201
temperatures higher than 26 °C. Lovelock (2008) attributed the benthic photosynthetic microbial community behind the reduction of this soil respired CO 2 . On the
contrary, Kirui et al. (2009) observed substantially high range of effluxes (a minimum magnitude of 16.9 g CO 2 m
−2
day
−1
; the highest tabulated amongst all the
observations of Table 7.2). It should be noted that most of the time in the study area
the soil temperature was significantly high (~36 °C) and they observed a statistically
significant relationship (positive) between the soil CO 2 effluxes and the soil
moisture.
7.3.7 Inundation of Forest Floor
The magnitude of fluxes was quite low and they examined a critical relationship
between the fluxes and the time of inundation of the mangrove forest floor. They
observed that the more the soils were inundated the lesser was the temperature and
consequently lower fluxes were observed. In this regard, they inferred that the spatial change in elevation of the mangroves from the vicinity of the river/estuary to the
inshore lands could play a deciding role in the magnitude of fluxes. In this regard,
Troxler et al. (2015) also observed low CO 2 emissions from the sediment surface of
the mangroves of Everglades National Park, USA during inundated conditions,
however, they inferred that during inundated phases a substantial increase in the
pCO 2 is also observed in the overlying water mass and it is subject to tidally driven
export mainly in the form of HCO 3
¯
.
7.3.8 Soil Chemistry
Chen et al. (2010, 2012, 2016) carried out many short term and long term studies in
several mangrove forests of South China and made many crucial observations.
Scarcely had they observed negative fluxes due to photosynthetic activities in the
soil surface, however, the range of fluxes varied significantly depending upon the
duration and season during which the respective studies were undertaken.
Chen et al. (2010) observed that CO 2 fluxes exhibit a positive correlation with
soil organic carbon, total phosphate, total nitrogen and total iron concentration of
the top soil. Leopold et al. (2013) further added that the redox conditions of the sediments, which in turn is controlled by the physiological activities of the root system
along with the position and elevation of the mangrove stands, could play a significant role in governing the soil CO 2 fluxes. Chen et al. (2012) also reconfirmed
higher magnitude of fluxes in the landward sites where soil organic carbon, total
Kjeldahl nitrogen, nitrate and phosphate concentration was significantly high compared to foreshore bare mudflats where the abundance of ammonium ions superseded the other nutrients.
7 CO 2 Fluxes in Mangrove Ecosystems
temperatures higher than 26 °C. Lovelock (2008) attributed the benthic photosynthetic microbial community behind the reduction of this soil respired CO 2 . On the
contrary, Kirui et al. (2009) observed substantially high range of effluxes (a minimum magnitude of 16.9 g CO 2 m
−2
day
−1
; the highest tabulated amongst all the
observations of Table 7.2). It should be noted that most of the time in the study area
the soil temperature was significantly high (~36 °C) and they observed a statistically
significant relationship (positive) between the soil CO 2 effluxes and the soil
moisture.
7.3.7 Inundation of Forest Floor
The magnitude of fluxes was quite low and they examined a critical relationship
between the fluxes and the time of inundation of the mangrove forest floor. They
observed that the more the soils were inundated the lesser was the temperature and
consequently lower fluxes were observed. In this regard, they inferred that the spatial change in elevation of the mangroves from the vicinity of the river/estuary to the
inshore lands could play a deciding role in the magnitude of fluxes. In this regard,
Troxler et al. (2015) also observed low CO 2 emissions from the sediment surface of
the mangroves of Everglades National Park, USA during inundated conditions,
however, they inferred that during inundated phases a substantial increase in the
pCO 2 is also observed in the overlying water mass and it is subject to tidally driven
export mainly in the form of HCO 3
¯
.
7.3.8 Soil Chemistry
Chen et al. (2010, 2012, 2016) carried out many short term and long term studies in
several mangrove forests of South China and made many crucial observations.
Scarcely had they observed negative fluxes due to photosynthetic activities in the
soil surface, however, the range of fluxes varied significantly depending upon the
duration and season during which the respective studies were undertaken.
Chen et al. (2010) observed that CO 2 fluxes exhibit a positive correlation with
soil organic carbon, total phosphate, total nitrogen and total iron concentration of
the top soil. Leopold et al. (2013) further added that the redox conditions of the sediments, which in turn is controlled by the physiological activities of the root system
along with the position and elevation of the mangrove stands, could play a significant role in governing the soil CO 2 fluxes. Chen et al. (2012) also reconfirmed
higher magnitude of fluxes in the landward sites where soil organic carbon, total
Kjeldahl nitrogen, nitrate and phosphate concentration was significantly high compared to foreshore bare mudflats where the abundance of ammonium ions superseded the other nutrients.
7 CO 2 Fluxes in Mangrove Ecosystems