22
12. Carbon store and Carbon sequestration
In USA, the national average urban forest
carbon storage density in biomass is 25.1 tC/
ha, compared to 53.5 tC/ha in forest stands. In
the Indian forest, as a thumb rule, one cubic
meter of growing stock in the natural forest is
equivalent to 1.1 tones of Carbon (including
Carbon in soil)
26
. In the TOF, only tree biomass is
accounted to estimate Carbon. Thus, one cubic
meter of growing stock may be equivalent to
about half tone of Carbon. A statistical analysis
reports that, on an average, one tree store about
181 kg of Carbon in the urban areas in USA
26
,
although it depend on the climatic and edaphic
condition of the area and composition of tree
species. In Washington DC, on an average, one
tree store about 274 kg of Carbon
12
. The rate of
annual Carbon sequestration has great variation
with increase in the girth of tree. For medium
growing tree species, Carbon sequestration
rate varies from 2.8 kg per year in about a five
years old tree to 5.1 kg in ten year old, 10.5 kg
in 20 years old tree, 23.5 kg in 40 years old tree
and then to 37.7 kg in sixty years in city of the
USA. Average Carbon sequestration per tree has
been estimated about 6.8 kg in urban areas in
USA, although it has great variation with change
in size of trees. The Carbon sequestration rate
varies from 1.0 kg/year in tree having 20 cm
GBH to 93 kg/year
26
having 240 cm GBH. A
study reveals that a good size tree of
Prosopis
chilensis
store Carbon at rate of about 7.5 kg
every year. The size of trees in urban areas of
Gujarat is relatively higher than tree in the rural
area. Average of eight municipal corporation
indicates that 1.31 % of total trees have GBH
over 200 cm. In Ahmedabad, about 3.70 % trees
have GBH above 200 cm. This reveals that some
cities in Gujarat have relatively more old trees
than in the other areas.
In India, the growing stock of 506.8 crore stems
of the TOF is about 154.8 crores cubic meters.
In Gujarat, about 26.8 crore trees (TOF) have
growing stock of 11.8 crore cubic meter and
Carbon store in biomass about 5.565 crore
tones
27,28
. The IndianCouncil of ForestryResearch
and Education, Dehradun has estimated Carbon
in the forest and TOF in India. As per this norm,
on an average one tree in Gujarat may store
about 207 kg of Carbon against India’s average
of 208 kg Carbon/tree
27
. The average size of
trees in urban areas in Gujarat, particularly in
Ahmedabad is higher than the average of the
TOF. As a result, the figure of Carbon store may
be high for trees in urban areas, particularily in
Ahmedabad.
Also, as per the present growing stock, the
annual potential production of timber and fuel
wood in India is 4.28 crore cubic meter and
1.93 crore tones, respectively. In Gujarat, the
corresponding figures are 31.0 lakh cubic meter
for timber and 21.2 lakh tones for firewood.
As per these data, the Carbon sequestration
rate per tree may be estimated about 7.86 kg
Carbon/year for the average of India. If the
growing stock of the TOF in Gujarat is co-related
to the number of trees (26.9 crore), the Carbon
sequestration rate may be estimated about
12.91 kg Carbon/year/tree for average of the
state
26,27
. These data can be used to help assess
the actual and potential role of urban forests
in reducing atmospheric Carbon dioxide, a
dominant greenhouse gas.
On one hand, average tree size in Ahmedabad
is higher than other cities but it is lower in
Bhavnagar due to a large number of small trees
(
Acacia senegal
) in Victoria Park. If it is assumed
that Carbon store of about 208 kg Carbon per
tree in Ahmedabad and 207 kg Carbon/tree for
the rest of cities, the Carbon store in different
municipal corporation may be estimated about
1.79 lakh Carbon tone (6.57 lakh tone of Carbon
di-oxide) for Gandhinagar, 1.28 lakh Carbon tone
(4.70 lakh tones of CO
2
) for Ahmedabad, 1.55
lakh Carbon tones for Vadodara, and 0.99 lakh
Carbon tones for Bhavnagar and 1.22 lakh tones
for the rest of other four municipal corporations.
