Climate Change Mitigation - Climate Resilient Agriculture for Ensuring Food Security - page 305

Fig. 13.13 Agro-forestry and carbon sequestration (Source: IGUTEK 2011 )

agricultural land management, such as the
adoption of tillage practices that reduce soil dis-
turbance and incorporate crop residues into the
soil, can remove carbon from the atmosphere
and store it in the soil as long as those land-use
and management practices are maintained. Agro-
forestry systems will vary by region. However,
crops and forests together will elevate the carbon
conserving capacity of the agroecosystem of a
region.
Agro-forestry is one of the important terres-
trial carbon sequestration systems. It involves a
mixture of trees, agricultural crops, and pastures
to exploit the ecological and economic interac-
tion of an agroecosystem. Agroecosystems play a
central role in the global carbon cycle and contain
approximately 12 % of world terrestrial carbon
(Dixon 1995 ). Increased C sequestration by agro-
forests is an important element of a comprehen-
sive strategy to reduce GHG emissions. According
to Richards and Stokes ( 2004 ), forest land can fi x
about 250 million metric tons of carbon each year
(12 % of total CO 2 emissions), cropland can
sequester about 4-11 % of atmospheric C/year,
and grazing land can sequester about 5 % of
atmospheric C/year in the USA. The system of
planting trees in strategic locations on farms to
compensate for the lost carbon due to cutting of
trees for agriculture is called agro-forestry. It has
the biggest potential for increasing agricultural

carbon sequestration in tropical countries
(Youkhana and Idol 2009 ).
Increasing agro-forestry may involve prac-
tices that increase emissions of GHGs including
shifting cultivation, pasture maintenance by
burning, paddy cultivation, N fertilization, and
animal production. On the other hand, several
studies have shown that including trees in agri-
cultural landscapes often improves the productiv-
ity of systems while providing opportunities to
create C sinks (Albrecht and Kandji 2003 ). The
trees play various functions, including shading
crops, erosion control, and nutrient cycling.
Shading crops and the rhizosphere by the trees
would signifi cantly reduce evapotranspiration
(ET) of the cropped area, although overall ET of
crops plus trees may increase. The soil organic
carbon content increases at the rate of
50 kg ha −1 year −1 in the top 10 cm depth of an
improved forestry plantation of Cassia siamia
where the high rate of litter fall under Cassia
(5-7 Mg ha −1 year −1 ) helps to maintain high soil
organic carbon content (Lal et al. 1998b ).
Bamboo is an especially effective agro-forest
sink of CO 2 with a C sequestration rate as high as
47 % amounting to 12-17 t CO 2 ha −1 year −1 . It
also generates 35 % more oxygen than other
timber species (Aggarwal 2007 ). Additionally,
bamboo plantations generate income and provide
a livelihood for forest-dependent people.