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Timber forestry can be adapted to increase the amount of carbon held in plantations.
Approximately 4% of the global forest area is represented by
plantations (FAO 2006). They supply a substantial proportion
of the demand for timber products. Plantations can sequester
significant amounts of carbon and are generally considered to
be carbon sinks, unless they replace natural forests, which are
usually richer in carbon. The largest potential carbon gains for
plantations are on marginal agricultural land and degraded
soils (Lal 2004b). However, in some cases plantations deplete
soil carbon stocks and careful management is therefore neces-
sary. By increasing the rotation period for cutting and imple-
menting site improvement strategies, soil carbon stocks can
be replenished and more carbon sequestered by the vegeta-
tion. The use of mixed stands instead of monocultures sees
beneficial effects on biodiversity and reduces the occurrence of
pests whilst enhancing timber production and carbon seques-
tration (Jandl
et al.
2007).
There may be other trade-offs too. Tree plantations can support
groundwater recharge and upwelling but may also consider-
ably reduce stream flow and salinise and acidify some soils,
thus leading to negative effects on water quantity and quality,
as well as soil quality (Jackson
et al.
2005). Negative impacts
on groundwater supplies and river flows from afforestation are
particularly prevalent in the dry tropics (Bates
et al.
2008).
PLANTATION FORESTRY
15
16
8
39
2
71
32
17
47
81
C stored in
below-ground
biomass
C stored in
above-ground
biomass
Net C uptake
(photosynthesis
minus respiration)
Total C emission
C stored below-ground
(soil and biomass)
Source: Pinard and Cropper, 2000;
Pinard and Putz, 1997.
Carbon fluxes and stocks
(Tonnes of C per ha per year for fluxes,
tonnes of C per ha for stocks)
Decomposition
of slash
Production
processes
Soil
loss
Conventional logging
4
C stored in
below-ground
biomass
107
C stored in
above-ground
biomass
Net C uptake
(photosynthesis
minus respiration)
3
27
58
24
25
45
13
7
Total C emission
Decomposition
of slash
Production
processes
Soil
loss
C stored below-ground
(soil and biomass)
Reduced impact logging
Source: Pinard and Cropper, 2000;
Pinard and Putz, 1997.