06-bioresourcesstatu.. - M. S. Swaminathan Research Foundation

Lakshadweep Islands
iii. The Natural Ecosystems
There are four natural ecosystems in the Islandsland,
lagoon, reef and ocean.
a. The Land
Topography: The islands consist of coral
formations built up on the Laccadive-Chagos
submarine ridge rising steeply from a depth of
about 1500 m to 4000 m of the west coast of India.
The Union Territory of Lakshadweep along with
the Maldives and the Chagos Archipelagoes form
an interrupted chain of coral atolls and reefs on a
contiguous submarine bank covering a distance of
over 2000 km. This ridge is supposed to be a
continuation of the Arravalli Mountains, and the
islands are .believed to be remnants of the
submerged mountain cliffs (P.S.B.R. James et al.
1986).
Table 2 : Island wise Area
Sl Island AreaSqKm
1 Minicoy 4.37
2 Kalpeni 2.28
3 Andrott 4.84
4 Agatti 2.71
5 Kavaratti 3.63
6 Amini 2.59
7 Kadmat 3.12
8 Kiltan 1.63
9 Chetlat 1.04
10 Bitra 0.1
11 Bangaram 0.58
Total 26.89
These islands are flat and scarcely rise more than
two meters. At an average they are 5-6 km long
and less than a kilometer in width, rising from the
floor of the ocean of 3.4 km depth. (Wafer, 1986).
They are made up of coral sand and boulders,
which have been compacted into sand stone.
There are many man made pits and inland
depressions in the islands dug out for coil' retting
industry and for growing cereal crops.
All the islands have a North South Axis, except for
Androtl that ha,s an East-West direction
lengthwise. All of them are wide in the North and
taper off towards the south. The human settlement
in nearly all the Islands is concentrated in the
wider northern part. Several of the islands have
small islets separated from them by a narrow
channel. It is possible to walk to these islands
106
during very low tides. The distance in between the
inhabited islands vary from 32 km to 182.5 km,
except in the case of Amini and Kadmat, which lie
only 9.5 km apart.
Soils: The soils of these islands are structure less,
formed by the disintegration of coral debris. The
shore is rocky and full of disintegrated corals in
the East and extreme North and South of the
Island. On the western side the soils are mostly
sandy, intermingled with patches of disintegrated
coral debris. Soil fertility and water holding
capacity are extremely poor in such parts and it
is difficult to grow plants except for coconut on the
western side of the islands. From the profile
studies in these areas a clear picture of the
process of coral weathering can be noticed.
Soil in rest of the part of the islands varies in color
I.e. brown to light brown, depending on the
vegetation and elevation of the area. On the basis
of dry sieving, this soil can be classified as sand as
there is practically no sand, silt or clay. Soils of
these areas get dissolved in acid and no residue is
left. They contain about 80-90 % Calcium
carbonate, less than two percent AI,O, and traces
of SiO,.Nutrient holding capacity of these soils as
well as water holding capacity are low. White
coral sands are found below 10 to 30 em from
surface. Thickness of the layer of white sand
varies from 10 to 60cms. The color variation of the
topsoil is due to the presence of organic matter.
The main sources of organic matter are household
wastes, other vegetation and livestock and bird
droppings. Organic content of these soils increase
as one travels from fringes of the island to the
center. The water table of the soil in swampy and
wetlands is very high and varies from 0 and to 40
em depending upon the elevation and the tidal
situation. During high tide water comes to the
surface inundating the entire area. Potash content
of these soils is very low while organic carbon,
Nitrogen and Phosphorous is medium to high. In
low lying areas and in areas on the fringes of open
depression the content or Organic carbon,
Nitrogen and Phosphorous and water retention
capacity are comparatively high in comparison to
other areas.
Hardpan is a characteristic feature of soil profiles
and is found at a depth of 15cm to 3 meter
depending upon the elevation and the water table.
Thickness of this hardpan ranges from 15cm to
120cm. Maximum thickness of this hardpan was
noticed in Kadmat Island where cut blocks of this