The analysis of growth traits (height, diameter, volume of mean tree, total volume per hectare) all indicate that the Vietnamese sources are performing well, especially the Dathien source. The results thus indicate that the Vietnamese sources represent an interesting genetic resource, and that introductions and further exploration of the provenance variation of material from within that region could be an interesting route to follow in the future.
Also the Zambia CSO source has a high volume production at the same level as the Vietnamese sources, and is a good choice of seed source for plantation establishment on sites similar to the trial site.
Philippine sources (esp. Coto Mines) are also performing well in regard to growth. They have a fast height growth (Coto Mines is the top-ranking provenance in height growth), but a slower diameter growth, making the volume production lower than would be expected based on the height alone.
The Zimbabwean seedlot from John Meikle CSO is not among the top-ranking sources, which is somewhat surprising. The seedlot originates from only one clone in the orchard, and this might explain the somewhat disappointing performance. A ‘normal’ seedlot, sampling all clones in the orchard, would probably perform better.
The analysis indicates very clearly that P. yunnanensis has no potential on sites similar to the trial site. It is performing very poorly both in height and diameter. The same with the Myanmar sources Aungban and Zokhua.
The growth analysis results are in accordance with the results of Mullin et al. (1984). They reported, based on results from trial 31 at John Meikle Experimental Station, that the Vietnamese source from Dalat and the Philippine source from Benquet performed considerably better in height growth than Burmese and Assam sources. The Dalat source is close to the seed collection sites of the Hothien, Dathien and Lang Hanh sources in the present series.
Production potential, based on the best performing sources and based on growth in the first 6 years, is 15-17 m3/ha/year.
The survival percentage is high for all provenances, and there are no statistically significant differences among the top-ranking provenances.
Vietnamese and Philippine sources, esp. the Vietnamese sources, have more foxtails than Thai, Myanmar and P. yunnanensis sources. Foxtails may also lower the quality of the wood. The Zambian and Zimbabwean sources are intermediate in regard to foxtails.
The results on cone-setting should not be given too much importance because of the early stage of assessment. The results at this early development stage indicate that the Myanmar and P. yunnanensis sources have higher cone-setting than the other sources, and that the Vietnamese, Philippine and Thai sources set fewer cones.
In regard to woolly aphid, John Meikle CSO and Zambia CSO show the lowest levels of infestion. Apart from that, the picture is rather confusing, and there are no clear patterns of provenance variation.
The analysis of ‘leaning trees’ should be interpreted with care. First of all, the reason for the strange growth habit shown by many trees in the trial is not known, and it has not been experienced in any other trial in the series. It maybe a result of over-fast growth on favourable sites resulting in tree collapse (flops) as reoported in Armitage and Burley (1980). There are significant differences among the tested sources, but no clear geographical pattern of variation. Results may indicate that sources with faster growth have more problems than slower growing sources, but the picture is not very clear.
Because of pruning, branching habit could not be assessed and analyzed.
The seedlots from the clonal seed orchards in Zambia and Zimbabwe have the best stemform, suggesting that selection and improvement work have been effective. The Vietnamese sources also have good stemform, as have the landrace from Madagascar. The Philippine sources have a slightly poorer form, but are still above average.
In regard to wood density, the Philippine sources, esp. Coto Mines, are outstanding. They compare favorable to the seed orchard offspring from Zambia and Zimbabwe. The Vietnamese sources have lower basic density than the Philippine and seed orchard material, and this – together with the relatively high levels of foxtails – may be a constraint for a wider use of these sources.
There is good accordance between the results (straightness and wood density) in the present trial and the results of Mullin et al. (1984). They also found the Vietnamese source to have better straightness than other sources, and with a lower basic density that the Philippine source. They further found a significant negative correlation between basic density and altitude of provenance collection site. The results of the present trial confirms this negative correlation for the Philippine sources (only three sources, though), whereas no such correlation is present in the material as such.