Agriculture Reference
In-Depth Information
Understanding the impacts of fire on carbon dynamics is fundamental to sound
land management recommendations; however, long-term effects of fire on SOC stor-
age, particularly in the savanna-woodlands, are poorly documented (Gattinger et al.
2012). Nineteen years (1992-2011) of exclosure and annual prescribed burning in
two Sudanian savanna ecosystems sites in Burkina Faso resulted in no significant
difference in SOC concentration between burned vs. unburned and closed vs. open
plots (Aynekulu et al. 2014). Sawadogo et al. (2005) investigated the effect of fire
frequency and grazing intensity on vegetation composition at the same sites, and
concluded that mean total biomass was reduced by the presence of livestock while
it was not significantly affected by prescribed fire. Coetsee et al. (2010) found no
significant influence of 50 years of frequent burning on SOC in a southern African
savanna. However, Oluwole et al. (2008) reported greater SOC by the decomposition
of roots of dead or burnt-off plants.
In addition to the external inputs of organic matter from fire-affected vegetation,
it is also necessary to consider that litter (which is usually removed before soil sam-
pling) turns, after fire, into particulate, fine-earth-sized (<2 mm) particles. These
mix with the whole soil material in the organic horizon, thus causing a net increase
in SOC content with highly friable charred organic matter and particulate charcoal
fractions (Yan et al. 2012). Additionally, fire stimulates the turnover of root materials
(Fynn et al. 2003).
Apart from these reasons, which could explain the lack of fire influence on
SOC concentration and stock, changes in SOC storage occur slowly (Ansley et al.
2006). Consequently, 19-year duration of controlled studies (Aynekulu et al. 2014)
could be insufficient to observe changes in SOC concentration in response to a fire
regime.
4.3.1.2 Grazing Management
Savory and Butterfield (1998) introduced the concepts of holistic management to
address, in a comprehensive way, the reversal of the complex interactive processes
that have led to degradation of extensive rangelands in arid to semiarid regions
of Africa and beyond. Today, the principles of holistic grazing planning are prac-
ticed by tens of thousands of people in many countries and contexts on as many as
12 million ha (Savory and Butterfield 2010; African Center for Holistic Management
2013). The largest impact has been on semiarid to arid rangelands and grasslands
where large herds of wild herbivores originated and where they have, for the most
part, disappeared. In holistic grazing planning, livestock are managed to mimic the
role that wild herds once played in maintaining ecosystem health by removing or
trampling senesced vegetation and loosening crusted surfaces and incorporating
dung and plant material into the surface. Neely and Butterfield (2004) described
the successful application of holistic management in a communal context in the
Wange community in Zimbabwe. On the basis of partnerships, the community is
applying holistic decision making to restore the natural resource base and empower
the community members. Beukes and Cowling (2003) found that short-duration,
low-frequency, intensive herbivory by livestock, leading to nonselective grazing,
resulted in a greater microbial activity, soil stability, and infiltration compared with
control treatments.
