Identifying the Authenticity of Plantscapes through Classics: A Case Study of Beijing Suburbs in the Qing Dynasty

Abstract

The plantscapes surrounding historical gardens hold significant value, reflecting the natural pristine state as well as demonstrating the cultural attributes of the landscape. This study aims to develop a method for identifying the characteristics of historic plantscapes and to recognize the authenticity of historic landscapes from the perspective of plant elements. Our method combines textual and geospatial data analysis to examine the plant species, their relationships and combinations, and spatial distribution. The case study focuses on the Beijing suburbs during the Qing Dynasty, as documented in A Collection of Past Events in Beijing. We identified 658 plants recorded, encompassing 44 families and 58 genera. These plants were categorized into 7 groups based on the growth type and morphological characteristics, leading to 54 plant relationship outcomes, 107 plant combination scenarios, 5 plant combination categories, and 7 representative plant combinations. Additionally, we mapped the spatial distribution of plants, forming 16 plantscape groups and depicting the spatial kernel density distribution of important plants. We also determined the characteristics of plantscapes in different directions in the suburb. Our findings advocate for respecting the historical development of the plantscape and understanding its evolution, particularly emphasizing the use of high-quality native plants and plant combinations.

1. Introduction

The design and formation of historic gardens not only reflect the profound respect ancient peoples had for and adaptation to the natural environment but also reflect the results of a long-term dynamic interaction between humans and nature [1,2,3]. In this process, plant elements played a pivotal role, serving as a link between nature and artistry and as vital living elements that bridge the internal and external spaces of historic gardens [4]. Plants have played a crucial role in the formation and evolution of garden landscapes, which encompasses not only the specific species planted but also the proportions, color schemes, spacing, and respective heights of the vegetation [5], demonstrating adaptability to climatic and environmental changes, as well as to human aesthetic and cultural preferences [4,6]. By meticulously arranging and positioning plants, the ancients were able to effectively respond to environmental shifts and shape the garden landscape in a manner that aligns with cultural and aesthetic standards while also fulfilling functional requirements [7,8]. This adaptability is reflected not only in the growth and evolution of plants but also in the long-term nature of garden design and the dynamic changes in the landscape [9], resulting in a historical garden system that is in harmony with the natural environment.

The Florence Charter [5] explicitly stated that in any work of maintenance, conservation, restoration, or reconstruction of a historic garden, or of any part of it, all its constituent features must be dealt with simultaneously. Isolating the various operations would damage the unity of the whole. However, previous cultural heritage landscape conservation theories and approaches predominantly concentrated on specific historic gardens or buildings [10,11,12], with a notable absence of consideration for the natural relationships and contexts. It is therefore imperative to consider historic gardens in a more holistic, sustainable manner, within the context of the landscape [13,14]. This entails focusing on the ecological and cultural landscapes of the areas in which they are situated. For decades, the ecological environment and landscape characteristics of vegetation in historic gardens have been altered by the process of urbanization [15,16], and the changes in vegetation planning practices have led to the homogenization of urban vegetation landscape [17]. In this context, scientists and natural resource conservationists have endeavored to identify multiple strategies for the protection of urban vegetation, biodiversity, and cultural values [15,18,19]. However, the majority of studies on historic gardens or cultural heritage vegetation tend to concentrate on modern perceptions of biodiversity and cultural diversity [18,19,20]. It is, therefore, necessary to reassess the authenticity of plantscapes from a historical perspective. This can facilitate a more profound comprehension of the intricate dynamics between humans and their environment [21], thereby paving the way for the long-term resilience of historic landscapes.

Chinese historic gardens are an important part of the world’s gardens and cultural heritage [22]. Beijing, as the capital of China and one of the first batch of declared historical and cultural cities, has many historic gardens and cultural heritage [23], which has had a profound influence on Chinese gardens and even oriental gardens [24]. During the Qing Dynasty (1644–1911 AD), the creation of Beijing’s historic gardens reached its peak, forming the “Three Hills and Five Gardens” historic garden clusters, and the urban plantscapes surrounding the garden clusters also paid more attention to the beauty and symbolic meanings of plant configuration [25]. Since the beginning of the 21st century, a substantial number of scholars have engaged in research on Beijing’s historical gardens [26,27,28], encompassing a range of topics including garden art and rationale [29], cultural thought [30], heritage protection and utilization [31], and other related areas of inquiry. The scope of the research encompasses a variety of garden-related subjects, with a particular focus on the Beijing Mountains and the Three Hills and Five Gardens Historic Garden Cluster region, as well as the Beihai areas [31,32,33]. These studies provide a comprehensive and valuable reference for introducing unique and individual information about Beijing’s historic gardens. Nevertheless, there is a paucity of studies that concentrate on plants within the broader public domain during the historical period. From our perspective, this is largely constrained by the historical material and the methodologies employed to examine it. It is, therefore, necessary to construct a comprehensive research framework in order to facilitate a more nuanced understanding of the relationship between historical documents and planted landscapes.

The historical material, especially works from specific periods, provides insight into the political and economic conditions of the region at the time [34]. However, these historical materials contain a substantial quantity of textual information and encompass comprehensive and intricate content, rendering it challenging to conduct a comprehensive and detailed review of a single issue. In recent years, interdisciplinary methods have emerged that can be applied between science and the humanities. These methods have the potential to be applied to the study of historical plantscapes. Text mining, as an interdisciplinary method drawing upon information retrieval, statistics, computational linguistics, and especially data mining, can disclose concealed information and can deal with a large number of words and structures in natural language on the one hand and ambiguity, uncertainty, and vagueness on the other hand [35,36]. As a result, it has gained wide application and attention in many research fields [37,38,39]. Furthermore, the Geographic Information System (GIS) spatial analysis is particularly important for studying the spatial distribution of plants, which can improve the methodology of historical plantscape studies and enhance the planning and management of plantscapes [40,41]. The combination of text mining and GIS is more likely to improve the disadvantage of the lack of objectivity in the study of historical evidence. Therefore, this study takes Beijing, China as an example to explore the possibility of text and geospatial data analysis in identifying the authenticity of plantscapes.

This study employs an authoritative official book of the Qing Dynasty, A Collection of Past Events in Beijing (hereafter, the Collection) [42], to examine the general pattern of distribution of regional native plants in Beijing during the historical period. It considers the application of plants with regional characteristics and cultural connotations, beginning in the suburban natural environment. In addition, it offers a novel perspective on the conservation of historic gardens, public spaces, and contemporary parks. In the past, Beijing’s urban growth, population increase, and land use patterns have changed considerably in the modern period (18th–19th century) [43]. Since urbanization, the number of urban vegetation has been drastically reduced, and a large number of domesticated plants have been introduced, leading to a drastic change in the ecological environment and landscape characteristics of Beijing’s urban greening [44,45], and the emergence of the problem of homogenization of the plantscape [27]. Therefore, how to balance the ecological development and the cultural heritage of historic plantscapes will be a research topic, as this will contribute significantly to the resilience of historical landscapes.

This study aims to add knowledge pertinent to the conservation of historic gardens, the assessment of historic plantscapes, and the cultural management of urban plantscapes. Furthermore, we examined an important historical document, the Collection, identified urban plantscapes outside of Beijing’s historic garden clusters during the Qing Dynasty, and quantified three main factors that may have influenced urban green landscapes, including plant species, plant configurations, and spatial distribution of plants.

2. Materials and Methods

2.1. Study Materials

The data material for this study is collected from an official book of the Qing Dynasty named A Collection of Past Events in Beijing. In 1773, the emperor ordered the publication of the book during the 50th to 52nd years of the reign of Emperor Qianlong (1785–1787 AD) [42]. As an official local journal of the Qing Dynasty, the book was compiled by nearly 1000 individuals with reference to more than 2000 ancient texts, combined with fieldwork to ensure its high degree of authenticity and objectivity. In contrast to other historical materials, this text provides a comprehensive account of the historical geography of Beijing. It encompasses a detailed topography, historical development, a delineation of notable sites, and their cultural backgrounds, as well as an examination of the products and customs of each region [46,47]. These meticulous records offer invaluable insights into the study of history landscapes, while also serving as a crucial reference for modern landscape planning and conservation.

The book is composed of 18 distinct volumes. One of the 18 volumes is entitled Suburbs. It provides a comprehensive account of the distribution of plants across the diverse geographic spaces of the suburbs of Beijing, encompassing the city’s eastern, western, southern, and northern suburbs. The volume is composed of over 190,000 Chinese characters and offers a detailed overview of the plants in these diverse urban environments. This volume contains 658 plant-related descriptive phrases (Figure 1) and includes records of plant cultivation, encompassing not only the natural growth of native plants and large areas of open field cultivation but also the ornamental plant cultivation activities and the floriculture activities. Therefore, the Collection is of paramount importance and significant influence in the study of historic plant landscapes.

2.2. Study Area

The study was conducted in the capital city of China, Beijing (115°24′–117°3′ E, 39°28′–41°05′ N). Beijing City is located in the north of the North China Plain, with a sub-humid continental monsoon climate. The elevation of the terrain in Beijing City is characterized by a high elevation in the northwest and a low elevation in the southeast. The mountainous area accounts for approximately 62% of the total area, while the plain area is characterized by a flat and open topography, accounting for approximately 38% of the total area [44,45].

However, the Suburbs volume of the Collection did not specify the exact extent of the suburbs. Furthermore, due to the political and historical reasons in Beijing during the Qing Dynasty, the boundaries of the suburbs that were part of the capital city at that time were unclear. Therefore, it is necessary to establish the study area. Our research area was defined based on the following resources (Figure 2):

Firstly, the 4 historical maps were superimposed based on the Qing Dynasty Beijing Suburbs Patrol and Arrest Battalion Residence Proposed Boundaries to obtain the core area and key geographical points. Secondly, the important landmarks, major river systems, and mountain ranges mentioned in the Suburbs volume of the Collection were marked out on the map. Finally, after careful consideration of the aforementioned content and expert consultation, the study area was determined (Figure 3a).

The geomorphology of the study area has remained static to date, with numerous World Heritage sites and historic gardens still extant in the central Beijing region and its surrounding suburbs. These include the Beijing Ancient City Historic Garden Cluster and the Three Hills and Five Gardens Historic Garden Cluster (Figure 3b). In addition to these historic gardens, the Beijing Municipal Government initiated the “Urban Park Loop” project in 2000 [49] (Figure 3c). The objective of the project is to mitigate the expansion of urban areas. As of May 2024, a total of 153 urban parks have been constructed, encompassing an area of approximately 203.2 square kilometers. The “Urban Park Loop” serves as a vital location for public recreation and fitness activities. However, the homogenization of these urban parks has become evident, underscoring the significance of this study in guiding plant landscape planning in contemporary urban environments.

2.3. Data Collection

The textual data originate from the 1985 Beijing Publishing House publication, the Collection. The historical map of Beijing was sourced from the Historical Map Network “http://www.txlzp.com/” (accessed on 1 March 2024). Information on historical gardens was obtained from the Beijing Parks Management Centre “https://gygl.beijing.gov.cn/” (accessed on 1 March 2024). Geospatial databases from multiple sources were utilized to identify the locations of historic sites. The first source was the National Catalogue Service for Geographic Information “https://www.webmap.cn” (accessed on 8 March 2024), which provides data on city boundaries, lakes, and rivers extracted in October 2023. The second data source was the Baidu Map Open Platform “https://lbs.baidu.com/” (accessed on 15 March 2024), which contains points of interest (POIs) of historical gardens in Beijing.

2.4. Data Preparation

The major steps of this study are shown in Figure 4.

The Collection is presented vertically in the traditional Chinese script and contains press notes in different font sizes (Figure 1); thus, it is difficult for direct text mining. Therefore, OCR text recognition software was used for text recognition, and the contents of the book were then subjected to a manual review and proofreading process in order to obtain accurate electronic versions of the book.

Concurrently, it is imperative to establish plant word extraction regulations during the manual inspection process, because certain plant names are utilized in the names of individuals, locations, and landscapes in the book. There are 6 specific scenarios:

• Plant names refer to surnames, for instance, Li (Prunus salicina), Yang (Populus), and Liu (Salix) were often used as surnames, so we removed personal names and surnames from the text.
• Plant names referred to place names, for instance, some Mulan (Yulania) and Shuangliushu (Salix), respectively, represented the names of the Mulan paddock and the scenic spots inside the South Garden, so we preserved the plant words inside the scene name when it was first mentioned.
• Plant names referred to verbs, for instance, Man (Vines) and Zao (Algae) were often used to express diffusion or modification, so we selected and excluded some words based on their context.
• Plant names referred to other meanings, for instance, some Lian (Nelumbo) represented supplies of Buddhism, so we selected and excluded some words based on their context.
• Plant homonymy, for instance, some Furong (Hibiscus) represented Hehua (Nelumbo), so we replaced plant words by combining relevant textual research [25,50].
• Plant synonyms, for instance, Ou (Lotus root), Jihe (Lotus leaf), Fuqu, Furong, and Hehua were another name for Lian (Nelumbo), so we unified synonymous words into standard words.

Subsequently, a plant list was compiled for the Suburbs volume of the Collection based on the data from the electronic version book and the plant word extraction regulations (

Table 1. A plant list for the Suburbs volume of the Collection.

Plant Types	Original Plant Words	Standard Words of Plants	The Genera of Plants	Plant Types	Original Plant Words	Standard Words of Plants	The Genera of Plants
Tree	song, gua, huangshansong, heisong, baisong, guosong, qiaosong, yansong	Pine	Pinus, Larix	Herbaceous flowers and ground cover	ju, ganju, huangju, yeju, jinzhan	Chrysanthemum	Chrysanthemum
					lan, lanshao	Orchid	Cymbidium
	bai, kuai	Cypress	Juniperus, Sabina, Platycladus		shaoyao	Chinese Herbaceous Peony	Paeonia lactiflora
	gui	Fragrans	Osmanthus		jiguan	Cockscomb	Celosia cristata
	shan	China fir	Picea, Abies		fengxian	Impatiens balsamina	Impatiens
	putishu	Linden	Tilia		kui	Sunflower	Helianthus
	zibai	Taxus	Taxus		shuixiang, zelan	Lycopus Lucidus	Lycopus
	liu, chuiliu, chuiyang	Willow	Salix, Tamarix		sou, qian	Radix rubiae	Rubia
	huai, panhuai	Pagoda tree	Styphnolobium		song	Artemisia	Artemisia
	yang, baiyang	Poplar	Populus		luo, luoshi	China StarJasmine	Trachelospermum
	yu	Elm	Ulmus		zhi, baizhi	Angelica dahurica	Angelica dahurica
	wutong, wu,tong	Phoenix Tree	Firmiana		ba, jiao	Plantain	Musa
	zhe	Cudrania	Maclura	Aquatic plant	he, jihe, furong, fuqu, ou, lian	Lotus	Nelumbo
	suoluo	Horse Chestnut	Aesculus		wei, lu, luhua	Reed	Phragmites
	sang	Mulberry	Morus		puwei, pu	Pampas Grass	Cortaderia
	chun	Chinese Toon	Toona		gu, jiao	Zizania Latifolia	Zizania
	pingpo	Apple	Malus pumila		jianjia, di	Silvergrass	Miscanthus sacchariflorus
	jiu	Chinese Tallow	Triadica		xing	Nymphoides Peltata	Nymphoides
	chu	Ailanthus Altissima	Ailanthus		ping	Duckweed	Lemna
	feng, danfeng, qi	Maple	Acer		qian	Euryale	Euryale
	yanshu	Cotinus coggygria	Cotinus		ling	Trapa	Trapa
	yinxing	Ginkgo	Ginkgo biloba		liao	Polygonum	Persicaria
	qiu, jia	Catalpa Bungei	Catalpa		suo	Sedge	Cyperus
	shi, wubi	Persimmon	Diospyros		zao, jue	Algae	——
	lizi	Chestnut	Castanea		meitai, taimei, tai, qingtai	Moss	——
	zao	Jujube	Ziziphus	Lianas	songluo, nvluo, biluo, luo	Cuscuta	Cuscuta
	hetao	Walnut	Juglans		teng, ziteng, tenghua	Wisteria	Wisteria
	wuhuaguo	Fig	Ficus carica		rendong	Honeysuckle	Lonicera
	tao, shantao, bitao	Peach	Prunus persica		lingxiao	Campsis Grandiflora	Campsis
	xing, wenxing, shanxing	Apricot	Prunus armeniaca	Crop	mai	Wheat	Triticum
	mei, hanmei, lamei, huangmei	Wintersweet	Chimonanthus		he, shu	Sorghum	Sorghum
	tang, haitang, xifuhaitang	Crabapple	Malus spectabilis		dao, daotian, daowa, daoting	Rice	Oryza
	li	Pear	Pyrus		gua, paogua, huanggua	Melon and Fruit	——
	li, lishu	Plum	Prunus salicina		cai, caiyuan, caipu, shupu. shuwa, yuanwa	Vegetable	——
	yulan, mulan	Yulan Mangnolia	Yulania	Shrub	mudan	Peony	Paeonia × suffruticosa
	naizi	Crab Apple	Malus asiatica		jiazhutao	Oleander	Nerium
	zhuying	Cherry Tree	Prunus pseudocerasus		yueji	Rosa Chinensis	Rosa chinensis
	ziwei	Crape myrtle	Lagerstroemia		meigui	Rosa Rugosa	Rosa rugosa
Bamboo	zhu, huang, jun, maozhu, zizhu	Bamboo	——		haitong	Pittosporum Tobira	Pittosporum

). Due to the fact that the ancient people recorded plants in a manner that differed from the contemporary recording method, the original plant words were collated with reference to the Chinese Flora. (The generic terms algae, moss, bamboo, melon, fruit, and vegetable, which are often used in articles, have been retained.) Although we identified all the plant species, and most of them presented a one-to-one correspondence, in cases of under-differentiation, we used the botanical genus as the standard plant words [51].

Finally, the original text was revised, and the electronic version of the Suburbs volume of the Collection in which the plants were corrected was obtained.

To analyze the results from a geographic perspective, the research data were obtained using the geographic coordinate picker in Google Earth to calibrate the geospatial coordinates of study areas. Subsequently, the historical maps and relevant data were imported into ArcGIS 10.8. The spatial coordinates in ArcGIS 10.8 were then matched and projected to create a spatial database of historical sites in Beijing during the Qing Dynasty and to visualize the location of plants on a map.

2.5. Data Analysis

To comprehensively examine and quantify the plant characteristics of the suburbs in which the historic gardens of Qing Dynasty Beijing were situated, this study adopted well-established methods and models that are widely accepted in textual analyses and geospatial studies. This study employs word frequency analysis and co-word analysis of ROST CM6, as well as clustering analysis of Origin 2022. The spatial distribution density of plants was estimated using kernel density analysis in ArcGIS 10.8.

2.5.1. Word Frequency Analysis

Word frequency analysis is employed to ascertain the frequency with which standard plant words are recorded in a text, thereby enabling the quantification of the ancient people’s attention and application of different plants [52]. The word frequency analysis function of ROST CM6 is employed to ascertain the frequency of each plant species. Origin 2022 is then used to sort the frequency of plants and calculate the outliers, mean, and median of plants [53,54].

2.5.2. Co-Word Analysis

Co-word analysis can be employed to describe the strength of connections between different plants, thereby enabling the inference of the relationships between different plants [55,56]. The social and semantic network analysis functions of ROST CM6 were employed to obtain the semantic networks of plants, which includes the co-word analysis. The formula for the co-word analysis is as follows:

$$S_{ij}={\displaystyle \frac{C_{ij}}{min\left(C_i,C_j\right)}}$$

(1)

where C_ij represents the number of Plant_i to Plant_j in the text; C_i is the frequency of Plant_i in the text; C_j is the frequency of Plant_j in the text; min (C_i,C_j) represents the minimum value of C_i and C_j frequencies.

2.5.3. Cluster Analysis

Cluster analysis can be employed to demonstrate the similarity between different plants, thereby inferring combinations formed by multiple plants [57]. The social and semantic network analysis functions of ROST CM6 were employed to obtain line features of text, which may be regarded as scenarios in which the plants are cultivated. The line features were transformed into a matrix of plant combination scenarios. If a specific plant was applied in a given scenario, this was noted as a value of 1, while the remaining plants were noted as a value of 0 (

Table 2. Two examples of the correspondence between the original text, line features, and plant combination scene matrix.

Scenario	Volume	Original Text	Line Features	The Matrix of Plant Combination Scenarios
				Sorghum	Pampas Grass	Reed	Moss
Scenario 1	Volume 90	Moss covers the water. In the setting sun, passing pedestrians stop their horses, the air is filled with loss and despondency, and sorghum is sparse.	Sorghum, Moss	1	0	0	1
Scenario 2	Volume 98	On both sides of the waterfront, the wind brings the scent of sorghum, the water rises and then falls a few feet, and the roots of the pampas grass still carry mud. The sudden rain on the night of the 21st of last month caused the water of Kunming Lake to vent, and you can still see the water marks on the mud of the reed roots.	Sorghum, Pampas Grass, Reed	1	1	1	0

). The plant combination scenario matrix was subjected to a systematic cluster analysis using Origin 2022 in order to generate clustering results for plant combination.

2.5.4. Kernel Density Analysis

Kernel density analysis is a nonparametric density estimation method, which represents the pattern of spatial points by analyzing the spatial density of the location of plants [58]. It can intuitively reflect the aggregation state of plants. The location of plant information was transformed into discrete point data with attributes using ArcGIS 10.8. Kernel density analysis was performed with a search radius of 5 km, and the kernel density results were classified into 10 classes using the natural discontinuity grading method. The formula for the kernel density analysis is as follows:

$$f_n\left(x\right)={\displaystyle \frac{1}{nh}}{\displaystyle \sum }_{i=1}^{n}k\left({\displaystyle \frac{x-X_i}{h}}\right)$$

(2)

where n is the number of the plants; k((x − X_i)/h) denotes the kernel function; x − X_i denotes the distance from the valuation point x to the X_i; and h denotes the bandwidth.

3. Results

3.1. The Composition and Frequency of Species

A total of 658 plants were recorded in the suburbs of Beijing during the Qing Dynasty, as documented in the Suburbs volume of the Collection. These plants can be classified into 77 standard plant words (Table 1), including 44 families and 58 genera. The families with a variety of plants are Rosaceae (10 species), Poaceae (7 species), Apocynaceae (2 species), Paeoniaceae (2 species), Lythraceae (2 species), Fabaceae (2 species), and Bignoniaceae (2 species).

The standard plant words were divided into 7 categories based on the type of growth and morphological characteristics of the plant. The most frequently recorded plant type was trees, with 391 records and 37 species. This was followed by aquatic plants, with 83 records and 13 species. The next most frequently recorded category was that of crops, with 65 records and 5 species. Bamboo was recorded on 45 occasions, herbaceous ground covers on 41 occasions, shrubs on 19 occasions, and lianas on 9 occasions (Figure 5a).

The standard plant words were divided into four categories: basic, key, common and uncommon plants, based on the outliers (17.57), average value (8), and median value (3) of plant-recording frequency (Figure 5b). The basic plants with outliers were pine (143), willow (51), bamboo (45), and lotus (31), accounting for 41.03% of all plants. The key plants recorded more frequently than average contained 8 trees, 5 crops, 2 herbaceous ground covers, and 2 aquatic plants, accounting for 35.10% of all plants. The common plants with recording frequencies between the average and the median contained 14 trees, 6 aquatic plants, 2 lianas, and 1 herbaceous ground cover, accounting for 16.87% of all plants. The uncommon plants with recorded less frequently than median contained 13 trees, 9 herbaceous ground covers, 5 aquatic plants, 4 shrubs, and 2 lianas, accounting for 43.42% of the plant species.

3.2. The Composition and Frequency of Species

The relationships between plant species were generated from an analysis of co-words in the Suburbs volume of the Collection; a total of 54 plants are related to other plants, of which 25 have a plant combination of greater than or equal to two species (Figure 6a). The plants that formed the greatest number of combinations with other plants were pine (20 species), willow (14 species), bamboo (8 species), lotus (8 species), and peach (6 species). The most frequent plant combinations were pine-bamboo (15), pine-willow (8), pine-cypress (7), pine-pagoda tree (7), and willow-elm (5).

The character lines of the Suburbs volume of the Collection reflect 107 plant combination scenarios (Table 2). The plants present within the scenarios were recorded and analyzed by clustering, resulting in the production of a dendrogram of plant combinations. This dendrogram shows five cluster categories and seven representative plant combinations (Figure 6b). These plant assemblages consisted of an average of eight plant species and, with the exception of Cluster D, were mixed with a variety of plant types that could form a tree–shrub–grass or tree–grass plant community.

3.3. The Spatial Distributions of Species

Figure 7 illustrates that the distribution of plants in the suburbs of Beijing during the Qing Dynasty was more concentrated, forming several plant groups that were scattered across various areas and closely related to historical sites. It can be demonstrated that the plant groups in Suburb West are mainly concentrated in the vicinity of the Three Hills and Five Gardens historical cluster, historical temples, and water systems by delineating a 5 × 5 km grid.

Among the clusters, the number of plant records in the Three Hills and the Five Gardens cluster is the largest (Grid 3–5, 7–9), with the majority concentrated on the edges of the historical gardens and among the Fragrant Hills. The historical temples with plant records include Dajue Temple (Grid 1), Tanzhe Temple (Grid 6), and Jietai Temple (Grid 13). The principal waterways with documented plant records include the Nanjian River (now it is called Jingmi Water Diversion Canal, Grid 2) and the Lugou Bridge (Grid 14). In contrast, the plant groups in Suburban North, Suburban East, and Suburban South are situated in close proximity to the old city of Beijing and are primarily concentrated around city gates and bridges, including Xizhi Gate, Qihua Gate (Grid 10 and 12), and the area around Cao Bridge (Grid 15).

As illustrated in Figure 8, an examination of the kernel densities of the basic and key plants reveals a noteworthy pattern. Firstly, from the perspective of the suburbs’ diverse geomorphic environmental characteristics, the western suburbs are predominantly mountainous, with a transition zone between the mountains and the plains. This complexity and variability in geomorphology provide a diverse range of habitats for plants, resulting in a rich variety of plant species and forms within the region. The region’s transition zone boasts superior natural conditions, proximity to the historic city center, many historical gardens, and a proclivity for developing external public spaces that are meticulously landscaped. The suburban western mountainous area is home to a multitude of temples, many of which feature ornamental flowers such as lotus and orchids. These flowers, with their strong religious and cultural connotations, serve to enhance the ornamental and cultural nature of the temple environments.

The Suburb North is situated in a transition zone. However, in contrast to the Suburb West, it exhibits a paucity of ornamental plants, including apricot trees, orchids, peonies, and crops such as rice, wheat, and sorghum. The northern suburb is less affected by human activities and presents an unaltered natural landscape. Suburb East and Suburb South are situated in a vast plain region. In comparison to Suburb West and Suburb North, the soil and water conditions are relatively concentrated and stable. This is evidenced by the prevalence of plants such as lotus, vegetables, and melons in the vicinity of water, which reflects the interdependence between plants and their growing environment in the plain region.

Secondly, from the perspective of the plant types, the spatial distribution of trees is the most extensive. Evergreen plants, such as pines and cypresses, are widely distributed in mountainous and transition zones. In contrast, willows, pagoda trees, and various types of ornamental deciduous trees are distributed in the plains. Aquatic plants are also widely distributed, though the locations of points with high nuclear density are not uniform. For example, lotus is distributed along the water bodies in the southern suburbs, while moss is distributed in the dense forests of the western mountains. With regard to crops, grain crops such as rice, wheat, and sorghum are primarily situated in the northwestern suburbs, whereas vegetables, fruits, and melons are distributed in proximity to water bodies in the southern suburbs. The Three Hills and Five Gardens area and the vicinity of the old city are the main locations for the growth of flowers and shrubs.

Finally, our findings revealed that certain areas exhibited a higher concentration of plants with elevated nucleation densities. These areas demonstrated a degree of specificity, with notable examples including the prevalence of wintersweet trees in the northern suburb and the clustering of plum and apricot trees in the eastern part of the suburb. Cudrania trees were planted in the vicinity of Tanzhe Temple (the name of the temple is derived from the large tracts of Cudrania trees in this area), sorghum was mainly planted along the drainage canal, and rice was concentrated in the area of the Three Hills and Five Gardens Historic Garden Cluster. This is due to two factors: the presence of microclimates conducive to the growth of specific plants and the influence of cultural and political factors on the distribution of plants.

4. Discussion

4.1. Authenticity of Plant Species

A total of 77 standard plant words were identified in the Suburbs volume of the Collection. The majority of these plants are native to Beijing, having originated from the city’s natural forests and cultivated land. They are also largely consistent with the types of plants that are currently common in the area [59], because the identification of native plants is based on their natural geographical distribution [60]. Beijing is situated at the intersection of the Yanshan and Taihang Mountains, where the climate is characterized by high temperatures and rainy summers, cold and dry winters, and low temperatures and precipitation in the winter. This climatic variation results in a relatively limited number of native plant species in Beijing [61].

However, the natural environment of Beijing has been subjected to human influence for a considerable period of time, during which the natural forests and cultivated land have undergone the process of plant introduction and replacement [62]. Some of the plants listed in Table 1 are not native to Beijing, particularly ornamental plants such as peonies, Chinese herbaceous peonies, fragrans, and ginkgoes, which were introduced to Beijing for artificial cultivation and breeding around the Liao Dynasty (907–1234 AD). Plum trees, the earliest recorded instance of which was planted in Beijing during the Yuan Dynasty (1271–1368 AD), are also included [63]. Other plants such as magnolias, hepaticas, and begonias were also introduced and planted in different historical periods [64]. The plant composition of the suburbs during the Qing Dynasty can be explained by the inherent natural properties of the environment and selective human interference based on ornamental value.

In addition, the number of plant species documented is considerably lower than the results of modern surveys of Beijing’s plant species [65]. This is partly because the ancients recorded plants in a different way and did not classify them as meticulously as we do today, and partly because a large number of exotic plants and new ornamental varieties were introduced to Beijing after the modern era [63,64]. For example, Zhao et al. found that the composition of plant species in Beijing’s urban areas differed significantly from that of natural habitats, with exotic species accounting for 53% [61]. Therefore, the plant species documented in ancient books from the Qing Dynasty can, to a certain extent, be used to reconstruct the authenticity of the plantscapes during the historical period.

4.2. Preferences of Plant Application

The application of plants is subject to intricate interrelationships with their social and environmental contexts [66]. The application of plants reflects the people’s understanding of plants from three aspects: culture, nature, and economy. The frequency of plant species demonstrated that the ancients were most concerned with trees, followed by aquatic plants, crops, and bamboos, and less concerned with groundcovers, shrubs, and vines (Figure 5). This may be attributed to the fact that the types of plants under consideration frequently possess cultural and productive value. Previous studies have shown that culture of plants is seen as powerful forces that play a positive role in people’s lives [67], and even in modern times, people are more concerned about plants that are useful to humans and plants with cultural symbols [68].

For instance, pines are perceived to possess the quality of longevity due to their resilience to drought and cold. The Chinese pronunciation of willow is similar to the phrase “stay behind”, which is often used to convey a sense of reluctance to part ways [69]. Conversely, the relatively limited number of documented shrubs and grasses may also be attributed to the absence of cultural and plant imagery [18]. Furthermore, the classification of basic plants, key plants, common plants, and uncommon plants is also related to the cultural value of plants.

We found in the relationships of species (Figure 6a) that only 15 species have more than two phyletic relationships. This result demonstrates the importance of ancient preferences for specific plants and the importance of these plant relationships. It is proposed that species relationships may be influenced by a combination of natural perceptions and cultural preferences [70]. Plants with two or more plant relationships are usually the dominant plants in coniferous and mixed coniferous-broad forests in the mountainous and shallow montane zones of Beijing and also grow in the vicinity of water systems in the plains [65]. The utilization of land in proximity to shallow knolls and watercourses for landscaping has the potential to exert a considerable influence on the environment, where plants are selectively retained and play a pivotal role in local natural and cultural systems.

Other relationships of species, in part derived from plant idioms, proverbs, and poems in the Chinese language and culture, reflect human-dominated cultural preferences. For example, the phrase “peaches and plums” represents a metaphor for the students cultivated by the teacher. This cultural preference for the use of plants was favored by the literati in ancient times. Previous studies have demonstrated that plant relationships can convey cultural values, enabling individuals to construct specific images or scenarios in their minds [51,71]. There is also a part of the plant relationship derived from the plant’s inter-organism relationship and the plant’s dependence on the environment [72], which reflects the ancient people’s observation of the environment, for example, the Cuscuta parasitized on pine trees, and the rice’s dependence on the water system makes the rice and the lotus also have a close connection.

4.3. Shaping of Plant Landscape

Plantscapes involve the integration of natural and cultural processes and are interdependent with vegetation management issues in human landscapes [73]. The results of the cluster analysis of plant combinations demonstrate the value proposition for shaping the plantscape (Figure 6b).

Category 1 (Cluster A) depicts a fundamental plant combination comprising evergreens and colorful foliage trees within a shallow suburban landscape. Category 2 (Cluster B and C) comprises vegetable, floral, medicinal, and fruit trees, which illustrate the economic and ornamental aspects of the plant combinations. Category 3 (Cluster D) is composed exclusively of apricot and persimmon trees. This is due to the traditional belief that planting an apricot tree and a persimmon tree in a farmyard is considered auspicious and has some feng shui value. Category 4 (Cluster E to H) encompasses plant combinations from disparate geographical locations. These combinations are observed in mountainous areas, courtyards, water, and the edges of water. In contrast, Category 5 (Cluster I) represents a plant combination with a distinctive, vibrant character.

These five plant combinations can be employed to inform contemporary plantscape design, while also reflecting the ancient peoples’ focus on respecting the conditions of the natural environment and balancing ornamental and economic values in their vegetation management. This is evidenced by the fact that even the royal palace plantations had to have a self-sufficient business model [74].

The spatial distribution of plants has shaped the wider botanical landscape. Our study reveals a phenomenon from a holistic perspective, demonstrating that the plantscapes in the suburbs of Beijing during the Qing Dynasty exhibited notable variations in different directions of the city. The primary reason for this outcome is that plant growth must be adapted to the natural environment. The Beijing region encompasses a diverse range of topographical features, including mountainous, moderately elevated, and low-lying areas [44,45]. The northwest region is situated upstream of the river, which is characterized by abundant water resources and a relatively favorable natural environment [31]. Accordingly, from the perspective of plant species diversity, the northwest suburbs exhibit the greatest richness, although melons, fruits, vegetables, and certain flowers are more conducive to cultivation in the plains. Furthermore, specific microclimates are present in select areas. For instance, some caves in the western suburbs experience winter temperatures that are sufficiently high to permit the overwintering of ornamental flowers. These areas are primarily utilized for the breeding of flowers.

The urban planning of Beijing in the Qing Dynasty was also influenced by the natural environment, which had an impact on the distribution of plants. In particular, the suburbs on the northwest side of the city had abundant water resources because they were situated at the upper water level of the water conservancy system [33]. Consequently, the number of royal gardens was much higher, and the external public environment was landscaped to a greater extent. Additionally, a significant quantity of rice and other crops were cultivated in the vicinity of the royal gardens on the west side of the suburb. This reflected the emperor’s political inclination to prioritize agriculture. However, the suburbs in the southeast of the city are situated at the lower water level. A considerable number of gardens in the upper reaches of the lower reaches have limited access to water, which presents a challenge in terms of water for gardening and living, water transport, and irrigation. This has led to difficulties in implementing large-scale, complex landscape transformations of the suburban environment [29]. Consequently, the species of plants are relatively homogeneous, often emphasizing a specific type of plant, and the plant landscape is more focused on economic value.

In addition, within the boundaries of Qing Dynasty Beijing, the closer one gets to the suburbs, the larger the area of the natural environment, the higher the percentage of the area occupied by plants, and even the more natural pristine landscapes are presented [33]. We compared the plants of the suburbs in the Qing Dynasty with scholars’ studies on the plants of historical gardens based on historical images and surviving remains [29,32,75] and found that there is a consistency between the plant species of the suburbs and the basic plant species within the historical gardens, which reflects the fusion of the public environment of the suburbs and the historical gardens. However, we also found that the plants applied in many characteristic nodes in the historic gardens were not consistent with the suburban public environment, mainly because more kinds of plants in the historic gardens were imported here from all over the country, which required fine management and care, and these plants were not suitable for growing on land in Beijing. Therefore, the research in this paper is more for the public environment construction when choosing tone tree species to provide reference.

At the same time, we also identified a relationship between the spatial distribution of plants in Beijing during the Qing Dynasty and the modern landscape layout of Beijing. This relationship reflects the continuity of the cultural lineage. For example, even in the modern era, the southern suburbs of Beijing remain the epicenter of the flower industry [76], boasting flower-themed parks such as the Flower Fragrance Park and the Beijing World Flower Grand View Garden. The eastern suburbs continue to house a significant number of nursery industries. The western suburbs remain mountainous, situated at the junction of mountains and plains. The natural substrate has undergone minimal change, yet the majority of the plants that were characteristic of the historical period have been supplanted by urbanized garden plants. The northern suburbs have been significantly impacted by the urbanization process, resulting in the replacement of the original natural landscape with residential areas and other construction sites.

Overall, it can be observed that, with the exception of the flower and nursery industries in the southern and eastern suburbs and the mountainous forested environment in the western suburbs, which have retained their historical characteristics, the remaining green areas that overlap with the study area have been replaced by ordinary green areas following urbanization. The plant species, combinations, and overall plantscape appearance of these areas have lost their regional characteristics and now exhibit a homogeneous appearance, which represents a significant difference in the existing green area structure in Beijing [61]. This phenomenon is particularly evident in the existing green space structure of Beijing, especially in the urban park loop.

5. Conclusions and Recommendations for Sustainable Conservation

The planting of native plants with authenticity contributes significantly to the sustainability of urban ecosystems and cultural systems in urban greening [19]. With the ongoing process of global migration and cultural integration, it is likely that the homogenization of plants across cities will become more pronounced [77]. This has the potential to negatively impact the ecological and cultural resilience of the landscape, particularly in cities with historic gardens.

As a culturally unified country, China’s similar cultural background has led to the emergence of greater similarities in the flora of various regions [70]. As the capital of China, Beijing is home to numerous historical gardens. Any significant alterations to the flora within these gardens, whether through the introduction of new species or the removal of existing ones, could have a detrimental impact on the gardens’ originality and cultural value. Accordingly, this study aims to reconstruct the botanical landscape of Beijing during the Qing Dynasty, employing a historical approach that integrates textual and geospatial data analysis. The main conclusions are as follows:

A total of 658 plants, including 44 families and 58 genera, were recorded in the suburbs of Beijing during the Qing Dynasty. These can be classified into seven categories according to the growth type and morphological characteristics of plants, forming 54 plant relationship results, 107 plant combination scenarios, 5 plant combination cluster categories, and 7 representative plant combinations. This illustrates the spatial distribution of the plants and the characteristics of the plantscape in different directions. Additionally, a graphical illustration of the spatial distribution of plants was created, resulting in the identification of 16 plantscape aggregation points. Furthermore, the spatial kernel density distribution of important plants was determined to gain insight into the characteristics of plantscapes in different aspects of the suburb.

We suggest that the use of high-quality native plants can be enhanced while emphasizing landscaping and biodiversity to avoid homogenization of urban greenery and that some native plants can be given appropriate cultural values based on historical information. At the same time, we recognize the introduction of new species into historic gardens and their external environments, and that over time introduced species can be adapted to local traditions through cultural adaptation [19]. Consequently, the ratio of native to introduced plants should be subject to reasonable control. Furthermore, our findings offer insights into the urban plantscapes of Beijing during the Qing Dynasty. They provide recommendations for the relationships, combinations, and spatial distribution of plants, which may inform the practices of those involved in urban greening.

In conclusion, in urban areas with historical gardens, it is imperative to consider not only the interior of these gardens but also the natural environment surrounding them. This approach is fundamental to an understanding of the authenticity of urban vegetation and may also provide a foundation for the resilience of historic landscapes. This approach also allows for a more balanced approach to the ecological development and the cultural heritage of historical plantscapes, which is also a crucial issue that must be taken into account when assessing the necessity of enhancing management in urban green spaces.

The present study is subject to certain constraints. One such limitation is that ancient people recorded plants in a manner that differs from the methods used today. This discrepancy may have introduced bias in the identification of plant species and the analysis of results. This study, meanwhile, focuses on exploring the characteristics of plant landscapes at the urban scale. This approach, however, does not provide direct guidance for the analysis of specific historical gardens or parks. Consequently, future studies will expand the sample size of the literature, enhance the scientific rigor and precision of the excavation of ancient texts, and incorporate specific historical gardens and modern parks into the study. This will facilitate the provision of references for the study of plant landscapes in traditional gardens and the planning of modern urban plant landscapes.