Land Use, Land-Use Change and Forestry

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Fact Sheet 4.16. Forest Harvest Quantity and Timing

Harvesting is the procedure by which a forest stand is logged, with an emphasis on meeting logging requirements and attaining silvicultural objectives. Harvest scheduling is a process for allocating cutting and other silvicultural treatments over a forest, with the emphasis on which treatments to apply as well as where and when to apply them. The practice relates to when and how harvesting is done (e.g., thinnings, including pre-commercial thinnings; selection; or clear-cut harvests) and the timber volume extracted.

Use and Potential
Harvest intensity affects the quantity and quality of timber produced. The carbon impact is directly connected to the end use of the wood products. For example, increasing the rotation time, lengthening the period between harvest operations, or reducing the volume extracted may lead to reduced growth rates and reduced carbon sequestration in the forest, as well as producing less wood for bioenergy or for replacing energy-intensive products such as steel, aluminum, plaster board, and concrete.

Burschel et al. (1993) calculated that longer rotation periods could increase carbon stocks in Germany by 0.7-1.8 Mt C yr-1 in the first 20 years but would have adverse effects (on industrial roundwood productivity and carbon sequestration) if further extended because of higher risk of natural damages. For forests in Russia and the northwestern United States, intensive management reduces forest carbon stocks below the levels found in native forests, whereas increasing rotation lengths, retaining live trees through harvests, and decreasing site disturbance related to harvest and regeneration can substantially increase forest carbon stock (Krankina and Harmon, 1994; Krankina et al., 1996). These two studies did not consider the end-use aspects, however. Several authors have studied the impact on carbon sequestration (e.g., Plantinga and Birdsey, 1994; Boscola and Buongiorno, 1997; Boscola et al., 1997; Hoen and Solberg, 1997); the conclusion is that including the benefit of carbon will encourage the rotation age to increase.

Forest growth studies have shown that the impact of different thinning practices on total growth (and carbon sequestration) is insignificant in Germany (Strich, 1998). Row (1996) found that a thinning regime produces lower total carbon stocks in a 50-year Loblolly pine rotation than thinned stands; Lunnan et al. (1991) came to the same conclusion regarding lengthening the rotation periods when studied at the stand level. In addition, the decrease in timber supply caused by increased rotation length may shift the demand for timber to other stands that will be harvested instead-creating a high probability of leakage.

Optimal thinning and clear-felling times (and quantities) are interlinked and depend on other forest management measures (e.g., fertilization or plant density) and objectives. Hoen and Solberg (1994) carried out one of the few studies that analyzes thinnings, clear-fellings, and other silviculture measures (e.g., fertilization, types and intensity of regeneration) simultaneously for a boreal forest region, keeping harvest levels constant and maximizing carbon storage (including the end use and decay of wood products) for the region over a long period. The study illustrates that thinning and clear-felling times will be significant and will complement each other. For example, thinnings on good site classes substitute for clear-fellings on low site classes that have high standing volumes (but low annual growth and carbon sequestration potential if harvested). Boscola et al. (1997) show that the combination of harvest cycles and minimum cutting diameters can maximize carbon sequestration, at costs of US$1.2 t-1 C sequestered, for an increase in cutting cycles from 40 to 50 years in lowland tropical rain forest in Malaysia.

Methods, Uncertainty, Time Scale, and Monitoring
Yield tables or ordinary inventories seem sufficient for measuring changes in carbon stocks with confidence.

Verifiability, Transparency, and Permanence
See Fact Sheet 4.12.

Associated Impacts
This practice could have positive and negative environmental benefits regarding biodiversity, recreation, and landscape management, depending on local circumstances. The main barriers are the lack of incentives, including the risk of negative economic incentives.

Relationship to IPCC Guidelines
See Fact Sheet 4.12.

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