Study of the effects of different intensities of Thinning on yield Quantity and Quality of Loblolly pine (Pinus taeda L.) Plantation.
2005
Gorgi Bahri, Yusef | Hemmati, Arsalan | Mahdavi, Reza
In a 18-year-old Pinus taeda plantation in Pylambra region (Gilan province), 1.5 hectare of well stocked stand at 3x2meter spacing in 4 Replications and 3 treatmentsa: light thinning with 15% removing of basal area at 3 years rotation, b: heavy thinning with 30% removing of basal area at 5 years rotation and c: control selected and the effects of thinning operations on remained tree growth were studied during 15years. D.b.h, total hieght and stem volume, were annually measured and all data analyzed by SPSS program. The results show that: the age of 8-10 is suitable for precommercial thinning. The mean d.b.h., total hieght and basal area of trees in thinned plots are greater than unthinned plots. In thinned plots d.b.h.and hieght (35.8 cm, 22.6 m respectively) compared with the year of beginning of project (20.8cm, 14.4m )differ significantly, and mean volume increased from 0.29 to 1.3 m 3 per stem during 15 years. Equations for volume estimation of trees in 10-25 cm and 20-40 cm d.b.h. are presented for the Pylambra region. It is concluded that the d.b.h, total height and volume per stem of Loblolly pine increased with thinning. Heavily and lightly thinned plots produced higher total stem volume compared with the controlled plots and differences are significant at 5%. The stem and crown quality were gradually improved. According to total standing and removed volume, the mean annual volume increment are estimated up to 18.7 m3 per hectare. In conformity with the results, Loblolly pine is introduced as a adapted, resistante and high volume growth species in the coastal plain of Gilan province.
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