Introduction

All biological products, other than timber or products of animal origin, that are harvested from forests and manipulated for human and animal use, are described as non-timber forest products (NTFPs) (Ros-Tonen et al. 1995). NTFPs play a vital role in supporting livelihood security, development, and poverty reduction, especially for the rural communities living around forest areas (Cocks and Wiersum 2003; Cocksedge 2006; Endamana et al. 2016). It also has substantial cultural significance and value for various ethnic groups around the world. However, the importance of NTFPs tends to be underestimated as they are not traded through organised markets and do not appear in national economic statistics even though millions of forest dwellers harvest large quantities of NTFPs for both subsistence and commercial use, either regularly or as an emergency (Shaanker et al. 2004).

In India, 90% of the plants supplied to the international market are from the wild stock (Mishra et al. 2009). It is therefore essential to develop a systematic and rigorous data collection system in all the developing countries for better utilisation of NTFPs. Moreover, if the government and stakeholders take the initiative to prioritise the sustainable use of NTFPs, the economic and social well-being of communities living in and around forest lands could be enhanced substantially (Agrawal et al. 2013). The increasing threat of large-scale deforestation and degradation of the natural habitat poses a significant hazard to various forest resources, particularly NTFPs. Therefore, it is important to urgently develop appropriate management strategies and practical plans before these elements are lost forever (Pandey and Saini 2007).

Northeast India spreads over an area of 255,088 km2, constituting 7.7% of the total geographical area of the country. A large number of different indigenous communities in this region are traditionally dependent on forest products, especially on NTFPs, which play a significant role in the maintenance of subsistence and provision of food and medicine. It is estimated that 60–94% of the tribal population in states like Arunachal Pradesh, Nagaland, Manipur, and Tripura are dependent on forest resources for various purposes (Dattagupta and Gupta 2016). Earlier studies of NTFPs in Assam are minimal in comparison to other Indian states (Sarma et al. 2016). One research has shown that forest dwellers of the Inner Line Reserve Forest of Cachar District in the Barak Valley region collect 67 plant species as NTFPs of 40 families (Dattagupta et al. 2010, 2014). Another study on the commercial uses of forest products in Karbi Anglong District of Assam has shown that the forest remains the backbone of the economy for the people living in this area (Timunpi 2017).

Quantitative ethnobotany is the application of quantitative techniques to direct analysis of contemporary plant use data (Phillips and Gentry 1993). This approach aims to describe the variables quantitatively and analyse the observed patterns to test different hypotheses about the relationship between plant species and humans (Höft et al. 1999; Reyes-García et al. 2006). One advantage of using this method, in addition to the systematic quantification, is that it helps to produce quality information, which in turn supplies substantially to resource conservation and development (Hussain et al. 2018). Quantitative ethnobotanical indices have so far been able to measure the various uses of plants whether as food, veterinary medicine, remedies for human disease, or economic value (Pieroni 2001; Upadhyay et al. 2011; Kim and Song 2013; Reyes-García et al. 2006). Although a few relevant ethnobotanical studies among the Karbi tribe have been conducted (Sankar and Chowdhury 2000; Kar and Borthakur 2008; Teron and Borthakur 2012; Teron and Borthakur 2013; Phongchopi et al. 2014; Terangpi et al. 2014; Teronpi et al. 2015; Singh 2017), none of them have been able to document those studies using quantitative ethnobotanical techniques. Ethnobotanical studies using quantitative approach have a significant potential to enhance the indicative value of ethnobotanical studies and can enhance the factual information available for conservation and development of the existing resources.

Apart from some plant diversity studies carried out in Karbi Anglong District, no extensive study has been carried out to evaluate the exact wealth of the hilly terrains present in the area. This study explores NTFPs used by the indigenous Karbi community, evaluates different ethnobotanical indices, and examines the dependence of the forest dwellers on this existing resource in East Karbi Anglong Wildlife Sanctuary in the Karbi Anglong District of Assam.

Methods

Study area

The present study was carried out in East Karbi Anglong Wildlife Sanctuary of Karbi Anglong District of Assam, which is one of the primary forests of the state covering an area of 221.81 km2 (Fig. 1). It is situated between 24° 33′ N to 26° 35′ N latitude and 92° 10′ E to 93° 50′ E longitude and is 80–600 m asl. It is an essential component of the Karbi Anglong-Kaziranga landscape. The topography of the study site ranges from undulating hills to wide valleys and steep gorges with rivers and creeks, as well as annual and perennial streams. The wildlife sanctuary holds different forest types ranging from moist semi-evergreen, moist mixed deciduous to miscellaneous type with scattered pure or mixed patches of bamboos. Some of the prominent tree species found in the sanctuary are Hoong (Dipterocarpus macrocarpus), Mekai (Shorea assamica), Nahar (Mesua ferrea), Sia-nahar (Keyea assamica), Sissoo (Dalbergia sissoo), Khair (Acacia catechu), Helika (Terminalia chebula), etc. The soil is well-drained, sandy loamy to clayey loamy, and the climate is warm and humid with an annual rainfall of 1800 mm. The average maximum temperature is around 30 °C in August, and the minimum goes down to 6.5 °C in winter.

Fig. 1
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Map of East Karbi Anglong Wildlife Sanctuary, Assam, indicating selected area for study

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Participatory rural assessment

The present field survey was carried out from 2015 to 2017, mainly in the villages surrounding the sanctuary. Seven out of the 14 villages were selected for the study, namely Borpung, Tarapung, Noralangso, Phanglangso, Langtuk hanse, Kanduwa bosti, and Langpratlangso (Table 1). These villages were purposively selected for their high tendency to use non-timber forest resources from the sanctuary. Selection of respondents was done through purposive stratified sampling from those villagers who accepted the request for an interview of their own free will. A total of 70 respondents (49 males and 21 females) from 70 households, i.e. 1 respondent from each house, were interviewed for the study. Two male forest officials were also included among the 49 male respondents, and they were from 1 of the selected villages (Borpung) representing 2 households from the village. The interviewed respondents were mainly the eldest persons in the household. Information regarding NTFPs harvested and their quantities, together with demographic details of the collector, was collected from the sample households through interviews by participatory interaction method supplemented by group discussions and semi-structured questionnaire (Martin 1995; Alexiades and Sheldon 1996).

Table 1 Demographic characteristics of informants for NTFPs surveys in East Karbi Anglong Wildlife Sanctuary
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Collection and identification of NTFPs

Collection of NTFPs was done in the company of respondents. Collection, pressing, and preparation of herbarium specimens were done following the methods suggested by Jain and Rao (1977) with suitable modifications. The collected specimens were identified with the help of available published literature (Kanjilal et al. 1939; Balakrishnan 1983; Haridasan and Rao 1987), as well as in consultation with experts from the herbarium housed at the Botanical Survey of India, Eastern Circle, Shillong (ASSAM), and the herbaria of the Department of Botany, North-Eastern Hill University. The scientific names were validated using the International Plant Names Index (IPNI) and an online resource, The PlantList (TPL).

Data analysis

Data collected was analysed using four quantitative indices: use report (UR), use value (UV), informant consensus factor (ICF), and fidelity level (FL). Whenever a plant was mentioned as being used for a particular purpose, it was considered to be one UR (Amiguet et al. 2005). The relative importance was analysed using the use value (UV), a quantitative measure for the relative importance of a species, which is based on the number of uses and the number of people that cite a given plant indicating the species that are considered most important by a given population (Phillips and Gentry 1993).

UV is calculated using the following formula:

$$ \mathsf{UV}=\mathit{\mathsf{U}}/\mathit{\mathsf{n}} $$

where U is the number of use reports cited by every respondent for a given species and n is the total number of respondents interviewed. The UV is high when there are many use reports for a given species, which implies that the taxa are important. When there are few reports related to its use, the UV decreases.

The informant consensus factor (ICF) was calculated as:

$$ \mathsf{ICF}=\left( Nur-\mathsf{Ns}\right)/\left( Nur-\mathsf{1}\right) $$

where ‘Nur’ is the number of use reports for a particular use category and ‘Ns’ is the number of species used, for each category mentioned by all respondents (Trotter and Logan 1986). ICF was used to test the homogeneity of knowledge about the plants. Before performing the analysis, all the ailments were broadly classified into various categories following Hussain et al. (2018). ICF gives information about the consensus of respondents regarding the utilisation of a certain use category. The data of this factor ranges from 0 to 1. Values close to 1 indicate high consensus agreement among the respondents for the use of the particular plant while a value close to 0 indicates least consensus agreement.

Fidelity level (FL) was calculated as:

$$ \mathsf{FL}\ \left(\%\right)=\mathsf{Np}/\mathit{\mathsf{N}}\mathsf{x}\mathsf{100} $$

where ‘Np’ is the number of respondents that claim to use a plant species for treating a particular disease and N is the number of respondents that use the plants as a medicine to treat any given disease (Alexiades 1996).

Analysis of percentage contribution of NTFPs to household income

Household income from the 70 respondents was calculated as the sum incomes of all the members of a particular household. It includes income from off-farm activities, agricultural incomes, and forest incomes (Endamana et al. 2016).

The mathematical presentation is as follows:

$$ \mathsf{THI}=\mathsf{OFI}+\mathsf{AI}+\mathsf{FI} $$

where THI = total household income, OFI = off-farm income, AI = agricultural income, and FI = forest income. The per capita household income (monthly) was calculated with the total gross household income divided by the total number of family members residing together under the same house.

Analysis of NTFP collector’s percentage based on gender typology

The percentage of gender categorisation regarding the collection of NTFPs was calculated from the total respondents interviewed, both male and female. It is based on their practice of collection of edible forest products, ethnomedicines, household building materials and utensils, spices and condiments, and herbal dyes from the study site.

Results

A total of 138 NTFPs plant species belonging to 59 families and 110 genera were collected from the East Karbi Anglong Wildlife Sanctuary. The highest number of NTFPs was extracted from trees (38%), followed by herbs (32%) and shrubs (23%), and the least was from climbers (7%) (Fig. 2). Out of the reported 138 NTFPs, 72 species (42%) had ethnomedicinal importance, 57 species (33%) are used as edible forest products, 25 species (15%) account for household building materials and utensils, 10 species (6%) are used as spices and condiments, and 7 species (4%) are used as herbal dyes (Fig. 3) (Tables 2, 3, 4, 5, 6, 7, 8, and 9). Several species used in traditional medicine and as edible food are in high demand in the local markets (Table 10). These include Aegle marmelos, Alocasia macrorrhiza, Alpinia nigra, Averrhoa carambola, Baccaurea ramiflora, Citrus assamensis, Dendracalamus hamiltonii, Dillenia indica, Dioscorea alata, Gnetum gnemon, etc.

Fig. 2
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Diversity of NTFPs as per habit

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Fig. 3
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Categories of non-timber forest products collected from East Karbi Anglong Wildlife Sanctuary

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Table 2 Details of villages surveyed in investigations of the NTFPs in East Karbi Anglong Wildlife Sanctuary
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Table 3 Enumeration of medicinal plant species used by the Karbi tribe in East Karbi Anglong Wildlife Sanctuary
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Table 4 Enumeration of edible plants used by the local people in East Karbi Anglong Wildlife Sanctuary
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Table 5 Enumeration of household building materials and utensils used by the Karbi tribe in East Karbi Anglong Wildlife Sanctuary
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Table 6 Enumeration of spices and condiments used by the Karbi tribe in East Karbi Anglong Wildlife Sanctuary
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Table 7 Enumeration of dye-yielding plants used by the Karbi tribe in East Karbi Anglong Wildlife Sanctuary
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Table 8 Consensus of agreement on the uses of medicinal plants among informants
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Table 9 Fidelity level (Fl %) of frequently cited plant species with major uses
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Table 10 Documented list of traded species in the markets locally available with prevailing price
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The statistical evaluation report of ethnomedicines was classified into 2 major categories and 25 sub-categories with regard to various ailments:

  1. a)

    Traditional medicine for human ailments

The sub-categories are as follows: cephalalgia; blood and circulatory problems; cold and cough; cuts and wounds; dermatological infections; ENT diseases; eye disease; fever; gastrointestinal disease; liver diseases; malaria; menstrual problems; dental and gum problems; muscle, bones, and joints; insect stings and bites; urinary tract and kidney problems; deworming; respiratory problems; and health tonic.

  1. b)

    Ethnoveterinary medicines

The sub-categories are as follows: ectoparasitic control, deworming, dermatological infections, gastrointestinal disease, fever, and muscle, bones, and joints.

Use value (UV) of all the 138 reported species ranges from 0.014 to 0.128 (Table 11). The ICF value for traditional medicines varied from 0.11 to 0.95, with an average value of 0.53. Menstrual problems have the highest ICF value of 0.95 with 63 use reports for 4 species, followed by malaria (ICF = 0.93; 50 use reports, 4 species), ectoparasitic control (ICF = 0.91; 50 use reports, 5 species), insect stings and bites (ICF = 0.88; 63 use reports, 8 species), etc. (Table 8). The species responsible for the high consensus for menstrual problems are Abroma augustum, Magnolia hodgsonii, Cissampelos pareira, and Zingiber officinale. Similarly, species responsible for the high consensus for malaria are Nyctanthes arbor-tristis, Abrus precatorius, Citrus assamensis, Physalis peruviana, etc. (Table 3).

Table 11 List of NTFPs with different categories of uses and their use value
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To determine the cultural importance of medicinal species in the society, the fidelity level (FL) of plants was calculated based on user reports for being used against a given ailment. The high value of fidelity level (%) is taken for selecting the most preferred plant species for each ailment category (Uddin and Hassan 2014). The results revealed that out of the 4 highest values of ICF species for treating menstrual problems, Abroma augustum (L.) L. f. is the most commonly used species in the study area (ICF = 0.95) with 63 use report and FL value (90%). Similarly, Amaranthus spinosus L. is the most widely used species for treating insect stings and bites with 62 use report and FL value (88.57%), followed by Geophila repens (L.) I. M. Johnst. with 61 use report and FL value (87.15%) for skin infections, Aegle marmelos (L.) Corrêa with 60 use report and FL value (85.72%) for dysentery, and Abrus precatorius L. with 50 use report and FL value (71.42%) for malaria (Table 9).

Percentage contribution of non-timber forest products to household incomes

The contribution of NTFPs to household incomes per month revealed that 50% of the respondents derived 50–90% of their total revenues from NTFPs, whereas about 30% derived 20–40% of their total household incomes from sales of NTFPs. While the remaining 20% of the entire interviewed households raised less than 20% of their incomes from NTFP-based enterprises in the study, this shows that NTFPs constitute an essential component of the rural household economy in the study area.

Non-timber forest product collection based on gender typology

The gender typology for NTFPs collection in East Karbi Anglong Wildlife Sanctuary revealed that both men and women were involved in the collection of NTFPs. However, men were the most dominant extractors. Most of the collectors of edible forest products (90%), ethnomedicines (80%), household building materials and utensils (80%), spices and condiments (50%), and herbal dyes (40%) were men, while most of the women were engaged in the collection of herbal dye (80%), spices and condiments (70%), ethnomedicines (60%), edible forest products (50%), and household building materials and utensils (40%).

Discussion

The data generated from the respondents interviewed were from seven randomly selected rural and mountainous villages, covering the entire extent of the study area. The spatial variation in the area has therefore been adequately represented in our samples. The present study shows that NTFPs play a pivotal role in healthcare and livelihood security for the Karbi community. They are vital for maintaining the community at large for household uses, healthcare, and income generation as indicated by half the households arising 50–90% of their incomes of half from NTFPs collected from the sanctuary. Most of the revenue is generated by selling these products in the local markets in the form of wild vegetables and fruits. The stem of Alpinia nigra, shoot of Dendracalamus hamiltonii, fruit of Dillenia indica, tuber of Dioscorea alata, leaves of Gnetum gnemon, inflorescence of Phlogacanthus thyrsiflorus, seeds of Piper nigrum, etc. are commonly sold in the market. Other ways in which the NTFPs are used to generate incomes include selling as fibres, traditional wooden mortars, and weaving implements as well as various handicrafts (Fig. 4). The findings of the current study validate those of Timunpi (2017), who reported that forest is the backbone of the economy of the people living in this district.

Fig. 4
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a–b Informants. c Market with various forest products. d Bamboo shoots. e Basket made from bamboo and cane

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The current study also highlights the diverse knowledge of ethnomedicinal plants exhibited by the Karbi community. Out of the 72 medicinal species recorded from the study area, the maximum number of species used as medicine was found in the family Fabaceae (6 species), followed by Malvaceae, Zingiberaceae, and Solanaceae (each with 5 species), while Rutaceae and Phyllanthaceae contribute 4 species each. Lamiaceae, Annonaceae, Moraceae, and Amaranthaceae each have 3 species, and Apiaceae, Apocynaceae, Verbenaceae, Rubiaceae, and Combretaceae have 2 species each while the remaining 18 families are monospecific. Plant species like Abroma augustum, Geophila repens, Habenaria dentata, Magnolia hodgsonii, Pseudocaryopteris foetida, Sarcochlamys pulcherrima, Stemona tuberosa, Tephrosia purpurea, Tragia involucrata, and Zingiber chrysanthum which have not been notified by earlier studies conducted elsewhere within the district among the Karbi tribe (Jain and Borthakur 1980; Teron and Borthakur 2012; Teron and Borthakur 2013; Terangpi et al. 2014; Teronpi et al. 2015) have been reported for their medicinal uses in this study. The present study along with the introduction of new medicinal plants also provides information of about the uses in treating 60 different types of ailments which include amenorrhea, dysmenorrhoea, dysentery, malaria, various skin infections, diarrhoea, bleeding gums cuts and wounds, helminthiasis, conjunctivitis, and constipation. This outcome supports the findings of Jain and Borthakur 1980 that ethnomedicines have always played a significant role in the healthcare system of the ethnic Karbis.

Data obtained using quantitative ethnobotanical studies have shown the significance of these plants among the Karbis. The plants (Centella asiatica, Cissampelos pareira, Dalbergia sisso, Ichnocarpus frutescens, etc.) with the highest UV are considered most important for the local people due to their multiple use reports and are therefore specifically conserved (Albuquerque et al. 2006). The ICF value for each of the 25 sub-categories ranged from 0.11 to 0.95. While sub-categories like malaria, menstrual problems, and ectoparasitic controls showed higher ICF values of ≥ 0.91, it is because only a few species for each category were used by the respondents. The plants associated with higher ICF value (Abroma augustum, Amaranthus spinosus, Geophila repens, Aegle marmelos, etc.) are used by a large portion of the community, implying that the communities at large have significant uses of these few plants for treating different ailments. Moreover, the variation in ICF value might be due to the availability and diversity of medicinal plants within the particular locality and restriction in exchange of ethnobotanical knowledge through generations (Hossain and Rahman 2018).

Most of the respondents used specific species for particular ailments as shown by the eight species having FL above 50%. More work needs to be done on those particular plants which have high ICF and FL values to validate their uses as traditional medicines and to check their bioactive constituents for further drug development (Bibi et al. 2014). This type of study could open new paths for future pharmacological research, which can serve as a reference, especially for quantitative ethnobotanical investigations among diverse ethnolinguistic indigenous groups (Ong and Kim 2014). Research based on indigenous knowledge of various communities can yield a tremendous amount of cultural information which can potentially be utilised for economic and welfare benefits. Such information with proper scientific research could be beneficial in solving many modern-day problems, viz. food shortage, health issues, to curb famine, drought, and ways to manage and maintain sustainable utilisation of the natural wealth surrounding us. In recent decades, in many of the developing countries, there is an increasing demand for NTFPs for subsistence and cash income generation (Shackleton et al. 2011; Steele et al. 2015). Thus, NTFPs can play a significant role in commercial purposes which contribute to local economies and hence contribute to community development. In our study area, the NTFPs are mostly utilised for subsistence as well as for moderate cash income generation. However, inefficient utilisation of these resources due to insufficient knowledge could lead to overexploitation and depletion of these resources. These multiuse resources are being hampered by habitat destruction, overexploitation, unlimited grazing, change in land use pattern, and dominance of invasive species. Even so, the role of NTFPs in supporting livelihoods of rural communities is possible to continue as long as the resources are utilised sustainably (Solomon 2016).

Conclusion

Various ethnobotanical indices in the study have demonstrated and underscored the dependence of the forest dwellers on this living resource for their livelihood and subsistence. In addition to the use of the listed NTFPs, plants such as bamboo can support the local paper industries and other handicraft enterprises helping to augment their income. The informant consensus factors and fidelity level suggest that the ethnobotanical knowledge of the locals of this area is significantly diverse and useful. Inputs of these tribal experts should be given priority in bioassay and toxicity studies. From this study, we recommend Abroma augustum, Amaranthus spinosus, Geophila repens, Aegle marmelos, and Abrus precatorius for further ethnopharmacological studies, since these species have high ICF and FL values.

Moreover, UV data can be used to highlight those plants which need to be effectively conserved as they are resources which can sustain the indigenous population. Non-timber forest product management is a process involving harvesting, gathering, utilisation, and management of resources within the given ecological, economic, social, political, institutional, and legal frameworks. An effective NTFP policy is urgently required to link the provision of livelihood security as well as sustenance with biodiversity conservation. The high level of dependency on forest products by the different indigenous groups can affect the status of their forest. However, the efficient and eco-sensitive extraction of these forest products can not only add value to the forest product but also provide a proper incentive for conservation and sustainable forest management.