An investigation was performed on Acacia mangium plantations planted at Longyandong Forest Farm of Guangdong province in 1994. Height, diameter at breast height (DBH) and growing stock were measured at 5, 10 and 15 years old to study the effects of altitude and density on growth of A. mangium. The results showed that under the altitude condition from 0 to 500 m, the altitude did not have significant effect on DBH growth, but had obvious influences on height at 5 years old and growing stock at 5 and 10 years old. The forest stands at altitude >250 m and ≤500 m had the highest growing stock. Three kinds of density (800,1 335 and 1 998 trees per hectare) were found to have apparent impacts on height, DBH and growing stock, and the density of 1 335 trees per hectare yielded the highest growing stock. Additionally,different degrees of altitude by density (ABD) interactions were observed among A. mangium plantations. An increasing trend of ABD interaction was found for both diameter growth and growing stock increment, but the effect on height at the age of 15 was no longer significant.
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