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Tundra
Boreal forest
Temperate forest
Temperate grasslands, savannas and shrublands
Desert and dry shrublands
Tropical and subtropical forests
Tropical and subtropical grasslands, savannas and shrublands
Source: adapted from Olson
et al
., 2001.
Much of the original area of temperate grassland has been cleared for agriculture.
Where natural vegetation remains, minimising human disturbance can prevent fur-
ther carbon loss.
Grasslands are found across much of the world as an early succes-
sional ecosystem in forested regions. They also form the natural
vegetation in climates where precipitation levels are inadequate
to support trees but higher than those of deserts (Woodward
et
al.
2004). Extensive areas of natural temperate grassland occur in
South America, the USA and Central Asia. Plant growth in these
grasslands is water and nutrient limited and plants allocate much
of their biomass below ground, where they produce slowly decom-
posing roots. Grazing animals typically play an important role in
maintaining grasslands in that they accelerate carbon cycling by
consuming and respiring large quantities of leaf biomass and re-
turning some of this to the soil as dung. This is a form of organic
carbon that is more decomposable than the leaf and root litter of
grasses. In many areas this role is now performed by livestock.
Overall, temperate grasslands have low levels of plant biomass
compared with forest or shrubland ecosystems (e.g. 0.68 and
7.3 t C per ha respectively in the temperate steppe of China,
Fan
et al.
2008). However, their soil organic carbon stocks tend
to be higher than those of temperate forests (133 t C per ha,
Amundson 2001).
HUMAN IMPACTS AND IMPLICATIONS FOR
CARBON MANAGEMENT
Despite only having intermediate productivity some temperate
grasslands are well suited to crop production and can produce
excellent agricultural soils. In much of their natural range, e.g.
the prairies of America, these have been cleared to make way
for intensive agriculture.
TEMPERATE GRASSLANDS