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Downes G.,Forest Quality Pty Ltd | Harwood C.,CSIRO | Washusen R.,University of Melbourne | Ebdon N.,CSIRO | And 3 more authors.
Australian Forestry | Year: 2014

Wood properties of 10-year-old trees in Eucalyptus globulus plantations at three sites in Western Australia were examined. Silvicultural treatments applied at age two years were stocking (unthinned, 1250 stems ha-1; thinned to 600 stems ha-1 or 300 stems ha-1) and nitrogen fertiliser application (0 or 250 kg ha-1 elemental nitrogen) in factorial combination. The three sites differed markedly in their annual rainfall (620-1100 mm), open-pan evaporation and soil water-holding capacity. Wood cores were collected at breast height from a total of 263 trees (~15 trees for each site-by-treatment combination), and radial samples prepared for analysis by SilviScan to produce radial profiles of air-dry density and microfibril angle (MFA) and modulus of elasticity (MOE), and by radial near infrared (NIR) surface scanning to produce radial profiles of NIR-predicted Kraft pulp yield (KPY) and cellulose content (CC). Sampling interval was 0.025 mm for density and 5 mm for the other properties. For wood property mean values (i.e. wood property averages of each pith-to-cambium sample), sites differed significantly only in air-dry density. The Boyup Brook site, which had low annual rainfall, the lowest climate wetness index and soil water-storage capacity and the slowest diameter growth, had the highest mean wood density (648 kg m-3), while Scott River, with the highest rainfall, had mean density that was 10% lower. The Wellstead site (low rainfall but highest soil water-storage capacity) was intermediate for density. The only other significant differences for mean wood properties were caused by fertiliser addition, which reduced NIR-predicted KPY from 54.6% (without fertiliser) to 54.1% and predicted CC from 43.7% to 43.1%. Clear radial trends were evident for all wood properties. Density, MOE, KPY and CC all increased from pith to the cambium, while MFA declined. From the innermost (pith) 10% to the outermost (cambial) 10% of the radius, density increased on average by 21%, MOE by 103%, KPY by 9% and cellulose by 11%, while MFA declined by 47%. NIR calibrations developed using the SilviScan and NIR spectral data explained 71% of variance in MOE for an independent set of radial wood samples of E. globulus from Victoria, but less than 50% of variance for density and MFA. Implications for paper pulp and veneer manufacture are briefly considered. © 2014 CSIRO.

White D.A.,University of Tasmania | White D.A.,Whitegum Forest and Natural Resources Pty. Ltd. | McGrath J.F.,Cooperative Research Center for Future Farm Industries | Ryan M.G.,Colorado State University | And 6 more authors.
Forest Ecology and Management | Year: 2014

This paper tests the hypothesis that thinning and nitrogen fertiliser can increase the mass of wood produced per volume of water used (evapotranspiration) by plantations of Eucalyptus globulus. We have called this plantation water productivity (PWPWOOD) and argue that, for a given genotype, this term integrates the effects of management, site and climate on both production and evapotranspiration. This is done using annual estimates of wood production and evapotranspiration from age three years to harvest age (~age 10years) in three E. globulus stocking density by nitrogen experiments. The ratio of annual rainfall to potential evaporation at these three sites varied from 0.85 to 0.45.Plantation water productivity (PWPWOOD) was calculated as the ratio of annual growth to annual evapotranspiration. In this study, the PWPWOOD of E. globulus varied from 0.2 to 3.1gkg-1 and was significantly increased by the application of nitrogen at two sites where growth was nitrogen limited. In fertilised stands, soil stored water was depleted early in the summer while in contrast, unfertilised stands used the water more slowly, thereby extending the growth season to late summer when average daily evaporation was much higher. Increased PWPWOOD in response to nitrogen was associated with an increase in water stress that could be mitigated by reducing stocking density without affecting either production or PWPWOOD.Plantations are managed at the compartment scale while water resources are monitored and managed at the catchment scale or larger. At the compartment scale, growth and PWPWOOD are correlated with evapotranspiration; managing plantations to maximise water use can also minimise the impact of wood production on water resources. © 2014 Elsevier B.V.

White D.A.,University of Tasmania | White D.A.,Murdoch University | White D.A.,Whitegum Forest and Natural Resources Pty Ltd | Beadle C.L.,CSIRO | And 3 more authors.
New Forests | Year: 2016

Wood volume growth per unit evapotranspiration was calculated from water balance and growth measurements in irrigated and water-limited Eucalyptus globulus and E. nitens plantations in the 3rd, 4th and 5th year of growth. Wood volume growth per unit evapotranspiration (plantation water productivity) was increased by irrigation for both species in the 3rd and 4th growing year but only in E. nitens in the 5th year. Irrigated trees required significantly less water than water-limited trees to produce 1 m3 of wood. At the same site, stomatal conductance was significantly greater in irrigated compared to water stressed trees through spring, summer and early autumn of each year. These data provide indirect evidence that leaf-scale measures of water-use efficiency are not well correlated with stand-scale measures of plantation water productivity. This was probably due to increased proportional allocation of assimilated carbon to stem wood in the irrigated compared to the water-limited stands. These results are consistent with recent studies in Brazil and Australia and suggest that plantation management systems, inclusive of tree breeding, that maximise growth rather than leaf-scale water-use efficiency, will also maximise the amount of wood produced from each unit of water used by the stand. © 2015, Springer Science+Business Media Dordrecht.

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