502
J. A. Dar et al.
least on the short-term drought stress is likely to have a negative impact on regional
carbon budgets. However, Beerling et al. (1996) stated that the trees are likely to
develop drought tolerance in the future, thereby leading to little impact of drought
on the net ecosystem productivity (Tyrrell et al. 2012).
A warmer world has increased soil temperature, which would greatly alter the rates
of decomposition and soil respiration. High summer temperatures are expected to
enhance ecosystem respiration processes by increasing soil temperatures (Yuan et al.
2008; Zhu et al. 2009; Tyrrell et al. 2012). In toto, the carbon cycle in temperate forests
is predominantly influenced by length of the growing season, cloud cover, snow
depth in winter and the extent of drought in summer. While the former two factors
strongly influence photosynthesis, the latter two factors regulate decomposition and
respiration (Goulden et al. 1996; Tyrrell et al. 2012). It has been projected that
high temperatures and high amounts of precipitation would bring about increases in
soil and microbial respiration processes and therefore, increase in carbon emissions
(Tyrrell et al. 2012).
Most temperate forests are also severely impacted by wind disturbances and highvelocity ice storms (Dale et al. 2001; Tyrrell et al. 2012). Small- to intermediate-levels
of disturbances are likely to result in either gap formation or gap expansion and
young slender trees die before attaining maturity (Worrall et al. 2005). Therefore,
there would be a decline in the overall regional carbon sequestration as only very few
young stands manage to develop into mature stands (Uriate and Papaik 2007; Tyrrell
et al. 2012). Moreover, such wind- and ice storms could cause injuries to trees from
branch breakages to severe tree mortality, depending on the local site conditions,
storm intensity and species involved (Bragg et al. 2003; Tyrrell et al. 2012). In the
event of such disturbances, carbon gets quickly transferred from living biomass pool
to dead biomass pool and gradually gets decomposed (Uriate and Papaik 2007; Tyrrell
et al. 2012), resulting in rapid loss of stored carbon. Apart from the above responses
of temperate forests to climate change, the tropospheric ozone concentrations also
could cause a drastic reduction in the carbon sequestration potential by causing
foliar injuries, reduced tree growth and hence lowering the above- and belowground
productivity (Augustaitis and Bytnerowicz 2008; Wittig et al. 2009; Lorenz and Lal
2010). Therefore, various environmental components and climatic events profoundly
influence the carbon cycling in temperate forests.
Despite the above, the climate change consequences in the temperate forests are
projected to be less severe than the other major forest biomes (Lorenz and Lal 2010).
This has been attributed that temperate forests currently exist on a stable balance due
to its relatively stable forest cover, successional patterns and age-class distribution
(Tyrrell et al. 2012). However, this balance is very fragile and small changes in
forest cover or age-class distribution could shift the temperate forest ecosystems
from carbon sinks to either carbon-neutral or carbon-releasing ecosystems (Tyrrell
et al. 2012).
J. A. Dar et al.
least on the short-term drought stress is likely to have a negative impact on regional
carbon budgets. However, Beerling et al. (1996) stated that the trees are likely to
develop drought tolerance in the future, thereby leading to little impact of drought
on the net ecosystem productivity (Tyrrell et al. 2012).
A warmer world has increased soil temperature, which would greatly alter the rates
of decomposition and soil respiration. High summer temperatures are expected to
enhance ecosystem respiration processes by increasing soil temperatures (Yuan et al.
2008; Zhu et al. 2009; Tyrrell et al. 2012). In toto, the carbon cycle in temperate forests
is predominantly influenced by length of the growing season, cloud cover, snow
depth in winter and the extent of drought in summer. While the former two factors
strongly influence photosynthesis, the latter two factors regulate decomposition and
respiration (Goulden et al. 1996; Tyrrell et al. 2012). It has been projected that
high temperatures and high amounts of precipitation would bring about increases in
soil and microbial respiration processes and therefore, increase in carbon emissions
(Tyrrell et al. 2012).
Most temperate forests are also severely impacted by wind disturbances and highvelocity ice storms (Dale et al. 2001; Tyrrell et al. 2012). Small- to intermediate-levels
of disturbances are likely to result in either gap formation or gap expansion and
young slender trees die before attaining maturity (Worrall et al. 2005). Therefore,
there would be a decline in the overall regional carbon sequestration as only very few
young stands manage to develop into mature stands (Uriate and Papaik 2007; Tyrrell
et al. 2012). Moreover, such wind- and ice storms could cause injuries to trees from
branch breakages to severe tree mortality, depending on the local site conditions,
storm intensity and species involved (Bragg et al. 2003; Tyrrell et al. 2012). In the
event of such disturbances, carbon gets quickly transferred from living biomass pool
to dead biomass pool and gradually gets decomposed (Uriate and Papaik 2007; Tyrrell
et al. 2012), resulting in rapid loss of stored carbon. Apart from the above responses
of temperate forests to climate change, the tropospheric ozone concentrations also
could cause a drastic reduction in the carbon sequestration potential by causing
foliar injuries, reduced tree growth and hence lowering the above- and belowground
productivity (Augustaitis and Bytnerowicz 2008; Wittig et al. 2009; Lorenz and Lal
2010). Therefore, various environmental components and climatic events profoundly
influence the carbon cycling in temperate forests.
Despite the above, the climate change consequences in the temperate forests are
projected to be less severe than the other major forest biomes (Lorenz and Lal 2010).
This has been attributed that temperate forests currently exist on a stable balance due
to its relatively stable forest cover, successional patterns and age-class distribution
(Tyrrell et al. 2012). However, this balance is very fragile and small changes in
forest cover or age-class distribution could shift the temperate forest ecosystems
from carbon sinks to either carbon-neutral or carbon-releasing ecosystems (Tyrrell
et al. 2012).