延安近郊达乌尔鼠兔种群数量与危害的调查

达乌尔鼠兔（Ｏｃｈｏｔｏｎａ ｄｌａｕｒｉｃａ）是陕北黄土高原延安附近的优势种，运用洞口系数法，对延安近郊３种样地的达乌尔鼠兔进行了初步的调查，发现达乌尔鼠兔种群数量与危害的面积率、生物量损失率呈正相关性，沟坡比山地危害严重，草地较林地、农田严重，农田与林地接近。

Preliminary investigation on the number and harm of daurian pikas nearby Yan'an

Daurian pika (Ochotona)is a dominant species of loess plateau nearby Yan'an in the north of Shaan.i province. A preliminary investigation on the harm of daurian pikas to three different habitats is carried out by means of coefficient-of hole. The result shows that there is a direct interrelation between the daurian pika population density and the rate of damaged area,harmed biomass. The damage in the ditch and the slope is more serious than that in the mountains,the grass land than the forest and the farm field; the damaged degree of farm field is similar to that of forest.