Plant diversity in homegarden

Many plant species are preserved in the homegarden of the Laifeng Tujia ethnic communities. Among the 243 homegardens surveyed, each encompassed between 17 and 121 species of plants, with an average of 40 species per household. A total of 414 homegarden plants from 114 families were recorded, and their scientific names, local names, family names, habits, sources, functions, utilization parts, utilization methods, and other information are provided in Table S4. These plants comprise three groups: ferns (4 species, 3 families, 0.97%), gymnosperms (11 species, 5 families, 2.66%), and angiosperms (399 species, 106 families, 96.38%). The 5 families with the greatest number of species were Asteraceae (29), Asparagaceae (19), Rosaceae (17), Lamiaceae (16), and Fabaceae (16) (Fig. 3a). Categorized by their habits, herbaceous plants (246, 59.42%) are the dominant component of homegardens, followed by shrubs (72, 17.39%), trees (68, 16.43%), and lianas (22, 5.31%) (Fig. 3b). Bamboo plants constitute the smallest number of species, with only 6. Multiple homegarden plants are fully utilized by the Laifeng Tujia ethnic community. Among them, the number of species that use whole plants (116, 28.02%) was the greatest, followed by flowers (95, 22.95%), leaves (72, 17.39%), fruits (66, 15.94%), and stems (61, 14.73%) (Fig. 3c).

Fig. 3

Plant distribution of the Laifeng Tujia ethnic communities. a Family distribution; b habit distribution; cuse parts distribution

Sources and functions of homegarden plants

The diverse sources of homegarden plants can be classified into five categories: market purchases (158), spontaneous species (107), wild introductions (103), neighborhood sharing (59), and self-preservation (36) (Fig. 4a). The market category includes three channels: purchasing at the market, online shopping, and local government unified procurement, with the highest number of species included. This is followed by spontaneous species, which refer to naturally growing species that are not artificially introduced and intentionally preserved in the homegarden.

Fig. 4

Plant sources and functions diversity in the homegarden of the Laifeng Tujia ethnic communities. a source; b function

The various functions and usage characteristics of homegarden plants can be divided into ornamentals (201), medicines (189), foods (165), trades (95), timber (34), forage (28), and others (11) (Fig. 4b). The high proportion of ornamental, medicinal, and food plants in the homegarden plants of the Laifeng Tujia ethnic community indicates that the homegarden provides an abundance of ornamental flowers, traditional medicinal plants, and edible fruits and vegetables for locals. The plants within these homegardens often possess multiple properties, indicating that a single plant usually performs multiple functions.

A correlation analysis of the sources and functions of homegarden plant species revealed that the main source of ornamentals is market purchases, including some grass flowers and potted plants (Fig. 5). Medicinal plants are sourced mainly from wild introductions and spontaneous species, consisting mainly of some folk herbs, some of which are also primary sources of trade plants. Foods are purchased predominantly from the market, primarily including seasonal vegetable seeds and seedlings.

Fig. 5

Chord diagram of the source and function association of plants in the homegarden of the Laifeng Tujia ethnic communities. Chord diagrams are used to demonstrate the correlation between the sources and functions of homegarden plants. The color of the chords is determined by the source of the homegarden plants. The thickness of the chords represents the strength of the connection between homegarden plants of different sources and functions

Ornamentals

The most prominent role of homegarden plants is providing ornamental beauty, a feature that contributes significantly to the aesthetic appeal of local homegardens. Osmanthus fragrans, Lagerstroemia indica, Impatiens balsamina, and Celosia cristata (Fig. 6a) represent the most prevalent ornamental species.

Fig. 6

Some homegarden plants. a Celosia cristata; b Polygonatum sibiricum; c Rosa chinensis; d Achyranthes longifolia; e Diuranthera major; f Benincasa hispida; g Capsicum annuum; h Allium fistulosum; i Paris fargesii

Medicines

Medicinal use constitutes another significant function of homegarden plants among the Laifeng Tujia ethnic communities. The locals maintain the belief that “all varieties of herbs can be medicinal, with the key lying in the knowledge of their proper use”. Our findings indicate that most households cultivate several to dozens of medicinal plants within homegardens.

Polygonatum sibiricum, a medicinal food plant, is cultivated in nearly every homegarden. Its rhizomes, when soaked in wine and consumed, can ameliorate lower back pain and exhibit a nourishing effect on muscle and bone fortification (Fig. 6b). Polysaccharides in P. sibiricum are essential components that have possessing biological activities, such as antioxidant, antiaging, antifatigue, and lipid-lowering activities [39]. Additionally, in periods of food scarcity, locals resort to roasting and consuming it. Presently, numerous medicinal herb merchants purchase it at a rate of approximately 16–20 RMB/kg, providing economic benefits to households.

Rosa chinensis, known for its highly ornamental flowers, is a beloved plant [40]. It serves both medicinal and ornamental purposes in the homegarden (Fig. 6c). According to local belief, its flowers and roots can be utilized to treat gynecological disorders, either through decoction or by soaking in wine for oral consumption. The medicinal effects of various R. chinensis varieties are also classified on the basis of their flower color. It is generally believed that R. chinensis with white flowers can address menstrual disorders, whereas varieties with red flowers are utilized to treat abnormal vaginal discharge.

Additionally, numerous medicinal plants, including Achyranthes longifolia (Fig. 6d), Diuranthera major (Fig. 6e), and Eleutherococcus nodiflorus, utilized for nourishment are present in the homegarden. These plants, which are typically employed in stewing meat, are widely accepted by the Laifeng Tujia people. Notably, local people also utilize certain vegetable species as traditional remedies. For instance, the roots of Cucurbita moschata can be used for the treatment of lymphatic inflammation, whereas the seeds of Allium tuberosum can be used to treat conditions such as hemorrhoids, toothache, and stomach ailments.

Foods

Among the homegardens of the Laifeng Tujia ethnic communities, vegetables, including Raphanus sativus, Cucumis sativus, and Benincasa hispida (Fig. 6f), constitute the primary edible plants. Plants in homegardens can provide an abundance of nutrients such as carbohydrates, vitamins, proteins, and dietary fiber, directly contributing to the sustenance of local inhabitants [41, 42]. Additionally, spice plants play a significant role in these homegardens. The Laifeng Tujia ethnic community states, “Using chili peppers as salt, with Hezha (a soy product stewed with vegetables), you can celebrate the Chinese New Year.” In the past, owing to limited transportation and resources, a variety of spice plants were cultivated in homegardens as substitutes for soy sauce, salt, and other seasonings. These include Capsicum annuum (Fig. 6g), Zingiber officinale, Coriandrum sativum, and Allium chinense, which were grown to enhance the flavor of the dishes. This practice persists today, forming an integral part of their dietary culture. This characteristic aligns with findings from research in the neighboring Larshan region in western Hunan [24].

Other categories

A significant portion of homegarden plants, encompassing edible and medicinal species, are used for trade. These plants serve as commodities for market trade or are procured by medicinal merchants to sustain or supplement livelihoods. Among the 34 species of homegarden plants used for timber, certain species, including Cunninghamia lanceolata, Cupressus funebris, Toona sinensis, and Liquidambar formosana, are utilized in the construction of characteristic Tujia stilt houses. Other varieties of homegarden plants are also employed in the fabrication of agricultural tools and as firewood. Local residents believe that plants edible to humans can also be consumed by livestock, resulting in various homegarden plants serving as forage for pigs, poultry, and livestock. Additionally, 11 species of homegarden plants are classified as other uses, predominantly encompassing cultural purposes, fence construction, and dyeing.

RFC value analysis of homegarden plants

The RFC value range for homegarden plants of the Laifeng Tujia ethnic communities is between 0.004 and 0.951. 24 homegarden plants presented RFC values greater than 0.5, indicating their high significance. Among these, Allium fistulosum had the highest RFC value (0.951), followed by Raphanus sativus (0.914), Brassica rapa var. chinensis (0.897), Brassica rapa var. glabra (0.881), and Cucurbita moschata (0.881).

A. fistulosum is a common condiment among the Laifeng Tujia ethnic communities, and virtually every household cultivates it for its own use, which results in the highest RFC value (Fig. 6h). R. sativus, B. rapa var. chinensis, B. rapa var. glabra, C. moschata, Vigna unguiculata subsp. Sesquipedalis, Lactuca sativa var. angustata, and Benincasa hispida rank among the most commonly preserved homegarden plants within the Laifeng Tujia ethnic communities, all with high RFC values.

Zea mays, Ipomoea batatas, and Solanum tuberosum are prevalent food plants of the Laifeng Tujia ethnic communities in mountainous areas, and can also serve as forage for livestock and poultry. Certain households cultivate these plants in fields rather than within homegardens, leading to their RFC values not being as high as those of fruits and vegetables. Nonetheless, they still play an integral role in the locals’ livelihood.

Most herbal plants, such as Eleutherococcus nodiflora, Mahonia belei, and Paris fargesii (Fig. 6i), presented low RFC values. Homegardens that preserve these plant species often belong to households that practice herbalism or possess some knowledge of herbal medicine.

Comparison of the homegarden plant species among the different towns

The Jaccard index results for homegarden plants across various towns are depicted in Fig. 7. According to the heatmap of the Jaccard index, the degree of similarity among homegarden plants in Geleche Town and Dahe Town was the most pronounced, at 0.590, whereas the similarity of homegarden plant species between Lvshui Town and Geleche Town was notably minimal, at 0.293 (Fig. 7a). In accordance with the multidimensional scaling outcomes of the Jaccard distance values, the seven towns are distributed across four quadrants (Fig. 7b). Dahe, Geleche, and Jiusi townships are situated in the elevated western region of Laifeng County, featuring proximate geographical positions. Manshui and Lvshui represent two neighboring townships situated in the eastern part of Laifeng County. Generally, the similarity among homegarden plants in towns with similar geographical locations is correspondingly elevated.

Fig. 7

a Heatmap of Jaccard index for courtyard plants in different towns; b Multidimensional scaling based on Jaccard Distance (ALSCAL)

Influences of homegarden characteristics on the sources and functions of homegarden plants

The DCA of the sources and functions of the homegarden plants revealed maximum gradient lengths of 0.6228 and 0.5264 along the four sorting axes, both of which were less than 3 (Table S2). Thus, RDA was selected to determine the sources and functions of homegarden plants. The RDA sorting results reveal that the eigenvalues of sorting axes 1 and sorting axes 2 for homegarden plant sources are 0.292 and 0.0144, respectively, accounting for 99.48% of the total eigenvalue (0.308) (Table S3). The eigenvalues of sorting axes 1 and sorting axes 2 of the homegarden plant functions are 0.2997 and 0.0073, respectively, reaching 98.90% of the total eigenvalue (0.3104) (Table S3). The first two sorting axes were selected as the RDA 2D sorting diagram (Fig. 8). The source and function of homegarden plants were significantly correlated with knowledge of herbal medicine and the homegarden area (p < 0.01) (Table 2). With respect to the source of homegarden plants, knowledge of herbal medicine and the homegarden area had the greatest impact on species from wild introductions (Fig. 8a). With respect to the function of homegarden plants, knowledge of herbal medicine and the homegarden area had the most significant impacts on the species used for medicine (Fig. 8b). Additionally, the average age of permanent residents has a notable negative correlation (p < 0.05) with the source and function of homegarden plants (Table 2).

Fig. 8

RDA ordination of plant sources and functions in the homegarden of the Laifeng Tujia ethnic communities. a source; b function A Altitude, Dm Distance to the nearest market, Dc Distance to the county town, Num Number of permanent residents in the household, Age Average age of permanent residents, Edu Average years of education, Ha Homegarden area, Hk Herbal medicine knowledge, Wi Wild introduction, Mk Market purchase, Nb Neighborhood sharing, Sf Self-preservation, Sp Spontaneous species, Md Medicine, Fd Food, Or Ornamental, Fg Forage, Ti Timber, Tr Trade, Oth Other

Table 2 Explanation rate of influencing factors of RDA