Coastal sand dune flora in the ThoothukudiDistrict, Tamil Nadu, southern India
Date of publication (online): 26
November 2011
Date of publication (print): 26 November 2011
ISSN 0974-7907 (online) | 0974-7893 (print)
Editor: Anonymity
requested
Manuscript
details:
Ms # o2634
Received 25 November 2010
Final received 10 October 2011
Finally accepted 02 November 2011
Citation: Muthukumar, K. & A.S. Samuel (2011). Coastal sand dune flora in the ThoothukudiDistrict, Tamil Nadu, southern India. Journal of Threatened Taxa3(11): 2211–2216.
Copyright:© K. Muthukumar& A. Selvin Samuel 2011. Creative Commons Attribution 3.0 UnportedLicense. JoTT allows unrestricted use of this
article in any medium for non-profit purposes, reproduction and distribution by
providing adequate credit to the authors and the source of publication.
Acknowledgements: Authors are grateful to Mr. T. Mallikaraj and J. Sundher for his
encouragement for during the field survey. We also thank the anonymous reviewers whose comments
improved this manuscript substantially.
Abstract:Coastal sand
dunes (CSD) are found in the Thoothukudi District and
the communities living close to the coastal sand dunes know the value of the
sand dunes and their bioresources. A study of sand dune flora along
coastal sand dune areas was done from March to August 2010. A total of 42 species belonging to 38
genera and 26 families were identified at different distances from the
shoreline. The CSD systems are
rich and diverse in their floral composition, even over the small areas of Manapadu and Kulasakarapattanamalong the Thoothukudi coastal line. CSD constitute a variety of habitats
and have vital ecological and economic importance. Such unique sensitive systems have to be protected from
habitat degradation in order to protect their native diversity and ecological
functions.
Keywords: Coastal sand dunes, ecological, Manapadu, Kulasakarapatinam, Tuticorin.
For
figures, images, tables -- click here
Coastal sand
dunes (CSD) are common in different parts of the world. CSD are natural
structures protecting the coast from high waves and saltwater intrusions (Corre 1991). The plants living in sand dunes are called Psammophytes. These psammophyticspecies play a vital role in protecting the coast from erosion and floods
(Desai 2000). The coastal length
of India is 7500km with many lagoons, beaches, estuaries, and mangrove swamps,
supporting rich biotic and abiotic micro-organisms(Anonymous 1987). With respect to
geographic location and physical distinctiveness, the coast of Thoothukudi District is part of the Gulf of Mannar Biosphere Reserve (08045’36”–9002’31”N
& 78007’17”–78019’18”E). The recorded forest area is 169km2,
which constitutes 3.66% of the geographic area of the district (Forest Survey
Report 2005). There are
different types of vegetation on the coast of Thoothukudi, this includes
mangroves and their associates—scrub jungles, aquatic vegetation, and
coastal sand dune vegetation. A
sand dune is a mound, hill or ridge of sand that lies behind the part of the
beach affected by tides. They are
formed over many years when windblown sand is trapped by beach grasses. Dune grasses anchor the dunes with
their roots, holding them temporarily in place, while their leaves trap sand,
promoting dune expansion. The sand
dune is maintained with the help of sand dune vegetation as wind traps, sand
binders and dune stabilizers (Wagner 1964). Temperate coastal dunes are well studied and documented (Koske & Gemma 1997; Sridhar
& Bhagya 2007) as compared to studies on tropical
coastal dunes (Kulkarni et al. 1997; Sridhar & Bhagya 2007). CSD comprise a variety of flora and fauna, which play a vital role in
provisioning ecological and economical services to the coastal communities
(Maun & Baye 1989; Martinez et al. 1997). The coastal communities closely
associated with sand dune habitats are dependent on CSD vegetation for a
variety of benefits: for food, fodder, health, manure and recreation. In fact, very few publications are
available on the floral diversity of Indian sand dunes (Sridhar & Bhagya 2007). The objective of the present study was to quantify the abundance,
species richness and diversity of the CSD plant community, to understand their
ecological and economic importance to the local community of Manapadu and Kulasakarapattanamcoastline of Thoothukudi District, Tamil Nadu.
Materials
and Methods
Study
area: Thoothukudi is located on
the south-eastern coast of Tamil Nadu (8037’15”–8039’97”N
& 78006’24”–78005’96”E; Fig. 1). Manapadu and Kulasakarapattanam are coastal villages with sand dune
coverage of about 3km2 and 4km2 extent respectively. The coastal border has a length of 20km
and a breadth ranging from 3 to 500m. Superficially, the coast is flat and sandy. The study area experiences a mean annual temperature
of 320C and a mean annual rainfall of 655mm and humidity 87%. The mean monthly temperature ranges
from 29–35 0C. The climate is tropical and dissymmetric with the bulk of the rainfall
occurring during the northeast monsoon October–December (Thoothukudi District website). CSD formations depend on accumulating size and prevailing
wind energy (Kumar et al. 1993). Their height differs in response to the availability of sand supply,
climate and local topographic features (Barbour et al. 1985). In Manapaduthe height of the sand dunes is very high (35m; Image 1) compared to Kulasakarapattanam (6.4m).
Data
collection: A total of 10 quadrates of 5 x 5 m were marked
randomly in 10 locations at different distance gradients from the shoreline in
each village. Every plant species
found along the 10 quadrates was enumerated. Species (Table 1) were identified by using
published flora (Daniel & Umamaheswari2001; Banerjee et al. 2002).
Results
& Discussion
In the study
area 42 species belonging to 38 genera representing 26 families were enumerated
during this survey. Out of
the total Indian CSD plants listed so far (154), nearly one-third (42) of them
were recorded in the study area. Indian CSDs consist of 154 species belonging
to 108 genera and 41 families (Arun et al. 1999; Rao & Sherieff 2002). The Poaceaefamily was most common and dominant with five species followed by Malvaceae (4), Asteraceae (3), Euphorbiaceae (3), Cyperaceae(2), Amaranthaceae (2), and Arecaceae(2). Nineteen families were
represented only by one species, and over all 25 were medicinal plants (Table
1). Several authors have pointed
out that the temperate CSD comprise mainly the members of Poaceae,
and the tropics with Asteraceae, Cyperaceae,Fabaceae and Poaceae (Arun et al. 1999; Rao & Sherieff 2002; Sridhar & Bhagya2007). During the present study Poaceae, Malvaceae, Asteraceae, Euphorbiaceae, Cyperaceae were the most common families. Many authors have mentioned that in
various parts of the world many dune ecosystems support high plant richness and
diversity values (Musila et al. 2001; Grootjans et al. 2004; Fontana 2005; Celsi& Monserrat 2008). The present study also indicates that the study area
preserves a rich floral diversity with a high number of sand dune medicinal
plants, because during the survey 25 medicinal plants were found in the two
small sample sites, Manapadu and Kulasakarapattanam. In addition, the different vegetation
formations together with the dune field geomorphologic heterogeneity provide a
wide variety of environmental conditions and habitat types.
We also
compared the floristic composition of the two coastal sites, Manapadu and Kulasakarapattanam. Among these
two sites Manapadu had 31 species compared to Kulasakarapattanam which had 22 species. The species composition varied across
these two sites. Species such as Fimbristylis cymosa, Spinifex littoreus, Launaea intybacea, were only found in the high tide
line in both the sites.
Coastal sand
dunes have been valued as an important coastal ecosystem offering protection to
the hinterland, in maintaining the water table of coastal areas and even
protecting the coastal agriculture from the salt laden winds blowing from the
sea (Namboothri et al. 2008). Dunes are known to prevent intrusion of
saltwater into the fresh aquifers of coastal areas. Coastal sand dunes are also important in maintaining
the groundwater level of coastal areas, which is essential to sustain not only
the flora and fauna, but also to provide an important source of freshwater for
coastal populations. The dunes are
occupied by a highly adapted group of plants specially suited to life in such
harsh conditions. Critical to the
formation, stabilisation and post-storm recovery process, is the presence of
specialised dune plants e.g. Spinifex littoreus. These plants are capable not only of maintaining dune
stability but can also colonize patches of bare sand and grow quickly down an
eroded dune face to help build and restore the dune profile. Spinifex littoreus are very effective in long-term
control of coastal erosion as they can grow to keep up with the movement of
sand whereas rigid walls and structures are soon buried or undermined. Spinifex littoreus is a sand binding grass found on
coastal fore dunes throughout the region. It is one of the few plants able to colonise the seaward face of the
fore dune, and it is also considered as a berm to
front dunes; primary stabilising plants consisting mainly of herbaceous
species, were recorded. This area
was composed of herbaceous species like Leucas aspera, Gisekia pharnaceoides, Tephrosia purpurea, coastal tree species like Borassus flabellifer and the introduced Casuarina equisitifolia.
Very often
extensive sand dune systems may have interdunal sand dunes which are also closely integrated to the socioeconomic
life of the coastal population. InManapadu, coastal villages have a high level of sand
dune formation and rich floral diversity as a single quadrate of 5 x 5 m harbored 10 different species, which was much higher when
compared to the other sand dune areas like Tiruchendur,Kayalpattanam and Kulasekarapattanamof Thoothukudi coast. A very good example of this is the Borassus flabellifer L. which is
quite common on the sand dunes of southern Tamil Nadu. Before sugar was introduced into
markets in India, B. flabellifer was a major
plantation in southern Tamil Nadu from which jaggerywas extracted. Jaggerywas not only a major substitute for sugar, it was also
a major source of livelihood for the coastal community of southern Tamil
Nadu. In another example of Spinifex littoreus (Burm.f.)Merr., the extract from the
grass was found to be very effective against bacteria and some fungi strains (Thirunavukkarasu et al. 2010) and this species is also very
common. Nine species of Spinfex and five
species of Fimbristylis were found,
these are also excellent sand binders with medicinal value. Dried grass is used
as fuel by fishermen and dry female inflorescence can be used for
interior decoration (Daniel & Umamaheswari2001). Important religious sites
were observed during the study. During religious celebrations floral diversity and environmental
conditions were affected as human waste, polythene bags, and other solid wastes
were deposited on the sand dunes. After the celebrations medicinal herbs and climbers were found
destroyed. It is important to initiate efforts to conserve the floral diversity
with the help of local communities through awareness creation.
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