School of Agriculture, Food and Ecosystem Sciences - Theses

Permanent URI for this collection

Search Results

Now showing 1 - 1 of 1
  • Item
    Thumbnail Image
    Growth of Pinus radiata (D.Don) stands in relation to intra- and inter-specific competition
    Bi, Huiquan ( 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.