Discussion of the trial results is based mainly on the Habinsaran trial. This is because of the many lost seedlings in the Aek Nauli trial (due to insufficient maintenance) that has influenced the growth and development.
The analysis shows not much promise for the tested sources of P. kesiya in comparison to the included controls - most of the tested controls have a considerably faster growth than the P. kesiya sources.
The two P. tecunumanii sources are superior to the other sources in regard to growth in both trials. The San Raphael provenance has a slightly better growth than the Mt. Pine Ridge provenance, but differences are not statistically significant. It would be interesting to test more sources of P. tecunumanii, as other origins may have an even greater potential. The company has such trials under way. Mean annual production – based on the results of the Habinsaran trial – is approx. 40 m3/ha/year.
Following P. tecunumanii are the two sources of P. oocarpa, but growth is considerably slower than P. tecunumanii. In the Aek Nauli trial, the two P. oocarpa sources have almost the same growth, whereas at Habinsaran, the Honduran source is faster.
Next in ranking is the local (Indonesian) P. merkusii source, and only then come the best P. kesiya sources.
Lang Hanh (Vietnam) and Bodana (Madagascar) are the best growth performers among the P. kesiya sources. It is interesting to note that the Madagascar source (landrace) almost certainly originates from the Central plateau of Vietnam (Armitage & Burley, 1980), i.e. from the same region as the Lang Hanh seed source. It was introduced from here to Madagascar in the 1920’s.
Doi Suthep (Thailand) may be mentioned together with the two other sources, mainly based on a relatively good growth in the Aek Nauli trial. It seems, however, that this source has a low survival rate.
P. patula shows little promise in the two trials. It is very slow growing, has a low survival rate, and generally looks unhealthy.
The poorest growth performer is the P. yunnanensis source with a volume production less than one fifth of the P. tecunumanii sources.
There are no statistical significant differences among top ranking sources in regard to survival. The best P. kesiya performers in regard to growth, Lang Hanh (Vietnam) and Bodana (Madagascar), also have a good survival. In the other end of the scale, P. patula, Doi Suthep (Thailand) and Aungban (Myanmar) have a low survival rate.
The P. yunnanensis source has a considerably lower frequency of foxtails than the P. kesiya sources, but the result has little practical value because of the extremely poor growth of this source. The high frequency of foxtails for the P. kesiya sources may be another constraint for a more intensive use of the species at sites similar to the test sites.
The P. tecunumanii, P. oocarpa and P. patula sources have the best stemform. P. merkusii has a considerably poorer stemform than the rest of sources, with the P. kesiya sources forming an in-between group. The Bodana (Madagascar) source is again among the best, whereas the Lang Hanh (Vietnam) has a poorer stemform.
The more slow growing sources generally have a better wood density (esp. Shangsi and P. merkusii) and thinner branches than the faster growing sources (esp. P. tecunumanii and P. oocarpa). The Lang Hanh and Bodana sources are again among the highest ranking sources of P. kesiya.