The predictive models derived adequately identified the clearwood which could be sawn from the range of pruned log types investigated. Comparisons with earlier results showed the clearwood potential of a large proportion of the "Transition Crop" logs was poorly represented under standard timber grades. Therefore it is proposed that appraisal of pruned sawlogs by their recoverable clearwood becomes standard practice. This would provide both an alternative and a complement to evaluations by timber grades, and promote better understanding of the potential of various pruned log types for sawn timber.

The negligible concentrations of clopyralid found in streamwater during this study, despite substantial rainfall (72 mm) within 3 days of spraying, were attributed to several factors: (i) the small proportion of catchment (16%) that was sprayed, (ii) the presence of unsprayed streamside reserves, (iii) the use of techniques that ensured accurate spraying and minimised spray drift, and (iv) the pattern of rainfall after spraying that included low-intensity storms followed by high-intensity storms.

The economic analysis included, for each species, the calculation of the internal rates of return and the net present values at the 5% and 10% real discount rates (on a pre-tax basis). The analysis indicated that the following real rates of return could be expected for each species: radiata pine 4.0-9.9%; cypresses 4.0-8.0%; eucalypts 3.1-7.5%; blackwood 5.3-8.0%; and black walnut 3.8-5.6%.

Significant differences in foliar nutrient concentrations among stands were unrelated to stand age. Total nutrient content was closely related to stand dry weight. There were considerable variations in soil nutrient concentrations which were unrelated to stand age except for phosphorus in the surface soils, which decreased with age. The weight and nutrient content of the litterfall was high and that of the forest floor low, compared with published data on Eucalyptus species. This indicates a high rate of nutrient cycling in New Zealand's E. regnans plantations which also have a relatively high level of productivity.

The most striking difference among the stands was their nitrogen economy. To a depth of 40 cm but excluding roots in the soil, the A. dealbata contained over 60% more nitrogen than P. radiata and 40% more than the E. regnans. Using pine as a basis, E. regnans and A. dealbata had accumulated 77 and 277 kg N/ha/annum for 8 years.

A Corrigendum to this paper is available here: Dry matter, energy, and nutrient contents of 8-year-old stands of Eucalyptus regnans, Acacia dealbata, and Pinus radiata in New Zealand

The weight of 1-year-old and total foliage peaked at about age 7, with older foliage forming an increasing percentage of total foliage weight as the stand aged. Live branch weight remained approximately constant but weight of dead branches increased with time. Loss of dead branch material through decay and shedding was about 5% per year. Maximum mean annual increment was 21 t/ha/yr and current annual production about 36 t/ha/yr.

The allocation of increment among components indicated a shift to stemwood production at the expense of needle, branch, and bark production throughout the 8 years of growth.