 software to analyze the co-occurrence mapping of keywords to derive the high-frequency keywords and the corresponding mediational centrality, and the keyword with higher mediational centrality indicates that the frequency of co-occurrence with other keywords is also higher, which can predict the research hotspots in the field.

Keyword co-occurrence mapping analysis
The 3227 articles in the SCOPUS database and 584 in the CNKI database were imported into CiteSpace 5.7.R5 software in RIS and Refworks formats, respectively.Set the node type as "Keyword", the time range as 2000-2022, the Selection Criteria as g-index, threshold k = 25, the network clipping method as Pathfinder, Pruning sliced networks, Pruning the merged network, resulting in the keyword cooccurrence mapping of recreational landscapes (shown in Figures 3 and 4).The size of a keyword node indicates the frequency of occurrence of that keyword, the larger a node is, the higher the frequency of occurrence of that keyword is.The diameter of each keyword node in the graph varies in size, indicating significant differences in the frequency of occurrence of each keyword.Numerically, the SCOPUS database recreational landscape keyword co-occurrence mapping, Merged network: Nodes = 741, Links = 3503, Density = 0.0043, Modularity Q = 0.7599 (>0.3),Mean Silhouette S = 0.8873.CNKI database recreation landscape keyword co-occurrence map, Merged network: Nodes = 444, Links = 885, Density = 0.009, Modularity Q = 0.6634 (>0.3),Mean Silhouette S = 0.904.The clustering structure of the keyword co-occurrence map is significant, and the clustering result is reasonable.Reasonable.Under the same threshold criteria, international journals have higher keyword co-occurrence connectivity and relatively concentrated research.The article counts the top 30 keywords in frequency, as shown in Tables 2 and 3. From the high-frequency keyword ordering and the keyword co-occurrence mapping in Figures 2 and 3, there are similarities and differences between the research on Chinese and international recreational landscapes.The following is a comparative analysis of the hot research topics on recreational landscapes based on the similarities and differences of keywords.
Analyses of similar aspects of research in recreational landscapes.Firstly, the high-frequency keywords show that research focuses on the theory and specific application of recreational landscapes, with the highest frequency word for rehabilitation landscapes in Chinese journal articles and the highest frequency for recreation in international journal articles, with an overall focus on specific theoretical research and application of recreational landscapes.Secondly, the keyword that appears simultaneously in the first thirty co-occurring keywords is forest, indicating that research on forest recreation is a common focus (Drábková & Šišák, 2013), and that forests are a common object of research in recreational landscapes (Li & Xu, 2018;Song, 2021).Thirdly, focusing on the research on parks, it can be seen from the co-occurring keywords that parks are also a common research object of interest, with international attention focusing on urban parks and recreational parks (Tomczyk & Ewertowski, 2016;Yu et al., 2021), and Chinese attention focusing on healing gardens with certain special needs such as medical gardens and rehabilitation gardens predominantly (Cao, 2019;Wang, 2018;Yang, 2020).Fourth, focusing on design thinking and theoretical research on relevant constituent elements and special groups in recreational landscapes, such as research on relevant constituent elements such as green space and facilities in co-occurring keywords, and research on special groups such as women, men, and the elderly (Bell et al., 2014;Tomczyk & Ewertowski, 2016;Yang et al., 2020;Zhang & Muñoz Ramírez, 2019).
Aspects of recreational landscape research differences.Firstly, the research scales are different, international research focuses on ecosystems and creating healthy ecological environments in cities (Hermes et al., 2018), and China focuses on creating recreational environments in a particular small-scale space (Lai et al., 2021).Secondly, the research groups are different, international research focuses on cities and human needs for public space in cities, and China pays more attention to special groups such as the elderly and the sick (Yan, 2019).Thirdly, the research progress is different, international research from recreation landscape planning and management to ecosystem construction, forward to recreation tourism, recreation landscape protection, and system construction; China's research from the recreation landscape theory research to forest recreation, development to the recreation landscape planning and design, forward to the recreation landscape needs of special groups, has not yet risen to the construction of the system, the recreation of the national parks and the public space of the urban Design.

Keyword clustering mapping analysis
To better understand the differences in the hotspots and trends of recreational landscape research and deepen the theme co-occurrence relationship, cluster analysis was conducted based on the keyword similarity based on keyword co-occurrence mapping.The clusters were named by extracting nominal terms from keywords through the log-likelihood ratio algorithm (LLR), which resulted in the clustering of the themes of the two databases of the recreational landscape research, as shown in Figure 5.  Figure 5. Modularity Q = 0.6634, Weighted Mean Silhouette S = 0.904 in Figure 6.It is generally accepted that Q > 0.3 implies that the clustering structure is significant and S > 0.7 means the clustering is convincing.
Comparative analysis by keyword clustering mapping: There are similarities between international and Chinese research on recreational landscapes, e.g., research on forest recreation, and research on special groups.From the clustered keywords, more differences in the clustering of themes, based on Table 4, the following in-depth analysis of the differences in the clustering of themes and research trends.
The thematic clustering features and trends in international research are as follows.Firstly, research started earlier, focusing on the sustainable development and conservation of cities and urban parks, urban public health, and wellness, and the multifunctionality and recreation of urban outdoor spaces, emphasizing creating green spaces.Research has shown that green space affects human health and life expectancy and that areas with more green space can extend life expectancy (Dahmann et al., 2010).Secondly, from urban public space design research to specific specialized design research, such as greenways, water quality, outdoor recreation, green space, etc., focusing on the complementary symbiosis of natural and humanistic landscapes (Kulczyk et al., 2018;Marion et al., 2022).Thirdly, focusing on environmental protection and biodiversity construction, global warming, depletion and destruction of the ozone layer, reduction of biodiversity, the spread of acid rain, atmospheric pollution, water pollution and other global environmental problems highlighted, threatening the survival and development of mankind, recreational landscape's from the environmental problems, and effectively improve the urban environment (Arslan & Kaymaz, 2020;Hermes et al., 2018;Yu et al., 2021).
The thematic clustering characteristics and trends of research in China are as follows.Firstly, the research started relatively late, mainly focusing on recreational landscape theory and design methods.Since implementing the "Healthy China 2030" planning outline, the research focus has shifted from single-plant recreation and the recreation of special groups to a healthy life, the construction of healthy environments, and the development of healthy industries (Cao, 2019;Yang, 2020;Zhang, 2018).For example, the research on health landscape and urban landscape.Secondly, the research method is based on case studies, which are transformed into a theorybased development of qualitative and quantitative analyses (Lai et al., 2021).Focusing on the current problems and theoretical excavation of recreational landscapes in China, with the return of visiting scholars in landscape architecture, the relevant theoretical research and application of recreational landscapes have been effectively promoted.Thirdly, the theory of evidence-based design has been effectively promoted in China, through which the purpose of healing is implemented, and the construction of a rehabilitation landscape is realized (Yuan & Zhou, 2020).In 2009, scholars of landscape architecture applied evidence-based design as an important methodology in the design of rehabilitation landscapes, which provides a scientific basis and empirical foundation for the design (Zhang et al., 2009).The fourth is the research discipline background towards diversification, from the clustering keywords can be seen that the research involves the knowledge of urban planning, architecture, landscape architecture, management botany, ecology, and other disciplines.Along with the impact of the new global coronavirus, recreational landscapes are getting more and more attention, and the scope of the disciplines involved is further expanded, such as medicine, literature, law, education, agronomy, art, and other disciplines involved (Li, 2021;Xu & Xianjin, 2021).

Analysis of development trend based on emergence rate detection
Based on keyword co-occurrence analysis, the detection of emergence rate by "Burstness" can reflect the research areas with high influence in a period.In CiteSpace 5.7.R5, the value of Minimum Duration is set to 2, and the value of γ[0,1] is set to 1.There are 194 keywords in SCOPUS database and 2 keywords in CNKI database.In order to obtain more emergent keywords from the CNKI database for effective comparison, the value of γ[0,1] is adjusted to 0.5.The value of Minimum Duration is 1, and 27 emergent keywords are obtained.The keywords that rank in the top 20 regarding the degree of emergence are taken, as shown in Figures 7 and 8.
Taking the top 20 emergent words for comparative analysis, it can be seen that the research theme of recreational landscapes has a prominent stage, and the keyword emergence rate varies significantly in different stages.The main emergent keywords for international research before 2004 are orientation, and it can be seen from Figure 7 that the research on recreation and wellness landscapes in Europe is relatively prominent.There are five emergent words from 2005 to 2019, and the keyword emergence tendency is not prominent.In 2020, the research on recreational landscapes is mainly concerned with urban parks, and the impact of urban public green space on health is valued.As can be seen from Figure 8, landscape healing is a crucial area of recreational landscape research in China.The keyword emergence rate is higher after 2019, focusing on recreational landscape design and theoretical research.In 2013, Several Opinions of the State Council of the People's Republic of China on the Promotion of the Development of the Health Service Industry promoted research related to the health field.Recreation landscape research focuses on recreation trails and forest recreation, emphasizing the impact of slow-moving environments on people's physical health.In 2016, implementing the "Healthy China 2030" planning framework led to a significant increase in research on recreation landscapes, with keywords such as evidence-based design, recreation, and wellness industry, medical and healthcare integration, and design strategies emerging.According to the World Health Organization, the proportion of sub-healthy people is increasing yearly, and the demand for and reliance on recreation and wellness environments is increasing; research on recreation landscapes will be a crucial direction for industry research for some time to come.

Conclusion of the study
Using SCOPUS and CNKI databases as data sources, this paper analyses the number of articles, keyword co-occurrence, clustering, and emergence rate of recreational landscapes using scientifically measured methods.It explores the hot topics and development trends of recreational landscape research.On this basis, we compare the differences between Chinese and international research on recreational landscapes to provide a reference for future research.Comparative analyses revealed that: (1) Regarding the number of publications and time distribution, Chinese and international research started relatively late, with China lagging in international research.Influenced by China's national strategies and policies, the research on recreational landscapes in China will develop rapidly in the next five years, and it is expected that the number of publications will exceed 120 in 2023.(2) Regarding research hotspots, there are some similarities between Chinese and international research on recreational landscapes, but the differences are significant.International recreation landscape focuses on the research process and research results, such as from biodiversity, environmental protection, and ecosystem construction to recreation value, indicators, and sustainable development perspective shift; China's recreation landscape is mainly concerned with the research object and research methodology, is in the exploration stage of the theory and application of the recreation landscape, is currently in hospitals, retirement institutions are more widely used, has not yet been popularized to the public space of the city.(3) From the perspective of keyword clustering, international recreational landscape focuses on environmental protection and ecosystem construction and the integration of natural landscape and humanistic landscape; China focuses on the preliminary exploration of recreational landscape theory research and design application and the application of evidence-based design theory in the direction of recreational landscape is more prominent.(4) From the perspective of keyword emergence, the research of recreational landscape has a prominent stage, especially after 2020, the keyword emergence rate is higher, which is directly related to the orientation of national policy and the current situation of social public health and affects the research direction and trend of recreational landscape.

Future research outlook
Regarding research populations, the current focus of recreation landscapes in China is mainly on the elderly and the sick (Cao, 2019;Li et al., 2018;Wang, 2018).Studies have shown that the demand for recreation landscapes from unhealthy and healthy people is also high (Koppen et al., 2014), so building a holistic recreation environment in cities is a direction for future recreation landscape efforts.From the perspective of research sites, the recreation landscape should not only focus on unique places such as hospitals and elderly institutions but also involve community landscapes, public green spaces, rehabilitation gardens, seaside retreats, hot springs, recreationthemed towns, and other kinds of landscape design for physical and mental healing, to focus intensely on people's needs and health and achieve the ultimate goal of making people emotionally stable and physically and mentally healthy through the interactive experience of physiology and psychology.
In terms of the construction of the recreation landscape environment, ecological science should be taken as the basic principle, and the topography, water features, plants, and structures should be reasonably matched according to the actual needs of the regional environment to ensure biodiversity and stability (Zhang & Muñoz Ramírez, 2019).Focusing on human participation, the construction of multiple recreation activities effectively enhances the recreation landscape's utilization rate and promotes the recreation environment's sustainable development.Pay attention to the protection and use of the natural environment, adhere to the basic principle of integration with the natural environment, and meet the natural ecology to avoid damage to the external natural environment to the maximum extent possible.Take complete account of regional culture, health and wellness culture, humanistic care, and other factors (Li, 2021).

Limitations of the study
This paper mainly selects SCOPUS and CNKI databases as the primary data sources, and there are certain limitations in selecting databases with insufficient coverage.The data selection time is from 1 January 2000 to 31 December 2022, and there may be innovative research on recreational landscapes in the data outside this period, which may be omitted in this paper.The literature is limited to English articles in the SCOPUS database and Chinese articles in the CNKI database; conference papers, dissertations, chapters, and so on in the two databases are not analyzed, and the analysis of the hot direction of the research may have the problem of insufficient comprehensiveness.

Figure 1 .
Figure 1.Article exclusion and inclusion process.
Figure 2. Trend analysis of the annual volume of literature on recreational landscapes.

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Figure 3. SCOPUS database keyword co-occurrence mapping for recreational landscape research.

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Figure 4. CNKI database keyword co-occurrence map for recreation and landscape research.

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Figure 5. WOS database keyword clustering mapping for recreational landscape research.

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Figure 6.CNKI database keyword clustering mapping of recreational landscape research.

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Figure 8. CNKI database of recreation and landscape research keywords popping up (top 20).