INVESTING IN TREES AND LANDSCAPE ... - PROFOR

Carbon storage in fertilizer tree systems
Carbon storage in tree biomass and in soils is one of the most important strategies to mitigate the
global greenhouse gas effect. Nair, Kumar, and Nair studied soil carbon under-tree systems in five
countries (Brazil, India, Mali, Spain, and the United States) and concluded that “tree-based agricultural
systems, compared to treeless systems, stored more carbon in deeper soil layers up to 1 m depth
under comparable conditions” (Nair et al. 2009). They also found that higher species richness and
tree density were associated with higher soil organic carbon and that C3 plants appeared to generate
more stable carbon in the soil than C4 plants. Studies in southern Africa have shown that improved
fallows can store large quantities of carbon stocks in plant biomass and in the soil (Kaonga 2005,
Makumba et al. 2007) and thus provide the opportunity to potentially mitigate global greenhouse
gas emissions (Sileshi et al. 2007). Several studies and reviews have highlighted soil carbon stored
at depths below the plow layer. The amount of carbon sequestered varies depending on the type of
fertilizer tree system, the specific tree species, and the depth of the soil.
Depommier, Janodet, and Oliver (1992) documented a 54 percent increase in soil organic carbon
in the first 20 cm soil depth and a 35 percent increase in the 20–40 cm depth under mature
Faidherbia compared with away from Faidherbia in Burkina Faso. Okorio documented a 9.3 percent
increase in soil organic carbon with seven-year-old Faidherbia trees in Tanzania. The data in table
5 support the theory that carbon stocks can be brought above 100 tonnes per hectare in eastern
Africa, where rainfall is sufficient. Contrast that to the performance of Gliricidia in Mali, with 300
mm rainfall, in the study by Takimoto, Nair, and Nair (2008). West African systems may develop
the same levels of soil carbon (see Dossa et al. 2007) but must be in a rainfall zone sufficient for
biomass production.
TABLE 1.5. CARBON SEQUESTRATION IN FERTILIZER TREE SYSTEMS (ALL FIGURES IN TONNES PER HECTARE)
SOIL DEPTH
BIOMASS
AUTHOR
TREE
(cm) Aboveground Belowground SOIL TOTAL
Dossa et al. Shade coffee 40 62 15 97.3 174
Nonshade coffee 40 13.8 9.2 95.8 119
Kaonga et al. (Msek-2 yr-coppicing) 6.1
(4.3–9.5) a 2.4
(1.7–3.7)
(Kalu-2 yr-coppicing) 5.5
(2.1–9.5)
(Kalu-2 yr-noncoppicing) 200 5.75
(3.0–7.9)
1.8
(0.8–3.2)
3.3
(1.5–9.0)
25.7
(23–31)
(Kali-2 yr-noncoppicing) 200 78 (48–127)
(Msek-4-noncoppicing) 200 120 (102.0–
184.5)
(Msek-10-noncoppicing) 200 255
(154–291)
Makumba et al. (MZ12-Gliricidia) 20 negligible negligible 30
200 negligible negligible 123
Makumba et al. (MZ21-Gliricidia) 20 negligible negligible 30
34.75
Chapter 1. TREE-BASED AND OTHER LAND MANAGEMENT TECHNOLOGIES FOR LANDSCAPE RESTORATION AND LIVELIHOOD IN AFRICA
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