Floristic diversity of Theog Forest Division , Himachal Pradesh , Western Himalaya

We provide a check list of the vascular plants of Theog Forest Division, Himachal Pradesh, Western Himalaya. Himachal Pradesh has been extensively surveyed in terms of flora by a large number of workers, albeit highly confined to prioritized areas. The floristic inventorization resulted in a total of 442 vascular plant species belonging to 311 genera and 117 families from an area of 512 km 2 . Out of these, 408 species belonged to Angiosperms, 7 to Gymnosperms and 27 to Pteridophytes. The predominant families among Dicotyledons were Asteraceae, Rosaceae and Lamiaceae. Among the Monocotyledons, the most represented family was Poaceae, followed by Liliaceae and Cyperaceae. Pinaceae and Pteridaceae were found to be the most represented families among the Gymnosperms and Pteridophytes, respectively. Species richness was highest in shrubberies, which formed an ideal habitat for many herbaceous species within different habitat types. Strategic eradication of weed species, especially obnoxious species such as Lantana camara and Parthenium hysterophorus is required for effective management in the area.


Introduction
The Indian Himalayan Region (IHR) comprises five bio-geographic zones including Trans, North-West, West, Central and East Himalaya (Rodgers and Panwar 1988), and supports more than 18,440 species of flowering plants -out of which 25 % are endemic to the region, covering an area of ca.419,873 km 2 (Singh and Hajra 1996;Samant et al. 1998).In particular, Himachal Pradesh has been regarded as a veritable emporium of plant resources, rich in medicinal and aromatic plants (Chauhan 1999(Chauhan , 2003)).The State is mountainous with an elevational range from 460 to 6,600 m.It has a deeply dissected topography, complex geological structure, wide elevational range and climatic conditions.There are six major forest types in the state, which include Tropical Dry Deciduous, Sub-tropical Pine, Sub-tropical Dry Evergreen, Himalayan Moist Temperate, Himalayan Dry Temperate, and Sub-alpine and Alpine forest types (Ministry of Environment and Forests 2001).The state is a rich repository of plant wealth and has been extensively surveyed in terms of flora by a large number of workers (Chauhan 1999(Chauhan , 2003)).The earliest attempt to collect plants from Himachal Pradesh was made by William Moorcroft (1765-1825) who collected plants from Kangra, Kullu, Lahaul and Spiti in 1821; with these collections sent to Wallich (Chowdhery and Wadhwa 1984).The floristics and the vegetation of the state are broadly known through a number of studies (Collett 1902;Champion and Seth 1968;Nair 1977;Chowdhery and Wadhwa 1984;Aswal and Mehrotra 1994;Chauhan 1999; Dhaliwal and Sharma 1999;Kaur and Sharma 2004).As a result, about 3500 species of higher plants have been identified in the state flora.Collett (1902) collected plants from Shimla and adjacent areas in 1885, covering an area of ca.804 km 2 with an elevational range of 600-3500 m Floristic diversity of Theog Forest Division, Himachal Pradesh, Western Himalaya Dinesh Kumar Pal 1 , Amit Kumar 2 * and Bhupender Dutt 1 1 Department of Forest Products.College of Forestry.Dr. Yashwant Singh Parmar University of Horticulture & Forestry.Nauni-Solan.173 230.
Himachal Pradesh.India. 2 Department of Habitat Ecology, Wildlife Institute of India, Post Box #18, Chandrabani. Dehra Dun. 248001. Uttarakhand. India.which forms the watershed between the Sutlej in the north and Giri in the south.Another main ridge is Shali-Dhar dividing Shimla and Theog Forest Divisions.The only river flowing through the study area is Giri, which originates from Garaog, near Kharapathar in Rohru Forest Division.It flows through the southern part and crosses over to Rajgarh Forest Division and drains into the river Yamuna, one of the main tributaries of the river Ganges.
The lithology is dominated by limestone, shale and quartzite in large areas of Theog and Balson ranges.Shale, phyllite, limestone, schist, gneiss and amphibolite are well exposed at Mahasu and Chambi areas while shale, sand, quartzite, limestone and shale conglomerates occur in areas just south of Kotgarh Division, at Chhaila, Ghund and near Deha.The soil type is more or less clayey or clayeyloam throughout the tract, except at few places where it tends to be sandy-loam.The climate is mostly temperate at the higher elevations and sub-tropical at the lower ones.The minimum and maximum temperatures remain between 16-26°C, and rise up to 35°C (summer) in the lower areas along the river Giri, but it remains between 15-22°C in monsoon season and drops to 0-10°C in winters.The precipitation in the form of snow is received in January-February and sometimes in November-December at higher elevations, whereas lower elevations receive rains in June-August.The area on average receives an annual rainfall of about 1200 mm.The major forests are Deodar-Kail, Fir-Spruce, Chir and Oak.The forests, throughout the tract are both coniferous and broadleaved, grouped as dry-tropical, montane sub-tropical and montane temperate types (Champion and Seth 1968).

Floristic survey
Elevation is deemed most important among the various factors which combine to create contrasts in habitat, climate and flora (Polunin and Stainton 1984).Our field visits were scheduled and the areas to be covered selected taking this into account.Extensive field surveys of the entire study area were conducted in different growing seasons between 2009 and 2010, including low-lying areas like Satog, Balag, Naina, Maipul and Sainj in the Giri Valley, as well as up to the highest peak of the division at Jaobag on Hatu Dhar.Field visits to these areas were planned to collect the plant species either in flowering or fruiting stage to facilitate the process of correct identification.Voucher specimen numbers for each collection were assigned and important field characters were recorded.Identification of the plant specimens was done based on field characters noted during the collection and with the aid of available monographs, taxonomic revisions and floras (Hooker 1872(Hooker -1897;;Collett 1902;Chowdhery and Wadhwa 1984;Polunin and Stainton 1984;Stainton 1988;Chauhan 1999;Khullar 1994Khullar , 2000)).The plant specimens were cross-checked with authentic specimens housed in the herbarium of University of Horticulture and Forestry (UHF), and were deposited here for future reference.Unidentified specimens were confirmed by comparison with specimens housed in the Dehradun herbarium (DD).Specimens were collected and preserved following Jain and Rao (1977).Based on modern phylogenetic studies, APG III classification (Angiosperm Phylogeny Group 2009;Haston et al., 2009) was followed to classify the Angiosperm species.Similarly, Gymnosperms and Pteridophytes were classified following Christenhusz et al. (2011a, b) respectively.
The number of families, genera and species and their respective percentage are accounted in Table 1.The enumerated plants were classified into their respective growth forms, including trees, shrubs (erect, under shrubs, epiphytic), herbs, climbers (woody and non-woody) and ferns (Table 2).Floristic details given in Table 3 include species and family, binomial and vernacular names, distribution and habitat specificity, flowering and fruiting times, elevational range and voucher specimen number.

Discussion
Theog Forest Division revealed a total of 442 vascular plants that represents about 33.3% and 12.6% of the Flora of Shimla and Himachal Pradesh respectively.High diversity of vascular plants in the region is mainly attributed to climatic, topographic and edaphic factors.Annual rainfall of the Theog Forest Division was recorded at ca. 1200 mm annually, which is similar to other floristically rich areas present in the Greater Himalayan Range (e.g., Kedarnath Wildlife Sanctuary and Valley of Flowers National Park).figure 2. Ten dominant families with their respective genera and species in Theog Forest Division, Himachal Pradesh, India.  ) and cultivated/fallow areas.Species richness was higher in shrubberies (98 species), followed by cultivated/ fallow areas (79 species), forests (62 species) and grassy and rocky open slopes (40 species).Shrubberies, the most frequent habitat in the region, transition to forests, grasslands and rocky open slopes and therefore were comparatively richer.These habitats also prevent livestock from grazing and therefore form ideal habitats for many herbaceous species.The high diversity in the cultivated/ fallow areas in the region is due to the high representation of alien and opportunistic species.Subsequently, the grassy and rocky open slopes are mainly confined to southern aspects, which are devoid of woody elements and are therefore comparatively poorer in vegetation.A total of 21 species were recorded as weed species.The most obnoxious and abundant species were Lantana camara (Verbenaceae) and Parthenium hysterophorus (Asteraceae).Other common weed species confined to wastelands near habitations and along roadside were Capsella bursa-pastoris, Stellaria media, Alternanthera sessilis, Cynoglossum glochidiatum, Veronica persica, Bidens
Figure 1.Map showing the location of Theog Forest Division, Himachal Pradesh, India.
, near cultivated areas and along streams; but drought resistant too and occurring on dry hill slopes and open habitats, in shallow drainage, roadsides, waste ground and deep loamy soils.

Figure 10 .
Figure 10.Alpine pasture in the forefront with alpine Abies pindrow (Fir)-Picea smithiana (Spruce) forest in the back view at 3150 m in Theog Forest Division, Himachal Pradesh, India.

Figure 7 .
Figure 7. Yucca gloriosa with typical southern aspect treeless mountain grassland at 2200 m in Theog Forest Division, Himachal Pradesh, India.

Table 1 .
Number of families, genera and species documented in the study area.

Table 2 .
Analysis of habit-forms of the documented flora.

Table 3 .
The floristic details of Theog Forest Division, Shimla, Western Himalaya with their Family, binomial, vernacular name, distribution and habitat, flowering and fruiting, elevational range and Voucher specimen