Phytodiversity assessment in Sangla valley , Northwest Himalaya , India

Materials and Methods Study area Sangla valley is located at Latitudes 31°10′01.00′′– 31°30′17.16′′ N and Longitudes 78°10′26.52′′–78°52′ 41.75′′ E and altitudes varying from 1800 to 4600 m (Figure 1). The mountains of the valley are composed of carbonaceous slates, quartz schists, phyllite, garnetiferous schists, quartzite and lenticular limestone (Srikantia and Bhargava 1998). The valley is highly glacierized and the winter run-off of the valley is mostly contributed by dry precipitation than wet precipitation, which is on an average <150 mm per annum. The climatic conditions vary from dry temperate to alpine, and vegetation is mainly of temperate, sub-alpine and alpine types. The flora is represented by alpine pastures, dwarf Juniper scrub, subalpine forests/scrubs and temperate forests (Champion and Seth 1968). The socio-economic livelihood of people (dominated by the tribal community Kinnauri) is largely based on agriculture and animal husbandry, along with seasonal collection of medicinal and other economic plants from natural habitats.


Introduction
Mountain regions of the world exhibit rich assemblages of species (Fu et al. 2006;Nowak et al. 2011;Rana et al. 2010;Khan et al. 2013) and endemic plants (Myers et al. 2000;Halloy and Mark 2003;Kazakis et al. 2007;Khan 2012). This is mainly attributed to their unique topography, diverse habitats, aspects and altitudinal ranges. The Himalayan region is a rich repository of extremely varied, native and endemic biodiversity and is recognized as one of the globally important biodiversity hotspots (Singh 2006;Rana et al. 2012;Khan et al. 2013;Sharma and Samant, 2014). The Himalayan range transecting India is popularly known as the Indian Himalayan Region (IHR) and represents 15% of India's geographical area, and 25-30% endemic species (Singh and Hajra 1996;Mittermeier et al. 2004;Sharma and Rana 2005;Phani Kumar et al. 2011). The study area falls in the state of Himachal Pradesh, which is a western segment of IHR and possesses ~3500 species of plants (Chowdhery and Wadhwa 1984;Aswal and Mehrotra 1994;Kaur and Sharma 2004;Singh and Sharma 2006;Sharma and Rana 2013). Literature review reveals a few extensive studies on floristic diversity of Kinnaur district of Himacha Himalaya (Chawla et al. 2012;Negi and Chauhan, 2009). The Sangla valley of Kinnaur has highly varied climatic conditions and is rich in plant diversity (Dutt and Negi 2007;Negi et al. 2007;Singh, 2004), however a comprehensive study of the floristic diversity in this valley has not been made so far. We undertook complete survey of the valley for two years and made a detailed account of the floristic diversity, and provide here a description of the proportion of native, endemic and threatened species.
were prepared for record and identification and assigned voucher numbers. The APG III classification system was followed and the nomenclature was updated from the website 'www.theplantlist.org'. The identified families were described alphabetically. The species were identified with help of various regional floras (Collett 1902;Kachroo et al. 1977;Nair 1977;Chowdhery and Wadhwa 1984;Polunin and Stainton 1984;Aswal and Mehrotra 1994;Dhaliwal and Sharma 1999;Singh and Rawat 2000;Murti 2001) and also from the herbarium of Botanical Survey of India (BSI) herbarium, Dehradun (BSD). The species restricted to the IHR were considered as endemic while those with an extended distribution to neighboring Himalayan countries (Nepal, Afghanistan, Pakistan, Bhutan, China-Tibet Province) were near-endemic (Nayar 1996;Samant and Dhar 1997;IPNI 2009). The endemicity of plant species to the IHR was assessed following Nayar (1996). The threatened status of the species was assessed following IUCN (Ved et al. 2003). The plant names and authorities were authenticated from IPNI (2009). The information on local names was collected from the local people.

Discussion
The present study carried out in Sangla valley elucidated a high floristic diversity of the area, which was found to possess a total of 639 species, 321 genera and 99 families of vascular plants. This floristic diversity has a large contribution to the Kinnaur (Chawla et al. 2012), where 881 plant species, 433 genera and 102 families and 30 species of ferns and fern allies were recorded. The Himalaya houses 25% of original habitat diversity to support native and endemic plants (Mittermeier et al. 2004), validating the present study in which 316 native, 69 endemic and 170 near endemic plants were recorded. We believe that native and endemic species have high conservation priority in a particular area   as compared to non-native species, which adversely impact the local biodiversity and ecosystem functions (Levine et al. 2003).
The predominance of 10 families that we observed in the valley conforms with Chawla et al. (2012) in Kinnaur (Table 3). Compositae, Poaceae and Rosaceae are dominant families in both Kinnaur and Sangla valley, whereas Brassicaceae and Caryophyllaceae were ranked comparatively lower. Polygonaceae and Apiaceae in Kinnaur have seventh and ninth rank respectively, whereas in Sangla valley they are ranked ninth and fifth respectively, due to different environmental variables. Altogether, these top ten families contribute a significant number of species, i.e., 49.6% of the total number of species in Sangla valley.
We compared our study with earlier works done in Kinnaur (Chawla et al. 2012) and other areas of Himachal Himalaya viz., Lahul-Spiti, PVNP (Pin valley National Park), Kullu and GHNP (Great Himalayan National Park) (Aswal and Mehrotra, 1994;Dhaliwal and Sharma, 1999;Chandrasekar and Srivastava, 2009;Singh and Rawat, 2000). Our study shows agreement with Lahaul and Spiti and GHNP, with eight of the ten families being dominant in both of these regions, whereas nine of ten being dominant in Kullu and PVNP (Table 3). Asteraceae is dominant in all the studies except in PVNP, where Poaceae is dominant. Moreover Scrophulariaceae, Cyperaceae and Liliaceae, are among the ten dominant families of Lahaul-Spiti, GHNP, Kullu and PVNP but not in Sangla valley.
The present study showed maximum diversity in the sub-alpine zone (i.e., 2800-3800 m), which highlights the importance of its diverse habitats, aspects, soil types and moisture regimes, as compared to other zones. Low distribution and diversity of the species in the alpine zone (i.e., >3800 m) of the valley owes to its harsh climate and precipitous mountains, little rainfall, poor moisture retention by substratum, and low humidity of the region. A varied distributional range of species in the valley may be due to micro-topographic features such as habitat, moisture availability, canopy cover and slope inclination etc., which can play a significant role in governing distribution (Uniyal et al. 2002).
The species categorized as critically endangered, endangered and vulnerable require high conservation priority in the valley. Our general findings were also endorsed by the local peoples, who feel that populations of some species like Aconitum heterophyllum, Aconitum violaceum, Arnebia benthamii, Dactylorhiza hatagirea, Jurinella macrocephala and Picrorhiza kurrooa have decreased significantly over a short period. Indiscriminate collection of plants for local and commercial use, over grazing by migratory livestock and changing climate (declining snow and rising temperature) were witnessed as the major reason for declining plant populations. It is therefore assumed that consistent qualitative and quantitative records of botanical data are required on regular basis (Clubbe et al. 2010), so that adequate strategies could be formulated for the conservation and management of habitats, species, and communities. The present list could play an important role for the local and regional authorities interested in future to conserve and promote sustainable use of the floristic diversity of this area, as part of sustainable development.