School of Agriculture, Food and Ecosystem Sciences - Theses
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ItemGrowth of Pinus radiata (D.Don) stands in relation to intra- and inter-specific competition( 1989)This study investigated the growth of even-aged Pinus radiata stands in relation to intra-specific and inter-specific competition. The first part of the thesis used a data set of 30 year experiments together with a glasshouse experiment. A maximum stand biomass-density line was estimated for the P. radiata stands undergoing self-thinning. This line constrained the stand biomass-density trajectories of the individual stands. Growing along the trajectories, most stands increased the skewness of tree size distribution and the size hierarchy of the population. This was closely related to competitive status-dependent growth and death of trees in the stands. Height/diameter ratio decreased with competitive status. The relationship between them did not change significantly during stand growth. The experiment with P. radiata seedlings implied that competition for light was relatively important in affecting the growth, allocation and allometry of P. radiata during intra-specific competition. The second part of the thesis studied a 10 year old P. radiata plantation invaded by Eucalyptus obliqua. The study was done in conjunction with a replacement experiment with P. radiata and Eucalyptus regnans seedlings. The experiment revealed that P. radiata was more aggressive towards Eucalyptus regnans at the seedling stage. In P. radiata stands invaded by E. obliqua, the size and stem form of P. radiata was closely related to the polygon area defined by its by' E. obliqua neighbours. As the density of E. obliqua increased, its rooting density also increased. This related closely to the decrease in (1) rooting density, (2) aboveground tree size, (3) total projected leaf area, (4) total stem volume and to the increase in the skewness of size distribution and the size hierarchy of the P. radiata populations. The results suggested that competition for water and nutrients was relatively important for P. radiata in competition with E. obliqua in these stands.
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ItemThe effects of fertilisation and wastewater irrigation on the biomass and nutrient content of Pinus radiata D. Don( 1985)Detailed measurements were made of soil and stand characteristics before experimental plots were designed and laid out by collaborators from CSIRO. Fertiliser and irrigation were applied in a 2 x 2 factorial design, giving four treatment combinations. Irrigation commenced when the stand was 15 years old, and continued for 29 months; phosphorus at the rate of 5 g m- 2 was evenly broadcast as superphosphate when the stand was 16 years old. The study of biomass and nutrient uptake was comprehensive. Above-ground biomass was estimated by regression analysis of weights and dimensions of 24 sample trees, six trees being selected from each treatment. Standing litter was sampled, and root biomass estimated from core samples and by excavating the roots of one tree per treatment. Uptake of nine nutrients was estimated after measuring their concentrations in all components of the stand. Fertilisation with phosphorus had no effect on total above-ground biomass over a two-year period. Foliar analysis at the start of the study indicated that the trees were mildly deficient in phosphorus, but there was no increase in foliage biomass after fertilisation, despite substantial uptake of the applied nutrient. The lack of growth response was attributed to limiting soil moisture. This finding reinforces results of studies elsewhere that fertiliser responses are site-specific. (From Summary)