Geoscience Reference
In-Depth Information
2001, 2005; Rice and Owensby, 2001; Conant and Paustian,
2002; Freibauer et al., 2004; Reeder et al., 2004; Liebig et al.,
2005). The effects are inconsistent as there are many types of
grazing practices involving diversified plant species, soil and
climate (Schuman et al., 2001; Derner et al., 2006).
Increasing productivity:
Carbon stock of grazing lands can
be increased by improving its productivity through alleviating
nutrient and moisture deficiencies (Conant et al., 2001; Schnabel
et al., 2001). Adding nitrogen and energy use for irrigation
stimulates N
2
O and CO
2
emissions, which may, however, offset
some of the benefits (Schlesinger, 1999; Conant et al., 2005).
Nutrient management:
The practices (discussed for crop-
land) that improve the plant nutrient uptake can reduce N
2
O
emissions (Follett et al., 2001; Dalal et al., 2003). Nutrient
management on grazing lands is made complicated through
deposition of faeces and urine from livestock that, too, are
uncontrolled and randomly added (Oenema et al., 2005).
Fire management:
Anthropogenic or natural on-site biomass
burning either contributes to climate change through GHG
emission, production of smoke aerosols (have either warming
or cooling effects on the atmosphere), albedo reduction of the
land surface for several weeks (causing warming) and disturbed
woody versus grass cover proportion, particularly in savan-
nahs which occupy about one-eighth of the global land surface
(Andreae, 2001; Andreae and Merlet, 2001; Menon et al., 2002;
Anderson et al., 2003; Beringer et al
.,
2003; Jones et al., 2003;
Van Wilgen et al., 2004; Andreae et al., 2005; Venkataraman
et al., 2005). Therefore, reducing the frequency or intensity of
fires through more effective fire suppression, reducing fuel load
by vegetation management and burning at a time of year when
less CH
4
and N
2
O are emitted can restrict these processes along
with an increased CO
2
sink into soil and biomass (Scholes and
van der Merwe, 1996; Korontzi et al., 2003).
Species introduction:
Introducing grass species with higher
productivity (legumes) or carbon allocation to deeper roots can
increase soil carbon (Fisher et al., 1994; Davidson et al., 1995;
Conant et al., 2001; Machado and Freitas, 2004; Soussana
et al., 2004), and perhaps also can reduce emissions from fer-
tiliser manufacture if biological N
2
fixation displaces applied N
fertiliser (Sisti et al., 2004; Diekow et al., 2005).
Manage ment of
organic/peaty
soils
Organic or peaty after draining can be used for agriculture, but
the accelerated aeration decomposition in these soils results in
high CO
2
and N
2
O fluxes (Kasimir-Klemedtsson et al., 1997).
The drainage of such soils should either be avoided in the first
