Floristic diversity of climbing plants in tropical forests of Similipal Biosphere Reserve, Odisha, India

Climbers influence the diversity and composition of forest ecosystem immensely. We have investigated the floristic composition of climbing plants in tropical forests of Similipal Biosphere Reserve (SBR), Odisha, India. A total of 120 climber plant species belonging to 74 genera and 33 families were documented in all forests. Among families, the most speciose families were Fabaceae (25 species) and Convolvulaceae (22 species) followed by Cucurbitaceae (11 species), Vitaceae (8 species), Dioscoreaceae (7 species) etc. Similarly, dominant genera were Ipomoea possessing the highest number of species i.e., 9 species followed by Dioscorea (7 species), Vigna (6 species) and Cissus (4 species) etc. There was a remarkable difference noted in the structure and climbing mechanism of different climbers. The climbing plants diversity of SBR not only contributing to the overall forest biodiversity significantly but also maintain the ecological balance of the whole ecosystem. Climbers are the major resource of economic value in and around the biosphere reserve and thus their use and sustainable management must be given principal attention.


Introduction
Tropical forest constitutes 52% of the total forest of the globe and it is the most important ecosystem for biodiversity. Lianas are most diverse and abundant group of plants in the world representing nearly 25% of the woody stem density and species diversity in tropical forests (Gentry, 1991a). In the Indian subcontinent, 15010 km 2 of the area is occupied by tropical wet evergreen forests, which constitute about 10% of total tropical forest cover in the country (IIRS, 2002). Climbers are the plants which grow by climbing on bigger plants and different objects with the help of their tendrils. Tendrils are the special structures present in climbers which provides support for climbing over other. The climbers, creepers, vines and lianas are some separate groups of flora, which are differentiated based on their climbing habit and nature of stem organisation. Twiners are the specialised climbers which use their stem and leaves as tendrils and coils around a plant. The stems are slender and due to their twining habit, these are called as twiner or stem climber. Creepers are another group of life forms different from others because they don't grow vertically, they grow horizontally and spread. Lianas are the woody vines which have a long and woody stem and sometimes climb from one plant to another with the help of tendrils, sucker root following the sunlight. Lianas are one of the most important understudied life forms found mainly in tropical forests although usual in many forests of the world (Schnitzer and Bongers, 2002). The great ecological and functional differences among the species are described by the variation in species composition of lianas in different forests. Despite of having similar forms of growth between lianas, they vary in functional traits like procedure of climbing (Putz, 1984;Putz and Mooney, 1991), size of flower and type of diaspore (Gentry, 1991a;Bullock, 1995;Cai et al., 2009;) and the need of light (Putz, 1984;Baars et al., 1998;Gianoli et al., 2010). Some biotic and abiotic factors like annual rainfall, seasonal rainfall, fertility of soil, structure of forest, regimes of disturbances represent the species diversity, abundance and distribution of lianas (Ibarra-Manriquez and Martinez-Ramos, 2002;Schnitzer and Bongers, 2002;Poulsen et al., 2005;Schnitzer et al., 2005;Addo-Fordjour et al., 2009a, 2009bDeWalt et al., 2010;Toledo, 2010;Addo-Fordjour et al., 2012).
Lianas cause compression and sometimes squeeze the host plant, as a result, the water movement, sap moment and rate of other physical and biological processes inside the host plant decreases (Dalling et al., 2012).
Hence, constriction of a long time on the plant may cause the death of the host plants. They damage physically the young plants and causes death whereas in case of matured plants they affect adversely both physically and compete with them in their biological processes. Lianas compete with host plants in nutrition, absorption of light and water and the growth rate of host plant decreases than the normal rate (Maria et al., 2017). They cause bending and squeezing of plants, as a result, the timber value of the plant decreases. Every living and non-living object produce both the positive and negative impacts on their surrounding environment. In this manner lianas also have both positive and negative impacts on surrounding environment. If we consider both the impacts of lianas, it has a huge positive impact on living organisms and the negative impacts are very low (Bonger et al., 2002). Besides adverse effects of lianas over the trees on which they climb, lianas cannot be neglected due to their ethnomedicinal values and importance in ecosystem functioning (Schnitzer and Bongers, 2002). They fulfil various purposes of human beings by providing edible fruits, vegetables and also have a great medicinal value. In distant or remote areas where the various advanced products and modern western medicines are unavailable and remain unreached, lianas play an important role for survival (Abbiw, 1990;Van Andel, 2000;Arnold and Ruiz Perez, 2001). But in some regions due to rapid human interference and exploitation, many of the valuable plants including lianas are coming towards extinction.
There are so many floristic, ethnobotanical and phytosociological studies were done in Similipal Biosphere Reserve (SBR) in recent past (Behera, 2006;Mishra et al., 2008;Dash and Behera, 2013;Panda, 2014). Most of the studies emphasized on trees, medicinal plants and other groups of plants in general. However, a study on the climber, in particular, has not been done so far. Therefore, here is an attempt taken to study in detail on climber diversity in SBR along with its uses, habit and climbing mode. This data will be helpful for gaining knowledge on climbers and their values in forest ecosystems, which may have implications for conservation of climbers in tropical forests.

Study area
Similipal Biosphere Reserve (SBR) is located in Mayurbhanj district of Odisha, India ( Figure 1). It extends between 20° 17' to 22° 34' N. latitude and 85° 40' to 87° 10' E. longitude, located in the centre of Mayurbhanj district and altitude ranges between 40 m to 1166 m above the sea level. The temperature here becomes minimum at 2 °C during winter and becomes maximum at 43 °C during summer. The average rainfall is 2200 mm. It stretches over an area of 5569.00 km divided into a core area of ca 1194.75 km , buffer area ca 1335.88 km and transition area ca 3038.39 km . It is a portion of Chhotanagpur biotic province of Deccan plateau and constituted in Mahanadian Biogeographic region. SBR is known as a prominent ecological hotspot and is one of the eighteen biosphere reserves of India because of its rich diversity and cultural significance.
Similipal exerts a large influence over the climatic conditions of Odisha and its neighbourhood and is an asset of floristic diversity of the state. Hence, it is also called as Himalayas of Odisha. The largest compact Sal bearing forest, Similipal is a Tiger Reserve, a proposed National Park, a Sanctuary and a Biosphere Reserve. Major rivers like Budhabalanga, Salandi, Baitarani and many rivulets flow through Similipal. It constitutes floral and faunal elements both from the Western Ghats and Eastern Himalaya. The forest supports more than 1200 plant species, with 300 species of medicinal plants and 94 species of Orchids (Sexena and Brahmam, 1989;Misra, 2004

Field method and data collection
The objective of the present study is to survey and document the diversity of climbers in SBR. The various species of lianas were collected from different parts of SBR with the help of local people and forest guards who had maximum knowledge about this. We had visited different parts of Similipal Biosphere Reserve from December 2017 to March 2018 for the collection of specimens and its uses practised by the local indigenous people. We have also tried to investigate the economic importance of the climbing plants by consulting the local communities residing in and around the biosphere reserve. The photographs of some specimens were taken as good as possible to figure out a clear view of those plants ( Figure 3). The plant materials were collected in plastic bags and handled very carefully. The specimens were identified with the help of regional floras Brahmam, 1994-1996;Haines, 1921Haines, -1925Gamble andFischer, 1915-1935) and other available literatures. Further, the specimens were processed and preserved in the herbarium of Biosystematics laboratory, Department of Botany, Maharaja Sriram Chandra Bhanja Deo University, Baripada, Odisha. All the species were enumerated with its botanical name, family, local name, habit, climbing mode, and uses.
Similarly, dominant genera were Ipomoea possessing the highest number of species i.e., 9 species followed by Dioscorea (7 species), Vigna (6 species), Clematis (3 species) and Cissus (3 species) etc. Out of 120 climbing plant species, 62 species were woody vines, 57 species were herbaceous vines and one parasitic vine representing 52.10%, 46.05% and 0.83%, respectively. The climbing plants of SBR were classified according to their habits i.e. woody vines, herbaceous vines and parasitic vines (Table 1). Local communities were using these climbers for various purposes. It had been observed that out of 120 species, 48 species had medicinal properties (39.669%), 16 species are edible (13.34%), 13 species had ornamental value (10.83%) and the remaining 43 had other uses (35.83%). The enumerated climbing plants showed 6 different climbing mode mechanisms which were stem twiners (63.02%), tendril climbers (21.84%), hook climbers (3.36%), straggler unarmed (8.4%), straggler armed (2.52%) and root climbers (0.84%) ( Figure 2). With the compilation of survey data and available literatures, we found a total of 97 species which had medicinal value. Out of these, 14 species were directly taken as food as well. The species which had both medicinal as well as nutritional values were Lasia spinosa (L.) Thw., Basella alba L., Ipomoea aquatic Forsk., Dioscorea oppositifolia L. etc. There were 24 species found edible in the study. There were 5 species in the study generally used in domestic and ornamental aspects. Ipomoea turbinate Lag. was the only species which is edible as well as ornamental value. Bauhinia vahlii W & A. was the only species which had house hold uses in preparation of ropes. The present study could not report any economic value for 8 species and such information is also lacking in the previous literature for these species. The species without any economic values were Rhaphidophora glauca (Wall.) Schott., Ipomoea barlerioides (Choisy) Benth. Ex C.B.Cl., Ipomoea sinensis (Desr.) Choisyssp., Dolichos trilobus L., Mucuna nigricans (Lour.) Steud., Vigna pilosa Baker., Clematis roylei Rehder. and Ampelocissus divaricata (Wall. ex Lawson) Planch.
The most abundant climber species in the study area were Combretum roxburghii Spreng.   Figure 3. Photographs of some climbers in SBR, Odisha, India Discussion SBR is known for its unique ecological conditions, species richness and biodiversity. Climbers plays an important role in the maintenance of several ecological processes in forest ecosystem. Although there are several observations and researches carried out in the area, still much more is remaining to be explored. During our survey out of climbing plants, 62 were lianas and other 58 were herbaceous climbers. The number is very less as compared to tropical evergreen forests of Peninsular India, Tropical forests of Northern Eastern Ghats of Andhra Pradesh and tropical forest of Southern Eastern Ghats of Tamilnadu in India which bears 148, 170, 175 species, respectively (Parthasarathy et al., 2004;Muthumperumal and Parthasarathy, 2009;Naidu et al., 2014). However, compared to few other forests in India, our numbers seem to be very high. Those are tropical forests of Coromandel coast of South India and tropical lowland evergreen forest of Agumbe in the central Western Ghats which have 39 and 40 number of species, respectively (Padaki and Parthasarathy, 2000;Reddy and Parthasarathy, 2003). Considering the species richness of different dry forests globally, the present value is much higher than several other forests. The liana species richness of the dry rain forest of New South Wales was 27 species in 21 ha area (Chalmers and Turner 1994). The tropical island sites of the West Indies harboured 3-14 liana species with an abundance of 6-34 in 0.1 ha area (Gentry 1991b). In the Central American Nicaraguan and Costa Rican dry forests, liana species richness was 16-24 in 0.1 ha area (Gillespie et al., 2000). The Mexican dry forest liana diversity, ranged from 8 to 22 species in 0.1 ha area. (Lott et al., 1987). Though the present study was not conducted within a particular area of SBR, it seems to be higher in species richness than the above discussed forests. Hence, the higher species richness of SBR indicates the importance of the forest in the country and globally.
Twinning habit of climbers is dominated in this study area followed by tendril habit. Twining habit of climbers is most common in tropical forests. Similar results were found in Malayasian forests (Putz and Chai, 1987). Disturbance usually leads to the proliferation of lianas (Wyatt-Smith, 1954;Webb, 1958;Putz, 1984;Putz and Chai, 1987). The present study revealed that due to rapid human interference, over exploitation of plant resources, habitat destruction and forest fires in the peripheral regions of SBR, many of the valuable climbing plants are coming towards extinction regionally and coming under threatened category. The invasion of weed species, Mikania micrantha is frequently observed during our study, which has negative impact on the diversity and supressing the host plant in many aspects. It is one of the 100 worst invasive alien species in the world (Lowe et al., 2001). Further, in some regions of SBR, such as Hatitop and Kachudhan, the dominance of climbers caused squeezing and compressing the host plant. Since, the climbers have significant impacts on the biodiversity. Hence, in such regions, the abundance of climbers must be checked for proper management of biological diversity. Therefore, sustainable use of forest biodiversity may be required especially in those forest zones where human utilization of the forest resources for different purposes is evident and inevitable.

Conclusions
The present study revealed that the climbing plants diversity of SBR not only contributing to the overall forest biodiversity significantly but also maintains the ecological balance of the whole ecosystem. However, the sites such as Hatitop, Kachdhan etc. the dominance of climbers have deleterious effects on the host plants. Many other tree species were suppressed and showing stunted growth due to the negative impact of these climbers. Therefore, management and sustainable use of climbers is required for which adequate knowledge of their diversity, biology and ecology is essential. Further research is required for better understanding of the dynamics and reproductive biology of climbing plants in order to recommend conservation strategies.