We studied the growth and water balance of young plantations of Pinus radiata D. Don and Eucalyptus grandis W. Hill ex Maiden irrigated with effluent for 3 years in a climate of high net evaporation. The plantations were irrigated weekly with secondary-treated municipal effluent at the estimated water-use rate, or at nominally twice or half this rate. Control plots were irrigated with bore water at their estimated water-use rate. Both species grew rapidly when irrigated with either effluent or bore water. The eucalypts irrigated with effluent at the estimated water-use rate closed canopy in 24 months, and at 34 months, mean dominant height was 12.1 m, stand basal area was 12.2 m(2) ha(-1), volume was 51.2 m(3) ha(-1), LAI was 5.7, and foliage mass was 6.5 Mg ha(-1). The pines in the corresponding effluent treatment had not closed canopy by 34 months. At this time, mean height was 5.0 m, stand basal area was 9.6 m(2) ha(-1), volume was 29.7 m(3) ha(-1), LAI was 3.5, and foliage mass was 7.3 Mg ha(-1). Water use by eucalypts was consistently higher than by pines, commensurate with their more rapid early growth, but the difference was not in proportion to the difference in leaf area. In the third year (when the eucalypts had a closed canopy), the eucalypts used 22% more water than the pines, but the annual mean LAI of the eucalypts was three times greater than that of the pines. The results suggest that (1) plantation water use by the two species on the same site will be similar for the same stage of canopy development, (2) eucalypts are not inherently more profligate consumers of water than pines when soil water is not limiting, and (3) stomatal control limits growth and water use of E. grandis in arid environments.

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The permanence and crediting of carbon storage in reforestation projects that are subject to timber harvesting is a key issue for project-level accounting of carbon sequestration in forests. With increasing momentum in the development of carbon markets, it is essential to establish a consistent and appropriate method for crediting that can be attributed to reforestation projects.Worldwide, the NSW Greenhouse Gas Abatement Scheme (NSW Scheme) is the first fully operational scheme that allows for the generation of carbon credits from sequestration in forests. The method used by the NSW Scheme to address the issue of permanence, known as the 100-Year Rule, limits the generation of credits from a given pool to the minimum carbon stocks that are maintained over a I 00-y period. This is an inequitable approach that does not adequately recognize the contribution that individual forest stands make in reducing levels of C0 2 in the atmosphere. It results in greater benefits to larger owners, and provides a disincentive for participation by smaller owners. This paper illustrates an alternative approach, based on the actual contribution by individual stands. The non-declining yield of a stand, when considered as part of a normal forest, provides a more equitable basis for crediting, especially for small-scale forest growers. This method is numerically equivalent to the 'average stocks' approach suggested by other authors, once pools of debris and soil carbon stocks are accounted for.This method of crediting is not only fairer in that it recognises more appropriately the contribution of projects, regardless of ownership boundary, but is far simpler to administer for managers of carbon pools aggregated over a number of forest owners. Greater benefits from carbon accrue to projects using longer rotations, providing incentive for the establishment of permanent forests that produce high-quality wood products.