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SWS 09-01
Soil and Water Science
Research Brwief
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Carbon Storage in Soils under Tree-based Land-use Systems
S. G. Haile, V. D. Nair and P. K. R. Nair
Silvopasture integrating trees into pasture
and forage plant production is the most
common form of agroforestry in North
America. The tree components in
agroforestry systems can be significant sinks
of atmospheric carbon (C), due to their high
and long-term biomass stock, and deep root
systems. Thus, tree-based land-use systems
are expected to have better soil C storage
potential than most mono-cropping
agricultural systems.
The objectives of the research reported here
were to quantify the total soil carbon content
at six different soil depths, down to 125 cm,
in silvopastoral systems (SP) with slash pine
(Pinus elliottii) + bahiagrass (Paspalum
notatum), and an adjacent open pasture (OP)
with bahiagrass at four sites in Florida. The
study sites were on soils belonging to two
soil orders: Ultisols (Alachua and Suwannee
counties) and Spodosols (Hardee and
Osceola counties).
Soil samples were collected from each depth
(0 5, 5 15, 15 30, 30 50, 50 75, 75
- 125 cm) and fractionated into three classes
(250-2000, 53-250, and <53 [m) using a
wet sieving procedure. The C content in
each soil sample was determined.
Open-pasture
SN
L o t'c-t
S 50 120 2 Mles
Location of study sites at Alachua and Suwannee,
Hardee and Osceola counties in Florida.
Soil fractionation
Macro Aggregale
LYT2W~2OOO~2Oml
Soil fractionation procedure
- - - - - - -
317
The study revealed that averaged across four
sites and all depths, the total soil organic
carbon (SOC) content was higher by 33% in
silvopastures near trees (SP-T) and by 28%
in the alleys between tree rows (SP-A) than
in adjacent open pastures. It was higher by
39% in SP-A and 20% in SP-T than in open
pastures in the largest fraction size
(250-2000 pm) and by 12.3% (SP-T) and
18.8% (SP-A) in the intermediate size
fraction (53-250 pm). Deeper soil layers (up
to 1.25 m) contained as much as 45 kg per
square meter more C in silvopasture than in
adjacent treeless pasture.
Soil carbon content (1.25 m depth) at the various
pasture locations.
Silvopastures generally contain more C in
deeper soil layers under similar ecological
settings, possibly as a consequence of a
major input to soil organic matter from
decomposition of dead tree-roots. The
contribution of the tree component to C
storage using stable C isotopic signatures
helps identify the C source tree vs grass
(see SWS 09-02).
Total C, k m 2
0 20 40 60 80 100 TotalC,kgm 2
0 20 40 60 80 100
20 0
240 20
60o 1 Alachua 40 Suwannee
so 8 60
100 80 -O
120 100
120
Total C, kg m2 Total C, kg m2
0 20 40 60 80 100 0 20 40 60 80 100
0 0
20 20
S40 E 40
S60 Hardee 60 Osceola
80 80
100 100
120 120
Soil organic carbon (SOC) with depth at silvopasture
(in-between tree rows [SP-T] and open pasture [OP]
locations for non-fractionated soil at the four sites.
From our results, the potential of
silvopasture as a strategy for C sequestration
seems clear. Further details of this study can
be found in:
Haile, S. G, P.K.R. Nair, and V.D. Nair.
2008. Soil carbon storage in different size
fractions in silvopastoral systems of Florida.
J. Environ. Qual. 37:1789-1797.
For additional information, contact the
authors at:
S.G. Haile: solomonh@ufl.edu
V.D. Nair: vdn(@ufl.edu
Soil and Water Science Department
P.O. Box 110510
Gainesville, FL 32611-0510
Tel: (352) 392-1803
P.K.R. Nair: pknair@(ufl.edu
School of Forest Resources and
Conservation
Tel: (352) 846-0880
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