Dynamic Variation of Pinus yunnanensis Forest Stands Infested by Tomicus piniperda

Each 847 sampled trees of Pinus yunnanensis infested by Tomicus piniperda in Changhu forest area of Lunan County and in Xiaobailong forest area of Yiliang County, Yunnan Province, were investigated separately during 1996~2000.There was obvious difference in growth status and infestation level by the beetle between the two localities at the initial stage, i.e., the growth status was worse while the infestation level was lower in Changhu forest area than those of in Xiaobailong forest area.The infestation by Tomicus piniperda developed quite differently between the two localities within the 4 years.The proportion of health trees dropped by 12.6%, 466 infested trees died and the mortality reached 55.0%, and the infestation was out of control in Changhu forest area.While the proportion of health trees increased by 29.7%, and only 219 trees died in the 4 years among the 847 sampled trees in the Xiaobailong forest area, and the mortality percentage was 25.9%, which sowed that the infestation was controlled to a certain degree.The results showed that the growth status of the pine trees was directly correlated to the infestation and damage level by the bark beetle.The growth status of the pine trees could influence the development cause of the infestation, and meanwhile the damage of the beetle constrained the growth status of the trees.