Management of Thyrsostachys siamensis gamble plantation for shoot and culm production

Field investigation was carried out at 6-year-old plantation of Thyrsostachys siamensis with 4x4 m. spacing at Thong-Pha-Phum forest Plantation, Kanchanaburi province. The effects of culm cutting and the effect of shoot harvesting on clump production were studied. The former study was composed of 4 treatments; no thinning (control), 25, 50 and 75 % thinning of culms in each clump. The latter study was composed of 6 treatments; no shoot harvesting (control), harvesting shoots but remained shoots at certain periods as follows: first sprouting until 2 weeks, 3rd to 4th week, 5th to 6th week, 7th to 8th week and 9th to 10th week, respectively. Experimental design for both categories is completely randomized design. Results showed that clumps with 50 % thinning produced maximum number of new shoots (average 18.92 shoots/clump). In the no thinning clump, new culms produced were highest (10.78 m) biggest diameter (dbh. 3.34 cm) and perform the highest culm quality. The thinning intensity had no effect on survival rate, growth rate and total aboveground biomass of new culms. Survival rate of new culms in no-thinning clump tended to be the best (61.82 %). The 50 % thinning clump tended to produce highest aboveground biomass (19.03 tons/hectare). For shoot harvested after sprouting up to 2 weeks, the number of shoots produced were biggest (29.58 shoots/clump) but the survival rate of shoots/clump was smallest (17.38 %). In no shoot cutting clumps the number of new shoots produced were smallest (12.42 shoots/clump) but the survival rate of shoots/clump was the biggest (66.17 %) and the total biomass aboveground level were greatest (15.372 tons/hectare). Harvesting shoots during each designed period caused no effect on growth rate, height, dbh. and the quality of culms remained. In the clump with shoots harvested but remained shoots during the 3rd to 4th week produced the longest culm (10.95 m). The clump with shoot harvested after sprouting up to 2 weeks tended to produce the biggest culm (dbh. 3.37 cm).