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during the mid day and in terms of season, during the dry season. During the cloudless skies, when the high temperature conditions coincided with highest photosynthetically active radiation (PAR), the peak –NEE values were recorded. On the
contrary, during October, when the frequency of thunderstorms increase, it lead to a
decrease in solar irradiance and hence the ambient temperature as well which eventually lead to lower NEE values during day time. They also observed a steep
decrease in light use efficiency of mangroves with a sharp increase of salinity at the
end of dry season due to lowest water column depth. This in turn showed that the
photosynthetic potential or light use efficiency of mangroves depends substantially
on the salinity stress and its response to factors like temperature and solar irradiance
under varying salinity profile in the adjacent water column and extent of inundation.
Barr et al. (2010) also observed significant month to month inter-annual variability
in CO 2 fluxes and they attributed differences in the mean temperature, rainfall, solar
irradiance to be the principal driving factors behind such variability.
7.2.5 Impact on NEE of a Mangrove Ecosystem Post
a Cyclonic Disaster
It is worth mentioning that in 24th October, 2005, Hurricane Wilma made landfall
in the very study site of Barr et al. (2010) and it enabled the authors to carry out a
natural disturbance experiment as they resumed measurements from the end of the
year 2006 (Barr et al. 2012). The hurricane brought upon a substantial damage to
the mangroves of those regions leading to widespread mortality of mangroves
(Smith et al. 2009). Barr et al. (2012) observed a significant reduction in the NEE
for five consecutive years after the hurricane. They attributed the complex leaf generation dynamics behind the reduced day time NEE and enhanced decomposition of
litter and coarse woody debris behind the enhanced night time NEE. Thus it can be
inferred that apart from anthropogenic encroachment towards mangrove forests witnessed throughout the world, natural disasters like cyclone, hurricane, storm surges
and so forth, are also capable of altering the sink strength of mangroves substantially and that too for a long period of time.
7.2.6 NEE of Mangroves and Tidal Cycles
Alike Barr et al. (2010), Li et al. (2014) also carried out NEE measurements in the
Zhangjiangkou & Zhanjiang Mangrove National Nature Reserve of China and they
mainly observed that magnitudes of NEE as well as soil respired CO 2 vary significantly between the spring and the neap tides. Maximum photosynthetic rate and
minimum soil CO 2 effluxes were recorded during spring tide and vice-versa.
A. Akhand et al.
during the mid day and in terms of season, during the dry season. During the cloudless skies, when the high temperature conditions coincided with highest photosynthetically active radiation (PAR), the peak –NEE values were recorded. On the
contrary, during October, when the frequency of thunderstorms increase, it lead to a
decrease in solar irradiance and hence the ambient temperature as well which eventually lead to lower NEE values during day time. They also observed a steep
decrease in light use efficiency of mangroves with a sharp increase of salinity at the
end of dry season due to lowest water column depth. This in turn showed that the
photosynthetic potential or light use efficiency of mangroves depends substantially
on the salinity stress and its response to factors like temperature and solar irradiance
under varying salinity profile in the adjacent water column and extent of inundation.
Barr et al. (2010) also observed significant month to month inter-annual variability
in CO 2 fluxes and they attributed differences in the mean temperature, rainfall, solar
irradiance to be the principal driving factors behind such variability.
7.2.5 Impact on NEE of a Mangrove Ecosystem Post
a Cyclonic Disaster
It is worth mentioning that in 24th October, 2005, Hurricane Wilma made landfall
in the very study site of Barr et al. (2010) and it enabled the authors to carry out a
natural disturbance experiment as they resumed measurements from the end of the
year 2006 (Barr et al. 2012). The hurricane brought upon a substantial damage to
the mangroves of those regions leading to widespread mortality of mangroves
(Smith et al. 2009). Barr et al. (2012) observed a significant reduction in the NEE
for five consecutive years after the hurricane. They attributed the complex leaf generation dynamics behind the reduced day time NEE and enhanced decomposition of
litter and coarse woody debris behind the enhanced night time NEE. Thus it can be
inferred that apart from anthropogenic encroachment towards mangrove forests witnessed throughout the world, natural disasters like cyclone, hurricane, storm surges
and so forth, are also capable of altering the sink strength of mangroves substantially and that too for a long period of time.
7.2.6 NEE of Mangroves and Tidal Cycles
Alike Barr et al. (2010), Li et al. (2014) also carried out NEE measurements in the
Zhangjiangkou & Zhanjiang Mangrove National Nature Reserve of China and they
mainly observed that magnitudes of NEE as well as soil respired CO 2 vary significantly between the spring and the neap tides. Maximum photosynthetic rate and
minimum soil CO 2 effluxes were recorded during spring tide and vice-versa.
A. Akhand et al.