Phytodiversity of Barail Wildlife Sanctuary , Assam , India : field ‐ based observations — I . Trees and lianas

Trees and lianas were inventorized in Barail Wildlife Sanctuary, Assam, India, which revealed the occurrence of 112 and 23 species of trees and lianas respectively. Two separate lists, one for trees and other for lianas, of all the enumer‐ ated taxa are presented here with their vernacular names, phenology, places of occurrence and collection number(s). Threat status of each taxon according to IUCN Red List categories is also provided. Anthropogenic activities and other natural calamities are causing serious threats particularly to the tree diversity of the sanctuary. In addition, destruction of one tree may eradicate many lianas from a particular area. Thus, many species of trees and lianas are under alarming threat in the sanctuary. Conservation through in situ and ex situ modi operandi is recommended.


Introduction
Inventorization of plants of a particular area comprises basic biodiversity studies and assessment of their conservation status.Among various ecoclimatic zones, tropical evergreen forests constitute one of the most biodiversity rich habitats on the globe (Khandekar and Srivastava 2014).An exhaustive inventory of tropical plant species is, thus, one of the primary objectives for the plant taxonomists.Within India, the tropical monsoon climate that prevails in the Eastern Himalayas, Northeastern India, and Western Ghats allows for a rich and diverse flora.Though steps have been taken towards cataloguing the biodiversity of protected areas in India, knowledge of the diverse flora of many protected areas, particularly in northeastern India, is still lacking.There was no comprehensive study on the diversity of angiosperms of Barail Wildlife Sanctuary (BWS), Assam, India, and hence, we initiated this study to investigate the same of BWS for the first time.Because the angiosperm flora of BWS is large, we have segregated the study into 2 parts.A second part, which will include herbs, shrubs, and non-woody climbers, is planned for a later publication.
Tropical vegetation, mostly dominated by angiosperm trees, is a large part of floral diversity.Trees are important in that they provide shade and shelter for herbaceous and epiphytic plants.They provide homes for wild animals, especially primates.They stabilise the soil, counteract rapid run-off of rainwater, and prevent desertification, and they have a role in climate control and in the maintenance of biodiversity and ecosystem balance (Bellefontaine et al. 2002).Trees are also economically important for yielding timber, fuel, and food.
Lianas, or woody climbers, are likewise important components of tropical forests and are importnt for the forest community and structure.They are generally longstemmed, reaching up into the tree canopy to get access to light.Their structural morphology and mechanisms of twining add to the complexity of the vertical structures of forests (Chaudhuri and Naithani 1985).According to Grubb (1977), dense vegetation of lianas in a particular area portray the nature of tropical lowland and lower montane forest types of that region.Like trees, lianas also contribute substantially to the diversity of the forests and provide food and arboreal pathways for forest animals.They are widely used for medicine, food, house construction, and artisan work.They have an important role in forest regeneration (Bongers et al. 2002).
Among the angiosperms of the BWS, while describing a new Asian genus of ginger, Larsenianthus, Kress et al. (2010) reported 2 species of the genus from the sanctuary viz.L. assamensis S. Dey, Mood & S. Choudhury (described as new to science from BWS) and L. careyanus (Benth.)W.J. Kress & Mood. Barbhuiya et al. (2012) and Barbhuiya (2013) described 2 new species, Ornithochilus cacharensis Barbhuiya, B.K. Dutta & Schuit. (Orchidaceae) and Toxicodendron bimannii Barbhuiya (Anacardiaceae), respectively.Barbhuiya et al. (2012a) rediscovered Ardisia keenanii C.B. Clarke (Myrsinaceae) after a gap of 138 years from the sanctuary.First collection of this species from the study area was made by R.L. Keenan in 1873.Later, C.B. Clarke (1882) described it in Flora of British India based on his own collection from Manipur in 1868 and Keenan's collection from Cachar in 1873.Barbhuiya et al. (2013) documented 96 species of grasses from Barak Valley, including 16 species from the BWS.
As can be seen from the literature, it is evident that baseline data on angiosperm diversity of the BWS is mostly scattered and inadequate.Hence, we initiated this study to provide a comprehensive list of angiosperms in the sanctuary.In this first part, we treat the trees and lianas of the protected area.

Methods
Study site.Barail Wildlife Sanctuary (BWS) is situated in the northern part of Cachar district of Assam and lies along the foothills of the North Cachar and Barail hills.It covers an area of just over 326 km 2 .The BWS is under the administrative control of the Southern Assam Forest Circle, Silchar, and consists of Barail Reserve Forest, which is part of the Cachar Forest Division (East Block) and North Cachar Reserve Forest, part of the Karimgunj Forest Division (West Block) (Fig. 1).
The climate is tropical and humid; the average annual rainfall is 3383.5 mm/year and the average humidity is 72-83%.The minimum and maximum temperatures recorded during our study were 12.6 °C and 32.7 °C, respectively.
Major rivers draining the sanctuary are the Jatinga, Daloo, Kayong, Gumra, and Boleswar.The sanctuary is characterized by undulating hills having altitudinal range of less than 30 m to more than 1800 m in the Barail hills, where the towering peaks are Hamplopet (1,867 m), Kuakaha (1,736 m), Maheo (1,739 m), and Sherpai (1,657 m) (Anonymous 2006).Geologically, the soils are sandystony to clayey (Anonymous 2006).The area is one of the richest treasure houses of flora as well as fauna due to its unique geographical position, diverse landscapes, wide range of physiographic conditions and high precipitation.
As per classification of Champion and Seth (1968), the sanctuary has 2 broad groups of forests, tropical wet evergreen and tropical semi-evergreen forests.
Field survey and data collection.We made extensive and intensive field observations and collections from 2013 to 2016 (Table 1), from various habitats and forest types (Figs 2, 3).Our surveys and collections were done with the permission from the Divisional Forest Officer, Cachar Division, Silchar (letter No.B/35/Misc.7344-45, dated Silchar, 21 November 2013).Although we surveyed in almost all seasons, most field surveys were done during the pre-monsoon and post-monsoon seasons.Specimens were collected mostly during their flowering and fruiting stages.Vernacular names, phenological data, and ecological notes were compiled from our field observations and a survey of the literature; these data were supplemented by collectors' notes on herbarium sheets.The IUCN Red List was used to categorize species (IUCN 2017) into different Red List categories.Processing of specimens.The drying, treatment with chemicals, and mounting of our specimens were done following the routine herbarium practices (Jain andRao 1977, Singh andSubramaniam 2008).Voucher specimens were deposited in the Plant Taxonomy and Biosystematics laboratory, Department of Life Science and Bioinformatics, Assam University, Silchar (here abbreviated as AULS; Tables 2, 3).

Identification of species.
We studied the external morphological characteristics, including those of dissected, mainly floral parts, of all collected specimens using an Olympus SZ61stereomicroscope. Characteristics of each species and infraspecific taxon were noted.Preliminary identifications were made using keys in authoratative literature (Brandis 1906, Kanjilal et al. 1934-1940, Chaudhuri and Naithani 1985).We confirmed the identifications of our specimens with authentic herbarium specimens housed in Indian herbaria (ASSAM, BSD, CAL, DD, GUBH, and LWG; acronyms according to Thiers 2011) and with images of type specimens available in online databases.The International Plant Name Index (IPNI 2012), The Plant List (2013) and Tropicos (2017) were consulted for current nomenclature of all taxa.The Angiosperm Phylogeny Group III Classification (APG III 2009) was followed for the classification of families.Families and species in our list are arranged in alphabetical order.

Results
Floristic diversity.Our study revealed 112 species of trees belonging to 86 genera and 43 families (Table 2), and 23 species of lianas in 17 genera and 13 families (Table 3).
The rest of the 9 families had a single species recorded.The dominant genera were Phenera (5 spp.) and Combretum (3 spp.).Among the monocotyledonous lianas, a single species (of Smilacaceae) was recorded.Flowering and fruiting phenology (Figs 6,7).For trees, the flowering was mostly in March (pre-monsoon) to August (post-monsoon), but peaked in June; the peak in fruit production was in the late dry season (August to December).For lianas, flowering peaked in April to July (pre-monsoon and monsoon) and fruit production peaked in the late dry season (August to December).
IUCN Red List categories.Of all species recorded, only 1 tree species (Vulnerable) is threatened; all other species are categorized as Least Concern, Data Deficient, or are Not Evaluated.

Discussion
Our results indicate a rich flora in the BWS, possibly due to the region's physiography of undulating hills and hillocks and tropical to subtropical climate.
Although, most parts of the BWS is still virgin, human habitations in and around the sanctuary exist (8 in East Block; 19 in West Block; Anonymous 2006).With an increasing population, villagers' demands on the forest and its products are increasing with the collection of bamboos, canes, and timber.Clearing of forests for the cultivation of areca nut, beetle leaf, pineapple, and banana is leading to a loss of biodiversity at the forest margins.Massive habitat loss in the buffer zone also      results in species destructions.Other human activities, like road construction, cutting of forests for jhum (shifting) cultivation, areca nut plantation etc., along with some natural phenomena like landslides due to heavy rain, thunderstorms, and hailstorms, are also serious threats to biodiversity.Therefore, there is an urgent need for developing and implementing conservation strategies for the BWS.

Figure 1 .
Figure1.Map of the Barail Wildlife Sanctuary in Assam, India.See Table1for numbered localities.

Figure 3 .
Figure 3. Forest environments of the study area.A-C.Dense forests in core areas.D-F.Liana dominated forests.

Figure 5 .
Figure 5. Dominant liana families with number of species and genera.

Figure 6 .
Figure 6.Phenology of the recorded tree species.

Figure 7 .
Figure 7. Phenology of the recorded liana species.

Table 1 for numbered localities.Table 1 .
Localities, with dates of collections (surveys were 4-5 days at each location), elevation, and geographic coordinates.Locality number corresponds to numbers in Figure1.