島根県海浜砂丘における無花果樹の根群分布について

To investigate the root system of vigorous 6th years old fig tree on the sand dune, roots of the fig tree were digged and grouped together by the method as follows ; the Root zone was devided hbrizontally around the stem by 5 concentric circles of which radii were 1, 2, 3, 4, and 5 m, and vertically by the depth of 30, 60, 100, and 150cm from the surface of the ground. Then digged roots of each block were classified into 6 parts of root stem special large roots (Dia. over 20 mm), large roots (10-20 mm), middle roots (5-10 mm), small roots (2-5 mm) and fibrous roots (under 2 mm).
1. The raw root weight % of each class to all roots was as follows ; root stem : 9.14, special large roots : 15.63, large roots : 11.89, middle roots : 15.96, small roots : 16.47, fibrous roots : 31.78.
2. Roots more than 67 % distributed horizontally within 2 m-radius and roots to 30 cm in depth were about 61 %: and roots to 60 cm in depth were about 95%.
3. Fibrous roots extended horizontally more than 5 m from the tree and 58.6 % roots of them gathered within the limit of 0 to 60 cm in depth.
4. Top to root ratio of the fig tree was 0.87.