Abstract:

It was investigated the harm of zokor for economic forest in Guyuan replacing agriculture by afforestation, the result showed that there was a marked correlative relation between the zokor density and the death rate of forest, y=-1.923 4+3.432 0x(r=0.934 8). On the basis of the losses of economic forest to various planting years damaged by zokor, the control cost, the tree price of almond etc., the control economic threshold value of zokor for economic forest was put forward. When the age of forest planted is 1 year, the control economic threshold value (density of zokor) is 1.907 ind·hm^-2 , when the age ranges form 2～4, the density is 0.989～1.273 ind·hm^-2 , when the age ranges form 4～6, the density is 0.859～0.989 ind·hm^-2 . According to the zokor density and the death rate of forest. The author established the divisiory standard of zokor harm to economic forest in replacing agriculture by afforestation.

Key words: replacing agriculture by afforestation, economic forest, zokor, economic threshold value