Conservation of Plant Diversity in Rural Homegardens with Cultural and Geographical Variation in Three Districts of Barak Valley, Northeast India1 TAPASI DAS* AND ASHESH KUMAR DAS Department of Ecology and Environmental Science, Assam University, Silchar, 788011, Assam, India *Corresponding author; e-mail:
[email protected]
Conservation of Plant Diversity in Rural Homegardens with Cultural and Geographical Variation in Three Districts of Barak Valley, Northeast India Homegardens are recognized worldwide as sustainable agroforestry systems that are repositories of species and genetic diversity. Species diversity and composition of homegardens are influenced by a number of environmental, socioeconomic, and cultural factors. The present study examines the tree species diversity in the homegardens of different cultural groups of Barak Valley, Assam, Northeast India. Complete enumeration was done for diversity analysis in 181 homegardens from 38 villages in the three districts of the Valley. Factors affecting plant diversity were analyzed, and the floristic composition of the homegardens was found to vary with garden size, ethnicity of the homegarden owners, and geographical parameters such as location and altitude. Results indicate high plant diversity, with a total of 161 tree species identified from 47 families. Tea garden labor communities were comparatively found to hold more diversity in their homegardens. Similarity and cluster analysis revealed the distinctness of the majority of the homegardens, and seven groups of homegardens with very low distance were revealed. Homegardens were also found to maintain considerable conservation value as repositories of many underutilized, wild, and rare plant species. Biodiversity conservation in the homegardens was found to be linked to the multiple values of the different plant species to the homegardeners and further highlight the concept of the Bconservation through use^ approach. For the preservation of such traditional agroforestry systems, which also have the potential to provide options for adaptation to climate change, proper documentation of traditional knowledge concerning the different plant species and the human-nature interaction in the homegardens is necessary before such systems are completely lost. Key Words: Homegardens, plant diversity, underutilized species, wild species, cultural groups, conservation.
Introduction Homegardens can be defined as Bland use systems involving deliberate management of multipurpose trees and shrubs in intimate association 1
Received 8 December 2013; accepted 29 January 2015; published online 5 March 2015. Electronic supplementary material The online version of this article (doi:10.1007/s12231-015-9299-6) contains supplementary material, which is available to authorized users.
with annual and perennial agricultural crops and invariably livestock within the compounds of individual houses, the whole tree-crop animal unit being intensively managed by family labor^ (Fernandes and Nair 1986). The basic objectives for maintaining this agroforestry system are to ensure availability of multiple products such as food, fuel, vegetables, fruits, fodder, and medicines, besides generating income and employment (Kumar and Nair 2004). Most homegardens are relatively small but highly diversified ecological niches (Galluzzi et al. 2010), and the plots are usually arranged to imitate forest layers, creating
Economic Botany, 69(1), 2015, pp. 57–71 © 2015, by The New York Botanical Garden Press, Bronx, NY 10458-5126 U.S.A.
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conditions for low-growing, shade-loving climbers and other plants (Fernandes and Nair 1986; Wezel and Bender 2003). A common practice is to grow small numbers of many species, creating high agrobiodiversity (Das and Das 2005; Fernandes and Nair 1986; Watson and Eyzaguirre 2002). Species diversity and composition of homegardens is influenced by ecological, socioeconomic, and cultural factors (Fernandes and Nair 1986; Kumar and Nair 2004). The maintenance of multispecies and multistrata agroforests is deemed worthwhile because of the growing interest in developing multifunctional land-use systems which contribute not only to production objectives, but also to the objectives of biodiversity and environmental conservation (Wiersum 2004). These complex homegardens, traditionally integrated within a larger surrounding ecosystem (Eyzaguirre and Linares 2004; Gliessman 1990), have been described as sustainable and diversified niches shaped by a close interaction between nature and human cultures (Galluzzi et al. 2010). Homegardens are living gene banks and a reservoir of plant genetic resources that preserve landraces, cultivars, rare and endangered species, and species neglected in larger ecosystems (Eyzaguirre and Linares 2001). The adoption of the Convention on Biological Diversity in June 1992 and the succeeding importance given to the conservation of plant genetic resources have resulted in increasing attention on traditional agroforestry systems such as homegardens. Homegardens have been highlighted in the past few decades as an important site for in situ conservation of plant diversity (Gajaseni and Gajaseni 1999; Watson and Eyzaguirre 2002), while some have considered the possibility of their potential to maintain species ex situ (Kabir and Webb 2007). The homegarden provides a bridge between the social and biological, linking cultivated species and natural ecosystems, combining and conserving species diversity and genetic diversity (Eyzaguirre and Linares 2004). The contribution of cultural and socioeconomic factors in generating and maintaining crop diversity in homegardens has received little attention, yet human cultures have profound influence on the diversity of the ecosystems they belong to (Eyzaguirre 2006), and it is often people’s cultural and economic values that explain differences even among neighboring fields and gardens. The objectives of this study were i) to quantify tree species diversity in the homegardens of different cultural groups, and ii) to analyze the factors
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affecting homegarden diversity in the three districts of Barak Valley, Assam, Northeast India. Since trees are the most important and dominant component in the homegardens of the different cultural groups, and presence of vegetables and other herbs is not common in all the homegardens and usually occupies a very small area of the homegardens to meet the occasional subsistence needs of the owner, the present study focused only on the different tree species in the homegardens of different cultural groups. Traditional homegardens are attracting increasing attention from scientists and conservationists. There have been many studies on their structure, floristic composition, functions, and management, and on the factors responsible for these features (Blanckaert et al. 2004; Gajaseni and Gajaseni 1999; Kabir and Webb 2009; Sunwar et al. 2006). The large majority of the available studies, however, remain rather descriptive, and quantitative methods including multivariate statistics to unravel causes of biodiversity patterns are rarely used (Blanckaert et al. 2004). Many studies have been done on homegarden structure and composition in different parts of India including Kerala (Kumar et al. 1994) and Karnataka (Shastri et al. 2002), with limited information available on the homegardens of Northeast India (Das and Das 2005; Ramakrishnan 1992; Saikia et al. 2012; Tangjang and Arunachalam 2009). Homegarden diversity is especially notable in areas where there is a high degree of socioeconomic and sociocultural variability such as Northeast India (Ramakrishnan 1992). Northeast India, having rich ethnic and cultural diversity, gives rise to diverse homegarden structures where important plant species are maintained to fulfill various needs. The rural homegardens in Barak Valley, Assam, Northeast India, are represented by a piece of land, mostly of less than 1 ha in size, individually owned and managed, which has a dwelling place. It includes cultivation and preservation of trees, shrubs, and some herbs such as ornamentals, medicinal plants, and sometimes vegetables, mostly to meet subsistence needs and often associated with the management of livestock within the same piece of land. Barak Valley harbors different cultural groups in the rural regions that are maintaining homegardens as part of their farming systems to meet their livelihood needs. However, studies on the homegardens in Barak Valley, Assam, Northeast India, are limited and have mostly focused on homegarden maintenance by a single cultural group in a village (Das and Das 2005; Devi and Das 2013; Ramakrishnan et al.
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1996) and the structural diversity of homegardens among the different cultural groups of the region has been disregarded until now. Both environment and culture play roles in influencing the characteristics of homegardens, but the relative importance of these and other factors on the features observed can be difficult to distinguish, especially because most studies have been limited to single villages or ethnicities (Bernholt et al. 2009). A comparative study of the homegardens in different regions maintained by different cultural groups can give an overview of the distribution of homegardens and their structural configuration among different cultural groups in the different regions.
The Study Area The present study was carried out in Barak Valley, Assam, Northeast India, including the three districts Cachar, Hailakandi, and Karimganj (Fig. 1). The Barak Valley region is situated between 24°8’ and 25°8’ N, and 92°15’ and 93°15’ E, covering an area of 6,922 km2. The study area has an undulating topography characterized by hills, hillocks (locally known as tillah), wide plains, and low-lying waterlogged areas (locally called beels). Physiographically the Barak Valley Zone may be divided into eight classes ranging from high hills with elevations exceeding 300 m to perennially waterlogged beels. The Valley experiences a warm
Fig. 1.
Assam.
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humid climate with a mean annual rainfall of 2,440–4,100 mm, most of which falls during the southwest monsoon season (May to September), and mean monthly maximum and minimum temperatures of 33.9°C and 9.2°C. The five cultural groups included in this study are the tea garden laborers, Meitei Manipuri, Bishnupriya Manipuri, Burman, and Khasi with their own cultural and geographical settings in the three districts. None of the five traditional communities are native to the Barak region, having immigrated during the eighteenth and nineteenth century due to internal conflicts in their homeland or in search of work (Mishra and Dutta 1999; Sengupta 1996). The tea garden labor communities are mostly concentrated in villages near the tea gardens of the three districts and are an important demographic component of the Valley. The villages tend to be located at high altitudes where homegardening is practiced. Agriculture and tea garden labor are the primary occupation of the tea garden labor communities in the three districts. Agricultural activities basically consist of rice farming and homegardening. The Meitei Manipuri, Bishnupriya Manipuri, and Burman mostly inhabit villages at low altitude and the Meitei Manipuri usually build their villages near the water bodies or river tributaries. Rice farming is the primary occupation for these three communities, with additional income from the sale of areca nut from their homegardens. The Khasi community, on the other
Location of the study area, Barak Valley, including three districts—Cachar, Hailakandi, and Karimganj—in
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hand, concentrate in villages (locally known as punji) on mountain sides at high altitude. Farming is the main lifeline of this community, including rice farming in terraces, traditional agroforestry production of Piper betle L., and collection of nontimber forest products (NTFP) from the surrounding forests. Homegardening is also practiced by the Khasi community with large-scale cultivation of areca nut which has commercial value and provides additional income to the homegarden owner.
Data Collection Sampling was done in 90, 59, and 32 homegarden units from 20, 11, and 7 villages in Cachar, Hailakandi, and Karimganj districts, respectively. Selection of homegardens was done by a stratified random sampling for the different villages dominated by different ethnic communities in the three districts. The three districts represented the first strata, followed by the villages in each district as the second strata, and the homegardens in each village were considered as the third strata during sampling. The rural homegardens in the three districts were extracted from satellite data of the study area (Das and Das 2014) and allotted random numbers before selection. The selected homegarden units were sampled only after obtaining permission from the village head. In cases where the village head was not accessible, a knowledgeable well-known elderly member of the village escorted the study group to the individual homegardens. The number and distribution of sampled homegardens were constrained by site accessibility, budget availability, and the time frame of the study. A pilot study was carried out in a single village to determine the number of adequate homegarden samples, the best sampling size of the homegardens, and the interaction methods with the homegarden owners. Sampling was done mostly with small holders (15 cm) were enumerated and their girth measured (Kumar et al. 1994; Perera and Rajapakse 1991), and all individuals per species were counted. Bamboo individuals were counted based on culm number. Inventory was carried out to estimate tree diversity, abundance, and allocation. Local names of plants were obtained from homegarden owners, and unknown plant specimens were collected for identification. The collected specimens were identified with the help of regional floras and other publications (Kanjilal et al. 1934– 40) and consulting the herbarium at Botanical Survey of India, Shillong. Vertical structure was measured by direct visual observation.
Data Analysis Field data were entered and transformed for analysis in MS Excel 2007. Floristic diversity in each homegarden was estimated using Shannon diversity index H' = -Σ (ni/N) x ln (ni/N) (Magurran 2004), where ni = Density of a species and N = Density of all species. Simpson’s index of dominance (D) was calculated as D = ∑ pi2 (Magurran 2004), where pi
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is the proportion of individuals in the ith species. Species richness was calculated as DMg = (S -1)/ InN (Margalef 1958), where S is total number of species in the homegarden, and N total density of all the species. One-way analysis of variance (ANOVA) followed by post-hoc Tukey tests were carried out using the values on floristic diversity and size in order to test whether there were significant differences between the homegardens belonging to different communities. Multiple linear regression analysis was performed to identify factors determining plant species richness and diversity in IBM SPSS Statistics for Windows v21.0. For these analyses, dependent variables were species richness and diversity expressed by the Shannon index and dominance index. The independent variables included garden size, proximity to roads and urban area, ethnicity (after coding the nominal categorical variables using dummy coding method), and altitude. Linear bivariate relations between variables were analyzed using Pearson’s correlation coefficients. Species similarity between any two villages was calculated with Jaccard’s similarity index. Variation in floristic composition between villages and among and between the cultural groups was analyzed with Hierarchical Cluster Analysis based on the presence/absence matrix. The cluster analysis was conducted using the coefficient of Jaccard and the complete linkage method.
Results HOMEGARDEN DIVERSITY The 181 rural homegardens studied showed variation in their size ranging from a minimum size of 170 m2 recorded from Karimganj district to a maximum size of 24,120 m 2 recorded from Cachar district and a mean of 2592 m2 in the three districts. A total of 161 tree species from 47 families were identified from the 181 homegarden units in the three districts (Electronic Supplementary Material [ESM1]). Native species comprised 155 or 86% of the total number of species. Of the total of 47 families recorded, Fabaceae was the dominant family with 13 genera and 18 species, followed by Euphorbiaceae, Myrtaceae, and Poaceae with 14, 11, and 9 species, respectively (Table 1). Out of the total of 161 tree species recorded, 39.13% belonged to the timber use category followed by 21.12% under the fruit use category (Fig. 2). Indigenous multipurpose
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Table 1. FAMILY-WISE DISTRIBUTION OF GENERA AND SPECIES OF SOME HOMEGARDEN PLANTS IN BARAK VALLEY, ASSAM. Family rank
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
Family
Species
Genera
Fabaceae Euphorbiaceae Myrtaceae Poaceae Lauraceae Moraceae Rutaceae Anacardiaceae Meliaceae Verbenaceae Annonaceae Arecaceae Clusiaceae Rubiaceae Combretaceae Myrsinaceae Sapindaceae Sapotaceae Sterculiaceae
18 14 11 9 8 8 6 6 6 6 5 5 4 4 3 3 3 3 3
13 11 3 5 6 3 3 4 5 5 4 5 2 4 1 2 3 3 2
trees such as Artocarpus heterophyllus Lam. and Mangifera indica L. were encountered in more than 70% of the homegardens in the three districts. Bamboo is an important component of the homegardens and found to be present in the majority of the sampled homegardens. It is often managed in a separate zone known as Bansh jhar (bamboo grove). Three bamboo species—Bambusa cacharensis R. Majumder, locally known as Bethua, Bambusa vulgaris Schrader, locally known as Jai baruah, and Bambusa balcooa Roxb., locally known as Katta baruah—were dominant in the homegardens of the three districts. Differences were recorded for the priority bamboo species in the homegardens of the three districts (Fig. 3). The homegardens exhibited complex structure with a multilayered configuration. A maximum of five vertical canopy layers were identified in the different homegardens units. Of the five vertical layers, three were frequently encountered during the enumeration of the tree species in the homegardens. The emergent layer had a height of more than 15 m and was composed mostly of timber species that are also represented in the canopy layer such as Albizia procera (Roxb.) Benth., Artocarpus lacucha Buch.-Ham., Bombax ceiba L., Callicarpa arborea Roxb., M. indica, and Toona ciliata M. Roem. The canopy layer was between
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45 39.13
40 35
Percent Trees
30 25 21.12 20 14.90 15 10.56 10 4.35
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Use categories
Percentage distribution of recorded tree species to different use categories from the homegardens in Barak Valley, Assam. Fig. 2.
10–15 m and was composed of Areca catechu L., A. heterophyllus, Cocos nucifera L., Gmelina arborea Roxb., Lagerstroemia reginae Roxb., and Bamboo sp. (B. cacharensis, B. vulgaris). The understory layer had the height of 5–10 m and dominated by fruit species such as Citrus spp., Ficus spp., Flacourtia jangomas (Lour.) Raeusch., Moringa oleifera Lam., and Musa spp. More than 50% of the homegardens studied were managed by the tea garden labor community. A small number of homegardens managed by the Meitei Manipuri and Burman communities were found to be semi-commercial based with cultivation of areca nut to meet local market demands.
FACTORS AFFECTING DIVERSITY IN RURAL HOMEGARDENS Exploration of possible relations between homegarden diversity and the biophysical and cultural factors by multiple linear regressions revealed several significant factors (Table 2). The independent variables for proximity of homegardens to major roadways and urban or large market areas were not significantly related to any of the dependent variables for homegarden diversity and were discarded from the multiple regression models. The number of species in the homegardens and species richness increased with the increase in homegarden size (P < 0.01 and P < 0.05, respectively), whereas the diversity variables, including Shannon diversity,
dominance index and species richness, were influenced by cultural variation and homegarden altitude. Homegarden size was significantly correlated with number of species, though with only a low average rate of increase in number of species with increase in garden size (r = 0.223; P
