Composition of homegarden plants

Homegardens are crucial in the conservation of beneficial plant species since they contain numerous species that are often absent or disappearing from other production systems. A total of 238 culturally important plant species were recorded, and this is supported by [12]. The composition and use of homegarden plants were studied in some parts of Northwest Ethiopia. For example, in the Jabithenan District, a total of 69 species from 40 families were reported [41], from the Bulen District, 22 plant species from 15 families were recorded [29], and from Southern Tigray, Northern Ethiopia, 32 plant species from 20 families were recorded [17]. Our findings indicated that a high number of culturally important plant species (238) were recorded in the homegardens of the Gozamin District. This relates to the rich culture of people in the area in conserving useful species at their gardens. About 110 (46%) plant species of the culturally important species that were conserved in the homegarden are emerged from the wild sources. The presence of 238 culturally important species at the homegarden of the study area showed that the homegardens are sites of in situ conservation; the finding conforms with that of [18, 19].

The size of homegardens used for plantation varies from 0.015 to 0.5 ha indicating variations in homegarden sizes harboring culturally important plants which are core sources of subsistence. Earlier reports also indicate the presence of size differences in homegardens of the Northwest Ethiopia. For example, the home garden size in Jabithenan District ranges from 0.05 to 0.5 ha [42], and it ranges from 0.031 to 0.75 ha in Bulen District (30). Of the total 357 homegardens (8.98hactares) sampled, 238 plant species were recorded. As shown in Fig. 3, the number of species grows as the size of homegardens increases but falls in homegardens with three plots. This is not surprising given that the number of home gardens that took three plots from 357 home gardens was 52 (14.6%) of the samples, and while the number of home gardens may affect the number of species, in other cases when the size increases, the number of species increases, and this is true in all the three agroclimatic zones. A comparable study conducted in Ethiopia's Oromia Region's Sebeta-Awas District [42] reported that as the size of a homegarden increases, so does the diversity of plant species. The plants recorded are trees, shrubs, herbs, and climbers. Of these, herbs were the most dominant species (39%). Reports of Mekonen et al. [42] and Regassa [43] also go in line with the findings of this study, whereas Mengitu and Fitamo [44] pointed out that trees were the dominating species in the Dilla Zuriya District. The Poaceae, Fabaceae, and Asteraceae families had the most species in the study area. This might be owing to the dominance of the Fabaceae, Asteraceae, and Poaceae families in Ethiopian and Eritrean flora, as mentioned in [45,46,47,48]. These homegarden areas, where many plant species live, have cultural importance and hence play an important role in the conservation of threatened species.

Diversity of homegarden plant species in three agroclimatic zones

Among the three agroclimatic zones where the homegarden plants were recorded, Woina Dega comprised the highest number of plant species (203) accounting for 85.3% of the total number of species in the samples, followed by the Kolla agroclimatic zone (130) (Table 2). The result indicated that Woina Dega agroclimatic zone was home to a wide variety of plant species. This is substantially owing to the fact that the Woina Dega agroclimatic zone might be ideal for the growth of many plant species. Abebe [25] also showed that the agroclimatic zones of Woina Dega have a high potential for perennial cropping. It also had the highest sample size (53.5%). Although the diversity of home garden plant species was lowest in Dega agroclimatic zone (88), it had the highest evenness, highlighting the importance of this agroclimatic zone. We discovered an Ensete ventricosum plantation (enset variety used as food) in the Dega agroclimatic zone; it was native to Ethiopia's south and southwestern regions, where it is now commonly farmed [25]. This is a promising start to conserve Ensete ventricosum and secure food availability in the research area, where the livelihood of the people mainly relies on cereal crops.

Homegarden plant species composition similarities

The highest similarity index was found between Yeboargina and Kebi, and Yboargena and Ytegan, indicating that they shared 60% of the plant species. This might be because they are found in a similar agroecological zone. On the other hand, Chimit and Graram had the lowest similarity values, meaning that they shared only 25% of the plant species. The reason could be the agroecology difference between them. The similarity index for 64% of the locations (Kebeles) investigated was less than 0.5, suggesting that there was less similarity to high species diversity in the area. This might be due to differences in agroecological conditions among Kebeles, as evidenced by Ertiro et al. [49] who demonstrated that agroecology has an impact on variation.

Plant use diversity

From sampled homegardens, plant species used for food, fodder, environmental uses, fuels, medicines, materials, socially useful plants, and rat poison were recorded. This finding agrees with Nair et al. [28], who showed gardens' enormous species diversity, which consists of food crops, medicinal plants, ornamentals, fruit trees, multipurpose trees, and fodder species, supporting a variety of ecosystem services. From the use composition of homegarden plants in the study area, the highest record of use composition was food, which means homegardens primary use value was food, secondly medicine for humans and animals, followed by social uses (ritual and religious uses, stimulant drugs, cosmetics, and baking agents) (Fig. 7). The same is true in the three agroclimatic zones; the first and second most important use diversity were recorded for food and medicinal uses, but the third cultural use in Dega and Kolla agroecology was environmental, and the third cultural use in Woina Dega agroecology was social use (Fig. 6). Plant composition varies between agroecological zones as a result of changes in niche quality and the adaptation of environmental gradients such as precipitation, temperature, and soil fertility, as agroecology variation is mostly related to altitudinal gradient. According to [26], elevation has an impact on species composition. The cultural value difference in different agroecological zones relates to species availability (which is based on variations in environmental factors), and people’s preferences corresponding to their different living trends. This finding is consistent with Song et al. [50], who found that gardeners' profiles were strongly correlated with community food provisioning services and may have social and environmental benefits. That is, plant species that were used for food, medicine, and social uses have been conserved more than others in the study area. This also shows that culture (cultural use) has a high value for conserving plant species. This finding agrees with [37].

The cultural importance of homegarden plants

People in the study area have designed diverse and adaptable homegardens that grow a variety of important livelihood crops. The homegardens remarkably possess plant species used for human and veterinary medicines, livestock feed, and plant species used to make different materials (such as handicrafts, construction materials, agricultural tools, roof thatch, instruments, toothbrushes, rope, mortar, and pestle), fuel, social utility (ritual and religious uses, stimulant drugs, smoking, cosmetics, and baking agents), environmental uses (such as live fence, dry fence, hedges, shade, ornamental and soil improvement), and this trend is also true in other studies [40]. The community members in the area have cultural knowledge in crop selection and information sharing with culturally knowledgeable people in the study area, which co-adapts agroecology and provides multiple benefits [51]. As shown in Figs. 8 and 3, the size of the homegarden increases the number of species and the use diversity, but not in the third instance (which took 3 plots). This scenario is similar to the previous one, in that fewer homegardens were collected and fewer species were documented, but in other cases, the number of species and use diversity of homegardens increased as homegarden size increased. Moore et al. [52] and Manne [53] also showed that species diversity and cultural diversity were intimately correlated. Gardens are located around water-abundant areas (rivers, ponds, and water wells). Amede and Taye [54] also showed that surface irrigation water (springs and rivers) had become a key motivator for cultivating fruits and vegetables in Ethiopian homegardens.

Fig. 8

Size of homegarden and cultural use of species in Gozamin District

Homegardens in the study area were mostly live-fenced or semi-fenced areas. Trees, shrubs, herbs, and climbers were used as live fences, serving as a barrier to keep predators away from fruits, vegetables, spices, and other items. This culture in the study site keeps diverse plant species around people’s homes and gardens and allows for in situ conservation of species which are still in use for fences and other cultural values. The present study identified that the majority of the homegardens analyzed were encircled by a live fence. This was also shown by other studies [16, 29]. In general, environmentally useful plants such as fences, shade, and ornamental plants cover 140 (58.6%) plant species under 66 families. This was supported by Kumar and Nair [4], who showed that homegardens were praised for preserving biodiversity and preventing environmental degradation.

Environmental variables and dietary preferences, as well as socioeconomic and commercial needs, are all reported for their influence on the distribution of species in homegardens [55]. As observed in the current study area, the number of plant species varied between kebeles. Since there was irrigation water, and Wenka is close to the main town of Debre Markos, it had a significant number of home garden species (130 species in 58 families). The site supplied food crops to Debre Markos town, primarily fruits, and vegetables, and this encouraged farmers to sell their homegrown produce in areas with strong market access [15, 25].

In the study area, homegardening provides subsistence food production and family food security by producing vegetables, fruits, cereals, spices, and beverages. Other authors [26, 42,43,44, 56, 57] have also reported on the widespread use and service of homegardens. Fruits were the most commonly utilized plant parts from food crops in the studied homegardens. The result goes in line with other reports [43, 44, 58].

Information about medicinal plants (passed from grandparents) was exchanged among indigenous peoples and neighbors and played its role in medicinal plants conservation. Exchange of plant resources and cultural information among communities has been reported as a useful tool to promote conservation [59]. A total of 83 therapeutic plants were recorded at homegardens of the study site. This demonstrates that gardening has placed a greater emphasis on human health and well-being [60], the main healthcare provider [61]. Dracaena steudneri was found with medicinal properties for treating livestock ailments. It was also cited for treating bad spirits, besides its decorative nature, fodder, shade plant, fence, and other cultures, and hence was common within the study area.

Some socially useful plants such as Ficus sur, Ficus vasta, and Prunus africana are used by local people in the area for different rituals and religious uses; Prunus africana, for example, is used for decorating wedding ceremonies in the area and hence conserved by local communities. Plants used for religious ceremonies, stimulants, smoking, and baking account for 50 (21%) of the species identified. This proves that cultural value has become the center point for preserving plants [42, 61, 62] and has also reported similar records. Coffea arabica, which was also used in households and for the market, was discovered in all the study kebeles, and Catha edulis, which was also utilized for the market to generate income, was also detected in most study sites (kebeles). This was also shown in other research findings [15, 29]. Also, Mellisse et al. [63] recently reported that there has been a dramatic movement away from conventional family gardens toward cash crop Catha edulis-based systems, especially in locations near to marketplaces. A total of 2 (0.84%) plants were found to be utilized in the preparation of bread and potatoes. Ensete ventricosum, which was used for baking bread, potting injera, and malting malt, was described as having a nutraceutical nature only [42, 64,65,66]; Galium aparinoides was a weed that was commonly used to cook potatoes since it cooked them quickly and had a wonderful flavor; however, Mekonen et al. [42] classified it as a weed that affects the variety and productivity of homegarden plants. Local communities also conserve fodder plants around their homegardens, mostly for fattening cattle and sheep. Snowdenia polystachya, which is a perennial plant species, was the highest fodder plant recorded, followed by Cenchrus ciliaris and Cynodon dactylon. Likewise, the root multifunctional plants that have high usable values are threatened since accessed by the local community for their multiple uses, even though they are the foundations of most tropical backyard gardens [28]. Multipurpose cultural plant species are threatened primarily for the production of various materials and fuel (firewood and charcoal) rather than for other cultural activities. The same was true in North Shewa Zone, Amhara Region, Ethiopia [67]. The direct matrix index revealed that Cordia africana, a multifunctional, culturally important plant in the area, was the most extremely endangered species, followed by Ficus sur. Cordia africana is exploited more for construction. People are also using Cordia africana to make different materials. Cupressus lusitanica was a common plant in all sampled kebeles with multipurpose functions including for purposes of ornamental use, construction and building, as gum used in food, forage, fence, and fuel, and this report matches with that of Mekonen et al. [42]. Similarly, by the cultural importance index, the first multifunctional plant, Cordia africana (FC = 125), is the most culturally significant species. It has a value of 2.23 on the CI index. This plant species is mostly used for food, fodder, environmental use, material and fuel (CI = 0.35), medicinal use (CI = 0.25), and social use (CI = 0.22), as shown in Table 5, contradicting the findings observed in the direct matrix ranking; the cultural value index considers not only the prevalence of use (number of informants) for each species, but also its versatility, i.e., the variety of its uses. The maximum value of the index is the entire number of various use categories in their garden (NC). That is, the CI index considers the species UR and FC (Cordia africana) has the first UR (795) and second FC value (125)) and also reflects the distribution of species because it is the total of the proportion of informants who mention each species' use in their garden. Vernonia amygdalina (CI = 2.17) is the second most culturally important species in the ranking. As shown in the figure for CI index components in Table 5, the most common uses from the seven uses categories are medicine, fuel, and social use (CI = 0.39), followed by feeding (CI = 0.36) and material use (CI = 0.25). Olea europaea subsp. cuspidata (CI = 1.32) was the third culturally significant species, and it was employed for the environment, material and social usage (CI = 0.3), medicinal usage (CI = 0.28), and fuel (CI = 0.14). Also, people in the study area believed that the fumigation of Olea europaea subsp. Cuspidata in the house using leaves and stems removed bad spirits and bad odors from the house and were also used to fumigate milk, Tela, and Tej (local beverages) pots [68]. This finding indicates the presence of high level of agreement on cultural relevance of species, and the sharing of common knowledge on useful species by homegarden owners. This finding is supported with that of [23, 38]. In this study, the multipurpose species that have been identified in a wide number of home gardens (greater FC) were given first place for conservation and cultural use. This was also true for Tardío and Pardo-de-Santayana [38].

There are some variations in the ranks of species analyzed using various indicators as shown in Table 5. Although the third, tenth, twelfth, thirteenth, and fourteenth species have the same rank in all three of the indices, The CI and CVI indices rank Cordia africana first and foremost because these two indices place greater emphasis on the multiplicity of uses, and the species was cited in a greater number of use categories (NU = 7). Vernonia amygdalina has a higher IFC since it predominates in homegardens and is present in a greater number of them. Preserving cultural importance entails expanding understanding and safeguarding culturally important plant species. Our results suggest considering cultural use and the cultural importance of floristic composition before designing biodiversity conservation in agroecosystems.