Comparative Study of Diversity and Community Characteristics of Trees in Natural (NFS) and Planted (PFS) Forest stands of Patharia Hills Reserve Forest (PHRF), Assam

doi:10.21203/rs.3.rs-2082208/v1

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Comparative Study of Diversity and Community Characteristics of Trees in Natural (NFS) and Planted (PFS) Forest stands of Patharia Hills Reserve Forest (PHRF), Assam

https://doi.org/10.21203/rs.3.rs-2082208/v1

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An investigation was undertaken to compare the diversity and community characteristics of trees in natural (NFS) and planted (PFS) forest stands of Patharia Hills Reserve Forest of Barak Valley (PHRF), Assam by random quadrat method. A total of 68 tree species belonging to 50 genera and 30 families were recorded from the two stands. Out of which, 67 species (49 genera and 29 families) were recorded from the NFS and 7 species (7 genera and 6 families) were recorded from the PFS respectively. The IVI revealed that in the NFS, Artocarpus lakoocha Roxb. (31.70) was the most dominant species and in the PFS, Tectona grandis L.f. (175.39) was the most dominant species. The total density was recorded to be 740 trees ha-1 and 770 trees ha-1in the NFS and PFS respectively. The Shannon-Weiner index, Simpson index, Margalef’s richness index and Pielou’s evenness index were recorded to be 3.7, 0.04, 11.16 and 0.88 respectively for the NFS; and 1.41, 0.37, 1.10 and 0.72 respectively for the PFS. The disturbance index was 32.22% in the PFS. The Sorensen’s similarity index was 16%. Population dynamics of trees revealed that the regeneration status of the NFS was much better than that of the PFS. Hutchenson’s t-test revealed that the NFS and the PFS were significantly different (P<0.001) in terms of tree species diversity. To avoid the rapid destruction of the forest in general and planted forest in particular, implementation of strict regulations and protective measures is urgent.

Barak Valley

disturbance index

dominant species

Hutchenson’s t-test

population dynamics

Assam is the second largest state of North-East India following Arunachal Pradesh. Assam compasses a diversified region and is geographically dissected into three segments, viz. – the Brahmaputra Valley; the Barak Valley; and the Hills of North-Cachar and Karbi Anglong. Of the three, the plain of Barak Valley supports vast agriculture. The forests in the valley consists of tropical evergreen, semi-evergreen, tropical deciduous, secondary forests, planted forests and tea plantation areas bestowed with a great diversity of flora and fauna (Talukdar and De, 2016). The Barak Valley of Assam holds many globally important species of plants and animals owing to its adequate temperature and high rainfall.

A great deal of studies have been undertaken to acknowledge the phytosociology around the world and understand the diversity of plant communities. Many floristic studies have been undertaken in the state of Assam. Plant diversity, population structure and regeneration status were investigated in the four tropical forests in Barak Valley Hojai (Borah et al., 2011), Reserve Forest and Kumortoka Reserve Forest (Dutta and Devi, 2013), comprehensive population structure of tree species in Hollongapar Gibbon Wildlife Sanctuary (Sarkar and Devi, 2014), reserve forests and private tropical forests of Barak Valley (Borah et al., 2016) and Bornewria forest, Assam (Barua et al., 2018).However, only few studies has been conducted for Patharia Hills Reserve Forest (PHRF) such as assessment of forest health (Talukdar et al., 2019), biodiversity of mushrooms (Vyas et al., 2014), importance of non-timber forest products (Talukdar et al., 2020a)and a few significant zoological studies like habitat suitability of the Asiatic elephant in the trans-boundary (Talukdar et al., 2020b), conserving wildlife wealth (Talukdar et al., 2017), as this reserve forest has always been ignored due to trans-border location (with Bangladesh) which is fairly inaccessible. Considering the gap in the study, the PHRF was selected as the study site for the dissertation work. This study particularly aims at a comparative analysis of diversity and community characteristics of trees in natural (NFS) and planted (PFS) forest stands of PHRF.

Study area:

The present study has been conducted in the year 2020–2021 in the PHRF, Assam, India. It is located at the Indo-Bangladesh border in the Karimganj district of Assam (Fig. 1). The forest falls under the jurisdiction of Patharkandi Range of Karimganj Forest Division, Assam. This reserve forest is positioned between the 24°45ʹ00ʺ N to 24°31ʹ59ʺ N latitude and 92°18ʹ56ʺ E to 92°11ʹ59ʺ E longitude and conceals a geographical area of about 7647.30 hectares. Running from south to the north, the length of the reserve forest is about 4500 ha and breadth about 1100–1300 ha (Dey et al., 2015). The Reserve Forest has diverse topographic features from hilly area to grassland. The reserve forest harbours tropical evergreen, semi-evergreen to tropical deciduous; and secondary forests and planted forests (approximately 60 years). There are 13 forest villages in the PHRF as notified by the Forest Department of Karimganj district. This range has forest continuity between the two countries (i.e. India and Bangladesh) and serves as trans-boundary corridors for many wild animals especially Asiatic Elephants (Talukdar et al., 2019; 2020c). This Reserve Forest marks the western boundary of the Karimganj district forming the International border with Bangladesh. With the reserve forest two forest stands were selected on the basis of types of forest, viz. – natural forest (NFS) and planted forest (PFS) for comparative study.

Climate wise the district has moderate temperature and high humidity. The area receives tropical monsoon with a hot and wet summer and a cool and fairly dry winter. It receives an annual average rainfall of more than 3068 mm. The warm humid climate of the area is distinguished by a dry winter from November to February, a hot dry summer from March to May, and a long rainy season from June to September. The temperature of this area ranges from 20°C to 33°C, but in the winter, the temperature sometimes decreases to 11°C. The average temperature falls at 24.5°C. The relative humidity ranges from 89–90% in the morning and 40–81% in the afternoon (Anon., 1).

Methodology:

Phytosociological studies were carried out using the random quadrat method (Misra, 1968). 50 quadrats each of 10 x 10 m² size for trees, 60 quadrats each of 5 x 5 m² size for saplings and 80 quadrats each of 1 x 1 m² size for seedlings were laid down in the NFS and 30 quadrats each of 10 x 10 m² size for trees, 40 quadrats each of 5 x 5 m² size for saplings and 50 quadrats each of 1 x 1 m² size for seedlings were laid down in the PFS. The tree species occurring in each of the quadrats were recorded and the circumference of each tree was measured at breast height, defined as 1.35 m above the highest point of ground at the tree’s base. The recorded tree species existing in each of the quadrats were identified with the assistance of their vernacular names and by addressing to published literature (Hooker, 1877–1887; Kanjilal et al., 1934, 1938, 1939) and the herbaria of the Department of Botany of Cotton University, Guwahati, Assam and thus were listed. In regard to tree species, the individuals were differentiated into three categories, viz. – (a) Seedlings [≤ 10 cm collar circumference at the base ], (b) Saplings [ 10–20 cm collar circumference at the base ], and (c) Trees[> 20 cm circumference at breast height (CBH) ] (Sagar et al., 2003).Subject to trees, the status of their regeneration was ascertained based on their population size of seedlings, saplings and adults (Duchok et al., 2005). If the population size is seen to follow the pattern – seedlings > saplings > adults, the regeneration status of the tree species is considered to be good regeneration. If the population size is seen to follow the pattern – seedlings > or ≤ saplings ≤ adults, seedlings ≤ saplings > adults, seedlings ≥ saplings and the species had no adults, then the regeneration status of the tree species is considered to be fair regeneration. If the surviving species is recorded only in sapling stage, but, no seedlings (saplings may be <, > or = adults) are reported, the regeneration status of the tree species is considered to be poor regeneration. However, if a tree species is found only in adult form, then the tree species is considered to be not regenerating. And, if a species is found only in either seedlings or saplings stage without any adults, then, the species is considered as new or new arrival (Duchok et al., 2005).

The community characters like frequency, relative frequency, density, relative density, dominance or cover, relative dominance, abundance, Importance Value Index (IVI) etc. were determined as per Curtis and McIntosh (1950) and Misra (1968). The ratio of abundance to frequency (A/F), called the Whitford’s index was calculated to determine the distribution pattern (Whitford, 1949).Several indices were calculated to measure the species diversity (Shannon and Weiner, 1949; Simpson, 1949), species evenness (Pielou, 1966), species richness (Margalef, 1958), similarity index(Sorensen, 1948) and disturbance index (Rao et al., 1990; Bhuyanet al.2003).A significant statistical test was done to compare the diversities of the two forest stands based on the Shannon diversity index, using Hutchenson’s t-test (Hutchenson, 1970).

In the course of the present study, a total of 68 species of trees belonging to 50 genera and 30 families were recorded from the study sites. 67 species belonging to 49 genera and 29 families were recorded from the NFS (Fig. 3), while, 7 species belonging to 7 genera and 6 families were recorded from the PFS (Fig. 4). In the NFS, the presence of Saraca asoca (Roxb.) Willd. was recorded which is vulnerable as per the IUCN Red List of threatened species (Anon., 2) and in the PFS, Aquilaria malaccensis Lam. was recorded which belongs to the critically endangered category as per the IUCN Red List of threatened species (Anon., 2). The plant families recorded in the study sites were taxonomically well represented families. In the NFS, Moraceae is the most dominant family with 9 species. Fabaceae is the second largest family with 8 species, followed by Anacardiaceae and Lamiaceae with 4 species and Burseraceae, Clusiaceae, Combretaceae, Meliaceae and Phyllanthaceae with 3 species each. In the PFS, Lamiaceae is the most dominant family with 2 species, followed by Clusiaceae, Moraceae, Phyllanthaceae, Simaroubaceae and Thymelaceae with 1 species. Tree species diversity of the study was comparable to the findings from Hollongapar Gibbon Wildlife Sanctuary, Assam (75 tree species) (Sarkar and Devi, 2014) but was found to be considerably below the findings from tropical moist forest of Mizoram (125 tree species) (Devi et al., 2018); tropical semi evergreen forest of Manipur (123 tree species) (Devi and Yadava, 2006) and Nongkhyllem Wildlife Sanctuary, Meghalaya (127 woody species) (Thapa et al., 2011).

In the NFS, the calculated frequency class (A > B > C < D = E) was compared to the Raunkiaer’s frequency class (A > B > C > = < D < E) (Raunkiaer, 1934) (Fig. 5). It was found that, the frequency class equation of the natural forest did not abide by the Raunkiaer’s law of frequency distribution (Raunkiaers, 1934), and thereby the NFS within the PHRF represents a heterogenous vegetation. In the PFS, the calculated frequency class (A > B > C = D < E) was compared to the Raunkiaer’s frequency class (A > B > C > = < D < E) (Raunkiaer, 1934) (Fig. 6). It was found that, the frequency class equation of the PFS followed the Raunkiaer’s law of frequency distribution (Raunkiaer, 1934), and hence the PFS within the PHRF represents a homogenous vegetation.

In the NFS, the highest important value index (IVI) was observed for Artocarpus lakoocha Roxb. (31.70), followed by Artocarpus chama Buch.-Ham. ex Wall (27.36), Alianthus integrifolia Lam. (22.64), Albizia lebbeck (L.) Benth. (22.06), Artocarpus heterophyllus Lam. (10.91), Vitex altissima L.f. (8.47), Ficus religiosa L. (8.38), Alianthus excelsa Roxb. (7.99), Neolamarckia cadamba (Roxb.) Bosser (6.95) and Tectona grandis L.f. (6.64) (Fig. 7). Higher IVI of a species designates its superior potential of regeneration and broader ecological amplitude (Singh et al., 1991). The values of IVI of the various tree species recorded in the NFS within the PHRF indicated that Artocarpus lakoocha Roxb. was the most dominant tree species of the NFS. This could be due to the fact that Artocarpus lakoocha Roxb. had naturally thriving populations in the NFS, corresponding to its dominance. However, in the PFS, the highest important value index (IVI) was noted for Tectona grandis L.f. (175.39), followed by Garcinia xanthochymus Hook.f. (33.70),Artocarpus lakoocha Roxb. (21.19), Alianthus integrifolia Lam. (19.84), Gamelina arborea Roxb. ex Sm. (19.45), Aquilaria malaccensis Lam. (16.12) and Baccaurea motleyana Mull. Arg. (14.30) (Fig. 8).

In the NFS, the total density of the study site was computed to be 740 individuals ha^− 1. Artocarpus lakoocha Roxb. accounted for the highest density for all three growth forms, viz., adult (120 individuals ha^− 1), saplings (38 individuals ha^− 1) and seedlings (160 individuals ha^− 1), followed by Artocarpus chama Buch.-Ham. ex Wall for trees (94 individuals ha^− 1), saplings (25 individuals ha^− 1) and seedlings (91 individual ha^− 1). The total basal area of trees was computed to be 64.44 m² ha^− 1. The maximum basal area was held by Ficus benghalensis L., for adult trees (3.26 m² ha^− 1).The tree density computed in the present study in the NFS within the PHRF was slightly less than the density of tropical semi-evergreen forest in Nongkhyllem wildlife sanctuary in Meghalaya (996 individuals ha^− 1) (Baishya et al., 2009) and tropical moist forest of Mizoram (2145 individuals ha^− 1) (Devi et al., 2018); while it was more than the density of both undisturbed tropical forests (708.67 individuals ha^− 1) and disturbed tropical forests (443.33 individuals ha^− 1) of Bhuban Hills of Barak Valley, Assam (Borah et al., 2014).The total basal cover reported (64.44 m² ha^− 1) was almost similar to that of the tropical forest of Mizoram (64.76 m² ha^− 1) (Devi et al., 2018) and slightly less than that of the Nongkhyllem wildlife sanctuary of Meghalaya (73.41 m² ha^− 1) (Baishya et al., 2009).

In the PFS, the total density of the study site was computed to be 770 individuals ha^− 1.Tectona grandis L.f. accounted for the highest density for the two growth forms, viz., adult (680 individuals ha^− 1) and saplings (40 individuals ha^− 1), followed by Garcinia xanthochymus Hook.f. for trees (40 individuals ha^− 1). No seedlings and saplings other than a few of Tectona grandis L.f. were recorded. The total basal area of trees was computed to be 3.47 m²ha^− 1. The maximum basal area was held by Tectona grandis L.f., for adult trees (1.19 m² ha^− 1). The tree density computed in the present study in the PFS within the PHRF was slightly less than the density of tropical semi-evergreen forest in Nongkhyllem wildlife sanctuary in Meghalaya (996 individuals ha^− 1) (Baishya et al., 2009) and tropical moist forest of Mizoram (2145 individuals ha^− 1) (Devi et al., 2018); while it was more than the density of both undisturbed tropical forests (708.67 individuals ha^− 1) and disturbed tropical forests (443.33 individuals ha^− 1) of Bhuban Hills of Barak Valley, Assam (Borah et al., 2014). The total basal cover reported (3.47 m² ha^− 1) was very much less than that of the tropical forest of Mizoram (64.76 m² ha^− 1) (Devi et al., 2018) and Nongkhyllem wildlife sanctuary of Meghalaya (73.41 m² ha^− 1) (Baishya et al., 2009).

Divergence in tree density and basal area of the forest may occur as a result of variation in altitude, composition of species, age structure, successional stage and degree of disturbance of the forest (Swamy et al., 2000).

In the NFS, the Shannon Weiner index of the study site was found to be 3.7 (Table 1) which implied relatively diverse region. The value of the Shannon Weiner index is within the range of the value for Indian forests, between 0.83 and 4.1 (Visalakshi, 1995; Devi and Yadava, 2006). The value of Simpson index was found to be 0.04 (Table 1) which lies within the range of different Indian forests, between 0.03 and 0.92 (Bhuyan et al., 2003; Devi and Yadava, 2006; Deb and Sundriyal, 2011; Kushwaha and Nandy, 2012). From the Simpson index, the value of diversity was calculated to be 0.96, which was significantly high. Margalef’s richness index was found to be 11.16 (Table 1) which was in reach of the range between 4.54 and 23.41 for Indian forests (Kumar et al., 2010; Sathish et al., 2013). This indicated relatively high richness of species within the NFS. The Pielou’s evenness index was found to be 0.88 (Table 1) which was commensurate with the forest of Mizoram (0.89) (Devi et al., 2018), Meghalaya (0.81) (Tynsong and Tiwari, 2011).

Table 1

Showing the different indices recorded in the NFS and PFS
INDICES	NFS	PFS
Shannon Weiner Index	3.7	1.41
Simpson Index	0.04	0.37
Margalef’s richness Index	11.16	1.10
Pielou’s evenness Index	0.88	0.72
Disturbance Index	00	32.22%
Sorensen’s similarity Index	0.16

Table 2

Phytosociological study of the different species recorded in the NFS within the Patharia Hills Reserve Forest
BOTANICAL NAMESOF SPECIES	F (%)	RF	D	RD	RDo	A	A/F	IVI	Density (ha^− 1)	Total Basal cover (m² ha^− 1)
Acacia auriculiformis Benth.	2	0.28	0.02	0.27	0.45	1.00	0.50	1.01	2	0.29
Aegle marmelos (L.) Correa	2	0.28	0.02	0.27	0.68	1.00	0.50	1.24	2	0.44
Aglaia spectabilis (Miq.) S. S. Jain & S.S.R. Bennet	2	0.28	0.02	0.27	0.75	1.00	0.50	1.30	2	0.48
Albizia lebbeck (L.) Benth.	72	10.23	0.74	10.00	1.84	1.03	0.01	22.06	74	1.18
Albizia lucida (Roxb.)	2	0.28	0.02	0.27	1.07	1.00	0.50	1.63	2	0.69
Albizia procera (Roxb.) Benth	8	1.14	0.08	1.08	1.31	1.00	0.13	3.52	8	0.84
Alianthus excelsa Roxb.	26	3.69	0.26	3.51	0.78	1.00	0.04	7.99	26	0.50
Alianthus integrifolia Lam.	76	10.80	0.82	11.08	0.77	1.08	0.01	22.64	82	0.49
Annona squamosa L.	4	0.57	0.04	0.54	0.41	1.00	0.25	1.52	4	0.27
Artocarpus chama Buch.-Ham. ex Wall.	92	13.07	0.94	12.70	1.59	1.02	0.01	27.36	94	1.02
Artocarpus heterophyllus Lam.	36	5.11	0.36	4.86	0.93	1.00	0.03	10.91	36	0.60
Artocarpus lakoocha Roxb.	100	14.20	1.20	16.22	1.28	1.20	0.01	31.70	120	0.82
Azadirachta indica A. Juss.	2	0.28	0.02	0.27	1.38	1.00	0.50	1.93	2	0.88
Baccaurea motleyana Mull. Arg.	2	0.28	0.02	0.27	1.07	1.00	0.50	1.63	2	0.69
Baccaurea ramiflora Lour.	14	1.99	0.14	1.89	1.02	1.00	0.07	4.90	14	0.65
Bombax ceiba L.	4	0.57	0.04	0.54	2.12	1.00	0.25	3.22	4	1.36
Bursera serrata Wll. ex Colebr.	2	0.28	0.02	0.27	1.17	1.00	0.50	1.73	2	0.75
Butea monosperma (Lam.) Taub.	4	0.57	0.04	0.54	1.32	1.00	0.25	2.43	4	0.85
Callicarpa arborea Roxb.	2	0.28	0.02	0.27	1.43	1.00	0.50	1.99	2	0.92
Canarium bengalense Roxb.	4	0.57	0.04	0.54	1.83	1.00	0.25	2.93	4	1.17
Careya arborea Roxb.	2	0.28	0.02	0.27	1.56	1.00	0.50	2.11	2	1.00
Castanopsis indica (Roxb. ex Lindl.) A.DC.	6	0.85	0.06	0.81	0.88	1.00	0.17	2.54	6	0.56
Chrysophyllum lanceolatum (Blume) A.DC.	2	0.28	0.02	0.27	1.65	1.00	0.50	2.21	2	1.06
Cinnamomum glanduliferum (Wall.) Nees	2	0.28	0.02	0.27	3.03	1.00	0.50	3.58	2	1.95
Dalbergia sisso DC.	14	1.99	0.16	2.16	1.92	1.14	0.08	6.07	16	1.23
Dillenia indica L.	2	0.28	0.02	0.27	1.37	1.00	0.50	1.93	2	0.88
Dillenia pentagyna Roxb.	2	0.28	0.02	0.27	1.12	1.00	0.50	1.68	2	0.72
Diospyros toposia Buch.-Ham.	2	0.28	0.02	0.27	0.52	1.00	0.50	1.07	2	0.33
Dipterocarpus turbinatus Gaertn.	2	0.28	0.02	0.27	1.48	1.00	0.50	2.04	2	0.95
Elaeocarpus floribundus Bl.	4	0.57	0.04	0.54	1.57	1.00	0.25	2.68	4	1.00
Ficus auriculata Lour.	2	0.28	0.02	0.27	2.47	1.00	0.50	3.02	2	1.59
Ficus benghalensis L.	2	0.28	0.02	0.27	5.06	1.00	0.50	5.62	2	3.26
Ficus benjamina L.	2	0.28	0.02	0.27	2.85	1.00	0.50	3.41	2	1.84
Ficus racemose L.	2	0.28	0.02	0.27	2.70	1.00	0.50	3.25	2	1.74
Ficus religiosa L.	12	1.70	0.12	1.62	5.05	1.00	0.08	8.38	12	3.25
Gamelina arborea Roxb. ex Sm.	14	1.99	0.14	1.89	1.77	1.00	0.07	5.65	14	1.14
Garcinia cowa Roxb. ex DC.	4	0.57	0.04	0.54	0.42	1.00	0.25	1.52	4	0.26
Garcinia pedunculata Roxb. ex. Buch.-Ham.	2	0.28	0.02	0.27	0.40	1.00	0.50	0.95	2	0.25
Garcinia xanthochymus Hook. f.	2	0.28	0.02	0.27	1.08	1.00	0.50	1.64	2	0.70
Garuga floribunda Decne.	2	0.28	0.02	0.27	1.61	1.00	0.50	2.16	2	1.03
Gynocardia odorata Roxb.	2	0.28	0.02	0.27	0.95	1.00	0.50	1.51	2	0.61
Haldina cordifolia (Roxb.) Ridsdale	2	0.28	0.02	0.27	1.17	1.00	0.50	1.73	2	0.76
Madhuca longifolia (J. Koenigex L.) J.F. Macbr.	2	0.28	0.02	0.27	1.35	1.00	0.50	1.90	2	0.87
Magnolia champaca (L.) Baill. ex Pierre	4	0.57	0.04	0.54	1.69	1.00	0.25	2.80	4	1.09
Magnolia insignis Wall.	2	0.28	0.02	0.27	1.33	1.00	0.50	1.88	2	0.85
Mangifera indica L.	2	0.28	0.02	0.27	0.97	1.00	0.50	1.52	2	0.62
Mangifera sylvatica Roxb.	16	2.27	0.16	2.16	0.95	1.00	0.06	5.39	16	0.61
Mesua ferrea L.	8	1.14	0.08	1.08	1.46	1.00	0.13	3.68	8	0.94
Morus laevigata Wall.	2	0.28	0.02	0.27	1.08	1.00	0.50	1.63	2	0.69
Neolamarckia cadamba (Roxb.) Bosser	20	2.84	0.20	2.70	1.41	1.00	0.05	6.95	20	0.90
Phyllanthus emblica L.	2	0.28	0.02	0.27	1.31	1.00	0.50	1.86	2	0.84
Rhus chinensis Mill.	2	0.28	0.02	0.27	0.88	1.00	0.50	1.43	2	0.56
Saraca asoca (Roxb.) Willd.	2	0.28	0.02	0.27	1.63	1.00	0.50	2.19	2	1.05
Shorea robusta Gaertn.	10	1.42	0.12	1.62	2.00	1.20	0.12	5.04	12	1.29
Spondias pinnata (L.f.) Kurz	6	0.85	0.06	0.81	1.11	1.00	0.17	2.78	6	0.72
Sterculia villosa Roxb.	20	2.84	0.20	2.70	1.07	1.00	0.05	6.61	2	0.69
Stereospermum chelonoides (L. fil.) DC.	2	0.28	0.02	0.27	1.44	1.00	0.50	1.99	2	0.93
Syzygium cumini (L.) Skeels	2	0.28	0.02	0.27	1.77	1.00	0.50	2.32	2	1.14
Tamarindus indica L.	2	0.28	0.02	0.27	0.80	1.00	0.50	1.36	2	0.52
Tectona grandis L.f.	16	2.27	0.18	2.43	1.93	1.13	0.07	6.64	18	1.24
Terminalia arjuna (Roxb.) Wight & Arn.	4	0.57	0.04	0.54	1.45	1.00	0.25	2.56	4	0.93
Terminalia bellirica (Gaertn.) Roxb.	4	0.57	0.04	0.54	1.65	1.00	0.25	2.76	4	1.06
Terminalia chebula Retz.	2	0.28	0.02	0.27	1.51	1.00	0.50	2.07	2	0.97
Toona ciliata M. Roem.	2	0.28	0.02	0.27	2.23	1.00	0.50	2.78	2	1.43
Vitex altissima L.f	26	3.69	0.26	3.51	1.26	1.00	0.04	8.47	26	0.81
Vitex peduncularis Wall. ex Schauer	2	0.28	0.02	0.27	2.15	1.00	0.50	2.70	2	1.38
Ziziphus jujuba Miller	2	0.28	0.02	0.27	1.75	1.00	0.50	2.30	2	1.13
Total	704	100	7.40	100	100			300	740
(*F = Frequency, RF = Relative Frequency, D = Density, RD = Relative Density, RDo = Relative Dominance, A = Abundance,
IVI = Importance Value Index)

Table 3

Phytosociological study of the different species recorded in the PFS within the Patharia Hills Reserve Forest
BOTANICAL NAMES OF SPECIES	F (%)	RF	D	RD	RDo	A	A/F	IVI	Density (Ha^− 1)	Total Basal Cover (m² ha^− 1)
Alianthus integrifolia Lam.	10	5.26	0.10	1.30	13.28	1.00	0.1	19.84	10	0.46
Aquilaria malaccensis Lam.	10	5.26	0.10	1.30	9.56	1.00	0.1	16.12	10	0.33
Artocarpus lakoocha Roxb.	20	10.53	0.20	2.60	8.07	1.00	0.05	21.19	20	0.28
Baccaurea motleyana Mull. Arg.	6.67	3.51	0.07	0.87	9.93	1.00	0.15	14.30	7	0.34
Gamelina arborea Roxb. ex Sm.	3.33	1.75	0.03	0.43	17.26	1.00	0.3	19.45	3	0.60
Garcinia xanthochymus Hook.f.	40	21.05	0.40	5.19	7.46	1.00	0.025	33.70	40	0.26
Tectona grandis L.f.	100	52.63	6.80	88.31	34.45	6.80	0.068	175.39	680	1.20
Total	190	100	7.70	100	100	12.8		300	770
(*F = Frequency, RF = Relative Frequency, D = Density, RD = Relative Density, RDo = Relative Dominance, A = Abundance,
IVI = Importance Value Index)

In the PFS, the Shannon Weiner index of the study site was found to be 1.41 (Table 1) which implied relatively low diverse region. The value of the Shannon Weiner index is within the Indian forests value range between 0.83 and 4.1 (Visalakshi, 1995; Devi and Yadava, 2006). The value of Simpson index was found to be 0.37 (Table 1) which lies within the range of different Indian forests, between 0.03 and 0.92 (Bhuyan et al., 2003; Devi and Yadava, 2006; Deb and Sundriyal, 2011; Kushwaha and Nandy, 2012). From the Simpson index, the value of diversity was calculated to be 0.63, which was moderately high. Margalef’s richness index was found to be 1.10 (Table 1). This indicated low richness of species within the PFS. The Pielou’s evenness index was found to be 0.72 (Table 1) which was commensurate with the forest of Mizoram (0.89) (Devi et al., 2018), Meghalaya (0.81) (Tynsong and Tiwari, 2011). The high evenness index value reveals more consistency in species distribution. This is because of the fact that the PFS within the PHRF is well maintained with mainly one species, other than a few, which accounts for the species evenness and low biodiversity. A few cut stumps were recorded in the PFS, and consequently the disturbance index was calculated to be 32.22 (Table 1), which was comparable to the disturbance index recorded at one of the study sites of Bhuban Hills of Barak Valley, Assam (34.3) (Borah et al., 2014). This could be due to the fact that the plantation area is exposed to anthropogenic interference, human intervention and because of its transborder location with Bangladesh, is under the threat of illegal logging by illegal immigrants and loggers. Hutchenson’s t-test revealed that the NFS and the PFS were significantly different (P < 0.001) in terms of tree species diversity.

Understanding the distribution pattern of organisms is a key point of conservation and management (Mao et al., 2009). In the NFS, the analysis of distribution pattern of tree species revealed that contiguous distribution was observed among the highest number of species (86.57%), followed by random distribution (7.46%) and regular distribution (5.97%). Majority of species exhibited the contiguous pattern of distribution which is a prime attribute of natural vegetation (Odum, 1971). In the PFS, the analysis of distribution pattern of tree species revealed that contiguous distribution was observed among the highest number of species (71.43%), followed by random distribution (28.57%) and regular distribution was not observed at all. This could be due to the fact that the PFS is under human maintenance, and as such the tree species were planted as per the planning administered by the officials in-charge of the plantation project.

In case of the NFS, from the population dynamics seen, it was comprehensible that some species viz., Artocarpus lakoocha Roxb., Artocarpus chama Buch.-Ham. ex Wall., Artocarpus heterophyllus Lam., Ficus religiosa L. (Fig. 9-A,B,C,D) showed expanding population. These plants displayed good regeneration capacity (Duchok et al., 2005). The number of adult trees were also sufficiently high. The number of saplings were found to be comparatively less than that of seedling and adult stage. This could have been due to selective collection (Bhuyan et al., 2003). In case of Artocarpus heterophyllus Lam. (Fig. 9 - C), the recruitment of regeneration at the seedling stage is high, however, no sapling was recorded. This could be due to collection of young plants by the forest villagers, local tribes and local extruders to be used as fuelwood. Similar was the case of Ficus religiosa L. (Fig. 9 – D) as a result of collection of saplings by the same crowd for religious purposes, beliefs and faith. However, both the tree species showed good biotic potential and regeneration. While some other species viz., Alianthus integrifolia Lam., Albizia lebbeck (L.) Benth, Alianthus excelsa Roxb., Neolamarckia cadamba (Roxb.) Bosser, Vitex altissima L.f, Sterculia villosa Roxb., Tectona grandis L.f. and Gamelina arborea Roxb. ex Sm., (Fig. 9 – E, F, G, H, I, J, K, L) showed fair regeneration capacity with moderate numbers of seedlings as compared to adult stage. Young seedlings of certain species do not survive under the mature trees (Cheeseman, 1914).

During the present study, in the NFS, it was recorded that some of the economically important plants as well as their parts might have been used for various purposes by the residents of the forest villages and local tribes residing within the PHRF. These tree species include Artocarpus lakoocha Roxb., Artocarpus heterophyllus Lam., Artocarpus chama Buch.-Ham. ex Wall., Alianthus integrifolia Lam., Albizia lebbeck (L.) Benth., Alianthus excelsa Roxb., Ficus religiosa L., Gamelina arborea Roxb. ex Sm., Tectona grandis L.f., Vitex altissima L.f, Sterculia villosa Roxb., Garcinia xanthochymus Hook.f., Dillenia indica L., Mangifera indica L., Baccaurea motleyana Mull. Arg, Syzygium cumini (L.) Skeels, Terminalia chebula Retz., Phyllanthus emblica L., Azadirachta indica A. Juss., Terminalia arjuna (Roxb.) Wight & Arn., etc. These tree species are primarily used for the purpose of timber, fuelwood, food, medicine, trade and commerce among others. However, in doing so, no serious damage was seen to be done to the forest ecosystem. In the PFS, exploitation of tree species of Tectona grandis L.f. by illegal logging was recorded, probably for the purpose of trade and commerce. Although this did not seem to have any serious impact on the health of the plantation, however, implementation of strict measures and better protection to cease this threat was thought to be necessary. The presence of Aquilaria malaccensis Lam. in the PFS could not be confirmed, whether it was grown naturally or introduced, as there was no particular record of planting Aquilaria malaccensis Lam. in the plantation site by the Forest Department. Nevertheless, Aquilaria malaccensis Lam. are planted and grown commercially in homegardens in Barak Valley (Das and Das, 2005; Nath et al., 2020). However, if the recorded Aquilaria malaccensis Lam. was indeed grown in the PHRF naturally, this reserve forest could act as a potential area of conserving this critically endangered tree in wild.

The present study, besides providing an insight to the comparison of diversity and community characteristics of trees in the planted and the NFS within the PHRF, also brings light to the causes of threats endangering the reserve forest. This reserve forest has faced its fair share of ignorance due to its trans-border location with Bangladesh, however, it has a good diversity of vegetation and habitat which makes it a home to a wide range of valuable flora, including a vulnerable (Saraca asoca (Roxb) Willd.) and a critically endangered species (Aquilaria malaccensis Lam.) and fauna. Therefore, there is an urgent need for justified recognition of this valued reserve forest to protect it at various levels and formulation of policies for the better management and conservation of its biodiversity.

Ethical Approval

This declaration is not applicable.

Competing Interests

The authors declare no competing interest.

Authors’ Contributions

S.N. and J.Y. designed research; S.N. performed research; S.N. and J.Y. analyzed data; and S.N. and J.Y. wrote the paper.

Funding

This declaration is not applicable.

Availability of data and materials

All study data are included in the article and/or supporting information.

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Comparative Study of Diversity and Community Characteristics of Trees in Natural (NFS) and Planted (PFS) Forest stands of Patharia Hills Reserve Forest (PHRF), Assam

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