AN INVENTORY OF VASCULAR FLORA OF THE LALMAI HILL AREA OF CUMILLA DISTRICT, BANGLADESH

In this study, the vascular flora of the Lalmai hill area of the Cumilla district has been thoroughly explored. This study reveals the occurrence of 923 species of vascular plants under 594 genera and 141 families in the study area, which represents 23.75% of the total 3886 plant species reported from Bangladesh until now. About 68.15% of these species are native and 31.85% are exotic to Bangladesh. Pteridophytes are represented by 30 species belonging to 21 genera and 11 families, whilst Gymnosperms are represented by eight species under seven genera and six families. Magnoliopsida (dicotyledons) comprises 661 species, including four subspecies and two varieties, from 429 genera and 96 families, accounting for 71.54% of the vascular flora of the study area. Liliopsida (monocotyledons) represents 225 species under 137 genera and 28 families, making up 24.35% of this flora. In Magnoliopsida, Fabaceae with 55 species is the largest dicot family, followed by Asteraceae, Malvaceae, Euphorbiaceae, Lamiaceae and Rubiaceae. Most of the species of Liliopsida (68%) are represented by the five families viz ., Poaceae, Cyperaceae, Araceae and Commelinaceae. Poaceae with 75 species is the largest monocot family, followed by Cyperaceae, Orchidaceae, Araceae and Arecaceae. The genus Cyperus is the largest in the study area. The species Antidesma roxburghii Wall. ex Tul. of Phyllanthaceae is rediscovered in Bangladesh. Most of the Magnoliopsida and Liliopsida are herbs (59.80%), which are followed by trees (21.02%), shrubs (17.23%), and palms (1.41%). About 64.57% of the species are recorded as wild, but a significant percentage (27.41%) is planted and cultivated (8.02%). The majority of the species are found to grow in eight categories of habitat viz ., roadside, fallow land, homestead, woodland, garden, scrub jungle, agricultural field and grassland. Eight plant species, listed in the Red Data Book of Bangladesh including six as Data Deficient (DD), one Not Evaluated and one Endangered (EN) species, are harboured in the study area. We strongly recommend the adoption of a master plan for minimizing all major threats to the vegetation and habitats of this area and sustainable development, utilization and conservation of its plant resources.


Introduction
It is essential to have a fundamental understanding of the biodiversity of a country to improve and use its biological resources sustainably and address and mitigate its environmental problems. Taxonomic studies using various non-molecular and molecular data lay the groundwork for understanding and assessing various aspects of plant biodiversity. These studies offer very important and pertinent information and expertise on plant species that are crucial for the confirmation of their identity, description, distribution, origin, evolution, relationship, classification, management and sustainable utilization. Such studies are useful for economic and environmental development based on plant resources, exploration of alternative plant species, recognition and conservation of threatened plant species, and assessment, monitoring, and mitigation of the negative effects of climate change on plant species. Due to these consequences, taxonomic studies have been considered pivotal in different regions and nations worldwide for more than a century (Ostertag et al., 2014).
In Bangladesh, a total of 3886 species of vascular plants have been reported through various taxonomic studies conducted sporadically so far (Hossain et al., 2022). These studies were conducted in different forests, regions and small to large administrative areas or small to moderate-sized families at different times since 1814 (Roxburgh, 1814). The plant species composition of many areas or most of the large plant families of this country is still unknown or partially and inadequately known (Hossain et al., 2022;Khan et al., 2021a,b). If adequate floristic surveys are conducted in the remaining areas and large plant families of this country, approximately a further 2000-2500 species of vascular plants might be explored. On the other hand, almost all of the large-scale (Prain, 1903;Siddiqui et al., 2007;Ahmed et al., 2008Ahmed et al., -2009Ahmed et al., 2009;Uddin and Hassan, 2018) and many small-scale (Rahman, 2013;Ara et al., 2007;Rahman, 2017;Rashid et al., 2018;Uddin and Hassan, 2010;Malaker et al., 2010;Uddin et al., 2003) taxonomic publications on the flora of this country do not provide information on the specific distribution and voucher specimens of the reported plant species, though some such publication include these kinds of information (Uddin and Rahman,1999;Islam et al., 2009;Tutul et al., 2010;Rahman et al., 2012;Sultana, 2012;Sarker, 2013;Rahman et al., 2015;Tabassum, 2015;Nahar and Rahman, 2016;Haque et al., 2018;Shetu et al., 2018;Roy and Khan, 2020a,b;Hossain et al., 2021;Khan et al., 2021a,b;Hossain et al., 2022). Therefore, further and adequate floristic surveys involving data collection on specific distribution and voucher specimens of the plant taxa of the unexplored or partially explored areas of this country are very crucial.
The Lalmai hills were once densely wooded and an area near Kotbari was earmarked as a forest belt (BBS, 2013). The vegetation was mainly deciduous and the dominant tree species was Shorea robusta C.F. Gaertn (Sal) . But in course of the last 20 years, the vegetation of this area has been modified to a semi-deciduous and mixed evergreen category, composed of mostly planted forests associated with many naturally grown plant species and a few small patches of S. robusta forest. Almost the whole of Lalmai hills has been cleared up and cultivation has been extended up to the foothills (BBS, 2013). Previously, no floristic or similar other study was carried out on this hill area except enlisting a few plant species in the District Gazetteer of Comilla and the booklet of Ismail and Mia (1973), generating the checklists of 103 undergrowth plant species by Rahman et al. (2001), and 151 angiosperms species by Hossain et al. (2005), and a hydrobiological study on three different water bodies of this area reporting the occurrence of 352 species of phytoplanktons (Bhuiyan, 2022). Most of the habitat-relevant threats to the flora and plant diversity of the Lalmai hill area are functional and have the potential to significantly reduce or change the plant diversity and floristic composition (Ali, 1999;Choudhury, 2002;Khan, 2008;Kulatunga et al., 2012). The hills of this area are going to be destroyed and the hills have already turned to be a hillock on the plain land. The land grabbers carry on their destructive activities. Due to unhindered earth cutting, the deep forest of this area is going to lose its existence.
Therefore, it makes logical sense to perform a thorough floristic study throughout this territory, particularly for understanding the current species composition and diversity, searching the potentially threatened plant species and knowing the changes in plant species composition of the area in course of time and the impacts of climate change, plant resource-based sustainable development, and providing invaluable baseline data necessary for effective conservation of the threatened species as well as assessment and monitoring of the impacts of anthropogenic climate change on the plants and ecosystems of this area. This study was carried out to provide basic taxonomic information on the vascular plant species extant in the Lalmai hill area, i.e., all hills of Lalmai and their adjacent area, based on detailed floristic inventories and examination of representative specimens.

Materials and Methods
The Lalmai hill area is a low-amplitude anticline and consists of three toposequence arrangements as hills, piedmonts, and floodplains Rahman et al., 2021). This area lies between the latitudes 23°20'N to 23°30'N and longitudes 91°05'E to 91°10'E, at about 8 km westward from Cumilla township (Fig. 1).
The Chittagong-Tripura Fold Belt, particularly the Raghunandan Hill of Indian Tripura Hills, borders this region on the east, the Meghna River on the west, the Gumti River on the north, and the Dakatia River on the south-southeast . It consists of a north-south elongated low hill range of about 17 km long and 1-2.4 km wide, covering an area of about 33 sq km and locally it is known as the Mainamati-Lalmai range (https://en.banglapedia.org). This hill range is mostly composed of some small to medium-sized hills of about 12 metres in In the study area, the majority of the species were found to grow in eight categories of habitat viz., Roadside (37.16%), fallow land (34.24%), homestead (26.54%), woodland (20.48%, garden (18.85%), scrub jungle (16.14%), agricultural field (14.08%) and grassland (12.89%), followed by other habitat categories namely, wetland (9.32%), hill slope (9.21%), forest margin (5.42%), hilltop (5.42%), other plants (2.28%), and brick wall (0.43%) (Fig. 2).
A comparison in the plant species composition of the study area (Lalmai hills and their adjacent area) with that reported previously from some localities of this country, composed of similar kinds of habitats, indicates that the number of species per square kilometre found in the study area is nearly similar to that of Rajkandi Reserve Forest (Haque et al., 2018), Hazarikhil Wildlife Sanctuary (Rahman, 2017), somewhat higher than that of Sitakunda Ecopark (Islam et al., 2016), Satchari National Park (Arefin et al., 2011), Baraiyadhala National Park (Rashid et al., 2018), and Teknaf Wildlife Sanctuary  but lower than those reported from Jahangirnagar University Campus (Khan et al., 2021a) and Lawachhara National Park   (Fig. 4). Rahman et al. (2001)'s recorded 24 species of Lalmai hills were not found to occur there during this study. These species belong to the families Annonaceae (one species), Apocynaceae (one species), Asteraceae (one species), Commelinaceae (one species), Convolvulaceae (one species), Euphorbiaceae (one species), Fabaceae (three species), Lamiaceae (two species), Passifloraceae (one species), Phyllanthaceae (two species), Poaceae (two species), Polygalaceae (one species), Polypodiaceae (one species), Rubiaceae (five species), and Zingiberaceae (one species). Similarly, 17 species belonging to the families Acanthaceae (one species), Apocynaceae (two species), Cyperaceae (one species), Elaeocarpaceae (one species), Fabaceae (four species), Lamiaceae (one species), Myrtaceae (one species), Phyllanthaceae (one species), Poaceae (three species), Primulaceae (one species) and Solanaceae (one species) reported by Hossain et al. (2005) from this area were not found during this study. A reason for the absence of these species in the study might be their direct missing due to habitat destruction and other anthropogenic activities. Another reason seems to be the incorrect identification of the species that could not be verified due to the lack of their voucher specimens.
Traditionally, the study area is being gradually converted from a natural deciduous forest area to a semi-urban area covered with cultivated, planted and natural plant populations. Currently, about 20%-25% of the area is already converted into a semi-urban area housing some infrastructures including a few institutions and a part of the regional cantonment. A notable part of the remaining area is notably disturbed through various anthropogenic activities including different plantation and cultivation programs following repeated vegetation clearing and habitat destruction. However, a huge number of plant species, as enumerated by this study, have been established in this area through the introduction of many exotic species (31.12% of the flora), mainly in the semi-urban localities including gardens, campuses, roadsides, tourist spots etc. and the introduction of diaspores of different plant species from different regions of the country through various biotic and abiotic agents. Some parts of the area, composed of roadside, fallow lands, homesteads, woodlands, gardens, and agricultural fields, are covered with dense vegetation.
The vegetation of the study area provides habitats for various animal groups (wildlife). The biodiversity of the study area is affected by different kinds of threats, mostly resulting from multifarious anthropogenic activities including hill clearing and cutting, land grabbing, agricultural expansion following vegetation clearing, infrastructure development, settlement, firing, grazing, leaf litter and fuel wood collection, and huge visits etc. are recognized as the major threats to its biodiversity. However, this area is harbouring a rich biodiversity with a huge number of plant species in its diverse ecosystems. As an original site of natural vegetation, this area might be an excellent choice for in situ and ex situ biodiversity conservation. Therefore, we strongly recommend the adoption of a master plan for minimizing all major threats to the vegetation and habitats of this area and sustainable development, utilization and conservation of its plant resources. In order to implement this plan, strengthening and improving the existing management of the area by adopting necessary conservation initiatives including effective policies, and legislation, adopting and strict enforcement of the necessary laws of natural resource utilization including lands, controlling and minimizing anthropogenic interferences, increasing public awareness, improving the quality of major natural habitats are highly recommended. We highly advise routine inventories and monitoring programs for this area's biodiversity. Adequate protection, conservation and development of the diminishing natural resources of this area including its biodiversity will improve its sustainable socio-economic and ecological services.