The surneyed area is situatad at the north of Chengtu in the Min-kiang Gorge between Kuanhsien and Ying-Siu-Wan in Wenchuan Hsien, Lying at thp contact zone of the Tibetan Plateau and the Szechnan Basin，it is essentially a region of sieep mountains dissected by deep valleys, Allu-vial plain is strictly limited, except narrow river terraces which form the chief centers of agriculture Sheltered by high mountains, the Minkiang Gorge receives insufficient sunshine with low temperature but high relat-ive humidity.