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Associated Title(s): Global Change Biology
Use of cloned trees increases biomass production, reduces emissions
In the EU, there is increasing pressure to expand timber and biomass production in a sustainable and cost-efficient way. Management techniques such as intensifying and optimizing forest management using higher initial stand density, establish a suitable thinning regime, nitrogen fertilization, and a shorter rotation time can achieve this increase.
Routa and coauthors propose that, in addition to proper management, the use of improved regeneration material (such as clones) in Norway spruce could offer a large potential for integrated timber and energy biomass production. The authors used ecosystem model simulations to study the production of timber and energy biomass and its economic profitability. They compare cloned Norway spruce with non-cloned trees and include different management techniques. Wood for timber production included saw logs and pulpwood and for energy biomass production included logging residuals (foliage, branches, and top parts of stems not suitable for timber), coarse roots and stumps. Management techniques considered were stand density (2000 to 3000 seedlings ha-1), the timing and intensity of thinning, nitrogen fertilization, and rotation length (from 60 to 100 years). The authors also employed a Life Cycle Analysis/Emission calculation tool to assess the total net CO2 emissions per unit of energy produced based on energy biomass.
The authors found that cloned Norway spruce trees had 30% higher trunk diameter growth than non-cloned trees. This resulted in an increase in both timber yield (29–41%) and energy biomass (1–22%) compared with non-cloned trees. In general, nitrogen fertilization enhanced the growth of the trees, but reduced the yield differences between the cloned and non-cloned trees. These yield differences were also reduced by increased rotation length.
Growth of cloned trees had lower net CO2 emissions per energy unit compared with the corresponding emissions if non-cloned trees were planted. Without fertilization, this decrease was as much as 74% for rotation lengths of 60 and 80 years and 40% for a rotation length of 100 years. With fertilization, CO2 emissions were reduced to 67–76% regardless of rotation length.
Although clonal propagation is expensive compared to seed planting, the profitability of management with cloned trees was substantially higher than that found for the non-cloned tree. In addition, the use of cloned trees may have a higher potential to mitigate CO2 emissions from energy production.
Johanna Routa, Seppo Kellomäki, Harri Strandman, Johan Bergh, Pertti Pulkkinen, Heli Peltola, The timber and energy biomass potential of intensively managed cloned Norway spruce stands. GCB Bioenergy, 5:1 43–52. doi: 10.1111/gcbb.12002 Read this paper.