Fig. 4. Color photos of IRIS. The IRIS numbers in parentheses refer to Table 1. The dotted black line represents the soil surface. (A) IRIS removed after 15 d in laboratory study (77), (B) IRIS removed after 24 d in laboratory study (73), (C and D) Duplicate IRIS show depletion of FH below 2 cm (53, 54); 4C shows several "white donut" patterns around 14 and 30 cm; 5D shows diagonal linear reduction pattern at 36 cm, probably caused by a root. (E) IRIS removed from natural soil during the year 2000 (19), (F) IRIS removed from filled soil pit near E the same year, (21), (G) IRIS removed from natural soil during 2001 (43), (H and I) (35 and 36) are duplicate IRIS, Fig. 5H shows depletion of FH below 2 cm, Fig. 5I represents three photos at 120° rotation and also shows depletion below 2 cm and shows "white donuts" at 14 cm and 18 cm, (J) IRIS installed in a Hamar soil shows complete removal of FH. (61), (K) IRIS installed in a Winger soil shows almost complete removal of FH from the upper part of the tube (65).