197
Moreover, the dependency of soil CO 2 effluxes on the soil temperature was much
less during the spring tide. Thus Li et al. (2014) on the whole pointed out these
aspects which should be kept in mind while budgeting or modeling the mangrove
ecosystems’ carbon dynamics under future sea level rise scenarios.
7.2.7 Factors Controlling Atmosphere-Biosphere CO 2
Exchange – Summing up
Salinity of the ambient water mass that is coming in contact with the forest floor was
found to potentially alter both the day time as well night time CO 2 fluxes between
the canopy and the atmosphere (Fig. 7.3a). The light use efficiency of the mangroves drastically reduced to half of its potential under high saline conditions compared to low saline conditions. Rainfall and freshwater discharge indirectly plays a
role in the atmosphere-biosphere CO 2 exchange by lowering the soil salinity. Under
low soil saline conditions the atmosphere-biosphere CO 2 exchanges increases to a
great extent and vice versa. Higher solar radiation or PAR led to more uptake of CO 2
in the canopy (i.e. more negative NEE), however, a threshold was observed in many
studies, i.e. beyond a certain value of PAR the ─ NEE did not increase equally.
Solar radiation is long known to be one of the principal factors regulating canopy
photosynthesis or atmosphere-biosphere CO 2 exchange during day time (Fig. 7.3a).
Ambient temperature also played a crucial role in atmosphere-biosphere CO 2
exchange (Fig. 7.3a). Increase in temperature which incidentally happened with
increasing photosynthetically active radiation led to increase in carbon uptake by
the canopy. In addition to these, factors like storm surges and water logging ultimately leads to increase in salinity in the forest floor which eventually leads to
decrease in light use efficiency and hence lesser CO 2 uptake is observed during day
time.
7.3 Soil CO 2 Fluxes from the Mangroves Around the World
7.3.1 The Area Coverage of Research Work
Table 7.2 reflects that compared to atmosphere-biosphere CO 2 exchange, soil CO 2
fluxes have received more attention in different parts of the world. Quite a many
works have been done covering the mangroves situated in China, Australia, New
Zealand, Caribbean Islands, Thailand, Indonesia, Brazil, USA and so forth, whereas
very few soil CO 2 flux related work have been done in Sundarban mangroves (discussed later in Sect. 7.5.2). Most of the studies are conducted in few seasons only;
however, some of the works are carried out throughout the year.
7 CO 2 Fluxes in Mangrove Ecosystems
Moreover, the dependency of soil CO 2 effluxes on the soil temperature was much
less during the spring tide. Thus Li et al. (2014) on the whole pointed out these
aspects which should be kept in mind while budgeting or modeling the mangrove
ecosystems’ carbon dynamics under future sea level rise scenarios.
7.2.7 Factors Controlling Atmosphere-Biosphere CO 2
Exchange – Summing up
Salinity of the ambient water mass that is coming in contact with the forest floor was
found to potentially alter both the day time as well night time CO 2 fluxes between
the canopy and the atmosphere (Fig. 7.3a). The light use efficiency of the mangroves drastically reduced to half of its potential under high saline conditions compared to low saline conditions. Rainfall and freshwater discharge indirectly plays a
role in the atmosphere-biosphere CO 2 exchange by lowering the soil salinity. Under
low soil saline conditions the atmosphere-biosphere CO 2 exchanges increases to a
great extent and vice versa. Higher solar radiation or PAR led to more uptake of CO 2
in the canopy (i.e. more negative NEE), however, a threshold was observed in many
studies, i.e. beyond a certain value of PAR the ─ NEE did not increase equally.
Solar radiation is long known to be one of the principal factors regulating canopy
photosynthesis or atmosphere-biosphere CO 2 exchange during day time (Fig. 7.3a).
Ambient temperature also played a crucial role in atmosphere-biosphere CO 2
exchange (Fig. 7.3a). Increase in temperature which incidentally happened with
increasing photosynthetically active radiation led to increase in carbon uptake by
the canopy. In addition to these, factors like storm surges and water logging ultimately leads to increase in salinity in the forest floor which eventually leads to
decrease in light use efficiency and hence lesser CO 2 uptake is observed during day
time.
7.3 Soil CO 2 Fluxes from the Mangroves Around the World
7.3.1 The Area Coverage of Research Work
Table 7.2 reflects that compared to atmosphere-biosphere CO 2 exchange, soil CO 2
fluxes have received more attention in different parts of the world. Quite a many
works have been done covering the mangroves situated in China, Australia, New
Zealand, Caribbean Islands, Thailand, Indonesia, Brazil, USA and so forth, whereas
very few soil CO 2 flux related work have been done in Sundarban mangroves (discussed later in Sect. 7.5.2). Most of the studies are conducted in few seasons only;
however, some of the works are carried out throughout the year.
7 CO 2 Fluxes in Mangrove Ecosystems