Náttúrufræðingurinn - 1988, Side 62

6.8). Considering the coarse nature of the
soils and lack of organic materials, there is
a surprisingly high level of cations and cat-
ion exchange capacity, which may relate
to allophane clays in the soil.
The B horizon has on the average a
slightly higher organic content and a high-
er level of cations than the A horizon.
There are several possible explanations
for the higher organic content of the B
horizon. Roots may contribute to the level
of organic content, but there may also be
remnants of the soil that covered the area
before it was eroded.
The vast acreage of denuded areas in
Iceland is unique and it is difficult to find
a resemblance elsewhere except north of
the fully vegetated areas of the world, i.e.
in the Polar Deserts. The climate of Ice-
land is more favorable than the climate of
the High Arctic. Natural succession is ex-
tremely slow on the denuded areas and
some possible reasons are discussed. They
include: grazing, cycles of freezing and
thawing, needle ice formation, a small
seed bank, abrasion by materials blowing
on the surface, desiccation of the surface
in dry weather, the low biological activity
in the soil, the low nutrient status of the
soil, and leaching.
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