Role of Major Forest Biomes in Climate Change Mitigation …
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structure and functioning, including that of the carbon cycle, which in turn provides
a feedback (mostly positive) to climate change.
7.1 Tropical Forests
Tropical forests are well-known for their rich species diversity and high productivity.
Tropical forests are located between 23° N and 23° S of the Equator (Hui et al.
2017). On the whole, tropical forests cover around 20 million square kilometres,
which is roughly 50% of the world’s forested land (Pan et al. 2011).The average
temperature is 20–25 °C and the annual rainfall is about >2000 mm. Tropical forests
are characterized by tall trees (25–35 m), with many hardwood species that contribute
on a large-scale to carbon sequestration in their multistoried profiles (Hui et al.
2017).The tropical forests are broadly classed into four types based on precipitation,
degree of seasonality as well as elevation: (i) ever-wet (or rainforest), (ii) semievergreen, (iii) dry deciduous and (iv) montane forest types (Meister et al. 2012).
Tropical forests are known to hold about 25% of the global terrestrial biosphere’s
carbon and they contribute to 33% of the terrestrial net primary productivity (Sabine
et al. 2004; Bonan 2008). According to Malhi et al. (1998), about 8% of the terrestrial
atmospheric carbon dioxide is cycled in tropical forests (Meister et al. 2012).
Several researchers have provided varying estimates on the biomass and carbon
stocks of tropical forests around the world. This is so because, different tropical
forest types across regions allocate biomass in different patterns due to varying
environmental conditions, stand structure and vegetation composition (Meister et al.
2012). According to Soepadmo (1993), tropical forests contain 428 Gt of carbon, of
which 58% is stored in vegetation, 41% in soil and 1% in litter (Watson et al. 2000;
Meister et al. 2012). Reichstein (2007), estimated that these forest biomes likely
store 206–389 Pg C in vegetation and 214–435 Pg C in soil, up to a depth of 1 m
(Lorenz and Lal 2010). Pan et al. (2011) estimated that tropical forests contain about
471 Pg C, which accounts for 55% of the carbon stored in world’s forests. Also, they
pointed out that tropical forests store 56% of carbon in vegetation biomass and 32%
in soil. The reason for less carbon stocks in soil is the rapid decomposition of dead
matter under the warm and humid conditions that prevails in the tropical forests and
the minerals rapidly leach out of the soils (Gorte 2007; Hui et al. 2017). Saatchi et al.
(2011) estimated that tropical forests stocked 247 Gt C in vegetation biomass, of
which 193 Gt C was aboveground and 54 Gt C was belowground. Tropical forests
of Latin America accounted for 49% of the total carbon stock of world, followed by
those in Southeast Asia (26%) Saharan Africa (25%). However, according to Sullivan
et al. (2017), the highest carbon density of tropical forests in Asia (197 Mg C/ha),
followed by Africa (183 Mg C/ha) and South America (140 Mg C/ha). Nevertheless,
tropical forests are known to account for about 60% of the global photosynthesis,
thereby sequestering around 72 Pg C every year, they also roughly release same
amounts of carbon via respiration by plants, microbes and animals (Beer et al. 2010;
Mitchard 2018).
499
structure and functioning, including that of the carbon cycle, which in turn provides
a feedback (mostly positive) to climate change.
7.1 Tropical Forests
Tropical forests are well-known for their rich species diversity and high productivity.
Tropical forests are located between 23° N and 23° S of the Equator (Hui et al.
2017). On the whole, tropical forests cover around 20 million square kilometres,
which is roughly 50% of the world’s forested land (Pan et al. 2011).The average
temperature is 20–25 °C and the annual rainfall is about >2000 mm. Tropical forests
are characterized by tall trees (25–35 m), with many hardwood species that contribute
on a large-scale to carbon sequestration in their multistoried profiles (Hui et al.
2017).The tropical forests are broadly classed into four types based on precipitation,
degree of seasonality as well as elevation: (i) ever-wet (or rainforest), (ii) semievergreen, (iii) dry deciduous and (iv) montane forest types (Meister et al. 2012).
Tropical forests are known to hold about 25% of the global terrestrial biosphere’s
carbon and they contribute to 33% of the terrestrial net primary productivity (Sabine
et al. 2004; Bonan 2008). According to Malhi et al. (1998), about 8% of the terrestrial
atmospheric carbon dioxide is cycled in tropical forests (Meister et al. 2012).
Several researchers have provided varying estimates on the biomass and carbon
stocks of tropical forests around the world. This is so because, different tropical
forest types across regions allocate biomass in different patterns due to varying
environmental conditions, stand structure and vegetation composition (Meister et al.
2012). According to Soepadmo (1993), tropical forests contain 428 Gt of carbon, of
which 58% is stored in vegetation, 41% in soil and 1% in litter (Watson et al. 2000;
Meister et al. 2012). Reichstein (2007), estimated that these forest biomes likely
store 206–389 Pg C in vegetation and 214–435 Pg C in soil, up to a depth of 1 m
(Lorenz and Lal 2010). Pan et al. (2011) estimated that tropical forests contain about
471 Pg C, which accounts for 55% of the carbon stored in world’s forests. Also, they
pointed out that tropical forests store 56% of carbon in vegetation biomass and 32%
in soil. The reason for less carbon stocks in soil is the rapid decomposition of dead
matter under the warm and humid conditions that prevails in the tropical forests and
the minerals rapidly leach out of the soils (Gorte 2007; Hui et al. 2017). Saatchi et al.
(2011) estimated that tropical forests stocked 247 Gt C in vegetation biomass, of
which 193 Gt C was aboveground and 54 Gt C was belowground. Tropical forests
of Latin America accounted for 49% of the total carbon stock of world, followed by
those in Southeast Asia (26%) Saharan Africa (25%). However, according to Sullivan
et al. (2017), the highest carbon density of tropical forests in Asia (197 Mg C/ha),
followed by Africa (183 Mg C/ha) and South America (140 Mg C/ha). Nevertheless,
tropical forests are known to account for about 60% of the global photosynthesis,
thereby sequestering around 72 Pg C every year, they also roughly release same
amounts of carbon via respiration by plants, microbes and animals (Beer et al. 2010;
Mitchard 2018).