A PRELIMINARY STUDY OF THE PTERIDOPHYTES, GYMNOSPERMS AND MONOCOTYLEDONS IN THE CHAPAINAWABGANJ DISTRICT'S FLORA OF BANGLADESH

This study demonstrates that the vascular flora (Pteridophytes, Gymnosperms, and Monocotyledons) of the Chapainawabganj district area consists of 247 species with two subspecies under 126 genera and 35 families. The pteridophytes and gymnosperms are represented by 19 and four species, respectively, whereas the monocotyledons (Liliopsida) are represented by 224 species. Poaceae, with 91 species, representing 36.84% of the flora, appears to be the largest family, followed by Cyperaceae 32, Araceae 19, Asparagaceae 12, and Arecaceae 11, which collectively constitute ca. 30% of this flora. Cyperus , comprising 18 species, is recorded as the largest genus, followed by Fimbristylis , Digitaria , Panicum , Bambusa , Urochloa , Dracaena , and Dioscorea . About 87.55% of this flora’s taxa are herbs, 4.42% are palms, 3.61% are shrubs, and the rest are bamboos and trees. Erect herbs, forming 61.04% of the flora, comprise the most common life form. In this flora, almost 74.30% of the taxa are native, and the rest, 25.70%, are exotic. It is found that nearly 74.70% of the taxa are wild, 14.06% are planted, and 11.24% are cultivated. About 23.29% of taxa commonly occur throughout all upazilas in this district. Most of the species are harboured in fallow lands, roadsides, gardens, and homesteads. All species of this district's flora are known to be economically useful. Most of its habitats and ecosystems are exposed to different threats. Adequate measures with effective management plans should be adopted and implemented for the sustainable use, improvement, and conservation of this precious flora.


Introduction
The basis for understanding biological diversity is laid by taxonomic studies, which provide crucial, important, and practical information on the identification, composition, distribution, dispersal, origin, variation, categorization, and relationships of biodiversity.A classical taxonomic study of plants provides the basic and adequate understandings of this biological entity found within a geographical region, a political or administrative area, an ecosystem, or a habitat, which are necessary for the characterization and sustainable use of plant resources, guiding resourcebased development, and resolution of various plant relevant environmental issues.Despite the fact that the angiospermic flora of Bangladesh is thought to be rich, with an estimated 5000 species (Khan, 1977), it has been incompletely inventoried through a variety of sporadic or focused taxonomic studies carried out since 1814 (Roxburgh, 1814) to the present day (Hooker, 1872(Hooker, -1897;;Prain, 1903 Khan et al., 2021).As a result, the floristic compositions in many areas of this country are either unknown or inadequately known, and the updated taxonomic knowledge of many plant groups in this country is lacking.*Corresponding author, E-mail: shahidul.labiba@gmail.com The district of Chapainawabganj, located in northwest Bangladesh, is composed of five upazilas and 45 unions, covering a total area of 1702.54 km 2 .It is situated between longitudes 88°01' and 88°30' east and latitudes 24°25' and 24°58' north (District Statistics 2011 Chapainawabganj, 2013; SFD Lite Report 2022; Fig. 1).Chapainawabganj's geography is primarily flat, with an average elevation of 25 metres above sea level (https://elevation.maplogs.com).The majority of the land is made up of homestead gardens, croplands, scrub jungles, grasslands, and some wetlands.In the basins of the Ganges, Mahananda, Pagla, and Punarbhaba Rivers, the soil is primarily (80%) alluvial, with the remainder being barren (https://elevation.maplogs.com).It experiences summertime wet monsoons and humid subtropical conditions  ).However, no taxonomic study based on field inventories spanning the Chapainawabganj district's geographic area has hitherto been carried out.Taxonomic studies on the flora of Chapainawabganj district are necessary to enrich the baseline data on the floristic composition and plant species diversity of this country, especially of its north-western region, to explore the plant genetic resources of this area, to adopt and implement appropriate conservation initiatives for threatened or near-threatened species, and to support future research on the floristic composition, plant species diversity, and vegetation of this area.This study was conducted to generate baseline information on the current composition, status, distribution, and habitats of plant species in this area of Chapainawabganj district.

Materials and Methods
Field surveys were carried out following the walk-through method throughout each of the upazilas of Chapainawabganj during the different seasons of 2018-2021.All native and exotic species of vascular plants that are wild, planted, or cultivated have been included in this study.The plant specimens were collected, processed, dried, preserved, and identified following standard herbarium and taxonomic methods.Nomenclatural information was confirmed using the techniques outlined in Khan et al. (2021) and Hossain et al. (2021).
Every voucher specimen has been stored at the Herbarium of Jahangirnagar University (JUH).The families of monocotyledons are arranged following Pichi (1977), Kramer and Green (1990), and Cronquist (1988), respectively (Table 1).The APGIV System (Angiosperm Phylogeny Group, 2016) has been used to place the families that are not included in Cronquist (1988).The checklist (Table 1) includes only the accepted names that are currently in use today, along with recent synonyms.A review of pertinent literature and interviews with locals during field inventories were followed to gather information on the use of the plant species (Ghani, 1998;Van Valkenburg and Bunyapraphatsara, 2002;Siddiqui et al., 2007;Ahmed et al., 2008Ahmed et al., -2009;;Ahmed et al., 2009).The Jaccard coefficient was used to determine how similar the species compositions of the five upazilas in the research area were (Jaccard, 1912).The rare and threatened plant species in the study area were recognised through field observation and estimation based on their population size, distribution range, and regeneration in the area.

Results and Discussion
In total, 249 taxa, including 247 species, and two subspecies of 126 genera, and 35 families of three plant groups, viz., Pteridophytes, Gymnosperms, and Monocotyledons (Liliopsida), were found to grow within the administrative boundaries of the Chapainawabganj district.In this article, 247 species were taken into account for the taxonomic enumeration of the species, genus, and families, while information on 249 taxa was utilised to categorise the taxa according to their habitat, habit, distribution, and economic applications.Pteridophytes consist of 19 species under 13 genera, and 7 families make up 7.63% of the species in this district flora, excluding the dicotyledons.Gymnosperms, grouped into four genera and three families, comprised only 1.61% of the species.The monocotyledons, or Liliopsida, made up of 226 taxa under 110 genera and 25 families, comprised 90.76% of the species in the three plant groups of this district flora (Table 1 and Fig. 1).
The taxa of three plant groups, growing in this district comprised 218 (87.55%) herbs, 11 (4.42%) palms, nine (3.61%) shrubs, eight (3.21%) bamboos, and a meagre three (1.21%)trees.The most common pattern of plant growth found in the district's flora was the erect, which accounted for 61.45% (153 taxa) of the flora and 70.18% of the herbaceous taxa.There were different kinds of herbaceous taxa, including vine (18 species), prostrate (15 species), creeper (10 species), free-floating (7 species), emergent (4 species), submerged (4 species), and epiphyte (3 species).Most of the flora of the Chapainawabganj district (74.30%) was found to be made up of native taxa (185).Nonetheless, 64 exotic taxa account for a sizable part (25.70%) of this flora.A total of 186 taxa, or 74.70% of the flora, were found in the wild, while 35 species, or 14.06%, were found to be planted, and 28 species, or 11.24%, were found to be cultivated.With five species, the Pteridaceae family was the largest in Pteridophyta.Aspleniaceae and Polypodiaceae, with four and three species each, were the next largest families.There were one or two species in each of the remaining families.The genera Adiantum L., Pteris L., Lygodium Sw., and Marsilea L. each had two species, while the remaining genera were each made up of one species.The genus Thelypteris Schmidel contained three species.Gymnospermae species were found in one or two families and one species in each of their genera, with the exception of Cycas L., which was found to be represented by two species.Species of Pteridophyte were all herbs that grew naturally, while three species of Gymnosperm were trees, and one was a shrub, all of which were planted.
In the Liliopsida (monocotyledons), Poaceae, with 91 taxa belonging to 45 genera, was the largest family, accounting for 36.55% of the Chapainawabganj district's vascular flora, excluding the dicotyledons.Cyperaceae, with 34 species of five genera; Araceae, with 19 species of 13 genera; Asparagaceae, with 13 species of five genera; and Arecaceae, with 11 species of 10 genera, were the next large families of Lilipsida in this district.These four families combined made up 34.07%, and the families Commelinaceae, Zingiberaceae, Dioscoriaceae, and Orchidaceae, each including fewer than 11 species, form only 11.06% of the district flora of these three plant groups (Fig. 2).The species names of seven taxa (2.8%) could not be validated because their voucher specimens lacked species-specific key characters, and therefore, only the generic names have been cited for these taxa.
With 18 species, Cyperus L. was the largest monocot genus.It was followed by Fimbristylis Vahl with nine species, Digitaria Haller, and Panicum L. with seven species, Dracaena Vand., Bambusa Schreb., Dioscorea L., and Urochloa P. Beauv.with six species, The taxonomic counts of the monocotyledonous species of the Gomastapur, Nachole, and Bholahat upazilas that this study completed (Fig. 3 The Jaccard coefficient also indicated that there was a 23.29% similarity in the composition of plant taxa among the five upazilas in the Chapainawabganj district (Fig. 4).It suggests that, rather than being similar, the species compositions in these upazilas, that is, throughout the district, were comparatively more variable.Nonetheless, a comparison of the plant species composition of the Chapainawabganj Sadar upazila with that of the other upazilas in the Chapainawabganj district reveals that there was a range of similarities, from 31.70% to 46.31%.The species of studied plant groups in Chapainawabganj district were found to be distributed in diverse habitats.But the majority of the species were well suited to grasslands, homesteads, roadsides, fallow areas, and agricultural fields; these were followed by gardens, marginal lands, marshes, scrub jungles, wooded areas, and riverbanks.A few tree species and brick walls also harboured some of the species (Fig. 5).
Every plant species found in the district of Chapainawabganj has economic value, and nearly 60.64% of these species have two or more uses (Table 1).A total of 62.35% (154 species) of the studied plant groups in this district are medicinally useful.In addition, 123 species are designated as cattle food, followed by 32 ornamental, 21 edible, 11 vegetable, 10 handicraft, 9 fuel wood, and 8 paper pulp species.In addition, seven species are recognised as fibre, six as fruit and fencing, fish food, five species each for green manure, four as aquarium plants and oil-, dye-, and spice-producing, and the remaining flora are recognised as economically valuable (Table 1).Among the plant groups studied, 53 taxa were common, whereas 108 were found to be occasional and 88 to be rare.
In terms of plant diversity and resources, the Chapainawabganj district in northern Bangladesh appears to be at risk.Critical issues and dangers to the degradation and destruction of its habitats and ecosystems, and eventually to its flora and fauna, include drought, river bank erosion, poor regeneration of many species, various anthropogenic activities, and a lack of appropriate management strategies.Drought, river bank erosion, poor regeneration of many species, different anthropogenic activities, a lack of proper management programmes, etc. were identified for knowing the critical problems and threats for degradation and destruction of its habitats and ecosystems, and ultimately for its flora and biodiversity.Eulophia picta, Rhynchostylis retusa, and Zeuxine nervosa are found to be threatened in the Chapainawabganj district based on field observation.
The taxonomic data provided by this study might be useful to know about the current species composition of the three plant groups in the flora of Chapainawabganj district and helpful as an important guiding database to track the trend of changes in the floristic composition, plant species diversity, vegetation, and status of threatened plant species over time, especially due to different natural and anthropogenic threats, contribute to undertaking appropriate biodiversity conservation initiatives and plant resource-based sustainable socioeconomic development, and estimate the impacts of climate change on the flora and biodiversity of this area.This study recommends improving and preserving the area's valuable flora, reducing threats to its natural habitats, conducting regular taxonomic inventories, monitoring studies and research programmes on the diversity of plants in the area, and implementing sufficient plantation programmes that use appropriate indigenous species and have effective management plans and strategies.

Fig. 1 .
Fig. 1.Map of Chapainawabganj district with its five upazilas.Some taxonomic studies on the flora of several districts of Bangladesh have been carried out (Sultana, 2012; Tabassum, 2015; Uddin and Hassan, 2018; Khanam and Khan, 2020; Khanam et al., 2020; Roy and Khan, 2020a, b; Hossain et al., 2021).However, any taxonomic literature on the flora of Chapainawabganj district based on field inventories throughout its entire geographical area is not known to have been published so far.A number of taxonomic investigations have been conducted on the flora of several districts of Bangladesh (Sultana, 2012; Tabassum, 2015; Uddin ) are higher than the accounts on the monocotyledonous species of other upazilas cited earlier, but somewhat lower than those of Chapainawabganj Sadar and Shibganj upazilas, almost similar to those of the Monohordi, Narshingdi Sadar, and Polash upazilas of the Narshingdi district (Khanam et al., 2020; Khanam and Khan, 2020) and Satkhira Sadar upazilas (Hossain et al., 2021) previously reported.