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Silvopastoral Systems and Biodiversity
By: F.J. Solorio and S.K. Basu*
The most common threat to biodiversity is the fragmentation of natural habitats. With the increase in human population the demand for food grains and other
food items like milk and meat has also increased, which has led to the loss of forests for the expansion of the agricultural frontier and
pastures, mainly in the tropics. The loss of forests is one of the principal negative impacts on biodiversity, due to the expansion of the agricultural
frontier, mainly in the tropics. Silvopastoral Systems can become an effective tool to mitigate this problem, because of its multiple benefits and
ecosystem services, coupled with increased productivity in livestock systems production.
Silvopastoral systems (SPS) are an agroforestry systems orientated mainly for livestock production. It also aims at providing environmental and soil
benefits, including biodiversity aspects. Biodiversity is a key aspect in the sustainability of the agriculture production systems and hence for
maintaining a SPS work in an integral way. Although, biodiversity depends on the structural heterogeneity of the land vegetation, SPS, is composed of a
multistrate vegetation with a diversity of herbaceous and woody species that create heterogeneity for increased below- and above-ground biodiversity. Trees
and shrubs provide habitat and food for diverse types of birds and bees, and, at the same time, birds and bees play a fundamental role in natural
reforestation and vegetation restoration through seed dispersal.
Silvopastoral Systems provide a number of ecosystem services including carbon sequestration, biodiversity conservation, soil enrichment, air and water
quality maintenance, and regulation of microclimate (Table 1).
Table 1.
Ecosystems services from silvopastoral systems.
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Parameter
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Benefit
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Nutrient Cycling
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In an SPS plant nutrients are in a state of continuous, dynamic transfer. Plants take up nutrients from the soil and use them for metabolic
processes. In turn, plants return nutrients to the soil either naturally as litter, or through root senescence.
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Carbon sequestration
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SPS represent an important alternative to the recovery of degraded areas and have high potential for carbon (C) sequestration. Net carbon
flux and primary productivity increases significantly due to integration of different woody species with grasses.
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Biological N Fixation
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A long-term, more sustainable and cost-effective solution to pasture degradation is the addition of vigorous forage legumes to the pasture
to boost soil N levels by biological N fixation. Leguminous nitrogen fixing-fodder species can fix >150 kg N/ha/yr (equivalent to 320 kg
urea/ha/yr), some of which is cycled to the pasture via animal dung and urine during grazing.
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Greenhouse gas mitigation
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Methane emission from ruminants is one of the sector´s largest greenhouse gas emissions. SPS is one of the most important approaches to
offsetting agricultural emission through improving animal diet quality and using forage rich tannin species.
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Microclimatic conditions
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The shade within silvopastoral systems reduces temperature and ameliorates environment and is beneficial for better animal performance.
Shade has been useful in increasing milk yields of dairy cattle and liveweight gains of feed cattle in hot climates,
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Recovering degraded land
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SPS with fast-growing leguminous nitrogen-fixing trees can, in a short to medium time, recuperate degraded land. The litter stocks and soil
C and N stocks in SPS indicate that the use of leguminous trees can increase efficiency in re-establishing the nutrient cycling processes
of the systems. These results also show that recovering degraded land with this technique is effective in sequestering carbon dioxide from
the atmosphere at high rates.
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Biological diversity
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SPS with a diversity of multipurpose species growth generate a rich habitat that increases the number and variability of living organisms
(below and above the soil). In the above-ground level, diversity of insects and birds increases which is beneficial for the productivity of
SPS, while in the belowground layer worm and beetle species thrive due to increase in the soil humidity created by the trees and shrubs
grown in the SPS.
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*UFL, Lethbridge, AB,
Canada. E-mail
[email protected]
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