Tree species of the Himalayan Terai region of Uttar Pradesh , India : a checklist

The study catalogues a sum of 278 tree species belonging to 185 genera and 57 families from the Terai region of Uttar Pradesh. The family Fabaceae has been found to exhibit the highest generic and species diversity with 23 genera and 44 species. The genus Ficus of Moraceae has been observed the largest with 15 species. About 50% species exhibit deciduous nature in the forest. Out of total species occurring in the region, about 63% are native to India. Almost all tree species have some importance in one and another way for the local people. In the study area about 80 species flower in the spring, 74 in the summer, 73 in the winter and 30 in rainy season. As per the existing IUCN Red List, 24 species of the area fall under different categories. Presence of these red listed trees in the study area enhances the importance of their proper management and conservation plan.


INTRODUCTION
Trees are not only the major components of the forest and the vital part of our ecosystem, rather they also provide shelter to lower organisms as well as wildlife, act as environment protector, reduce the pollutants and provide a number of useful things such as timber, fuel, fodder, food, medicine, charcoal, gum, resins, rubber, pulp for paper etc. for human beings in day to day life.Many natural habitats are under threat and the species within them face potential extinction.The trees are fast disappearing and genetic diversity in tree species has become more vulnerable than other plant species (Tripathi et al. 2013).Thus it is imperative to document and conserve the tree flora of any area before they become threatened and lost.For any conservation programme of the tree species and their sustainable use and management, the proper assessment of the diversity of tree species are highly needed (Chaudhary et al. 2014).The information on phenology, uses, native origin, and vegetation type of the tree species provide more scope of such type of assessment study in the field of sustainable management, conservation strategies and climate change etc.In the present study, the Terai region of Uttar Pradesh has been selected for the assessment of tree species as it consists of considerable number of species and has not been worked out during the recent time.
The low lying land stretch in the north of Indo-Gangetic Plain along the foothills of Central Himalaya is known as 'Terai' (Chauhan et al. 2010).The similar region below the foothills of eastern Himalaya is distinguished from the Terai and is termed as 'Dooars' (Rodgers et al. 2002).It is dispersed in three Northern Indian States namely Uttarakhand, Uttar Pradesh and Bihar and the southern Nepal (Rodgers et al. 2002).It forms an ecotone where the Sub-Himalayan foothills encounter the plain region.Due to the edge effect this region exhibits the vegetation of both the contiguous regions and becomes one of the highly diverse regions of the country (Shukla 2009) and is one of the most diverse eco-regions of the world (De 2001;Kumar et al. 2002).The region covers a geographical area of ca.92,911 km 2 with a forest cover of ca.8,108 km 2 (Anonymous 2008).About 68% forest cover (5,501 km 2 ) of this region comes under the boundary of Uttar Pradesh covering 21 districts (Anonymous 2008;Jha 2007).

Diversity assessment and data collection
The entire study area has been explored comprehensively to collect and document the tree diversity during the years 2011-2013.The plant specimens were randomly collected from the aforesaid vegetation types.The herbarium specimens have been prepared following Lawrence (1951) and Jain and Rao (1977) and were deposited at LWG.The identification of the species has been done with the pertain either to small areas or have become out dated due to changes in nomenclature, distribution and circumscription of various taxa.Therefore, the present study is a cumulative effort that includes review on the existing literature, herbarium specimens housed at Botanical Survey of India, Central circle, Allahabad (BSA), Birbal Sahni Institute of Palaeobotany, Lucknow (BSIP), Central Drug Research Institute, Lucknow (CDRI), National Botanical Research Institute, Lucknow (LWG) and collections made in the present study to prepare a checklist of tree species from the Terai region.The study will provide baseline information for floristic diversity assessments and updating flora in future.

Study area
The Terai region in Uttar Pradesh spreads from Saharanpur to Deoria covering 21 districts of the State (Jha 2007).It is situated between 28°45′-26°15′ N and 079°51′-084°24′ E as a 30-50 km wide and ca.1,670 km long strip with the elevation ranging between 100-300 m.For the safeguard of the biodiversity, one national park and six wildlife sanctuaries have been declared in this region (Figure 1).The study area comes under the monsoon type of climate which witness three different seasons: winters (November-February), summers (April-June) and rains (July-September) with one  Kumar et al. 2011;Maliya 2011Maliya , 2012;;Bajpai et al. 2012a;Chaudhary et al. 2014) regional work.The deciduousness and ever greenness of the species has also been noticed during these visits.The economic values of the species have been assessed by interviewing the local Tharu tribal persons as well as from published work from the area.The native orgin of the species has also been traced out with the help of different available on-line data bases (http:// www.flowersofindia.net;http://www.efloras.org;http:// www.ipni.org;http://www.worldagroforestrycentre.org).In the checklist, the plants whose, herbarium specimens have not been seen, the references of the previous reports have been cited to know the source of occurrence of the species in the study area.

RESULTS
The present analysis includes 278 tree species under 185 genera of 57 families from the Terai region of the Uttar Pradesh.Each species has been provided with phenology, economic importance, native origin, vegetation type, vernacular name and collection number/references (Table 1).Fabaceae has been found as the largest family representing 44 species under 23 genera.Twenty families (Araliaceae, Capparaceae, Casuarinaceae, Celast raceae, Dipterocarpaceae, Loganiaceae, Olacaceae, Oxalidaceae, Pandanaceae, Pittosporaceae, Primulaceae, Proteaceae, Putranjivaceae, Rhizophoraceae, Sabiaceae, Santalaceae, Simaroubaceae, Symplocaceae, Urticaceae, Verbenaceae) are represented by only single species and genus (Figure 2).About 146 species show the deciduous nature followed by 102 evergreens, 19 semi-deciduous and 11 semi-evergreen species (Figure 3).The area encompasses about 63% (177) species native to India.This clearly reflects that the Terai region has its own natural diversity which supports the stable ecosystem with well adaptability for the area.The remaining species belong to Asian, American, African or Australian origin (Figure 4).The present documentation also recognizes the importance of tree species, as about 204 have been observed to be used for medicinal purposes in different human ailments.Similarly, 90 tree species       15), gum and resin (11) and seven species for dye production (Figure 5).In addition, six tree species namely Calotropis gigantea (L.) Dryand., Bauhinia racemosa Lamk., Guazuma ulmifolia Lamk., Ficus benghalensis L., Ficus religiosa L. and Aegle marmelos (L.) Correa have also been found of religious faith.The phenological assessment discloses that the maximum species flowers in the spring (ca.80 species) followed by 74 in summer, 73 in winter and 30 in rainy season (Figure 6).On an average about 21.8±8.2tree species have been observed in fruiting throughout the year which fitswell for wildlife as well as forest ecosystem.About 9% trees belong to various threat categories under IUCN Red List of Threatened Species (IUCN 2013), among them two are Endangered, seven are Vulnerable, one is Near Threatened, 11 are Least Concern, and three are Data Deficient (Table 2).

Figure 1 .
Figure 1.Study site in the Terai region of Uttar Pradesh, India.

Figure 3 .
Figure 3. Number of species distributed across different vegetation types.

Figure 2 .
Figure 2. Dominant families with corresponding number of species and genera.

Figure 5 .
Figure 5. Number of species used for different purposes.Figure 4. Number of species of different native areas.

Figure 4 .
Figure 5. Number of species used for different purposes.Figure 4. Number of species of different native areas.

Table 1 .
List of tree species with their phenology, economic importance, native origin, vegetation type, vernacular name and collection number/reference. continued
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Table 1 .
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Table 2 .
Conservation status of the tree species as per IUCN Red List of Threatened Species (EN = Endangered, VU = Vulnerable, NT = Near Threatened, LC = Least Concern and DD = Data Deficient).