Environmental Engineering Reference
In-Depth Information
especially low pH, can affect plant establishment and development. Elevated moisture
contents can increase flow characteristics of soil and reduce soil stability. The availability of
nutrients is also a determining factor on soil stability. Finer sands tend to be higher in
nutrients than coarser grain soils.
Fresh, brackish, and saline waters are distributed in a salt marsh along a gradient from the
upland headwaters to the marine environment. Salt marshes occur in areas where salinities in
the overlying water range from 0.5 ppt to that of seawater (30 to 32 ppt) (Wiegert and
Freeman, 1990). The salinity varies from moderate at flood tide, to high following
evaporation at low tide, to low during rains at ebb tide (Gallagher
,
et al.
,
1980; Pomeroy et
al.
,
1981). Halophytic plants are adapted to tolerate the salinities of both the overlaying water
and soil waters. Tidal creeks have salinities similar to adjacent saline water bodies. The
salinity within the soils is also similar to that of overlying water bodies and depends on
several factors including the frequency of tidal inundation, rainfall, drainage slopes and tidal
creeks, soil texture, vegetation, depth to water table, freshwater inflow, fossil salt deposits
(Mitsch and Gosselink, 1993).
Saltmarsh plants have similar nutrient requirements to non-saline-tolerant species and
like these species they need a well-developed root-system for the effective uptake of
nutrients. Root growth can be restricted both by raised salinity and low oxygen concentrations
in the soil and this can restrict the ability of the plant to acquire sufficient quantities of
phosphorus and nitrogen. It has been shown that flooding can restrict the ability of saltmarsh
plants to take up nutrients (Bouma et al., 2001). Dutch and American studies have shown that
raising nitrogen levels can result in an enhancement of plant growth (Valiela and Teal, 1979;
Kiehl et al., 1997).
Halophilic plants like
P. coarctata
may provide valuable models for identification of
basic mechanisms of plant salinity tolerance (Flowers and Colmer, 2008). Wild plant varieties
are often resistant to several stresses and thus are valuable genotypes. The Asian wild rice,
Porteresiacoarctata
is such a highly salt resistant plant and can survive safely even up to 30-
40‰ (Bal and Dutt, 1986). It is widely prevalent in almost all the islands of mangrove forests
in Sunderbans (West Bengal, India and Bangladesh) where the soil is inundated twice a day
with saline river or sea water of 20-40‰. This species can withstand submergence with
saline water for quite a long period (Bal and Dutt, 1986).
In Bangladesh very little information on the hydropedological factors of salt marsh
environment (Das and Siddiqui, 1985; Huq, 1986; Abu Hena et al.
,
2007a, 2007b, 2009;
Uddin et al.
,
2010) are available while there is extensive research has been done in some parts
of the world (Adam, 1990; Pomeroy and Wiegert, 1981; Paulo and Claudia, 1991; Wenner
and Beatty, 1998; Scott
et. al.,
2000; Craft and Sacco, 2003; Yuhas et al.
,
2005). Therefore
the present research was undertaken in order to characterize the important hydropedological
factors of salt marsh,
P. coarctata
bed of Fauzderhat coastal area of Chittagong, Bangladesh
and also to explore their changing pattern over time along with the relationship within the
factors studied.
M
ATERIALS AND
M
ETHODS
The whole research works were conducted by adopting the following procedure:
