Successive variation in phytosociological aspects and threat categorization of Picrorhiza kurroa Royle ex Benth . in Kumaun Himalaya of Uttarakhand

The present work is a part of a three years extensive study to observe the annual changes in phytosociological characters of Picrorhiza kurroa Royle ex Benth. (FamilyScrophulariaceae) in high altitudinal regions of Kumaun Himalaya, Uttarakhand. The work was undertaken with the objective of observing the annual variation in relative values of frequency, density, abundance and importance value Index (IVI) of the plant species suffering from threats and categorized as critically endangered by International Union for Conservation of Nature (IUCN).


INTRODUCTION
Phyto-sociology is the study of the characteristics, classification, relationships, and distribution of plant communities.It is useful to collect such data to describe the population dynamics of each species studied and how they are related to the other species in the same community.Subtle differences in species composition and structure may point to differing abiotic conditions such as soil moisture, light availability, temperature, exposure to prevailing wind, etc.When tracked over time, species and individual dynamics can reveal patterns of response to disturbance and how the community changes over time.The term phyto-sociology was coined by Jozef Paczoski in 1896.
The aim of phyto-sociology is to achieve a sufficient empirical model of vegetation using plant taxa combinations that characterize univocally vegetation units.Vegetation units as understood by phytosociologists may express largely abstract vegetation concepts (for example, the set of all hard-leaved evergreen forests of Western Mediterranean area) or actual readily recognizable vegetation types (for example, cork-oak oceanic forests on Pleistocene dunes with dense canopy in SW-Iberian Peninsula).Such conceptual units are called "syntaxa" (singular "syntaxon") and can be set in a hierarchy system called "synsystem" or syntaxonomic system.
In this work, the phyto-sociological aspects of Picrorhiza kurroa Royle ex Benth.belonging to the family Scrophulariaceae (Plate 1) were observed and analyzed to sculpt the annual fluctuation in various aspects of *Corresponding author.E-mail: deepika_bhatt59@rediffmail.com.Author(s) agree that this article remain permanently open access under the terms of the Creative Commons Attribution License 4.0 International License

Study area
The present study area, Kumaun Himalaya (Sub-Himalayan tract of IHR), lies between the altitudes 28° 44 ' N and 30° 49' and longitudes 78° 45' and 81° 1' E Kumaun, The eastern boarder of the region separates from Nepal by Kali river, High transverse mountain spurs separate it from the Chamoli and Pauri districts of Garhwal, a natural water separates from Tibet and the southern limit of the Tarai belt demarcates its southern boundary.All the ten selected study sites (Laspa, Burfu, Bilju, Martoli, Ganghar, Milam I, Milam II, Tejam, Shimdum and ShimdumII) are situated at the higher altitudinal ranges (2780 to 3680 masl) of district Pithoragarh (Figure 1).

MATERIALS AND METHODS
The surveys were made for three successive years viz., 2009 to 2010, 2010 to 2011 and 2011 to 2012 to record the annual variation in phyto-sociological aspects such as relative values of frequency, density, abundance and IVI for the selected species.For the phytosociological study, the area of each and every study site was surveyed extensively and ten populations (7 in Johar valley, 3 in Chaudus valley) were identified (Table 1) on the basis of (a) habitat attribute (altitude), (b) population size and, (c) accessibility for data collection.The herbaceous species was studied by laying 30 quadrats of 1 m × 1 m (1 m 2 ) size randomly in each study site (Misra, 1968).The size and the number of quadrats were determined by the species curve (Misra, 1968) and the running means methods (Kershaw, 1973).In each quadrat, trees were recorded with > 31.5 cm cbh (circumference at breast height that is, 1.37 m above the ground).Individuals within the cbh range of 10.5 to 31.4 cm were considered as shrubs + saplings and individuals < 10.5 cm cbh were considered as herbs + seedlings.Individuals of all species were counted in each quadrat.The important quantitative analyses such as density, frequency and abundance of the species were determined as per Curtis and McIntosh (1950).
Similarly, relative values of frequency, density, dominance and IVI were calculated following the methods of Curtis (1959).IVI was calculated through the sum of relative frequency, relative density and relative dominance.The threat category of P. kurroa Royle ex Benth.was identified using six attributes (that is, habitat preference, distribution range, population size, use pattern, extraction trend, native and endemic species) as per the methods advocated Samant et al. (1998) and Ved et al. (2003).Species with a combination of these criteria (serial number 1, 2 and 3) were given marks accordingly (Table 1).

RESULTS
In the phyto-sociological survey it was observed that the Kumaun region of Uttarakhand has a rich floristic wealth where many plant species are prevalent in the socio-consciousness as medicine, fodder, healer etc.In this piece of work P. kurroa Royle ex Benth.was investigated from its phyto-sociological perspective in which the R Fr, R Den , R Dom and IVI were calculated.This work was done for three successive years viz.2009 to 2010, 2010 to 2011 and 2011 to 2012 and the data of every year was compared to depict the annual variation in the phytosociological status of this plant.The minute observation of the data revealed that the phyto-sociological status of this plant varied to a great extant every year.

DISCUSSION
It is clear from the observation that P. kurroa Royle ex Benth.had the maximum value in the year 2011 to 2012 which were 5.68, 3.03, 3.89 and 12.60 for relative frequency, relative density, relative dominance and IVI, respectively.These values were found fluctuating in every successive year (Figure 2A to D).So, it becomes evident that the phyto-sociological status of P. kurroa Royle ex Benth.varies annually to a great extent.The threat assessment of the species also shows that the species is getting diminished day by day at higher rate, probably due to climatic and seasonal changes, habitat fragmentation/destruction, over grazing, over exploitation in trade and lack of pollinator in the higher alpine region.To conserve the species, in-situ conservation is the best option (Arya et al., 2013).Identification of preferred habitats, altitudinal range and the elite populations with respect to below ground biomass will pave the way for re-introduction of the species.Furthermore, to preserve the important medicinal flora, it is necessary to make the local people aware of the value and use of the plant and restrict overexploitation of plant species from the natural habitats.

Figure 2 .
Figure 2. (A) Relative frequency values of Picrorhiza kurroa Royle ex Benth. in Successive years, (B) relative density values of Picrorhiza kurroa Royle ex Benth. in successive years, (C) relative dominance values of Picrorhiza kurroa Royle ex Benth. in successive years and (D) IVI values of Picrorhiza kurroa Royle ex Benth. in successive years.

Table 1 .
Threat assessment of the medicinal plant diversity.