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International Journal of Biodiversity Science, Ecosystem Services & Management, 2013 Vol. 9, No. 2, 104–113, http://dx.doi.org/10.1080/21513732.2012.748691 Comparing tree diversity and population structure between a traditional agroforestry system and natural forests of Barak valley, Northeast India a, b Subrata Nandy * and Ashesh Kumar Das Forestry and Ecology Department, Indian Institute of Remote Sensing, Indian Space Research Organisation, Dehradun 248001, India; Department of Ecology and Environmental Sciences, Assam University, Silchar 788011, Assam, India We studied population structure, composition and diversity in a traditional Indian agroforestry system, called paan jhum, in comparison to natural forests of the Barak valley, Assam, northeast India. The phytosociological data from these forests were analysed quantitatively, to determine species richness, diversity, importance value, stand density and the basal area. The analysis showed that species richness and diversity were higher in paan jhum than in natural forests, in all three study sites. A total of 47, 37 and 48 tree species were recorded in paan jhum, compared with 35, 32 and 42 species in natural forests of the three study sites, respectively. Paan jhum had higher stand density (790, 934 and 763) and basal area (74.05, 2 −1 41.60 and 55.88 m ha ), whereas natural forests had lower stand density (775, 865 and 522) and basal area (68.75, 2 −1 40.50 and 48.04 m ha ) in all the study sites, respectively. An F-test showed signiﬁcant differences in the variance in species richness, basal area and the stand density at 95% conﬁdence level in the two forest categories. Paan jhum might become a component of a forested landscape that is valued for contributing to resource production, other ecosystem services and biodiversity conservation. Keywords: diversity; population structure; Paan jhum; traditional agroforestry; Khasi tribes; conservations Introduction agroforestry system practiced by the Khasi tribes in Bangladesh. In addition, Wiersum (2004) described them Due to the rapid rise of human population and their con- as ‘forest gardens in which wild and cultivated plants coex- sequent increased demands for more utilization of forest ist such that the structural characteristics and ecological resources, the natural forests in India as well as in many processes of natural forests are preserved’. They are char- other countries are shrinking at an alarming rate. The acterized by their evolution within the local communities conversion of forests has led to habitat loss, which is rather than as a result of formal agroforestry systems. the greatest threat to biodiversity (Wong 2011). Hence, Similar examples of forest gardens forming a compo- conservation and judicious use of natural resources are fun- nent within a forested landscape have been described damental to the sustainable development. For sustainability for Indonesia (Mary and Michon 1987; Aumeeruddy and of natural resources, i.e. planned utilization of natural Sansonnens 1994) as well as the Philippines (Olofson resources taking full account of the needs of the present 1980; Fujisaka and Wollenberg 1991), Thailand (Withrow- and future generations, traditional knowledge plays a vital Robinson et al. 1998) and the Amazon region (Denevan role. Ramakrishnan (1998) emphasized that the way tra- et al. 1984; Posey 1985). Chase (1989) suggested the ditional societies are linked to natural ecosystems and term ‘domiculture’ for the creation of such forested land- landscapes provide important clues for biodiversity conser- scapes with a series of localized areas (domuses). The term vation. Tribal communities have identiﬁed themselves as ‘in domo’ conservation of biodiversity was suggested by part of the ecosystem and have acquired empirical knowl- Wiersum (2003) for the interaction between people and edge on the basis of their experience while living close to forest vegetation with each area having a speciﬁc set of natural resources. Based on traditional knowledge, socio- management practices. Agroforestry represents a variety cultural practices and religious beliefs, tribal communities of nature–human relations; they reﬂect multiple forms of have maintained the natural resources in a diverse and pro- human creativity in dealing with forest resources (Wiersum ductive state. The multifunctional nature of agroforestry 1997a, 1997b). systems plays an important role in biodiversity conserva- In Barak valley, the Khasi tribe is associated with the tion, providing goods and services to society, augmentation practice of paan jhum (Piper betle cultivation in natural of carbon storage, enhancing the fertility of the soils and forest) that is considered as having signiﬁcant implica- providing social well-being to people (Pandey 2007). tions on forestry management (Unlocking ... 2005). Paan Paan jhum is a traditional agroforestry system prac- (Piper betle), a perennial creeper, is cultivated for its leaf. ticed by the Khasi tribes of Barak valley in northeast India. In paan jhum, it is planted as a subordinate crop mixed with Rahman et al. (2009) also described this kind of indigenous *Corresponding author. Email: email@example.com © 2013 Taylor & Francis International Journal of Biodiversity Science, Ecosystem Services & Management 105 forest trees to get the economic beneﬁt and also the ecolog- 92 31 43.3 E longitude) (Figure 1). These sites are ical beneﬁts from the resultant interaction. In this study, a located in Barak valley, situated in the southern Assam of comparative phytosociological analysis of tree species was northeast India. The region shares its borders with North carried out in paan jhum and nearby natural forests. Cachar Hills district of Assam and Meghalaya in the north; Manipur in the east; Mizoram in the south and Tripura and Sylhet district, Bangladesh in the West. The valley has Materials and methods an undulating topography characterized by hills, hillocks Study area (locally known as tillah), wide plains and low-lying waterlogged areas (locally called beels). Badshahitila lies Three sites were selected for the present study, namely ◦ ◦ in Karimganj district, Loharbond is in Cachar district and site 1 – Badshahitila (24 20 54.2 –24 25 43.7 Nlat- ◦ ◦ Sultani is located in Hailakandi district of Assam, north- itude and 92 20 53.3 –92 21 29.4 E longitude), site ◦ ◦ east India. For the purpose of study, in each of these sites 2 – Loharbond (24 34 37.5 –24 35 9.5 N latitude and ◦ ◦ two areas were selected, one in paan jhum and the other 92 45 10.9 –92 46 42.1 E longitude) and site 3 – Sultani ◦ ◦ ◦ in nearby natural forest, to observe the difference in tree (24 20 54.6 –24 21 46.6 N latitude and 92 31 21.4 – Assam India Cachar Site 2 Karimganj Hailakandi Site 1 Site 3 Plot location Barak valley Figure 1. Location of study area. 106 S. Nandy and A.K. Das diversity and population structure in both the areas. The Methodology study sites have a warm humid climate with mean annual For the phytosociological analysis in paan jhum as well as rainfall of 2660 mm, most of which is received during in natural forest, a total of 60 quadrats were laid (10 ran- the south-west monsoon season (May to September). The dom quadrats in each site). The size of the quadrat was mean maximum temperature ranges from 25.4 C (January) determined by species area curve method (Misra 1968; to 32.6 C (August) and the mean minimum temperature Mueller-Dombois and Ellenberg 1974) and was found to ◦ ◦ varies from 11 Cto25 C (August). The dry season usually be 0.04 ha. The sites were selected to represent the major corresponds to the period from December to February. The vegetation. In each quadrat, the girth at breast height (gbh forest types in these areas are mainly Cachar tropical ever- at 1.37 m from the ground) of all the trees with gbh green forest (1B/C ) and Cachar tropical semi-evergreen ≥30 cm were measured and recorded. The vegetation data forest (2B/C ) (Champion and Seth 1968). were quantitatively analysed for abundance, density and frequency (Curtis and McIntosh 1950). The importance value index (IVI) for the tree species was determined as the sum of the relative frequency, relative density and rela- Piper betle and the Barak valley tive dominance (Curtis 1959). The ratio of abundance to Piper betle is native to Malaysia and is cultivated through- frequency was used to interpret the distribution pattern out south-eastern Asia (The wealth ... 1969). The leaves of the species (Whitford 1949). The ratio of abundance form the well-known masticatory with the addition of lime, to frequency indicates regular distribution if below 0.025, catechu, areca nuts and other ﬂavouring ingredients. It is random distribution between 0.025 and 0.05 and conta- aromatic, carminative, stimulant and astringent. The betel gious if >0.05 (Curtis and Cottam 1956). Species diversity leaf occupies a signiﬁcant place in the everyday life of the of each site was determined using Shannon–Weaver index people of northeast India. Chewing of paan is an ancient (1949): habit among all classes of people of northeast India. To the farmers, a betel leaf garden provides the much-needed cash H =− (n /N) log (n /N) (1) i i for meeting their day-to-day requirements. The cultivation of the vine under relatively natural conditions is limited to tropical forest areas on the south-western coast of peninsu- where, n is the total number of individuals of species i and lar India and the hill areas of Assam, where the cultivation N is the total number of individuals of all species in that of crop is done in the shade of forest trees or in established stand; log implies to natural log. areca nut gardens. Under artiﬁcially created conditions, An F-test was carried out to work out whether the however, it is grown almost in every part of the country, population attributes, namely species richness, basal area although in a scattered fashion (Chagule 1960). and stand density differ signiﬁcantly in both the forest In the hilly areas of Barak valley, the cultivation of the categories under study. A questionnaire-based survey was vine, known as paan jhum, is practiced in large scale. The undertaken in the individual households of the Khasi tribes practice involves pollarding of trees in a forest and subse- who practice paan jhum. During the survey, the infor- quently planting the stem cuttings of the vine at the base of mation regarding the details of the paan jhum practice such trees. This is done during June–July. The pollarding including the yield of paan and the income generated were helps sunlight to penetrate through the forest canopy, which noted down. is essential for the growth of paan. The vines are propa- gated by terminal stem cuttings collected from sufﬁciently mature plants. Within 1 month of planting, new buds start Results coming up from the newly planted paan plants. The vine is Species richness and diversity grown on all the trees in the paan jhum area. The collec- In all study sites, species richness was found to be higher in tion of paan starts after 3 years of plantation and continue paan jhum than the natural forest (Table 1). Highest species all the year round. But collection is more during June–July, richness was observed in paan jhum of site 3. A total i.e. during rainy season, as high rainfall facilitates high of 48 species was observed in paan jhum compared to production of the leaves. Table 1. Phytosociological analysis of natural forest and paan jhum in three study sites in Barak valley, Assam, Northeast India. Badshahitila Loharbond Sultani Variable Natural Forest Paan jhum Natural Forest Paan jhum Natural Forest Paan jhum Number of species 35 47 32 37 42 48 Number of genera 32 41 30 31 36 41 Number of families 22 30 23 24 28 32 Shannon–Weaver index 3.00 3.30 3.07 3.12 3.27 3.36 2 −1 Basal area (m ha ) 68.75 74.05 40.50 41.60 48.04 55.88 −1 Stand density (stems ha ) 775 790 865 934 522 763 International Journal of Biodiversity Science, Ecosystem Services & Management 107 42 species in natural forest. Species richness ranged from whereas in middle and higher girth classes stand density 32 to 42 species in the natural forest, whereas in paan jhum were higher in paan jhum. In site 2, the stand density in it ranged between 37 and 48. The number of genera as well the lowest girth class (30–60 cm) was more in paan jhum −1 −1 as number of families was found to be higher in paan jhum (600 stems ha ) than in natural forest (495 stems ha ). areas than in natural forest in all the three sites. Shannon– The mean basal area contribution in the lowest girth class Weaver index showed the highest species diversity in site 3, (30–60 cm) was higher in natural forest compared with where diversity in paan jhum (3.36) was more than the nat- paan jhum, but in the middle as well as in the higher girth ural forest (3.27); similarly in other two sites also species classes, mean basal area was found to be higher in paan diversity in paan jhum was higher than the natural forest jhum of site 1 (Figure 3). In site 2, the basal area of lowest (Table 1). girth class (30–60 cm) was 73.59% greater in paan jhum 2 −1 2 −1 (9.24 m ha ) than the natural forest (6.8 m ha ), while the other girth classes were represented almost equally in Density, basal area and importance value both the areas. The mean basal areas in lower and middle −1 Table 1 shows the stand density (stems ha ) in all the girth classes of site 3 were more in paan jhum, whereas study sites. Highest stand density was observed in paan the higher girth classes in natural forest were represented −1 jhum of site 2 (934 stems ha ), whereas lowest stand den- by higher values. The F-test showed that the variance in species richness, basal area and stand density differ signiﬁ- sity was observed in natural forest of site 3 (522 stems −1 cantly at 95% conﬁdence level in both the forest categories ha ). It was observed that the stand density was higher in all the sites except species richness and basal area of in paan jhum than the natural forest of all the sites. The site 2. basal area was found to be slightly higher in paan jhum than in the natural forest (Table 1). The basal area ranged 2 −1 from 40.50 to 68.75 m ha in natural forest and between 2 −1 41.60 and 74.05 m ha in paan jhum. Distribution pattern The IVI of top ten species in paan jhum as well as nat- The analysis of distribution pattern of trees is shown in ural forests of all the study sites is shown in Figure 2. The Figure 3. In site 1, most of the species were regularly dis- result showed that in site 1, the highest IVI in natural forest tributed both in natural forest and in paan jhum.The same was represented by Amoora wallichii (41.56), whereas in trend was observed in site 2 also. But comparison shows paan jhum area of the same site Dipterocarpus turbina- that the species in paan jhum were more regularly dis- tus was the dominant tree species having IVI of 43.43. tributed than the natural forest in sites 1 and 2. In site 3, A comparison of the IVI values in natural forest and paan most of the species in both natural forest and paan jhum jhum area of this site allowed several noteworthy obser- were contagiously distributed (Table 3). vations. Dipterocarpus turbinatus, which is an evergreen species, has more IVI in paan jhum area (43.43) than in the natural forest (7.64). One more interesting observation Economic beneﬁts is that Mangifera sylvatica (a rare species), a wild mango, The Khasi tribes get economic beneﬁts by selling paan, has an IVI of 11.06 in paan jhum area, whereas in the which is their main occupation. The annual yield of paan natural forest of the same site it is absent. In site 2, the is approximately 2,52,000 individual leaves per hectare. highest IVI in natural forest was represented by Ziziphus The economic life span of paan plant is about 30 years. rugosa (40.51), whereas in paan jhum area of the same site, The vine starts yielding paan from the age of 3 years. the highest IVI was represented by Palaquium polyanthum The production is more during June–July (rainy season). (67.93), an evergreen species. In the third site, the highest During January–March (winter season), paan production IVI in natural forest was represented by Cynometra polyan- is relatively low, as the leaves fall due to abscission. New dra (53.46), whereas in the paan jhum area of the same leaves start coming up on the onset of monsoon. Due to site, Alseodaphne owdenii has the highest IVI (55.32). less production of paan during February–March, the price Alseodaphne owdenii is the best tree species available in becomes higher, i.e. Rs.350 per kuri (1 kuri = 6720 leaves) this region used for making furniture. (Rs.69.68 = 1C). But, in other months, the price is less (Rs.40–50 per kuri) because of more production. Stand density and forest structure Tree species richness, stand density and Shannon–Weaver Discussion index across girth classes in all the areas showed a decreas- ing trend with increase in stem girth classes (Table 2). Different tribal communities around the world practice var- Tree size class distribution in both the categories of forest ious types of agroforestry systems for their livelihood. areas followed a reverse J-pattern. The mean tree density in Khasi tribes, like other tribal communities, practice shift- lower and middle girth classes (30–60 cm, 60–90 cm and ing cultivation for many years (Bareh 1967). These tribes 90–120 cm) of site 3 was 50% greater in paan jhum than have also developed their own market-oriented sustainable in the natural forest (Table 2). In site 1, stand density in tree crop production system (Nath et al. 2003). Paan jhum lowest girth class (30–60 cm) was more in natural forest areas are conserved and protected imbued with the reli- −1 −1 (275 stems ha ) than in paan jhum (210 stems ha ), gious beliefs and taboos of the local people. Felling of trees 108 S. Nandy and A.K. Das Paan jhum Natural forest 43.43 41.76 39.76 41.56 41.45 34.81 21.68 20.52 20.29 14.58 13.76 12.76 11.06 15 9.43 8.21 7.64 6.62 6.65 6.35 5.70 0 0 Site 1 40.51 67.93 31.16 30 24.62 24.05 19.27 17.66 31.45 29.93 12.70 12.33 11.25 10.81 11.57 10.66 10.60 9.58 8.67 7.09 6.51 0 0 Site 2 55.32 60 53.46 39.49 32.54 25.64 21.17 22.11 16.18 14.18 14.76 12.37 12.09 12.35 7.56 9.77 8.73 8.55 8.14 9.42 6.21 Site 3 Name of species Figure 2. Ten dominant species encountered in natural forest and paan jhum of the three study sites in Barak valley, Assam, Northeast India. is not allowed inside paan jhum areas. Rather fast grow- Rahman et al. (2009) investigated the cultural and ing species like Amra (Spondias pinnata), Simul (Bombax ﬁnancial management technique and the conservation role ceiba), Bajrang (Zanthoxylum rhetsa), Udal (Sterculia vil- of paan (betel leaf) based agroforestry practiced by the losa) and Tula (Tetrameles nudiﬂora) are planted in gaps, Khasi community of Sylhet district of Bangladesh. They if required. Hence, paan jhum practice helps to conserve found that the mean annual income from one hectare of biological diversity along with income generation. betel leaf plantation was Tk.80979 (Tk.105.19 = 1C). The Importance value index (IVI) Importance value index (IVI) Importance value index (IVI) Zizphus rugosa Cynometra polyandra Amoora wallichii Palaquium polyanthum Mesua floribunda Palaquium polyanthum Castanopsis indica Dipterocarpus turbinatus Syzigium cuminii Syzigium cuminii Palaquium polyanthum Magnolia hodgsonii Diospyros melanoxylon Holigarna longifolia Cynometra polyandra Mesua floribunda Syzigium cuminii Chukrasia tabularis Chrysophyllum Artocarpus chama lanceolatum Dipterocarpus turbinatus Vatica lanceaefolia Saraca asoca Garcinia xanthochymus Podocarpus neriifolius Bischofia javanica Mesua ferrea Sterculia foetida Diospyros melanoxylon Cinnamomum cacharensis Palaquium polyanthum Dipterocarpus turbinatus Alseodaphne owdenii Gynocardia odorata Cynometra polyandra Syzigium cuminii Syzigium cuminii Amoora wallichii Kayea floribunda Zizphus rugosa Palaquium polyanthum Palaquium polyanthum Garcinia xanthochymus Syzigium cuminii Saraca asoca Cynometra polyandra Artocarpus chama Amoora wallichii Semecarpus anacardium Magnolia hodgsonii Alphonsea ventricosa Schleichera oleosa Mangifera sylvatica Chukrasia tabularis Saraca asoca Bacaurea ramiflora Toona ciliata Zanthoxylum budrunga Holigarna longifolia Gynocardia odorata International Journal of Biodiversity Science, Ecosystem Services & Management 109 −1 Table 2. Mean tree species richness, stand density (stems ha ) and Shannon–Weaver index for different girth classes in natural forest and paan jhum of the study sites in Barak valley, Assam, Northeast India. Natural forest Paan jhum Site girth Mean species Mean stand Shannon–Weaver Mean species Mean stand Shannon–Weaver class (cm) richness density index richness density index 130−60 190.00 275.00 2.68 140.00 210.00 2.81 60−90 160.00 190.00 2.68 180.00 255.00 2.90 90−120 120.00 130.00 2.62 130.00 150.00 2.78 120−150 75.00 75.00 1.89 40.00 45.00 2.62 150−180 45.00 45.00 1.98 50.00 60.00 2.04 180−210 30.00 30.00 1.10 15.00 15.00 1.79 210−240 35.00 35.00 1.79 35.00 35.00 1.95 >240 10.00 10.00 1.39 20.00 20.00 0.69 230−60 295.00 495.00 3.00 308.33 600.00 2.79 60−90 115.00 195.00 2.43 133.33 166.67 2.29 90−120 90.00 100.00 2.44 66.67 83.33 1.89 120−150 30.00 30.00 1.56 41.67 41.67 1.61 150−180 20.00 20.00 1.39 33.33 33.33 1.04 180−210 10.00 10.00 0.69 16.67 16.67 0.69 210−240 5.00 5.00 0.32 0.00 0.00 0.00 >240 10.00 10.00 0.69 0.00 0.00 0.00 330−60 93.75 125.00 2.80 175.00 279.17 2.93 60−90 100.00 118.75 2.75 170.83 208.33 3.20 90−120 93.75 115.63 2.81 141.67 187.50 3.07 120−150 40.63 50.00 1.99 20.83 20.83 1.61 150−180 43.75 43.75 2.35 29.17 29.17 1.75 180−210 12.50 12.50 1.39 4.17 4.17 0.69 210−240 34.38 40.63 2.10 16.67 20.83 1.05 >240 15.63 15.63 0.95 12.50 12.50 1.10 practice was proved to be a proﬁtable business where the disturbed and highly disturbed tropical wet evergreen for- beneﬁt cost ratio was calculated to be 4.47. Moreover, the est in and around Namdapha National Park, Arunachal species composition in the betel leaf plantation area was Pradesh, India were found to be 50, 22 and 18 belonging found to be very promising to play a signiﬁcant role in to 41, 22 and 16 genera and 25, 16 and 16 families, respec- conservation of biological diversity, making the practice a tively (Nath et al. 2005). A total of 82 species belonging sustainable agroforestry system. to 59 genera and 39 families and 80 species belonging to In the present study, the numbers of tree species in 62 genera of 41 families were recorded in 0.5 ha plots in the natural forest were 35, 32 and 42 belonging to 32, the Ialong and Raliang sacred groves of the Jaintia hills in 30 and 36 genera and 22, 23 and 28 families, respec- Meghalaya, northeast India (Upadhaya et al. 2003). Hence, tively, in the three study sites. In paan jhum areas of it was observed that in all the protected forests as well as in the three study sites, it was observed that there were 47, the undisturbed forests, the number of species, genera and 37 and 48 tree species belonging to 41, 31 and 41 gen- family are higher compared with unprotected forests. era and 30, 24 and 32 families, respectively. The number The Shannon–Weaver index of all the paan jhum of species, genera and families were found to be higher areas is higher (3.12 to 3.36) compared with the natural in paan jhum areas compared with natural forest in all forest (3.00 to 3.27) in the study sites. It shows that this the three sites. The native primary tropical forests, sec- traditional agroforestry system helps in conserving the ondary forests and sal plantations of the Garo hills in biodiversity of this region. The Shannon–Weaver index of western Meghalaya had higher number of species (162, paan jhum areas correspond to the study done by Upadhaya 132 and 87 tree species belonging to 54, 53 and 37 families, et al. (2003) in Ialong and Raliang sacred groves, repre- respectively) than the present study (Kumar et al. 2006). sented by subtropical broad-leaved forest, of the Jaintia Khumbongmayum et al. (2006) observed 96 woody species hills in Meghalaya, northeast India, where they found in four sacred groves dominated by subtropical forests in diversity value of 3.42 and 3.55, respectively. Shannon– the Imphal east and Imphal west districts of Manipur. The Weaver index for tree species in the Garo hills of western species richness in undisturbed wet evergreen forest in Meghalaya were found to be 4.27, 3.78 and 2.47 for Arunachal Pradesh, eastern Himalayas, India, was found to primary forests, secondary forests and sal plantations, be 47 belonging to 28 families and 42 genera (Bhuyan et al. respectively (Kumar et al. 2006). Tree species diversity 2003). Number of tree species in undisturbed, moderately ranged from 0.70 to 2.02 in highly disturbed, moderately 110 S. Nandy and A.K. Das Natural forest Paan jhum 14 300 14 12 12 250 250 10 10 200 200 8 8 150 150 6 6 100 100 4 4 50 50 2 2 0 0 0 0 30–60 60–90 90–120 120–150 150–180 180–210 210–240 >240 30–60 60–90 90–120 120–150 150–180 180–210 210–240 >240 Site 1 700 10 700 10 9 9 500 500 6 6 400 400 5 5 300 300 4 4 3 3 200 200 100 100 1 1 0 0 0 0 >240 30–60 60–90 90–120 120–150 150–180 180–210 210–240 >240 30–60 60–90 90–120 120–150 150–180 180–210 210–240 Site 2 300 18 300 18 200 12 200 12 100 6 100 6 4 4 50 50 2 2 0 0 0 0 >240 >240 30–60 60–90 90–120 120–150 150–180 180–210 210–240 30–60 60–90 90–120 120–150 150–180 180–210 210–240 Site 3 Girth class (cm) Figure 3. Stand structure based on tree density (solid line) and basal area (dotted line) in natural forest and paan jhum of the study sites in Barak valley, Assam, Northeast India. Table 3. Species distribution pattern in natural forest and paan disturbed, mildly disturbed and undisturbed stands of trop- jhum of the study sites in Barak valley, Assam, Northeast India. ical wet evergreen forests of Arunachal Pradesh (Bhuyan et al. 2003). The diversity in undisturbed, moderately dis- Distribution pattern (%) turbed and highly disturbed tropical wet evergreen forest in Site Forest type Random Regular Contagious and around Namdapha National Park, Arunachal Pradesh, India was found to be 1.46, 0.96 and 1.17, respectively 1 Natural forest 38.30 51.06 10.64 (Nath et al. 2005). In the same region, where the present Paan jhum 42.86 51.43 5.71 study was carried out, Borah and Garkoti (2011) found 2 Natural forest 28.13 62.50 9.38 Paan jhum 16.22 67.57 16.21 out that the Shannon–Weaver index was higher in undis- 3 Natural forest 9.52 26.19 64.29 turbed forests (1.69 and 1.77) compared with disturbed Paan jhum 4.17 31.25 64.58 forests (1.46 and 1.52) of Barak valley, south Assam. –1 –1 –1 Tree density (stems ha ) Tree density (stems ha ) Tree density (stems ha ) -1 2 –1 2 –1 2 –1 Basal area (m ha ) Basal area (m ha ) Basal area (m ha ) International Journal of Biodiversity Science, Ecosystem Services & Management 111 Shannon–Weaver index in undisturbed forest and protected et al. 2003; Upadhaya et al. 2003; Khumbongmayum forests, like sacred groves and paan jhum,ofthisregionis et al. 2006). Tree size class distribution in both the much higher than the unprotected forest, which shows the categories of forest areas, namely paan jhum and natural role of local tribes in conservation of biodiversity. forests, followed a reverse J-pattern. The same trend was The basal area was also found to be higher in paan jhum observed by Nath et al. (2005) in undisturbed tropical wet 2 −1 (41.6 to 74.05 m ha ) than the natural forest (40.5 to evergreen forests in Namdapha National Park, northeast 2 −1 68.75 m ha ) in the present study. The basal area of India, which indicates good regeneration of the constituent paan jhum areas are close to the basal cover, 57.46 and species. 2 −1 77.44 m ha , in Ialong and Raliang sacred groves, Comparative study of IVI in natural forest and paan respectively, of the Jaintia hills of the Meghalaya state of jhum shows that Palaquium polyanthum and Dipterocarpus India (Upadhaya et al. 2003). Kumar et al. (2006) observed turbinatus has more IVI in paan jhum than the natural for- 2 −1 that tree basal area (m ha ) ranges from 29–162 in native est. Both the species are evergreen and yields good timber primary tropical forests, 12–151 in secondary forests and used for making furniture. Because of the economic impor- 39–74 in sal plantations of the Garo hills in western tance, both the species have been exploited in the natural 2 −1 Meghalaya. Basal area (m ha ) in undisturbed, moder- forest, whereas being a protected area it is safe in paan ately disturbed and highly disturbed tropical wet evergreen jhum. One interesting observation was the occurrence of forest in and around Namdapha National Park, Arunachal Mangifera sylvatica in paan jhum and its absence in natu- Pradesh, India was found to be 98.58, 21.38 and 7.81, ral forest. The species is utilized as timber and fuelwood, 2 −1 respectively (Nath et al. 2005). The basal area (m ha ) and fruits are edible. It is medicinal also (Barbhuiya et al. of undisturbed forests (36.88 and 42.12) was found to be 2009). Due to its multiple uses, it is exploited very much in higher than that of disturbed forests (9.47 and 16.96) of the wild. Alseodaphne owdenii, which yields good quality Barak valley, south Assam (Borah and Garkoti 2011). timber for furniture, has higher IVI in paan jhum compared Basal area also seems to be higher in sacred groves and with natural forest. This tree species is in great demand paan jhum compared with unprotected natural forests. The in this locality and has been exploited heavily in its natu- protection provided by the local tribes facilitates higher ral condition. However, paan jhum acts as a conservation basal cover in protected forests. plot to protect the species. Most of the paan jhum areas In the present study, the stand density in natural for- showed high species diversity than the natural forest, which −1 est ranged from 522–865 stems ha and 763–934 stems is possible because of the protection provided by the local −1 ha in paan jhum. Density of trees (30 cm gbh) per tribes. As the people living nearby are not allowed to enter hectare in tropical forests ranged from a low value of in paan jhum, the anthropogenic pressure on the species 245 (Ashton 1964), to intermediate values of 420–617 in reduces. This facilitates in better conservation of natural Brazilian Amazon (Campbell et al. 1992) and to a high resources. value of 639–713 in Central Amazonian upland forest Agroforestry systems provide four major ecosystem −1 (Ferreira and Prance 1998). The tree density (stems ha ) services: carbon sequestration, biodiversity conservation, in undisturbed forests (846 and 1110) was found to be soil enrichment and air and soil quality improvement higher than the disturbed forests (572 and 396) of the Barak (Jose 2009). The traditional agroforestry systems play a −1 valley (Borah and Garkoti 2011). Tree density (stems ha ) very signiﬁcant role in conserving biodiversity (Khumalo varies from 417–1023 in native primary tropical forests, et al. 2012). These agroforestry systems are complex sys- 620–1111 in secondary forests and 724–980 in sal plan- tems that have been developed to mimic natural systems. tations in the Garo hills of western Meghalaya (Kumar These practices beneﬁt biodiversity through in situ con- et al. 2006). It was also observed that in the present study, servation of native tree species (de Souza et al. 2012). paan jhum has higher tree density per hectare than natural The positive impact of paan jhum agroforestry system on −1 forest in all the sites. Tree density (stems ha ) in undis- biodiversity conservation can mainly be attributed to the turbed, moderately disturbed and highly disturbed tropical reduced pressure on the natural forest due to the ability wet evergreen forest in and around Namdapha National of this agroforestry system to sustain the daily liveli- Park, Arunachal Pradesh, India were 610, 251 and 34, hood of the tribal community. Hence, paan jhum areas respectively (Nath et al. 2005). Khumbongmayum et al. are socially, economically and ecologically viable systems, −1 (2006) observed tree density (stems ha ) of 359–1218 in as this agroforestry practice provides economic support four sacred groves dominated by subtropical forests in the to the Khasi tribes in addition to its ecological role for Imphal east and Imphal west districts of Manipur. Tree biodiversity conservation. −1 density (stems ha ) was found to be 1476 and 938 in two sacred groves of Ialong and Raliang, respectively, of Conclusions the Jaintia hills of Meghalaya (Upadhaya et al. 2003). In the present study, species richness, stand density and Paan jhum forms a unique example of traditional farming Shannon–Weaver index across girth classes in all the study practice which was adopted by the traditional society as sites showed a decreasing trend with increasing stem girth a livelihood security and biodiversity conservation. This classes. The same trend was observed by other studies traditional agroforestry system can be a viable land-use conducted in different parts of northeast India (Bhuyan option which, in addition to alleviating poverty, offers a 112 S. Nandy and A.K. Das number of ecosystem services and environmental bene- Borah N, Garkoti SC. 2011. Tree species composition, diver- sity, and regeneration patterns in undisturbed and disturbed ﬁts. In the present study, it was found that the species forests of Barak valley, south Assam, India. Int J Ecol Env richness and diversity in paan jhum were higher than the Sci. 37(3):131–141. natural forests. The stand density and basal area were also Campbell DG, Stone JL, Roses A. 1992. A comparison of the found to be higher in paan jhum compared with the natural phytosociology of three ﬂoodplain (varzea) forests of known forests. The species composition in the paan jhum area was ages, Rio Jurua, Western Brazilian Amazon. 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International Journal of Biodiversity Science, Ecosystem Services & Management – Taylor & Francis
Published: Jun 1, 2013
Keywords: diversity; population structure; Paan jhum; traditional agroforestry; Khasi tribes; conservations
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