Current World Environment

Introduction

Planting indigenous tree species and mixing with several other species significantly improve the conservation of biodiversity. Numerous scientific publications are offered the justification for biodiversity conservation (Frankham et al., 2002; Pregernig, 2006). The number of ecological niches in an ecosystem can be increased by growing a higher number and diversity of tree species. This has been sequentially enhanced the associated species such as understory plants (Kanowaski et al., 2003) and animals (Wunderle, 1997). Therefore, growing diversity of many tree species on a location not only conserves numerous trees but also other organisms (Markku, 2008).

Oldfield et al., (1998) reported that ten percent of all trees in the world are threatened with extinction. In situ conservation methods are more suitable and successful for conservation of rare, vulnerable, threatened species to reduce extinction. There is a increasing awareness that conservation efforts outside the ecosystem (ex situ conservation) are essential for species survival (Kramer et al., 2011; Oldfield and Newton, 2012; Pritchard et al., 2012). In situ conservation methods are not viable for those tree species with a little population size or edging with threat. Ex situ conservation method is the only alternative to avoid its immediate extinction (McNamara, 2011; Ma et al., 2013). Since 1980s, the botanical garden plays a vital role in the field of ex situ conservation (Bramwell et al., 1987; Falk, 1987; Falk and Holsinger, 1991; Guerrant et al., 2004). The gardens grown in the urban environment also play vital role in conservation of trees. Trees are our wealth on planet earth. Trees represented in all vascular plants such as tree fern, Gymnosperms include cycads, conifers etc. and Angiosperms include all flowering trees. In a city the streets, parks, playgrounds and backyards of the home are lined with trees that create a peaceful, aesthetically pleasing environment. Being District Science Centre, Tirunelveli, is a government and non-profit organization can be effective to excite better involvement by gardens in plant conservation.The objective of this study was to evaluate the diversity of tree species in District Science Centre, Tirunelveli, Tamil Nadu, India. The District Science Centre campus consists of a diversity of plants and the perusal of literature reveals that there is no published record on the flora of this campus which represents an interesting floristic composition.

Study Area

District Science Centre

The District Science Centre (DSC) was opened to the public on 27^th February 1987. It is started with a gallery on "Treasures from Ocean" and a Science Park. It is located near the Collector Office, Kokkirakulam, Tiruneveli Corporation area. It has lot of exhibits, science working models and many displays to gain knowledge. Before long the Center got one of the most well known Centre in National Council of Science Museums (NCSM) due to the tremendous support from the local community. National Council of Science Museums, Government of India is the controlling authority of the centre. Popularize science and technology among public and to supplement science education in schools and colleges to foster a spirit of scientific enquiry among the students is major objective of the centre. The beautiful architectural main building of the centre locates in the middle of the campus. Many outreach programmes such as rural science camp, workshops, seminars, science quizzes, science fair vacation hobby courses etc., are regularly organized.

Methodology

During the course of present study, regular field trips were carried out to the area in 2019 in different seasons to explore the various tree species. Standard methodology was used to elicit the knowledge of trees. All the relevant information of each tree species was recorded in an index card.  The plants specimens collected were processed at the laboratory of Botany, Rani Anna Govt. Arts College for Women, Gandhi Nagar and identified with the help of available literature. The identification of plants was done using The Flora of Tamil Nadu Carnatic by K.M. Mathew (1983 -1988), Flora of Tamil Nadu, India by A.N. Henry et al, (1987), Flowering Plants of Chittoor District, Andhra Pradesh, India by Madhavacheetty et al. (2008), Tropical Garden Plants by Bimal Das Chowdhury et al. (1991) and Flora of Presidency of Madras by Gamble (1915 – 1936). The families and nomenclatures are arranged according to online Tropicos database 3.0.2, Missouri Botanical Garden, 2020.

Results and Discussion

On the basis of field survey conducted in The District Science Centre campus area,  80 tree species were collected and identified. They belong to 68 genera and 29 families. Out of the identified tree species 75 are dicot and belong to 63 genera and 27 families; 5 tree species are monocot and belongs to 5 genera and 2 families (Table 1). Among the dicots, 53 species are Polypetalae and family Fabaceae is the most dominant with 16 genera and 20 species. In Gamopetalae 15 genera covering 15 species are recorded and Bignoniaceae is the most dominant family. In Monochlamydeae 7 species covering 4 genera are recorded and Euphorbiaceae is the most dominant family. In the present study 15 families reported with only one species, 9 families represented by more than 2 species. Present study recorded 12 fruit yielding trees, 9 medicinal trees, 26 ornamental trees, 29 timber value trees and 1 fibre yielding tree. The total number of trees observed during the period of study was 338.

Table 1: List of trees available in the campus

Polyalthia is the dominant species followed by Lagerstomia species. Many introduced tree species like Lagerstomia flos-reginae, L. reiginae, Parkia bigalandulosa, Sterculia foetida also recorded in the study area. The timber yielding trees like Dalbergia sisso, Acacia auriculiformis, Tectona grandis, Neolamarckia cadamba, Casuarina littorea also recorded. The two scared trees Aegle marmelos, Couroupita guianensis was observed. The fruit yielding tree like Syzigium cumini, Mangifera indica, Carica papaya etc. are also observed. Neolamarckia cadamba, Madhuca longifolia, Alstonia scholaris, Ficus religiosa, F. racemosa, Millingtonia hortensis, Erythrina variegata are huge trees in the campus. Some tall trees like Cassine paniculata are now in the shrub state.

Two endanger tree Saraca asoka also grown in the study area. This small tree has become threatened in some parts of its range mainly through the loss of its habitat and overexploitation for medicinal use. Considering the conservation need of this species, it has been listed under the threat category of ‘Vulnerable’ by International Union for Conservation of Nature (IUCN, 2013) and ‘Endangered’ by Conservation Assessment and Management Prioritisation (CAMP, 2001). Santalum album is another IUCN listed vulnerable species (The IUCN Red List of Threatened Species 2019). Pterocarpus santalinus (Red sanders) is listed as an endangered plant species on the IUCN red data list as a result of the exploitation of its wood and essential oil. Holarrhena pubescens and Couroupita guianensis are classified as 'Least Concern' in the IUCN Red List of Threatened Species 2013.

The number of viable tree saplings grown under the shade of the tree is a crucial aspect within the study of biodiversity. They might determine the regeneration of new plants in the study area. Additionally, it plays a crucial role in carbon trapping and sequestration. The previous reports suggested that the dense young tree saplings trap more carbon from the atmosphere than the mature trees. Thus the germination of seeds and associated survival of the saplings is a positive indicator of the healthy ecosystem. Moreover, it also provides information about the ability of plant species to adapt, compete and grow in several climates. The campus was recorded many tree saplings of Cassia fistula and Millingtonia hortensis. Less number of tree saplings was recorded for Holarrhene pubescens. The most remarkable tree species in this area of study includes Delinia indica, Saraca asoca, Holarrhene pubescens and Sterculia foetida.

Flowering Phenology

Summer flowering species such as Azadirachta indica, Lannea coromandelica¸ Erythrina variegata, Cassia fistula, Moringa pterygosperma and Delonix regia are initiate flower buds on foliated shoots during the hot-dry period (March–June). For these species probable flowering cue increasing day length/temperature. South west monsoon rainy flowering species such as Syzygium cumini, Eucalyptus globules, Peltophorum pterocarpum, Mangifera indica, Averrhoa carambola are initiate flower buds on foliated shoots during the warm-wet period (June–August). The first significant rains after the summer may act as flowering cue for these species. Autumn flowering species such as Malpighia emarginata, Bauhinia purpurea, Bauhinia variegata initiate flower buds on shoots with mature leaves (September–December) during the period of decreasing day length. In such species, the frequent rain and less photoperiod may signal the flowering. Dry-season flowering species such as Terminalia catappa, Dalbergias sissoo, Hardwickia binata, Leucaena leucocephala, Parkia biglandulosa, Lagersroemia indica, initiation of flowering occur on twigs during cool dry season (December–March), soon after sporadic winter rains.

Characteristic tree species with large branches are nurtured and given preferences by the management to create picnic/play spaces for tourist. Routine weeding of the gardens ensured only desired trees are allowed to thrive while naturally regenerated seedlings are removed for easy human movement and excellent scenic view. This is in line with the report of Agarwala et al. (2016) who asserted that tree species populations and regeneration is impacted by purpose and level of human use in India.

The present study recorded many man-made activities that are not favourable to conserve the available vegetation in the campus. Cutting of branches of trees, plastic bags and plastic bottle thrown around the vegetated area of the campus are supported the unpleasant anthropogenic activities. The following measures should be taken in the campus to maintain and enrich the biodiversity.

1. The pruning or cutting of branches should be avoided during the summer season. This promotes bird populations and insect diversity in the campus.
2. A green house should be constructed to maintain the tree saplings.
3. A separate model star garden is an immediate need of the hour.
4. Planting endemic and endangered trees should be given more importance.

Role of Gardens in Conservation

The present study reveals the District Science Centre is one of the most suitable areas to conserve important tree species. Presently the garden in DSC critically contributes to conservation of biodiversity. Tree conservation should include in all aspects of garden operations and activities. Gardens can work more collaboratively by establishing or joining a hub of conservation action. The participation of non-traditional gardens in tree conservation and provides an exponential increase in the number of threatened trees protected. These gardens can collaborate with leading gardens by volunteering to grow threatened tree species. Empowering smaller gardens it is particularly important for the global garden community to build capacity for tree conservation in biodiversity (Nicole et al., 2015).

Suggestions

The Distract Science Centre, Tirunelveli is known for its Science related programmes and training camps. The entire campus is planted with a variety of trees. It is a valuable asset. It provides space for people to engage in recreational activities. People from the local area regularly visit this centre, thus provides space to interact with each other and meet new people. It will be more informative, if more interpretation panels are setup at many locations giving data of the fauna and flora throughout the campus. This will able to produce awareness among the visitors towards the conservation of flora and fauna. In near future the entire campus to be converts into an ecological laboratory.

1. Still Campus area is not fully used for the garden making, so the entire campus should be utilized for the garden development.
2. Government should appoint gardener and a Botanist for maintenance of the garden.
3. Growing Gymnospermous trees give more attraction
4. Naming of trees give more exposure on medicinal plants to the students and visitors.

At present, diversity and number of plants in an ecosystem is degraded at an exponential rate. This reduction in the diversity of flora is directly associated decrease in ecosystem services (Gao Chen and Weibang, 2018). Recently, the increasing agricultural and forestry practices cause over-harvesting and over-exploitation of vegetation, rapid increasing urbanization, various serious environmental pollution, change in land use pattern, invasion of alien species, and world climate change due to the numerous anthropogenic activities, encompass tremendous pressure on vascular plants. This resulted in a third of the world's 300,000 - 450,000 vascular plant species face extinction (Pitman and Jørgensen, 2002; Ren and Duan, 2017). Hence, there is a greater need to widen integrative conservation approaches to conserve the rare and vulnerable plant species in the natural habitats (Li and Pritchard, 2009) and therefore our approaches on the plant conservation should be an integrative. Gardens in the scientific institutions offer their resources to the study and conservation of plants, as well as making the world's plant species diversity known to the public.

Acknowledgement

We thank everyone in the District Science Centre, Tirunelveli, who participated in the insightful discussions.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

Conflict of Interest

The authors do not have any conflict of interest.

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