Environmental Engineering Reference
In-Depth Information
have caused many changes in the coastal geo-
morphic pattern. The strandline has moved sea-
ward exposing vast stretches of seabed and the
fringing coral reefs. Upper reaches of the tidal
creeks and streams that
however, extremely species-speci
c depending
on the mode of salt regulation. We monitored the
aboveground stem biomass (AGSB) in the same
set of species in two stations selected in western
and central Indian Sundarbans (marked in red
dots in Fig.
7.8
). Ten experimental plots (of
dimension 10 m
ow from the hilly
interior of the island to the sea have dried up,
leaving dry streambeds with stagnant pools of
water. The boundary of the tidal zones has
migrated towards the central drainage channels,
converting the upper intertidal swamps to sub-
aerial coastal uplands (Fig.
7.7
). It was docu-
mented that after 2 years, the vegetation of the
supra-tidal zone died and there was mass mor-
tality in blue carbon reservoir due to non-avail-
ability of tidal water.
There are also instances of complete blockage
of freshwater supply due to plate tilting that not
only caused massive alteration of coastal and
estuarine
fl
10 m) were selected at random
in each of these stations. The species-wise AGSB
of individual trees was estimated using non-
destructive method in which the diameter at the
breast height (DBH) was measured with a mea-
suring tape and height with laser beam (
BOSCH
DLE 70 Professional
). Form factor was deter-
mined as per the expression outlined by Koul and
Panwar (
2008
) and volume (
×
V
) was estimated
2
using the expression
П
R
HF
, where
F
is the form
factor,
is the radius of the tree derived from its
DBH and
R
H
is the height of the target
tree.
oral composition, but also resulted
in stunted growth of some mangrove species.
Neo-tectonic movements in the Bengal Basin
between the twelfth and
fl
Speci
) was estimated taking the
stem cores of each species considered in the
study, which was further converted into stem
biomass (
c gravity (
G
fteenth century AD
resulted in an easterly tilt of the deltaic complex
(Chaudhuri and Choudhury
1994
). During the
sixteenth century, the River Ganga changed its
course to shift eastwards and join the Brah-
maputra (Deb
1956
; Blasco
1975
; Sneda-
ker
1991
). Later, in the mid-eighteenth century,
the combined Ganga (now called Padma) and
Brahmaputra again tilted eastwards to empty into
the River Meghna (Snedaker
1991
). This
continuing tectonic activity greatly in
.
To understand the effect of salinity on coastal
vegetation, we compared the stem biomass in
natural
B
S
) as per the expression
B
S
=
GV
plantation
of
the
selected
species
(
11 years plantation age) in the western and
central Indian Sundarbans during January 2010
and observed consistency in the data of
*
Rhizo-
phora mangle
in both the regions. However, for
species such as
Sonneratia apetala
,
A. marina
,
Avicennia ofcinalis
and
Heritiera fomes
,
the
uenced the
hydrology of the deltaic region because of
changes in the sedimentation patterns and the
reduction in freshwater
fl
difference in biomass was signi
cant. The bio-
mass of these species was much lower in the
central sector around the Matla River compared
to those around the River Hooghly receiving
freshwater from the Himalayan glacier after
being regulated by barrages on the way. It
appears from the AGSB data set (Table
7.2
) that
salinity has reduced the yield/ha in
ows. Most rivers
(distributaries) other than the Hooghly, that
contributed to the formation of the Ganga Delta
(from west to east: Muriganga, Saptamukhi,
Thakuran, Matla, Gosaba and Bidya), have lost
original connections with the Ganga because of
siltation, and their estuarine character is now
maintained by the monsoonal run-off (Cole and
Vidyaraman
1966
) and tidal actions (Mitra et al.
2009
,
2011
). The aquatic salinity of these rivers
has increased that resulted in the stunted growth
of the mangroves. Aquatic salinity has profound
in
in
fl
S. apetala
,
A. marina
by 24.10,
18.03, 33.94 and 64.45 %, respectively, in the
central sector, but
,
A. ofcinalis
and
H. fomes
in case of
R
.
mangle
,
the
AGSB has increased by 1.38 % con
rming the
ability of the species to resist the hypersaline
environment. The signicant decrease of AGSB
of
in central Indian Sundarbans (by
64.45 % compared to western sector) is a clear
indication of the sensitivity of the species to high
H. fomes
uence on the growth and biomass of man-
grove
fl
fl
oral species. The degree of in
fl
uence is,
