Studies on the standard of cleaning and thinning based on the crown diameter and the relative spacing for the ijyu (Scima wallichii Korthals ssp. liukiuensis Bloemb.) plantation
2003
Asato, I. (Ryukyu Univ., Nishihara, Okinawa (Japan). Coll. of Agriculture) | Touma, H. | Lu, Y. | Asato, O.
Ijyu (Scima wallichii Korthals ssp. liukiuensis Bloemb.) is one of the important reforestation tree species in Okinawa district. Cleaning and thinning have to be promoted for the healthy growing of the Ijyu plantation. However, the standard of cleaning and thinning have not been prepared yet. The standard of number of standing trees for cleaning and thinning was studied based on the crown diameter and the relative spacing. For Ijyu plantation, the first cleaning and thinning are necessary at age class 3 , before the mean d.b.h. reaches 10 cm. Then, the standard of operation is to regulate mean d.b.h. of 8cm, mean t.h. of 9m, number of standing trees per ha, of 3,000. It suggests that the suitable number of standing trees for management is about 15 % of the relative spacing.
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