Effect of different Acacia acuminata variants as hosts on performance of sandalwood (Santalum spicatum) in the northern and eastern Wheatbelt,Western Australia

The effect of seven ‘jam variants’ (Acacia acuminata typical variant, A. acuminata narrow-phyllode variant, A. acuminata small-seed variant, A. acuminata/burkittii variant I, A. acuminata/burkittii variant 2, A. burkittii and A. oldfieldii) on the survival and growth of sandalwood (Santalum spicatum) was examined in two relatively low-rainfall locations, Dowerin and Morawa, in the northern and eastern Wheatbelt of Western Australia. During the course of the trial (2000–2008) the mean annual rainfall was only 326 mm at Dowerin and 259 mm at Morawa. In July 2000, seedlings from 84 families from 18 separate populations and representing each of the seven different jam variants were planted on cleared farmland at both locations. A total of 4032 host seedlings were planted at each site. At host age 2 y (April 2002), S. spicatum seeds were sown near 1807 host plants at the first site and near 1397 hosts at the second.

The different jam variants were associated with clear differences in sandalwood performance at both sites. At age 1 y, mean survival of sandalwood was significantly greater near A. acuminata small—seed variant (64%) and A. acuminata narrow-phyllode variant (50–54%) than near A acuminata typical variant (21–34%). This pattern of sandalwood survival between the different jam variants was similar at age 6 y.

At age 6 y, the mean stem diameter (at 150 mm above ground) of sandalwood was the greatest near A. acuminata small-seed variant within each site: 62 mm at Dowerin and 47 mm at Morawa. The mean stem diameter of sandalwood near A. acuminata typical variant was 51 mm at Dowerin and only 25 mm at Morawa.

Stem borers were more common in A. acuminata typical variant than in the other jam variants at Dowerin. No borers were observed in the jam variants at Morawa. At both sites, gall rust was observed in each of the jam variants except A. oldfieldii.     

Ips grandicollis in South Australia

The present distribution of Ips in Australia and the probable reasons for it are discussed, and the effect of the thickness of the Lark of the host on the patterns of attack and the development of the brood are examined.     

Eucalyptus growth in relation to combined nitrogen and phosphorus fertiliser and soil chemistry in Tasmania

Two experiments were established to determine the early nutrient requirements for plantations of Eucalyptus globulus (Nabowla site) and E. nitens (Westfield site) in Tasmania, Australia. Nitrogen (N) and phosphorus (P) were broadcast together, 2 and 26 months after planting, at cumulative rates of up to 1200 kg N ha^?1 600 kg P ha^?1. Soil chemistry was characterised at each site in three profiles, and in all plots at the Westfield site. Nabowla has a relatively infertile, poorly structured soil, low in N and P, and receives about 800 mm of rainfall per annum. Growth was very poor without fertiliser, but trees responded rapidly and strongly to added NP. Stem volume increased directly with the rate of applied fertiliser, with no evidence that the response had peaked at the highest rate. Even at the highest rate of NP fertiliser, however, productivity was relatively low (mean annual increment about 15 m ha^?1 y^?1). Establishment of plantations on such sites is unlikely to be economically viable, with or without fertiliser, but fertile ex-pasture sites that are otherwise similar should be considered. Westfield has a relatively fertile, well-structured soil, and receives 1400–1500 mm of rainfall per annum. Response to NP fertiliser was delayed at this site, with first responses measured 33 months after planting. The response in stem volume was sigmoidal in relation to fertiliser rate, with a plateau at an application rate of 400 kg N ha^?1 and 200 kg P ha^?1. This rate of fertiliser is expected to increase mean annual increment from 20 (without fertiliser) to 25 m ha^?1 y^?1. Splitting applications of fertiliser at the highest rate did not alter the growth response.

Although high rates of N and P fertiliser may be required to maximise growth of eucalypt plantations in Tasmania on ex-forest sites, rates required during the first few years might be lower than those reported here if the timing and placement of fertiliser is optimised. Soil chemical analyses were indicative of N and P requirements, and about a third of the variation in growth across the Westfield site was accounted for by natural variability in initial concentrations of total P and exchangeable K in surface soil.