500
J. A. Dar et al.
Tropical forests of Southeast Asia and the Amazon are expected to suffer from
droughts, especially during El Nino Southern Oscillation events. Although they could
withstand short-term droughts, become more susceptible to forest fires, both after
short-term and long-term droughts (Meister et al. 2012). The severity of the effects
of the drought varies depending on the forest type and water availability (Meister
et al. 2012; Hisano et al. 2018). In the event of drought, when tropical forest soils
become dry, not only carbon dioxide gets released, but also methane, another important greenhouse gas (Cattanio et al. 2002; Meister et al. 2012). Moreover, when
vegetation dries out, human-induced fires could spread and engulf large-portion of
the tropical forest landscape creating widespread damage. Since both photosynthesis
and respiration of plants are directly tied to temperature, water availability, sunlight,
atmospheric carbon dioxide concentration, oxygen, etc., climatic alterations would
have pronounced effects on these primary metabolic pathways. If the carbon uptake
is increased by photosynthesis, hence will result in increased productivity. This happens because of greater carbon fertilization. In such case, the forest trees might
eventually attain a point of saturation and become constrained due to limitation in
some other resource(s) (Phillips et al. 2008; Meister et al. 2012). Further, with a
rise in temperature, respiration increases leading to more release of carbon, while
the rate of photosynthesis remains at the threshold level (Meister et al. 2012). Consequently, they may switch over their functioning from being ‘sinks’ to ‘sources’.
When the plants reach this saturation point, litter production also levels off, which
would cause changes in the soil biotic communities, influencing soil respiration as
well, that would cause further soil carbon losses (Coley 1998; Meister et al. 2012).
In general, tropical forests exert a strong control over climate change (Pravalie 2018) by acting as large carbon reservoirs. In addition, they also alleviate climate change by means of evaporative cooling and cloud formation (which reflects
the incident radiation back to space) (Bonan 2008; Jackson et al. 2008; Pravalie
2018). Tropical forests could become vulnerable to a warmer climate which in turn
accelerate the pace of global warming via a positive feedback that would lessen
the evaporative cooling, increase the amounts of carbon dioxide released back to the
atmosphere and gradually begin forest dieback (Betts et al. 2004; Bonan 2008; Malhi
et al. 2008). Nonetheless, tropical forests do occupy an important place in mitigating
global climate change due to its huge carbon sequestration ability.
7.2 Temperate Forests
Temperate forests cover approximately 8 million square kilometres and occur
between 25–60° N and 25–55° S latitudes, accounting approximately for 20% of
the world’s forests (Pan et al. 2011; Hui et al. 2017; Pravalie 2018). Most of these
forests lie in the Northern Hemisphere, whose southern limit is just a little above the
Tropic of Capricorn (Tyrrell et al. 2012). These forests experience a clearly manifested seasonality in the climate, with warm summers alternating with cold winters (Reich and Bolstad 2001; Lorenz and Lal 2010). The temperature in temperate
J. A. Dar et al.
Tropical forests of Southeast Asia and the Amazon are expected to suffer from
droughts, especially during El Nino Southern Oscillation events. Although they could
withstand short-term droughts, become more susceptible to forest fires, both after
short-term and long-term droughts (Meister et al. 2012). The severity of the effects
of the drought varies depending on the forest type and water availability (Meister
et al. 2012; Hisano et al. 2018). In the event of drought, when tropical forest soils
become dry, not only carbon dioxide gets released, but also methane, another important greenhouse gas (Cattanio et al. 2002; Meister et al. 2012). Moreover, when
vegetation dries out, human-induced fires could spread and engulf large-portion of
the tropical forest landscape creating widespread damage. Since both photosynthesis
and respiration of plants are directly tied to temperature, water availability, sunlight,
atmospheric carbon dioxide concentration, oxygen, etc., climatic alterations would
have pronounced effects on these primary metabolic pathways. If the carbon uptake
is increased by photosynthesis, hence will result in increased productivity. This happens because of greater carbon fertilization. In such case, the forest trees might
eventually attain a point of saturation and become constrained due to limitation in
some other resource(s) (Phillips et al. 2008; Meister et al. 2012). Further, with a
rise in temperature, respiration increases leading to more release of carbon, while
the rate of photosynthesis remains at the threshold level (Meister et al. 2012). Consequently, they may switch over their functioning from being ‘sinks’ to ‘sources’.
When the plants reach this saturation point, litter production also levels off, which
would cause changes in the soil biotic communities, influencing soil respiration as
well, that would cause further soil carbon losses (Coley 1998; Meister et al. 2012).
In general, tropical forests exert a strong control over climate change (Pravalie 2018) by acting as large carbon reservoirs. In addition, they also alleviate climate change by means of evaporative cooling and cloud formation (which reflects
the incident radiation back to space) (Bonan 2008; Jackson et al. 2008; Pravalie
2018). Tropical forests could become vulnerable to a warmer climate which in turn
accelerate the pace of global warming via a positive feedback that would lessen
the evaporative cooling, increase the amounts of carbon dioxide released back to the
atmosphere and gradually begin forest dieback (Betts et al. 2004; Bonan 2008; Malhi
et al. 2008). Nonetheless, tropical forests do occupy an important place in mitigating
global climate change due to its huge carbon sequestration ability.
7.2 Temperate Forests
Temperate forests cover approximately 8 million square kilometres and occur
between 25–60° N and 25–55° S latitudes, accounting approximately for 20% of
the world’s forests (Pan et al. 2011; Hui et al. 2017; Pravalie 2018). Most of these
forests lie in the Northern Hemisphere, whose southern limit is just a little above the
Tropic of Capricorn (Tyrrell et al. 2012). These forests experience a clearly manifested seasonality in the climate, with warm summers alternating with cold winters (Reich and Bolstad 2001; Lorenz and Lal 2010). The temperature in temperate