Vascular plant diversity with special reference to invasion of alien species on the Doon University Campus , Dehradun , India

1 G.B. Pant National Institute of Himalayan Environment and Sustainable Development, Himachal Unit, Mohal-Kullu175126, Himachal Pradesh, India 2 School of Environment and Natural Resources, Doon University, Dehradun-248001, Uttarakhand, India. 3 Botanical Survey of India, Northern Circle, Dehradun-24803, Uttarakhand, India. 4 Forest Survey of India, Dehradun-248006, Uttarakhand, India. 5 Himalayan Institute for Sustainable Environment and Research, THDC Colony, Dehradun, Uttarakhand. 6 Federal University Lafia, Nasarawa State. Nigeria


INTRODUCTION
India is one of the 19 megabiodiverse countries of the world and consists of 48,158 species of plants (Anonymous, 2016) and 97,514 species of animals (Anonymous, 2016) in its ten biogeographic regions.The Shivalik or sub-Himalayan region is the youngest and ecologically fragile mountains have been categorized under the Indo-Gangetic plains with unique significance which integrates ecosystem of Indo-Malayan and palaearctic regions (Shivkumar et al., 2010).Shivalik Himalaya ranges over a stretch of 1500 miles long and 20 to 30 miles wide from the Indus to Brahmaputra in Assam (Kohli, 2002).In Uttarakhand State, the Shivalik Himalaya covers Tarai-Bhabhar, Shivalik and lesser Himalayan zones which include the part of district Pauri, Tehri, Dehradun and Haridwar, etc (Sharma et al., 2011).
Invasion of alien species has been considered a significant threat to an ecosytem which trigger the alteration of ecological characteristics of a habitat.Organisms immigrating to new habitats have been specified as alien, adventative, exotic, introduced and non-indigenous (Mack et al., 2000;McGeoch et al., 2010).Invasive species may occur through accidental, import for a limited purpose and subsequently escape or persistent introduction on a large scale (Ehrenfeld, 2003).These species affect natural ecosystem structure and function (Sekar et al., 2012), although have significant ecological benefits too.Alien species differ in their nutrient requirement, mode of resource utilization which cause changes in soil structure and profile (Negi and Hajra, 2007;Raizada et al., 2008).Invasion of exotic plant species might have significant adverse changes on the biodiversity and ecosystems functioning (Sharma and Raghubanshi, 2011) which further affect the environment as well as human health (Sekar, 2012).Over the years, invasion of various alien species of diverse origin has been increased in India and reported mainly from regions like Doon valley (Negi and Hajra, 2007), Kashmir Himalaya (Khuroo et al., 2007;Khuroo et al., 2010), Uttarakhand (Tewari et al., 2010), Uttar-Pradesh (Singh et al., 2010), Himachal-Pradesh (Jaryan et al., 2013), Assam (Das and Duarah, 2013), Jammu (Kaur et al., 2014), North-Eastern Uttar Pradesh (Srivastava et al., 2014), Karnataka (Kambhar and Kotresha, 2011), Madya-Pradesh (Wagh and Jain, 2015), Delhi (Mishra et al., 2015) and Haryana (Singh and Mohammed, 2015).
Over the years, as developmental activities are continuing to modify the natural ecosystem throughout the world, native floral and faunal species are continuously decreasing with their diminishing habitat.Therefore, it is important to document the current biodiversity status (diversity, life form, habitat, use values and phenological patterns) and monitor the changes in vegetation pattern over the time.Considering these facts, the present study has been conducted to assess plant diversity within the Doon University campus which would be important to monitor the change in near future and implementation of suitable management plan.

Study area
The present study was conducted in the Doon University campus, situated in the foot hills of Shivalik mountains, lying between 30°15'60''-30°16'10'' latitudes and 78°2'36''-78°2'50'' longitudes with an altitudinal range of 600 to 630 m asl and covering an area of approximately 0.199 km 2 (Patwal and Naithani, 2014) (Figure 1).It is situated in a mosaic of various habitat types which includes thick deciduous forest, riverine habitat, agricultural fields and human settlements.Tectona grandis, Shorea robusta, Terminalia alata, Anogeissus latifolia, Mallotus phillippensis and Melia azedarach are major tree species in the forest.The riverine habitat is constituted by river Rispana which flows through eastern side of the campus and further join Song River, a tributary of the River Ganga.The average temperature remains moderate year round ranging from 35 to 40°C in the summers to 15 to 25°C in winter.The average annual rainfall recorded for the area is 2073 mm and most of the rainfall received during the month of June to September.Due to its unique location in the vicinity of different habitat types, the campus consist suitable environmental conditions to supports a variety of floral and faunal species.

Nativity
Among the 191 recorded species, 70 (36.64%)are native, while 121 (63.35%) are non-natives or exotic species.Thus, the study reveals that the floristic diversity is dominated with exotic species and most of them are planted for ornamental purposes in the campus.

Native plant species
The native species diversity within the University campus are comparatively low.Among these species, Barleria cristata L., Cryptolepis dubia (Burm.f.) M.R.
The findings from literature and discussions with local inhabitants indicate that several invasive species are also used for various other purposes.For example, leaves of A. spinosus are edible and used as fodder while leaves and stem of G. parviflora are used for medicinal (anti-itch) as well as fodder purposes while Tagetes erecta is considered and used as religious plant species.A total of 67 species were reported to use for medicinal purposes by the local inhabitants and 42 exotic species planted for ornamental purposes within the campus.The economic uses of 3 species namely Barbarea vulgaris R.Br., Ipomoea triloba L. and Pteris vittata L. are not known (Table 2).
Bird community structure play vital roles in seed dispersal in human-altered landscapes            (Gosper et al., 2005;Ruxton and Schaefer, 2012).However, seed dispersal of invasive species through avian communities in the important eco-regions like Shivalik could have adverse ecological consequences on the native flora.

Conclusions
The study provides baseline information on floristic diversity of a modified habitat from riverine and agricultural to concrete jungle and plantation in Shivalik landscape.These finding would be important in monitoring the changes in vegetation pattern in the near future.At present, the exotic floras dominate the native flora and are important in terms of influencing local environmental condition of the habitat.The flowering period of plants species of different origin would help in prediction of climate change over the years and role of interaction between local environmental conditions as well as their native behavior.Regular monitoring of vegetation and scientific inputs are crucial to promote native species and proper management of floristic diversity is crucial as they provide unique habitat to more than 138 bird species (used for perching, foraging, nesting, breeding, etc) and about 41 lepidopteron species.Further studies on their beneficial uses through phyto-chemical investigation would be important to conserve the important gene flow in a managed landscape to validate and sustain their ethno-medicinal importance.

Figure 2 .
Figure 2. Distribution of vascular plants families in Doon University Campus.

Figure 3 .
Figure 3. Phenological data on vascular plants in Doon University Campus.

Figure 4 .
Figure 4. Distribution of different life from the aspect of use value.

Figure 5 .
Figure 5. Number of plants species on the basis of use of plant parts.

Table 1 .
Floristic detail of Doon University Campus.

Table 2 .
List of vascular plants in Doon University campus.