Climate Change Mitigation - Climate Resilient Agriculture for Ensuring Food Security - page 306

Degraded lands can be used for plantations of
fast-growing clones of bamboo species up to an
altitude of 1,800 m. Bamboo grows much faster
than other trees with some species growing up to
150 ft in just 6 weeks, occasionally more than 4 ft
per day. Bamboo is a pioneering plant that can
also grow in over grazed soil using poor agricul-
tural techniques (Aggarwal 2007 ).

• An agro-forestry-induced microclimate
improves quality and increases the yield of
some crops, although it is diffi cult to provide
an estimation of the yield increase (Ebeling
and Yasue 2008 ).
• Increasing soil carbon greatly benefi ts agricul-
tural productivity and sustainability.
• Cost of carbon sequestration through agro-
forestry appears to be much lower than through
other CO 2 -mitigating options (Albrecht and
Kandji 2003 ).

13.1.7.1 Advantages
• Trees act as a buffer against storms to prevent
crop destruction.
• Dryland forests apparently manage to seques-
ter carbon by reducing respiration rates and
growing rapidly in early spring to take advan-
tage of temperatures most favorable for
growth (Rotenberg and Yakir 2010 ).
• Trees send their roots considerably deeper than
crops, thereby placing organic matter at deeper
depths in the soil where tillage would not
accelerate its decomposition and the release of
CO 2 . In some instances, trees have extracted
water from deeper depths which has become
redistributed at shallower depths with positive
effects on the growth of understory plants. In
other cases, negative effects have also been
reported, so the phenomenon remains contro-
versial (Prieto et al. 2012 ). While such redistri-
butions could be ecologically important,
allowing some species to survive that would
otherwise perish, it is less clear that the
amounts of water involved would enable sig-
nifi cant increases in the yield of agronomic
crops.
• Leaf litter generates compost and serves as
mulch that reduces runoff from rainfall. It also
slows soil water loss from evaporation into the
atmosphere.
• Agro-forestry trees also improve land cover in
agricultural fi elds in addition to providing car-
bon inputs (root biomass, litter, and pruning)
to the soil. These often reduce soil erosion,
which is a crucial process in soil carbon
dynamics.
• Carbon sequestration continues beyond har-
vest if boles, stems, or branches are processed
into durable products that do not decompose
and release CO 2 .

13.1.7.2 Disadvantages
• This technology involves a very slow process
of marginal carbon conservation.
• Soil carbon increases only in drier sites and
actually decreases in wetter sites of agro-
forestry regions (Jackson et al. 2002 ). As a
result, the net carbon balance was marginally
positive for the dry sites but negative for the
wet sites.
• Under dry environments, the tree crop compe-
tition for water usually results in low crop
yields, which makes this technology unattract-
ive for dryland farmers. Under dryland condi-
tions, trees with their effective rooting systems
take more water compared to crops with
relatively less effective rooting systems, so the
crops are more vulnerable to water stress with
consequent lower yields (Schroeder 1995 ).
• Various species of damaging insects, pests,
and diseases have been associated with dead
or dying trees. These are a major threat to the
development of agro-forestry in the tropics.
• Emissions of other greenhouse gases such as
N 2 O and CH 4 in the atmosphere may increase,
which reduces overall mitigation potential.
Agro-forestry is practiced to some extent all
over the world. It is especially used for crops that
benefi t from the quality improvements associated
with shading. However, the other benefi ts, includ-
ing carbon sequestration, are being more recog-
nized, and agro-forestry appears to be growing in
popularity.
Light is a limiting factor for crop production
in agro-forestry system, and most crops yield less
when shaded with higher plants. Therefore,
unless the several advantages such as quality