202
However, observations contrary to these regulating factors were also made by
Chen et al. (2014). They observed that despite having high organic carbon content,
the soil CO 2 fluxes were very low suggesting an extremely slow metabolic rate in
the soil microbial community, which actually leads to higher stock of organic carbon accompanied by low emission of CO 2 . Chen et al. (2016) inferred that a substantial part of the soil respired CO 2 was consumed by the mangrove canopy during
day time as a part of photosynthetic process and hence they recommended to reconsider the measurement of net soil CO 2 efflux from the perspective of total CO 2
budgeting in the terrestrial compartments of mangroves.
7.3.9 Anthropogenic Disturbance
Anthropogenic impacts especially clearing of mangroves for various activities like
aquaculture and shrimp farming has become widespread throughout the world. Few
studies in the recent past intended to see the effect of such anthropogenic disturbances on the rate of soil CO 2 fluxes but several interesting findings were recorded
from such studies. Lovelock et al. (2011) investigated the soil CO 2 flux rates from a
cleared mangrove patch and observed that initially after the clearing the CO 2 effluxes
from the soils were substantially high; however, after 20 years of the clearing the
magnitude was almost 4 times lesser than that observed initially. They also experimented by artificially disturbing the mangrove peat soils and observed that the soils
could emit CO 2 at a rate as high as 102 g CO 2 m
−2
day
−1
, however, it came back to
the normal rate within 2 days. Despite these observations, Lovelock et al. (2011)
estimated that almost 10,600 tonnes CO 2 km
−2
was lost annually due to the clearing
of the forest. Hence they inferred that simply preventing deforestation can serve as
an excellent approach towards preservation of threatened carbon stocks.
Bulmer et al. (2015) observed that the rate of CO 2 efflux from soils in the temperate regions [only 1.4% of the global mangrove cover falls under temperate region,
the rest being in tropics and subtropics (Morrisey et al. 2010)] was comparable to
the tropical mangroves. Furthermore they also observed that there was practically
no difference between the rate of soil CO 2 efflux between the cleared and the intact
mangrove site and that the soil CO 2 efflux in the cleared sites was mainly controlled
by sediment organic carbon concentration, nitrogen concentration and sediment
grain size.
Contrary to these observations, Nóbrega et al. (2016) observed that intact mangroves emitted more CO 2 compared to the sites which were anthropogenically disturbed. They argued that higher degree of labile organic carbon stock along with
lower degree of pyritization, (i.e. lesser degree of iron sulphide formation during
decay) in the intact mangrove soils was principally responsible for the higher magnitude of fluxes.
A. Akhand et al.
However, observations contrary to these regulating factors were also made by
Chen et al. (2014). They observed that despite having high organic carbon content,
the soil CO 2 fluxes were very low suggesting an extremely slow metabolic rate in
the soil microbial community, which actually leads to higher stock of organic carbon accompanied by low emission of CO 2 . Chen et al. (2016) inferred that a substantial part of the soil respired CO 2 was consumed by the mangrove canopy during
day time as a part of photosynthetic process and hence they recommended to reconsider the measurement of net soil CO 2 efflux from the perspective of total CO 2
budgeting in the terrestrial compartments of mangroves.
7.3.9 Anthropogenic Disturbance
Anthropogenic impacts especially clearing of mangroves for various activities like
aquaculture and shrimp farming has become widespread throughout the world. Few
studies in the recent past intended to see the effect of such anthropogenic disturbances on the rate of soil CO 2 fluxes but several interesting findings were recorded
from such studies. Lovelock et al. (2011) investigated the soil CO 2 flux rates from a
cleared mangrove patch and observed that initially after the clearing the CO 2 effluxes
from the soils were substantially high; however, after 20 years of the clearing the
magnitude was almost 4 times lesser than that observed initially. They also experimented by artificially disturbing the mangrove peat soils and observed that the soils
could emit CO 2 at a rate as high as 102 g CO 2 m
−2
day
−1
, however, it came back to
the normal rate within 2 days. Despite these observations, Lovelock et al. (2011)
estimated that almost 10,600 tonnes CO 2 km
−2
was lost annually due to the clearing
of the forest. Hence they inferred that simply preventing deforestation can serve as
an excellent approach towards preservation of threatened carbon stocks.
Bulmer et al. (2015) observed that the rate of CO 2 efflux from soils in the temperate regions [only 1.4% of the global mangrove cover falls under temperate region,
the rest being in tropics and subtropics (Morrisey et al. 2010)] was comparable to
the tropical mangroves. Furthermore they also observed that there was practically
no difference between the rate of soil CO 2 efflux between the cleared and the intact
mangrove site and that the soil CO 2 efflux in the cleared sites was mainly controlled
by sediment organic carbon concentration, nitrogen concentration and sediment
grain size.
Contrary to these observations, Nóbrega et al. (2016) observed that intact mangroves emitted more CO 2 compared to the sites which were anthropogenically disturbed. They argued that higher degree of labile organic carbon stock along with
lower degree of pyritization, (i.e. lesser degree of iron sulphide formation during
decay) in the intact mangrove soils was principally responsible for the higher magnitude of fluxes.
A. Akhand et al.