Planting configuration affects productivity, tree form and survival of mallee eucalypt in farm forestry plantings
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Planting configuration affects productivity, tree form and survival of mallee eucalypt in farm forestry plantings Beren Spencer
. John Bartle . Amir Abadi . Mark Gibberd . Ayalsew Zerihun
Received: 24 February 2020 / Accepted: 18 September 2020 Ó Springer Nature B.V. 2020
Abstract Mallee eucalypts have been extensively planted in the Western Australia wheatbelt for salinity mitigation and as a short-rotation coppice crop for the production of cineole and bioenergy feedstocks. Mallee has been planted in wide-spaced narrow belts (2–6 rows) within annual crops and pasture, but optimal planting configurations have not been determined. Here, we assess the biomass yield responses of Eucalyptus loxophleba ssp. lissophloia and E. polybractea to; four row treatments (1, 2, 4 and 6 row belts) and five within-row spacing treatments (1, 1.5, 2, 3 and 4 m). Thirteen years after planting, the row effects on plot-level biomass productivity of E. loxophleba ranged from 4.3 to 21.2 Mg ha-1 year-1. For E. polybractea, both row number and within-row spacing affected yield, which ranged from 2.7 to 18.8 Mg ha-1 year-1. For both species, the highest growth rates were observed in the one-row belts with shorter (\ 3 m) within-row spacing. Within the belts, reductions of growth rate were observed with additional rows, due to increased competition and significant suppression of internal rows; and with wider within-row spacing, due to lower initial planting B. Spencer (&) A. Abadi M. Gibberd A. Zerihun School of Molecular and Life Science, Curtin University, GPO Box U1987, Perth, WA 6845, Australia e-mail: [email protected] B. Spencer J. Bartle Department of Biodiversity, Conservation and Attractions, Kensington, WA 6151, Australia
density. However, when including the area between belts, wider belts generated more biomass. For both species, average tree size decreased with additional rows and shorter within-row spacing. For both species, the number of stems per tree increased with wider within-row spacing, and also for E. polybractea, with fewer rows. The substantial variation in productivity, tree size and form found in these results will affect harvestability and ultimately the economic viability of future mallee plantings. Keywords Agroforestry Alley farming Tree belt design Bioenergy crops Oil mallee Spacing trial
Introduction Over the last three decades research has been undertaken to develop woody perennial crops to complement annual crops and pastures in the Western Australian (WA) wheatbelt. Economically viable perennial crops could help mitigate dryland salinity (Olsen et al. 2004; Bartle et al. 2007; Bartle and Abadi 2010). Lefroy and Stirzaker (1999) examined tree crop planting options for salinity management and concluded that integrated plantings would be preferred to segregated or rotated tree crop systems. In this case integrated plantings would take the form of wide-
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spaced narrow belts within the existing annual
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