Definition

Surface boulder frequency

Surface boulders must be partly visible at the soil surface or their contours distinctly apparent at the surface. A surface boulder must not be covered by mineral soil, but it may have an all-over humus blanket (although it must not be covered by peat). It should be possible to loosen the humus blanket with a ’light‘ kick so that part of the boulder is exposed. (This rule may only be applied theoretically, since actions that affect the test area are not permissible. However, this test can be calibrated on boulders outside the test area.)

Surface boulders - number

The number of surface boulders within the test-/sub-area must be estimated and the frequency class recorded as one of the following:

Surface boulders - diameter

The diameter of a surface boulder must be represented by the average of the greatest and least widths in the soil plane, i.e. the area of the boulder should be projected on the soil plane and the lines for the greatest and least widths drawn through the centre of gravity of the projected area (thus the height of the boulder above the soil surface is not included).

If the test area has five surface boulders at most, their mean diameter should be specified. When there are more than five surface boulders, a typical boulder belonging to the most abundant size group must be identified and the diameter of this boulder specified.

The diameter of surface boulders should be recorded as one of the following: