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7.5.2.5 Factors Regulating Atmosphere-Biosphere CO 2 Exchange
The atmosphere-biosphere CO 2 flux observed from the various studies carried out in
Sundarbans portrayed that the magnitude of fluxes were 8–10 times higher than that
observed in Everglades National Park. However, it was at par with the values
observed in the mangroves of China and Thailand. Only two studies analyzed the
relationship of NEE and PAR in Sundarbans (Chanda et al. 2013a, b; Rodda et al.
2016). Both the studies observed an exponential relationship between PAR and
NEE.
Rodda et al. (2016) plotted the NEE vs PAR for two different sessions (one session being September to December and the other comprising January to August).
Notably during the September to December session, despite having lower temperature as well as lower PAR values compared to summer months of April and May, the
study showed higher NEE values. This observation was unique as most of the other
studies reported higher NEE during higher temperature conditions. Barr et al.
(2013) mentioned that the light use efficiency of mangroves sometimes get saturated beyond a certain threshold of PAR, which might have taken place in Sundarbans
as well during the peak of summer. The effect of salinity and tides on the atmospherebiosphere CO 2 exchange was not taken into account in any of the studies on
Sundarbans yet.
7.5.2.6 Soil CO 2 Flux Studies
Compared to eight published papers on atmosphere-biosphere CO 2 fluxover
Sundarban mangroves, only two papers are published until yet on the soil CO 2
effluxes of mangroves (Chanda et al. 2011; Chanda et al. 2014).The soil CO 2
effluxes varied between 0.6 and 8.9 g m
−2
day
−1
throughout the year and the mean
efflux was much less than the NEE observed in Sundarban, thus it can be inferred
that Sundarban’s terrestrial compartment at present is acting as a net sink for CO 2 .
The soil CO 2 effluxes mainly varied with the varying soil temperature and seasonally a mild effect of soil moisture was found to play a regulating role (Chanda
et al. 2011; Chanda et al. 2014). Excessive soil moisture was found to reduce the
effluxes as the top soil was virtually super saturated with water, especially during
the spring tide phase. The inward sites of the mangrove forest floor which exhibited
high organic carbon content showed higher magnitude of fluxes, whereas, the near
shore sites showed lower emission of CO 2 .
7.5.2.7 Factors Regulating Soil CO 2 Flux
The magnitude of soil CO 2 fluxes observed were very much comparable to the findings in other mangroves of the world. The principal regulating factors were soil
temperature and soil moisture, which is also found to be more or less the same in all
A. Akhand et al.
7.5.2.5 Factors Regulating Atmosphere-Biosphere CO 2 Exchange
The atmosphere-biosphere CO 2 flux observed from the various studies carried out in
Sundarbans portrayed that the magnitude of fluxes were 8–10 times higher than that
observed in Everglades National Park. However, it was at par with the values
observed in the mangroves of China and Thailand. Only two studies analyzed the
relationship of NEE and PAR in Sundarbans (Chanda et al. 2013a, b; Rodda et al.
2016). Both the studies observed an exponential relationship between PAR and
NEE.
Rodda et al. (2016) plotted the NEE vs PAR for two different sessions (one session being September to December and the other comprising January to August).
Notably during the September to December session, despite having lower temperature as well as lower PAR values compared to summer months of April and May, the
study showed higher NEE values. This observation was unique as most of the other
studies reported higher NEE during higher temperature conditions. Barr et al.
(2013) mentioned that the light use efficiency of mangroves sometimes get saturated beyond a certain threshold of PAR, which might have taken place in Sundarbans
as well during the peak of summer. The effect of salinity and tides on the atmospherebiosphere CO 2 exchange was not taken into account in any of the studies on
Sundarbans yet.
7.5.2.6 Soil CO 2 Flux Studies
Compared to eight published papers on atmosphere-biosphere CO 2 fluxover
Sundarban mangroves, only two papers are published until yet on the soil CO 2
effluxes of mangroves (Chanda et al. 2011; Chanda et al. 2014).The soil CO 2
effluxes varied between 0.6 and 8.9 g m
−2
day
−1
throughout the year and the mean
efflux was much less than the NEE observed in Sundarban, thus it can be inferred
that Sundarban’s terrestrial compartment at present is acting as a net sink for CO 2 .
The soil CO 2 effluxes mainly varied with the varying soil temperature and seasonally a mild effect of soil moisture was found to play a regulating role (Chanda
et al. 2011; Chanda et al. 2014). Excessive soil moisture was found to reduce the
effluxes as the top soil was virtually super saturated with water, especially during
the spring tide phase. The inward sites of the mangrove forest floor which exhibited
high organic carbon content showed higher magnitude of fluxes, whereas, the near
shore sites showed lower emission of CO 2 .
7.5.2.7 Factors Regulating Soil CO 2 Flux
The magnitude of soil CO 2 fluxes observed were very much comparable to the findings in other mangroves of the world. The principal regulating factors were soil
temperature and soil moisture, which is also found to be more or less the same in all
A. Akhand et al.