Trials of 16-26 years old progenies from Yingde Loblolly Pine Seed Orchard were investigated by sample plot investigation.The trial fields were located at Yingde Loblolly Pine Seed Orchard,Yingde Forest Research Institute,Jiuqushui Forest Farm of Wengyuan County,Shaoguan Forest Farm and Renhua Forest Research Institute respectively.The growth process and performance level were studied by stem analysis based on average trees.Compared with that of local Masson pine(Pinus massoniana),the seedlots of loblolly pine(Pinus taeda) from Hubei and the seedlot of slash pine(P.elliottii) from Taishan Slash Pine Seed Orchard,the growth potential of progenies from Yingde Loblolly Pine Seed Orchard in North Guangdong was comprehensively evaluated.The results are as follows: The fast-growing period of height for the progenies from Yingde Loblolly Pine Seed Orchard began at the age of 3 and lasted for five to nine years.For diameter at breast-height(DBH) it began at the age of 5 and lasted for five to eight years.The fast-growing period for volume in Yingde Loblolly Pine Seed Orchard began at the age of 10 and lasted to 25 years old,while it began at the age of 10 both in Yingde Forest Research Institute and Jiuqushui Forest Farm,and at the age of 12 both in Shaoguan Forest Farm and Renhua Forest Research Institute.The progenies from Yingde Loblolly Pine Seed Orchard performed well generally in North Guangdong.Shaoguan and Renhua were suitable for the cultivation of large-dimension timber with the rotation longer than 25 years.In order to cultivate largedimension timber,suitable fertilizer shall be used when the DBH growth reaches the fast-growing period,and thinning operation shall be conducted when the mean annual increment for DBH reaches the maximum.
