sundarban soil carbon
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National Academy Science Letters ISSN 0250-541XVolume 35Number 3 Natl. Acad. Sci. Lett. (2012) 35:147-154DOI 10.1007/s40009-012-0046-6
Spatial Variation in Organic CarbonDensity of Mangrove Soil in IndianSundarbans
Abhijit Mitra, Kakoli Banerjee & SaurovSett
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Spatial Variation in Organic Carbon Density of Mangrove Soilin Indian Sundarbans
Abhijit Mitra Kakoli Banerjee Saurov Sett
Received: 5 March 2012 / Accepted: 19 May 2012 / Published online: 14 June 2012
The National Academy of Sciences, India 2012
Abstract Soils from intertidal mudflats of mangrove
dominated Indian Sundarbans were analyzed for soil
organic carbon, bulk density and organic carbon density
during 2009 in two different sectors: western and eastern.
Samplings were carried out at 12 stations in four different
depths (0.010.10, 0.100.20, 0.200.30 and 0.300.40 m)
through three seasons (pre-monsoon, monsoon and post-
monsoon). High organic carbon density is observed in the
stations of western Indian Sundarbans, which is relatively
close to the highly urbanized city of Kolkata, Howrah and
the newly emerging Haldia port-cum-industrial complex.
The mangrove forest in the eastern Indian Sundarbans
exhibits comparatively lower organic carbon density.
Anthropogenic activities are almost negligible in this sector
because of its location almost within the protected forest
area. The bulk density of the mangrove soil increased with
depth, while organic carbon and carbon density decreased
with depth almost in all the stations. We observed signif-
icant spatial variations in soil organic carbon and organic
carbon density in the study area.
Keywords Sundarban mangrove Soil organic carbon (SOC) Bulk density Organic carbon density (OCD) Spatial variation
Human activities have led to considerable emissions of
greenhouse gases . In particular, for the period from 1980
to 1989 carbon dioxide emission from fossil-fuel burning
and tropical deforestation amounted to 7.1 billion tons of
carbon being released a year (Table 1) . Increase in
atmospheric carbon dioxide concentration can account for
about half of the carbon dioxide emission for this period .
This has led to study the capacity of carbon sequestration in
forests and other terrestrial and wetland ecosystems. Most
of the studies so far available are related to forest ecosys-
tems and crops, and there is not enough information on
carbon sequestration potential of wetland soil. Wetlands
provide several important ecosystem services, among which
soil carbon sequestration is most crucial particularly in the
backdrop of rising carbon dioxide in the present century.
Wetlands cover about 5 % of the terrestrial surface and are
important carbon sinks containing 40 % of SOC at global
level . Estuarine wetlands have a capacity of carbon
sequestration per unit area of approximately one order of
magnitude greater than other systems of wetlands  and
store carbon with a minimum emission of greenhouse gases
due to inhibition of methanogenesis because of sulphate .
The reservoirs of SOC, however, can act as sources or sinks
of atmospheric carbon dioxide, depending on land use
practices, climate, texture and topography .
Vertical patterns of SOC can contribute as an input or
as an independent validation for biogeochemical models
and thus provide valuable information for examining
the responses of terrestrial ecosystems to global change
. A large number of biogeochemical models, how-
ever, do not contain explicit algorithms of below-ground
ecosystem structure and function . Most of the studies
primarily focused on the topsoil carbon stock, and carbon
A. Mitra (&) S. SettDepartment of Marine Science, University of Calcutta,
35 B.C. Road, Kolkata, West Bengal 700 019, India
School for Biodiversity and Conservation of Natural Resources,
Central University of Orissa, Landiguda, Koraput 764020, India
Natl. Acad. Sci. Lett. (MayJune 2012) 35(3):147154
Author's personal copy
dynamics in deeper soil layers and driving factors behind
vertical distributions of soil organic carbon remain poorly
understood [11, 15, 16]. Thus, improved knowledge of dis-
tributions and determinants of SOC across different soil
depth is essential to determine whether carbon in deep soil
layers will react to global change and accelerate the increase
in atmospheric carbon dioxide concentration [16, 17].
With this background the present study was undertaken to
estimate the SOC in four different depths in the mangrove
dominated Indian Sundarbans that sustains some 34 true
mangrove species and some 62 mangrove associate species
. This deltaic lobe together with Bangladesh Sundarbans
constitutes the worlds largest brackish water wetland. Hence
it is essential to establish a base line data of soil carbon pool of
this mangrove ecosystem. In this study, we used our unpub-
lished data of SOC and bulk density to evaluate the spatial
variations of OCD in the intertidal mudflats of western and
eastern Indian Sundarbans that are markedly different with
respect to anthropogenic activities and mangrove vegetation.
Materials and Methods
The Study Area
The Sundarban mangrove ecosystem covering about one
million ha in the deltaic complex of the Rivers Ganga,
Brahmaputra and Meghna is shared between Bangladesh
(62 %) and India (38 %) and is the worlds largest coastal
wetland. Enormous load of sediments carried by the rivers
contribute to its expansion and dynamics.
The Indian Sundarbans (between 21130N and 22400Nlatitude and 88030E and 89070E longitude) is bordered byBangladesh in the east, the Hooghly River (a continuation of
the River Ganga) in the west, the Dampier and Hodges line in
the north, and the Bay of Bengal in the south. The important
morphotypes of deltaic Sundarbans include beaches, mud-
flats, coastal dunes, sand flats, estuaries, creeks, inlets and
mangrove swamps . The temperature is moderate due to
its proximity to the Bay of Bengal in the south. Average
annual maximum temperature is around 35 C. The summer(pre-monsoon) extends from the mid of March to mid-June,
and the winter (post-monsoon) from mid-November to
February. The monsoon usually sets in around the mid of
June and lasts up to the mid of October. Rough weather with
frequent cyclonic depressions occurs during mid-March to
mid-September. Average annual rainfall is 1,920 mm.
Average humidity is about 82 % and is more or less uniform
throughout the year. This unique ecosystem is also the home
ground of Royal Bengal Tiger (Panthera tigris tigris). The
deltaic complex sustains 102 islands, 48 of which are
inhabited. The ecosystem is extremely prone to erosion,
accretion, tidal surges and several natural disasters, which
directly affect the top soil and the subsequent carbon density.
The average tidal amplitude is around 3.0 m.
We conducted survey at 12 stations in the Indian
Sundarbans region through three seasons viz. pre-monsoon
(May), monsoon (September) and post-monsoon (Decem-
ber) in 2009. Station selection was primarily based on
anthropogenic activities and mangrove floral diversity.
Because of rapid industrialization, urbanization, unplanned
tourism, navigational, pilgrimage and shrimp culture activi-
ties; the western Indian Sundarbans is a stressed zone (Stn.
16). On the contrary stations 712 (in the eastern sector)
are the areas with rich mangrove biodiversity and have been
considered as control zone in this study. The major activi-
ties influencing the carbon pool in the selected stations are
highlighted in (Table 3).
Table 2 and Fig. 1 represent our study site in which sam-
pling plots of 10 9 5 m2 were considered for each station.
Table 1 Anthropogenic carbon fluxes; 19801989 (IPCC 1994)
Carbon dioxide sources
Fossil-fuel burning, cement production 5.5 0.5
Changes in tropical land use 1.6 1.0
Total anthropogenic emission 7.1 1.1
Partitioning among reservoirs
Storage in the atmosphere 3.2 0.2
Oceanic uptake 2.0 0.8
Uptake by northern hemisphere forest regrowth 0.5 0.5
Additional terrestrial sinks: CO2 fertilization, nitrogen
fertilization, climatic effects
Table 2 Sampling stations in western and eastern Indian Sundarbans
Station Station no. Geographical location
Kachuberia Stn. 1 8808004.4300 2152026.5000