Woody plant wealth of Therikadu Reserve Forest, Tuticorin, India: a checklist

: A qualitative survey was conducted to record the woody plant wealth of Carnatic Umbrella Thorn Forest (CUTF) existing within the Therikadu Reserve Forest (TRF), Tuticorin district, southeastern Coast, Peninsular India. A sum of 35 man-days was spent on the field to prepare a woody plant checklist. All collected specimens were identified up to the species level with the help of floras. A sum of 105 species belonging to 83 genera in 37 families were recorded from the study area. The family Fabaceae represented by a large number of species (36 species) followed by Bignoniaceae (5) and Rubiaceae (4). Eight families represented by three species each, while 16 families represented by a single species each. CUTF acts as a home for one of the IUCN’s endangered species, Pterocarpus santalinus . The reserve forest and sacred grove status are keeping TRF as an intact and relatively undisturbed ecosystem.


INTRODUCTION
Forests play a vital role in regulating the climate and provide a large number of ecosystem services to all living organisms including human beings (Montagnini & Jordan 2005).Thorn forest is one of the highly neglected forest ecosystems; information related to biodiversity wealth, carbon stock, and sequestration are very limited.Thorn forests act as a home for a large number of woody plant species (liana, shrub, and tree).The forests flourish in the larger part of dried regions in India.Thorn forest covers 16,491 km 2 of the geographical area in India.Indian states namely, Punjab, Haryana, Rajasthan, Gujarat, Tamil Nadu, Karnataka, Madhya Pradesh and Uttar Pradesh are endowed with thorn forest vegetation (Champion & Seth 1968).The thorn forest is characterized by short thorny bush and shrub vegetation and experiences dry season for about six to nine months in a year.Plants are leafless for the most part of the year, usually have very thin leaves protected by sharp structures such as spines, thorns or prickles.Sharp structures are part of the structural defence, protecting photosynthetic tissue from herbivores.Besides, the roots are predatory in nature and spreading near the soil surface as concentrations of essential macro and micronutrients are very limited in dry forests (e.g., Udayakumar & Sekar 2017).A type of thorn forest occurring in Dharmapuri, Kanyakumari, Krishnagiri, Madurai, Thoothukudi, Tirunelveli and Ramanathapuram districts has been designated as Carnatic Umbrella Thorn Forest by Champion & Seth (1968).A checklist of the species at national, state, district and ecosystem level is highly useful to estimate the plant wealth and habitat of species (Udayakumar & Parthasarathy 2012).Earlier, Nair & Srinivasan (1981) found Acacia planifrons and Borassus flabellifer as dominant species of CUTF in Ramanathapuram district, Tamil Nadu.Singh et al. (1999) found CUTF as one of the homes for slender Loris.

Study area
Therikadu

Field survey
As a part of the establishment of 50 ha forest dynamics plot in Therikadu Reserve Forest a qualitative survey was conducted to record the woody plant diversity.A sum of 35 man-days spent on the field to record woody plant wealth of TRF.About 10 sacred groves are located within the TRF.TRF housed large number of temples and local deities, among them Arunchunaikaththa ayyanar and Karukkuvel ayyanar temples (Tamil) are notable and visited by large number of people during festival seasons.All the woody plants, viz., shrubs, lianas and tree growing in TRF were collected and identified up to species level with the help of regional floras and available checklists (Gamble & Fischer 1921-1935;Nair & Henry 1983;Matthew 1991).Author citation followed The Plant List (http://theplantlist.org) and POWO (2021).

Reproductive phenophase of trees
A total of 525 individuals, five individuals each per species were marked with paint to record flowering, and fruiting phenophases of trees.All the marked individuals were observed monthly (during first week of the month) for the period of two years.Woody plants which had flowers and fruits (young, mature and dried) were considered as 'reproducing'.

Species richness and lifeform
The qualitative plant survey allowed us to record a sum of 105 woody plant species spread in 83 genera and 37 families.The most speciose family in the study area is Fabaceae (36 species) followed by Bignoniaceae (5), and Rubiaceae (4).Ten families had two species each, J TT eight families represented by three species each, while 16 families represented by just single species' each in CUTF (Table 1; Image 2, 3).
Of 105 woody species 78 are trees, 17 are shrubs and 10 lianas.One-third of the recorded species are introduced to the ecosystem by the forest department.The study area also had a significant number of economically important and cultivated species (Table 1).The forest department planted this species, and they are growing well within TRF.However, species richness of TRF is similar to that of southern dry mixed deciduous forest, Hosur, Tamil Nadu (56 trees, 7 lianas, and 42 shrubs, total 105 species; Tiwari & Ravikumar 2018a).Conversely, species richness of study area is lower than that of the tropical dry evergreen forest (TDEF) of Coromandel Coast, Tamil Nadu (86 trees and 44 lianas; as in Udayakumar & Parthasarathy 2012).The study also designated 149 woody species as core TDEF species.

Reproductive phenology of woody plants
Among 105 woody species, 23 species started to produce flowers and fruits during the month of February, gradually the number reduced in to one during the month of August.Notably, one-fourth of all the recorded species flowered and fruited throughout the year (Table 1).The length of the reproductive phenophase varied from two to twelve months.A sum of 26 species had 12 months of reproductive phenophase, three species had 10 months, while two species had just three months in study area.The mean length of reproductive Image 1. Map of study area wherein qualitative study was conducted to record woody plant wealth.

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phenophase recorded as 7.25±3.26months.The TRF is relatively undisturbed compared to other forests.Reserve forest category and the presence of sacred groves within the TRF are reasons behind the protection.In addition, people dwelling around the TRF never collect any part of the plant for personal uses, they consider TRF as a home for their deity.

CONCLUSION
Woody plant wealth of CUTF existing within the Therikadu Reserve Forest is higher than in CUTF of Krishnagiri and Dharmapuri districts of Tamil Nadu.The forest flourishing in a dry environment and endowed with a moderate diversity of native trees.The occurrence of the larger specimens of Acacia planifrons indicates that TRF is relatively undisturbed for at least 50 years.Additionally, one can witness a large number of downed and decaying dead woods and trees within the forest, no one collect these deadwoods for any uses.The reserve forest and sacred grove statuses are keeping TRF as an intact and relatively undisturbed ecosystem.
forest ecosystem is protected as a reserve forest by the Department of Forests, Government of Tamil Nadu since 21 July 1982.Study area located in Tiruchendur taluk of Tuticorin district in Tamil Nadu.The geographical coordinates of the study area are 8.73345-8.74976N & 77.98351-78.07294E (Image 1).The altitude of the study area is 30 m, while the mean annual rainfall and minimum & maximum temperature are 750 mm and 28 & 32 0 C. The study area receives a major proportion of the rainfall during the north-east monsoon (October to December), (Thoothukudi District Website 2021).

Table 1 . Binomial, family, life form, flowering and fruiting seasons of woody plants recorded from CUTF of Therikadu Reserve Forest, southern India. (Introduced species are marked with an asterisk '*' symbol).
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