The Botany of Iceland - 01.12.1930, Page 134

124
H. M0LHOLM HANSEN
We may distinguish between an area in whicli the moisture of
the soil is entirelj^ dependent on the precipitation throughout the
year, an area whose moisture throughout the year depends also on
the ground-water, and an intermediate area in wliich the moisture
of the soil depends on the precipitation in the summer, while in the
winter it is also dependent on the ground-water. This area is re-
presented bj' the jaðar vegetation.
If, on a gently sloping surface, we pass upwards from the jaðar
vegetation, we may distinguish here between three different zones
of moisture: a lower zone in the mo, where the influence of the
grQund-water is still demonstrable, the mo itself, where this influence
no longer exists, and an upper zone (the melar vegetation), which,
on account of its open vegetation, is exposed to a stronger desicca-
tion than the more densely covered mo.
If, from the jaðar vegetation, we pass downwards, we can like-
wise distinguish between three different zones of moisture: an upper
mýri formation, not very damp in the summer, a lower mýri for-
mation saturated with water, and frnally the flói, which is covered
with water throughout the year.
Thus we may distinguish between 7 different zones of moisture
in Iceland.
Z o n e I
Zone II
Z o n e III
Zone IV
Zone V
Zone VI
Z o n e VII,
comprises the Elyna mo at Bjork and the melar vege-
tation on Lýngdalsbeiði, at Lækjamót, and on Arnar-
vatnsheiði.
comprises the Arctostaphylos mo at Bjork, the ordinary
mo at Lýngdalsheiði, the high mo at Lækjamót, the mo
at Norðtunga, and tbe Betula nana mo on Arnarvatns-
heiði.
comprises the Calluna-Empetrum mo at Bjork, the moist
mo on Lýndalsheiði, and at Lækjamót, and the knolly
mo on Arnarvatnsheiði.
comprises the jaðar vegetation at Bjork, on Lýngdals-
heiði, and on Arnarvatnsheiði.
comprises the Salix mýri at Bjork and on Lýngdalsheiði,
and the knolly mýri on Arnarvatnslieiði.
comprises the Betula nana mýri at Lækjamót and Bjork
and on Lýngdalsheiði, and the level mýri on Arnar-
vatnsheiði.
íinally, comprises the flói vegetation at Bjork, on Lýng-
dalsheiði at Lækjamót, and on Arnarvatnsheiði.