Potential genetic gains for carbon sequestration: a preliminary study on radiata pine plantations in New Zealand

Abstract

Preliminary estimates of gains in carbon sequestration, obtainable by applying genetic improvement, were calculated for radiata pine plantations in New Zealand. Data on height, diameter and wood density from New Zealand progeny trials were used to estimate family-mean heritability ( h F 2) and the phenotypic variance of half-sib family means for stem dry-weight production. Estimates of h F 2 ranged from 0.15 to 0.59 for the different trials. Based on unweighted averages of these genetic parameter estimates, the predicted gain for selecting the best 50 of 500 parents for dry-weight production, and the best 10 of 1000 parents, and making crosses between these parents, was 14.6 and 22.2%, respectively. The amount of carbon sequestered in the stem, branches and roots of typical stands of unimproved radiata pine was simulated using the C_Change option in the stand growth simulator stand treatment and growth simulation (STANDPAK). The amounts of carbon sequestered at the end of a rotation, and the long-term average (carbon held on site by growing radiata pine over successive rotations) were estimated. Carbon sequestered under a standard (‘direct sawlog’) management regime would differ among regions, from 211.2 tonnes at the end of a 28-year rotation in Canterbury to 322.3 tonnes on the East Coast. A ‘plant-and-leave’ low-cost regime sequestered more carbon than the direct sawlog regime with long-term averages at Kaingaroa of 102.9 tonnes carbon per ha and 85.3 tonnes per ha, respectively. The highest simulated genetic gain in long-term carbon sequestration for the standard regime was 29.3 tonnes per ha, for a stand grown in the East Coast region, using seed from the best 10 of 1000 ranked parents. Based on the highest estimated rate of carbon sequestration (East Coast, best 10 of 1000), and a value of 20 NZ$ per tonnes of carbon, the extra carbon credits attributable to genetic improvement, under the direct sawlog regime, would be worth 307 NZ$ per ha; the corresponding figure for the Canterbury region would be 151 NZ$ per ha. Owners of large post-1990 radiata pine plantings on converted farmland or pasture could gain large financial benefits attributable to genetic improvement, if trade in carbon credits becomes established. Assumptions for this study included extrapolating genetic parameter estimates to rotation age, and a similar allocation of biomass (to stem, branches and roots) for both genetically improved and unimproved radiata pine. Now that the potential has been established, more definitive estimates of genetic parameters, and better understanding of the effect of genetic improvement on carbon dynamics, are indicated.