Woody species composition and distribution

We planted 95,582 saplings of 31 tree species representing 27 genera and 20 families on 150 hectares of degraded habitat in the Dering-Dibru Saikhowa Elephant Corridor (Table 2). Each woody species’ relevant traditional ecological knowledge was recorded, including family, local name, habitat, citation, and use value (Table 2). The families with the most species having traditional ecological uses were Combretaceae (four species) followed by Fabaceae (three species) and Anacardiaceae (two species) (Table 2). A clear relationship (y = 3.9012 × − 0.499; R2 = 0.8652) between family and species pattern was observed (Fig. 3). The species diversity was similar to other parts of the wider region. Elliott et al. [41] evaluated the potential of 34 tree species for forest restoration in China. Similarly, [42] employed 37 forest tree species to accelerate forest restoration in Doi Suthep-Pui National Park, Thailand. Krishnamurthy et al. [43] similarly reported Combretaceae as the dominant family in Bhadra Wildlife Sanctuary, Karnataka, India. Sen et al. [44] also found Combretaceae as the dominant family in the forests of Dadra and Nagar Haveli, India.

Table 2 List of tree species with family, species, local name, habitat and ethno usage, citation, and use valueFig. 3

Relationship between families and species pattern in the Dering-Dibru Saikhowa Elephant Corridor in Arunachal Pradesh, India

Traditional knowledge on enlisted species

We classified the documented species based on the ecological knowledge of the local inhabitants, i.e., as pioneer species, food, fodder, timber, fuelwood, medicinal, livelihood, habitat, and forage. Upon interpreting the documented results, pioneer species accounted for 16% of all woody species, followed by habitat and forage for wildlife (15%), food, timber, and livelihood species (13% each), fuelwood (12%), fodder (11%), and medicine (7%) (Fig. 4 and Table 2). De Arruda et al. [45] reported the dominance of ethno-woody species as pioneer species in forests of Northeast Brazil. For indigenous people who live in or close to forests, non-timber forest products have grown to be a significant source of revenue and sustenance. Such traditional conservation of woody and related plants serves as a “safety net” and “resource ground” for the community as well as helping to preserve biodiversity and natural resources [46].

Fig. 4

Woody species distribution according to usage by native communities’ in Dering-Dibru Saikhowa Elephant Corridor in Arunachal Pradesh, India. The direction of the lines shows which woody species are associated with which types of usage, and the thickness of each bar shows the number of species in each usage category. The complete name of species is shown in Table 2

This result was further verified by PCA analysis (Fig. 4), which yielded separate groups depending on preferences for woody species utilization. The two axes accounted for 62% of the variation in the biplot. PC1 accounted for 45% of the variation in species utilization, with PC2 accounted for the remaining 17%. The individual uses, i.e., food, fodder, timber, fuelwood, pioneer species, habitat, and forage closest to 1 (positive) or -1 (negative) have the greatest correlations, whereas medicinal and livelihood show less correlation. Timber and fuelwood were clearly segregated on the one side of the PCA from the rest of the uses on the other (Fig. 5). In a similar manner, [47,48,49] employed multivariate analysis in TEK and ecological restoration.

Fig. 5

Principal component analysis (PCA) illustrating the relationship of woody species and the usage by native communities’ in Dering-Dibru Saikhowa Elephant Corridor in Arunachal Pradesh, India

Woody vegetation usage patterns

During the present study, the ecological usage pattern of woody species across the local inhabitants was categorized into single, double, or multi-uses (Fig. 6). We found ten species with more than five applications, with Azadirachta indica, Phyllanthus emblica, and Syzygium cumini (six each) having the greatest use value, and Mesua ferrea having the lowest number of uses (single use).

Fig. 6

Woody species and their usage (single, double, and multi) in Dering-Dibru Saikhowa Elephant Corridor in Arunachal Pradesh, India. The direction of the lines shows which woody species are associated with which types of usage patterns, and the thickness of each bar shows the number of species in each category. The complete name of species is shown in Table 2

Single use

These were the woody species used for only single purpose, including Chionanthus ramiflorus, Mallotus nudiflorus, Manilkara kauki, and Mesua ferrea. The single usage species constituted 19% of the total used species.

Double use

Woody species used for two purposes were Artocarpus chama, Bischofia javanica, Magnolia baillonii, and Neolamarckia cadamba. Double uses species constituted 13%.

Multi-use

Woody species such as Albizia lebbeck, Artocarpus heterophyllus, Azadirachta indica, Bombax ceiba, Dalbergia sissoo, Dillenia indica, Lagerstroemia speciosa, Phyllanthus emblica, Syzygium cumini, and Terminalia chebula were used for multiple purposes. Multi-use species constituted 68% of all species. We employed the use value (UV) index to elucidate a relation between each species and the uses allocated to them. The UVs of different species are given in Fig. 7. Among the reported species, the highest use value was calculated for Artocarpus heterophyllus (UV = 0.74) and the lowest for Spondias mombin (UV = 0.2). The high use value (UV) of the Artocarpus heterophyllus was due to its multiple usage as well as the familiarity local people in its usage since ancestor times (Fig. 7). According to [50], the use of plant species highly depends upon social factors and differs across locations. Such patterns have been observed around the globe, e.g., Mariscal et al. [51] found the number of uses of a species ranging from one to a maximum of five in Cloud Forest Ecosystem Restoration in Ecuador, Guariguata et al. [52] reported different usage patterns of species for forest restoration from Costa Rica. Similarly, [53] reported a variety of species applications from tropical montane forests. According to [54], there is abundant TEK existent in the Arunachal Himalayan hill communities. This knowledge, which has been adapted to the local ecosystem and is valuable for sustainable resource use and conservation, is based on millennia of spontaneous observations of the local environment. Hazarika and Merentoshi [55] reported the maximum use value of Artocarpus heterophyllus from Nagaland, India. Similarly, [56] reported the same while investigating the traditional agricultural practices in Meghalaya, India.

Fig. 7

Relationship between used value (UV) and frequency of citation (FC). The plant names as they appear in Table 2

Ecological knowledge on enlisted species

In the present study, we found that the local people were quite knowledgeable and provided detailed information on species required as pioneer store a variety of habitats (Table 2). It is important to mention that local people use forestland for agriculture, for which they burn the vegetation on a patch of land, which, in turn, increases the fertility of land. The obtained land is used for 3–4 years, after which a second patch is selected, and TEK is applied to restore the left behind patch rapidly. We incorporated this traditional ecological knowledge into ecological restoration programs by planting mixed pioneer tree species. An overall of 16% of species including Bombax ceiba, Albizia lebbeck, Dillenia indica, Syzygium cumini, Phyllanthus emblica, Lagerstroemia speciosa, Alstonia scholaris, and Averrhoa carambola were reintroduced to restore the degraded habitats. Throughout the world, local people possess an extensive traditional ecological knowledge of the indigenous species with relation to habitat [57]. The traditional knowledge and well-adapted traditional agricultural techniques of the indigenous communities allowed them to maintain an ecological balance [58].

We classified the habitat of enlisted species into different categories including, natural forest, riverine, roadside, cultivated field, and degraded habitat. Based on the similarity of woody species in different habitats, two primary clusters (clusters 1 and 2) were obtained (Fig. 8). Cluster 1 included eight species that grew mostly in degraded habitat. Cluster 2 included two branches displaying the classified habitats such as natural forest, riverine, roadside, and cultivated field. However, the species that are closely grouped in close clusters are more similar in habitat preference. Most of the species grew in more than one habitat (see Table 2 for habitat preferences). Our results are in line with [59] from Kerala, [60] from southeastern Mexico, [61] from Madhya Pradesh, and [62] from Himalaya.

Fig. 8

Heat map illustrating the relationship of woody species and the habitat types in Dering-Dibru Saikhowa Elephant Corridor in Arunachal Pradesh, India

Our results were further supported by PCA, which showed variation depending on habitat preferences of woody species. The two axes account for 59.9% of the variation in the biplot. PC1 accounts for 32.7% of the variation in species habitat preference, with PC2 accounting for the remaining 27.2% (Fig. 9). The habitat types, i.e., natural forest, riverine, degraded, and cultivated field closest to 1 (positive) or -1 (negative) had the greatest correlations. Our study found that tribal people based on their surrounding environment recognized woody species. One example is species such as Lagerstroemia speciosa, Chionanthus ramiflorus, Canarium strictum, Gmelina arborea, and Manilkara kauki that were regarded as the indicator species for natural forest. Subashree et al. [63] found Chionanthus ramiflorus and Canarium strictum as the key pioneer species in a study on the structure and regeneration potential in Western Ghats. Species such as Albizia lebbeck, Bombax ceiba, Syzygium cumini, Spondias mombin, Mesua ferrea, and Artocarpus heterophyllum were associated the degraded habitats. Similarly, [64] reported Albizia lebbeck and Bombax ceibaas characteristic for degraded habitats. Riverine habitat included species such as Artocarpus chama, Bischofia javanica, Samanea saman, and Neolamarckia cadamba. Similarly, [65] reported Artocarpus chama and Bischofia javanica as the major riverine species from Assam, India. Roadside habitat included species such as Dillenia indica, Phyllanthus emblica, and Dalbergia sissoo, and the cultivated field habitat included Psidium guajava and Azadirachta indica, and [66] also reported Dillenia indica in roadside and cultivated field habitats from Northeast India.

Fig. 9

Principal component analysis (PCA) illustrating the relationship of woody species and the habitat types in Dering-Dibru Saikhowa Elephant Corridor in Arunachal Pradesh, India

Among the species were introduced to the corridor, 69% were tied to indigenous societies through ethno uses as food, timber, fuelwood, medicine, and fodder, thus integrating resource use patterns and societal and cultural values in restoration design is a significant goal. Artocarpus heterophyllus, Artocarpus chama, Albizia lebbeck, Bombax ceiba, Canarium strictum, Chukrasia tabularis, Dalbergia sissoo, Elaeocarpus serratus, Gmelina arborea, Magnolia baillonii, Mangifera indica, Neolamarckia cadamba, Samanea saman, Terminalia chebula, and Terminalia myriocarpa were used by native communities for food, timber, and fuelwood. Intensive afforestation/reforestation based on planting native tree species offer a wide range of ecosystem services for the local community. Local peoples’ knowledge of plant species is an important source of information on species distribution, rarity, ethno usage, and long-term vegetation change [67]. In northeastern India, tribal people share vest a variety of forest products from privately owned and community-maintained woods for a variety of uses [68]. In this setting, Lagerstroemia speciosa and Mesua ferrea were considered the best fuelwood plants. Similarly, Azadirachta indica, Psidium guajava, Terminalia arjuna, Terminalia chebula, and Terminalia arjuna were also of medicinal importance and were reintroduced given that the local native communities still rely on these natural resources for their health care. Kiran et al. [69] reported Terminalia arjuna as medicinally important species utilized for reclaiming degraded land in India. Similarly, [70] reported species like Azadirachta indica for conservation and restoration of degraded terrestrial ecosystem in Central India. These diverse plantings represent a system-level move away from monoculture plantations in order to increase biodiversity and aid in the recovery of ecosystem functioning. Planting multiple tree species frequently includes legumes, i.e., Albizia lebbeck that fix nitrogen; this nitrogen supply, together with litter from vegetation, reduces or eliminates the need for additional fertilizer. Forage plants such as Dillenia indica and Elaeocarpus serratus can also be grown to provide fuelwood and fruit, enabling sustainable land use. Furthermore, increased soil fertility may reduce farmers’ need to expand their farming activities (Jhum cultivation) into the forest. We must reestablish a healthy relationship with the ecosystems that support us. Restoration is critical to reducing climate change, maintaining food security for a growing population, and reversing biodiversity loss. We also require solutions that are natural, such as restoration.

Enhancing biodiversity

A total of 15% of the total woody species reported were restored for animal habitat and forage, aiming to achieve the primary goal of restoring biodiversity and functionality of degraded habitats. Chionanthus ramiflorus, Artocarpus heterophyllus, and Dillenia indica are among the plants valuable to wildlife, providing both food and habitat (perching and nesting grounds) for a variety of birds and animals. Maintaining biodiversity requires a multifaceted concept that includes species richness, and diversity is a priority in the ecological restoration design [71, 72]. A preferred plant species is defined by the extent to which the species is consumed in relation to its availability in the environment [73]. Sathya et al. [74] reported the Chionanthus ramiflorus and Artocarpus heterophyllus as the species being exploited by the elephants in Sathyamangalam Tiger Reserve, southern India; elephants prefer the woody species, such as Bischofia javanica and Neolamarckia cadamba. Mathew [75] also reported the preference of woody species like Bischofia javanica by the elephants and other wild animals. Birds and other animals eat and live in woody plants such as Phyllanthus emblica, Mangifera indica, Psidium guajava, Syzygium cumini, Artocarpus chama, Averrhoa carambola, Elaeocarpus serratus, and Manilkara kauki. Thakur et al. [76] found the use of many foraging species (Artocarpus heterophyllus) when investigating the feeding behavior of elephants in Chhattisgarh, India. Land use efficiency could make more space available for wildlife than traditional single-species plantations. Multiple trees are introduced to boost biodiversity at the landscape level by giving wildlife habitat and structural connectivity. If this method, which combines parts of sharing and protecting land, was supported by legislation, it would probably be able to prevent deforestation and the degradation of elephant corridors. It can also be effective in limiting Jhum expansion. We need to halt the loss of natural habitat, preserve what is left, and restore damaged ecosystems if we want to reverse the trend of biodiversity loss [77].

Community engagement and livelihood

Poverty can worsen damage to ecosystems and is a contributing factor to land degradation [78]. The health of young people and elders, women, the poor, indigenous peoples, those with chronic health conditions, and those who are the targets of racism are all at risk due to degradation, which also adversely affects indigenous and local communities whose livelihoods are directly dependent on natural resources [79, 80]. People in the developing world are highly dependent on woody species [34], from which they generate means for their livelihoods. However, wild trees are often threatened and decline in abundance and diversity. The main reason behind is agricultural expansion and overexploitation [81]. Large size, poor dispersal capacities, and low reproductive rates are the characteristics that render species susceptible to local extinction. At the same time, over exploitation is influenced by cultural and economic factors. They were introduced 13% of the enlisted species as a source of income for the native people, fitting one of the restoration design’s primary objectives. Artocarpus heterophyllus, Averrhoa carambola, Mangifera indica, Phyllanthus emblica, Psidium guajava, and Syzygium cumini were planted to help the community relying on the natural forest for their livelihood. Rahman et al. [82] reported on similar initiatives from Southeast Bangladesh, where they distributed saplings of a variety of medicinal and fruit tree species and supported the cultivation of medicinal plants in homestead forests and inside a sanctuary, distributed seeds of a range of seasonal vegetables for immediate cash returns, and established a committee through the Village Conservation Forum to protect these plantations. The success of any integrated science-based plan requires good conservation management in the field especially at the local level, and TEK is a step toward a management strategy for ecosystem restoration. An adaptive management plan makes it easier to combine various information sources, educate the public, and launch conservation policies in an iterative process that would develop as well earn how to protect these vulnerable ecosystems. Creating an action plan for forest protection should begin by convening local communities, scientists, resource managers, and government representatives in workshops [83]. Such a strategy would be in accordance with the UN Decade of Ecosystem Restoration (2021–2030), which requires governments across the countries to integrate local communities and their indigenous knowledge with management goals [84].

Revitalization of local plant knowledge

TEK systems representing cultural diversity are intricately linked to biological diversity, and the loss of either can have a significant effect on the other. If plant knowledge is lost, there is a chance that this will have a domino effect that causes the depletion of natural resources, a loss of biodiversity, and the extinction of plant species. Contrarily, a drop in diversity may also cause a loss or transformation of knowledge in the variety and number of used species. It has also been demonstrated that the continual loss of TEK due to cultural and linguistic extinction undermines conservation efforts. Because of social and ecological changes, the subsequent loss of land tenure, changes in educational practices, traditional livelihoods, and beliefs, as well as the loss of rights, all pose threats to the integrity of TEK on a larger scale [85, 86]. The frequent inability of indigenous people to access and defend their own ancestral lands endangers the survival of TEK given that cultures decline in the absence of suitable environments [87, 88]. Prioritizing indigenous rights may increase the possibility of achieving global conservation goals with positive effects on all life on Earth. Greater co-benefits are also largely predicated when respecting traditional knowledge systems and directly promoting indigenous leadership in restoration initiatives, in addition to rights [89]. Therefore, we suggest a thorough dialog with indigenous peoples to be undertaken in order to considering TEK collaborations in restoration. We further stress that any knowledge exchange must be conducted primarily via careful listening and appropriate engagement in a way that supports indigenous leadership and communication customs, and guards against the degradation of ecological and cultural integrity. Ecological restoration strategies that consider the intertwined features of biodiversity and ecosystem services can only be successful if the people who will benefit from them are considered throughout policy development and implementation.

Monitoring of restoration success

Traditional ecological knowledge can provide a strong foundation for ecological restoration success because it co-evolved with the natural ecosystem. Techniques for restoration should consider such cultural interactions. We engaged the local community in conservation efforts by documenting traditions and livelihoods that depend on the environment, some of which had only been retained by elders, and then educating community members accordingly. To measure the important long-term ecological characteristics, permanent plots were installed in the restoration sites, and data are continuously gathered during the peak of the growing season each year. Site photographs and data supplied as field notes are included in the documentation. In order to record the total number of species in the restoration sites, including tree species newly regenerated due to our efforts, an annual survey is being carried out in the restoration sites. The annual report also calculates the importance value index for each species, the survival rate of newly planted tree saplings, and the status of quantifiable biodiversity indicators.

Recommendations

Ethnobiological studies can improve communication between researchers, management plan developers, and local communities, which is crucial for the creation of effective conservation measures. For example, a better grasp of specific knowledge of wildlife can aid in the development of elaborate community-based conservation activities. Because local communities are aware of the paths and locations of the specific species that a visitor or wildlife photographer is hoping to see, the knowledgeable local inhabitants play an important role in tourism development. The influx of national and international tourists seeking to see and photograph elephants and other wild animals can greatly improve the local economy and raise public awareness. The wildlife department and wildlife NGOs like the Wildlife Trust of India (WTI) have supported local communities in wildlife-rich areas through natural-based livelihoods such as homestays, piggery, fishery, and eco-tourism organizations, which help to improve the livelihood of the fringe communities. In addition, wildlife NGOs (WTI) are facilitating the linking of programs like self-help groups where these villages receive loans without interest to start small businesses to empower the women in order to improve local income, reduce dependency, and gain support for wildlife conservation. We believe that more effective knowledge system bridging will raise the likelihood of success and lead to better collaboration between conservation practice, academic science, and indigenous and traditional knowledge holders. Traditional knowledge bearers and their knowledge, in our opinion, can help to promote the protection of species and habitats, stimulate the sustainable use of biodiversity, and raise awareness of the need of conservation more effectively.