Carbon Assessment Process

Forest occupies a total of 5.96 million ha which is 44.74% of the total area of the country. Forest offers a wide range of tangible and intangible benefits.  Global warming and climate change are perhaps the most pressing issues these days. It has been estimated that deforestation contributes to about 17.4 per cent of greenhouse gas emission (IPCC, 2007).

 Forest offers a cost-effective way to mitigate greenhouse gases, through carbon sequestration.

Carbon Sequestration

Carbon sequestration refers to the capture or removal of carbon dioxide

(CO2)  from the atmosphere and stores it in tree biomass (Jindal et al. 2008)

 Carbon dioxide (CO2) is absorbed through the process of photosynthesis and stores carbon in biomass (tree trunks, branches, foliage and roots). All part of a plant contains carbon but the proportion in each part varies enormously.

 Carbon status in Forest of Nepal

   Total carbon stock in Forest, OWL and Other Land (OL) is 1,157.37 million tons.

   Forest: 1,054.97 million tons (176.95 t/ha)

   OWL: 60.92 million tons (105.24 t/ha)

   OL: 41.48 million tons (7.84 t/ha)

Need for Carbon Assessment?

■ It gives ecological and economic benefits to the local people.

■Quantification of sequestered Carbon could be important for better planning of natural resources.

■Useful making of a good mitigation strategy for climate change effects.

■Crucial to account carbon accumulation in a forest to make the communities get benefited from carbon credit.

■To provide somewhat base-line information regarding REDD+ and to improve the carbon sink of the forests.

Carbon pools

■Above-ground tree biomass (AGTB)

■Above-ground sapling biomass (AGSB)

■Below-ground biomass (BB)

■Soil organic carbon (SOC)

■Leaf litter, herbs, and grass (LHG)

■Deadwood and fallen stumps (DW)

Stratification of Forest

■Forest types- Tropical Sal (Shorea robusta) forest, subtropical, temperate forest.

■Age of trees

■Aspect and position of hill slopes

■Altitude

Size and shape of sample plots 

■Carbon measurement can be carried out in both rectangular and circular plot; the radius of 8.92 m is made for a tree;

■The subplot with a 5.64 m radius is established for saplings;

■Sub-plot with a 1 m radius is established for counting regeneration;

■0.56 m radius is established for sampling leaf litter, herbs, grass, and soil.

Forest carbon stock measurement

Above-ground tree biomass (AGTB)

■A circular plot of 250 m² with8.92 m in radius using diameter tap is used.

■ The DBH (at 1.3m) and height of individual trees greater than or equal to 5cm DBH are measured.

■Each tree is recorded individually, together with its species’ name if identification is possible.

Above-ground sapling biomass (AGSB)

■ Nested subplots having a 5.64 m radius inside larger plots are established for sapling measurement.

Below Ground biomass (BB)

■Below ground biomass estimation is much more difficult and time-consuming than estimating above ground biomass.

■One of the most common relationships between root (below-ground) and shoot (above-ground) biomass is the root-to-shoot ratio.

Soil sampling

■Soil samples are taken from 0.56 m radius plot, with metal Soil Sampling Corer.

■Samples are collected at 0-10, 10-20, and 20-30 cm depths

■ Samples of exactly 100cm³ are taken and transferred to pre-weighed sampling bags.

Data analysis

Above-ground sapling biomass (AGTB):

For estimating above ground sapling biomass, the logarithmic transformation of the algometric formula is used (Tamrakar 2000).

Log (AGSB) = a +b log(D) Where,  AGSB = above-ground tree biomass [kg];  Log = natural log,

 a = intercept of allometric relationship for saplings (dimensionless)

b = slope allometric relationship for saplings (dimensionless)

D = diameter (cm)

■Biomass stock is converted to carbon stock using the default carbon fraction of 0.47. (IPCC, 2006) 

Below ground biomass (BB)

■For estimating below-ground biomass, it is recommended that the root-to-shoot ratio value of 1:5 is used; i.e. 20% of above-ground tree biomass MacDicken (1997).

■The carbon content in below-ground biomass (BB) was calculated by multiplying BB with the IPCC (2006) default carbon fraction of 0.47. 

Leaf litter, herb, and grass (LHG) biomass

■For the forest floor (herbs, grass, and litter), the amount of biomass per unit area is given by:

LHG = W_field/A* W_{sub sample, dry}/W_{sub sample wet}* 1/10000

■The carbon content in biomass (above-ground tree, sapling, leaf litter, herb and grass) is calculated by multiplying the respective biomass with the IPCC (2006) default carbon fraction of 0.47

Soil organic carbon (SOC)

■The carbon stock density of soil organic carbon is calculated as (Pearson et. al 2007), SOC = p × d × %C,

where,

SOC = soil organic carbon stock per unit area

p = soil bulk density (g cm-3),

d = the total depth where the sample was taken from (cm), and

%C = carbon concentration (%)

Total carbon stock density

 It is calculated by summing the carbon stock densities of the individual carbon pools.

C(LU) = C(ABTG) + C (AGSB) + C (BB) + C(LHG) +SOC 

where,

C(LU)  = carbon stock for a land use category (t c/ha)

 C(ABTG) = carbon in above ground tree biomass (t c/ha) 

C(AGSB) = carbon in above ground sapling biomass (t c/ha) 

C(BB) = carbon in below ground (root) biomass (t c/ha)

 C(LHG)   = carbon in litter, herb and grass (t c/ha)

SOC = soil organic carbon (t c/ha)

             

        Thank You!