The Natural Fix?

PLANTATION FORESTRY

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).

Reduced impact logging

Conventional logging

Total C emission

39

24

Total C emission

Net C uptake (photosynthesis minus respiration)

Net C uptake (photosynthesis minus respiration)

3

2

Production processes

Decomposition of slash

Soil loss

Production processes

Decomposition of slash

Soil loss

8

7

4

16

15

13

107

C stored in above-ground biomass

71

C stored in above-ground biomass

81

45

32

25

C stored in below-ground biomass

C stored in below-ground biomass

17

27

C stored below-ground (soil and biomass)

C stored below-ground (soil and biomass)

47

58

Carbon fluxes and stocks (Tonnes of C per ha per year for fluxes, tonnes of C per ha for stocks)

Source: Pinard and Cropper, 2000; Pinard and Putz, 1997.

Source: Pinard and Cropper, 2000; Pinard and Putz, 1997.

40