Comparative phytosociological assessment of three terrestrial ecosystems of Wayanad Wildlife Sanctuary, Kerala, India

Phytosociological studies were conducted in three vegetation types in the WS II area of Wayanad Wildlife Sanctuary. In each vegetation type, 85 quadrats (10 x 10 m) were laid to quantify the vegetation. Natural forest showed comparatively higher species richness than plantation and vayal (swamps/low lying grassland). In natural forest 96 plant species were present while it was 70 and 66 respectively in plantation and vayal. Fabaceae was the dominant family in all the three vegetation types. The natural forest was dominated by Chromolaena odorata, followed by Lantana camara, Mimosa pudica, Terminalia elliptica, Glycosmis pentaphylla. In the plantations, Chromolaena odorata, Tectona grandis, Mimosa pudica and Glycosmis pentaphylla showed dominance. The vayal was dominated by Arundinella leptochloa. The second most dominant species in the vayal was Chromolaena odorata. Other dominant species were Kyllinga nemoralis and Sporobolus tenuissimus. Among the three, vayal recorded the highest Simpson Diversity Index. The highest Berger-Parker Dominance Index value in plantation indicates the presence of dominant species. Natural forests recorded highest Margalef Richness Index and the least was in vayal. The highest Pielou’s Wiener Equitability Index in vayal indicated all species are evenly distributed.


INTRODUCTION
Forests are the principal bio-resources and repositories of natural wealth that support human well-being and ecological sustainability (Sarkar 2016). Phytosociological studies are necessary for protecting the biodiversity and natural plant communities (Rao et al. 2015). These are very essential components for understanding the changes accomplished in the past and future (Hamzaoglu 2006). The environmental safety of a country depends on the health of its forest area (Lloyd & Ghelard 1964) as it is the forest ecosystems which allocate disparate share to the world's biodiversity (Battles et al. 2001). For the conservation of biodiversity, it is crucial to attain forest sustainability (Chaubey et al. 1988). It is proven that long-term sustainability of forest ecosystems is greatly related to plant diversity and their phytosociological attributes. Most of the forests in the world today are under extensive anthropogenic disturbances and require careful management intervention to maintain overall biodiversity and sustainability (Kumar et al. 2006). As plants provide both food and habitat for other organisms (Das et al. 2015), the total forest diversity is a dependent factor of plant diversity. The overall strength of the forest rests on its plant composition, and hence the information on its composition, diversity and ecological aspects is of primary importance in conservation planning and implementation.
Tree species control the growth of other vascular plants as they regulate sunlight availability of the forest floor. Analysis and estimation of tree diversity, through which a combination of physical habitat, vegetation, physiognomy, species composition and community relationship are unlocked, are useful datasets in forest management interventions (Battles et al. 2004). The inherent variation within communities and ecosystems must be documented and used as base-line data to effectively predict the outcome of disturbances, such as regeneration and harvest methods on floristic diversity and richness (Sarkar 2015).

Study area
The study was carried out in Wayanad Wildlife Sanctuary (WWS), Kerala State located in southern India, between October 2016 and February 2017. WWS is spread over to 344km 2 and comprises two discontinuous land areas of 77.67km 2 (WS-I) and 266.77 km 2 (WS-II) ( Figure 1). The larger of these two, WS-II lies within the geographical extremes of 11 0 35'-11 0 49'N and 76 0 13'-76 0 27'E. The other area WS-I lies within 11 0 50'-11 0 59'N and 76 0 02'-76 0 7'E. The phytosociological study was done in WS-II which has been divided into three forest ranges, namely, Muthanga, Kurichiat, and Sulthan Bathery. The dominant natural vegetation here is characterized by moist and dry deciduous forest (Image 1), teak and eucalyptus plantations (Image 2), and bamboo brakes (Management Plan 2012-2022. Swamps, which are low lying grasslands are spread over 715.79ha. The land area locally known as vayals (Image 3), represent an edaphic climax with its deep clayey soils and are waterlogged during the monsoon, but sustain grasses throughout the year.
The quadrat method was employed for phytosociological analysis of all vegetation. Three ecosystems, viz., natural forest (NF), plantation, and swamps/vayal (low lying grasslands) were compared. In each vegetation type, 85 quadrats (10 × 10 m) were randomly laid to quantify the tree vegetation. Tree species found within each quadrat were photographed. Those plants which could not be immediately identified were recorded by their vernacular names (information from range officer, beat officer, forest guards, and local people). These species were later identified and their scientific names recorded by consulting dendrologists, books, articles, and internet. The other vegetation inside the 10 × 10 m quadrat was further surveyed using 2 × 2 m nested quadrats. In the nested quadrats, for all the species identity, origin (native or alien), growth form (herb, shrub, and climber), and abundance of other vascular plant species were recorded. In order to analyse the diversity of tree vegetation, frequency, relative frequency, density, and relative density were calculated using the following formulae. Sum of frequency of all species Importance value index (IVI) was calculated by adding relative frequency, relative density and relative J TT basal area.

RESULTS AND DISCUSSION
Overall 129 plant species representing 111 genera were recorded from the three ecosystems (Table 2). Of these, 55 were trees, 24 were shrubs, 35 herbs, and 12 climbers (Table 1). Natural forest showed comparatively higher species richness than plantation and vayal. In natural forest there were 96 plant species. Plantation and vayal had 70 and 66 plant species, respectively. The species recorded in natural forest represented 84 genera in 46 families (Table 1). Fabaceae was the dominant family across the three ecosystems ( Figure 2   Calotropis gigantea, Catunaregam spinosa, Dendrocalamus strictus, Flemingia strobilifera, Glycosmis pentaphylla, Ludwigia peruviana, Melastoma malabathricum, Sida acuta, S. alnifolia, and Solanum aculeatissimum were the shrubs commonly seen in vayal. Among these, Calotropis gigantea and Flemingia strobilifera were only seen in vayal.
Among the 11 climbers, Hemidesmus indicus and Ziziphus oenoplia were seen in all the vegetation types. Caesalpinia mimosoides, Cosmostigma racemosum, Elaeagnus kologa, and Piper nigrum were seen in NF. In vayal, Chonemorpha fragrans was only climber which was seen. No climber could be recorded in the plantation.
The vegetation analysis in NF showed that Chromolaena odorata has maximum abundance (81.6) and frequency (61.1) ( Table 3). Next to Chromolaena odorata, Stachytarpheta jamaicensis (31.3) has maximum abundance. The abundance of Senna spectabilis and Lantana camara were 17.7 and 9.8, respectively. The density of Lantana camara was 532.9 stems ha -1 . After Lantana camara, Glycosmis pentaphylla (338.8 stems ha-1) and Mitracarpus hirtus (195.2 stems ha-1) were the densely seen plant species in NF. The most densely seen tree species in NF is S. spectabilis (188.2 stems ha -1 ). Among the first ten highly dense plant species in NF, five were IAPS. Maximum frequency in NF was shown by Chromolaena odorata (61.1) and Lantana camara J TT *indicates non-native species   The most densely seen plant species in vayals was Arundinella leptochloa (11,662 stems ha -1 ) ( Table 5). Density of Chromolaena odorata in vayal was (58,10.6 stems ha -1 ). The lowest density in vayal was recorded for Bauhinia malabarica, Chonemorpha fragrans, and Lannea coromandelica. The most abundantly seen plant species in vayals was Kyllinga nemoralis (173.6). It was followed by Arundinella leptochloa (165.3) and