Study On The Relationship Between The Damage Of Dendroctonus Valens LeConte And Forest Habitat Condition

Dendroctonus　valens　LeConte, was one of the most destructive pests to Pinus tabulaeformis, it's damage to trees was tightly associated with forest habitat condition. The relationship between forest habitat condition and the damage of Dendroctonus　valens　LeConte was studied at 81 sample areas in Huanlong county, Yichuan county, Hancheng county during 2002 to 2003. The results showed that this pest destroyed mainly the pines which its chest-high diameter were between 15cm-32cm, and the damage in pure pine stand is more severe than mixed stands. The pine stands in 1270m-1420m altitudes and in fattish slope were damaged severely. While at hillslope forest, the trees in lower slope and forest edge were damaged most severely, and then were the trees in middle slope and upper slope. The trees in shade-slope and semishade-slope were also damaged severely. All those damage conditions were associated with the pest's behavior and its preference to high humidity.