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CARBON CONTENT IN
CACAO
AFS
Field studies are conducted in Bokito in the central region of Cameroon, this area is known as a patchwork of savannah, forest, agricultural area and AFS. Savannahs in these area are yearly burnt for hunting practices and land clearance is carried out for agricultural practices. Carbon measurements were taken in cacao plantations setup on two previous land-use types (savannah and gallery forest) with an age gradient of 0 to 80 years. Results were compared with two control groups in gallery forests and savannah. Carbon content and accumulation were assessed both in cacao trees and associated tree species as well as in plantations’ soil.
• Afforestation of savannah has a positive effect on the total
above ground carbon with an annual accumulation of 5.7%
resulting in similar carbon levels as cacao plantations after
forest in ± 60 years.
• Setting up a cacao plantation after forest decreases the
mean above ground carbon stock but no significant change
was shown with aging of the cacao plantations.
• Soil carbon and soil clay content of plantations set up after
savannah are strongly correlated but also correlations are
found between soil organic carbon and the plantations age.
Introduction
Results
y = 0.87x + 15.04 R² = 0.420** 0 20 40 60 80 100 120 140 160 180 0 10 20 30 40 50 60 70 80 90Above Ground Carbon (Mg/ha)
Annual accumulation 5.7% A R² = 0.609** 0 0.5 1 1.5 2 2.5 3 3.5 5 10 15 20 25 30 35 40 Clay Content (%) C R² = 0.368* 0 0.5 1 1.5 2 2.5 3 3.5 0 10 20 30 40 50 60 70 80 90
Soil Carbon content 0-15 cm (%)
Plantation Age (years)
B
Annual accumulation 9.7‰
Annual accumulation 6.0‰
Afforestation of Savannah as a Carbon Storage Opportunity in Central Cameroon
Afforestation of savannah areas by cacao agroforestry
systems (AFS) is relatively rare
1–4. Soil and climate
conditions are generally considered undesirable for this
type of perennial production system
5. However, previous
studies in a forest-savannah transition zone in Central
Cameroon have shown that smallholder farmers were able
to afforestation on savannah land by establishing cacao
plantations on it
4,6. Compared to plantations setup after
formal forests in the same region, cocoa production levels
and associated tree species densities were found to be
comparable on the long-term
4. Considering the low level of
carbon storage in savannah, partly due to yearly burning of
these areas, afforestation with cacao plantations could be
of great potential in the light of climate change mitigation
due to their increased carbon storage capacity.
Nijmeijer, A.
1,2Bouambi, E.
2Harmand, J.M.
3,4Saj, S.
11. CIRAD, UMR System, Montpellier, France 2. IRAD, Nkolbisson, Yaoundé, Cameroon 3. CIRAD, UMR Eco&Sols, Montpellier, France 4. ICRAF, Yaoundé, Cameroon
Methods
Results
Mean total above
ground carbon is around 40%
lower in cacao p l a n t a t i o n s set-up after forest compared to forest control plots. Above ground carbon stocks of plantations set up after savannah have increased by 1011% compared to the m e a s u r e m e n t s
that have been taken on savannah (Fig.2).
Conclusion
Cacao plantations after forest Forest control Cacao plantations after savannah Savannah control Correlations cacaoplantations after savannah*
Legend
Clay content >15% Clay content <15%
*No correlations were found between plantations after forest and above- and belowground carbon.
Fig. 2: Mean total above ground carbon stocks in forest- and savannah control plots, cacao plantations after forest and after savannah.
The above ground total carbon and soil organic carbon (SOC) of the first 15 cm of savannah plantations are significant correlated with the age of the plantations (Fig: 3A,B). For the same parameters no correlations were found in forest plantations and the soil layer 15-30 cm.
Even though, a correlation between age and SOC was found an even stronger correlation was found between soil clay content and SOC content (Fig: 3C). When separating cacao planta-tions after savannah into two groups 1) low (<15%) and 2) high (>15%) clay content, SOC tended to increase at an annual reate of 9.7‰ for the plantations on soils with a high clay content and 6.0‰ for the plantations on soils with a low clay content (Fig: 3B).
Fig. 1: What influence has converting savannah or forest to complex- cacao agroforestry systems on the long-term carbon budgets?
References
1. de Foresta, H. & Michon, G. The agroforest alternative to Imperata grasslands: when smallholder agriculture and forestry reach sustainability. Agrofor. Syst. 105–120 (1997).
2. Ruf, F. et al. From slash-and-burn to replanting: Green revolutions in the Indonesian uplands. World Bank Regional and Sectoral Studies (The world bank, 2004).
3. Gockowski, J., Weise, S., Sonwa, D., Tchtat, M. & Ngobo, M. Conservation Because It Pays : Shaded Cocoa Agroforests in West Africa . Habitat 29 (2004).
4. Jagoret, P., Michel-Dounias, I., Snoeck, D., Ngnogué, H. T. & Malézieux, E. Afforestation of savannah with cocoa agroforestry systems: a small-farmer innovation in central Cameroon. Agrofor. Syst. 86, 493–504 (2012).
5. Wood, G. A. R. & Lass, R. A. Cocoa. (Blackwell Science, 2001).
6. Saj, S., Jagoret, P. & Todem Ngogue, H. Carbon storage and density dynamics of associated trees in three contrasting Theobroma cacao agroforests of Central Cameroon. Agrofor. Syst. 87, 1309–1320 (2013).
Fig 3: Evolution with plantation age of (A) above ground carbon stocks and (B) soil carbon content (C) Correlation between soil carbon content and soil clay content.
0 a ab b c 20 40 60 80 100 120 140 Forest
control Plantationsafter forest Plantationsafter savannah
Cacao trees
All woody species including cacao
Savannah control
Above-ground Carbon (Mg/ha)
Complex Agroforestry systems
Precedent Forests Precedent Savannah
