Fróðskaparrit - 01.01.2007, Síða 182

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THE IMPACT OF GRAZING ON MOUNTAIN VEGETATION
AND THE ARBUSCULAR MYCORRIIIZAL SYMBIONT
Methods
Sampling method
In 2000, two 25 x 50 m enclosures were es-
tablished in the area in order to exclude the
sheep. The vegetation was sampled in
eight meso-plots of 0.25 m2. These plots
were subdivided into 25 (0.01 m2) micro-
plots and the presence of all plant species
was measured. The abundance of each
species, ranging from 1-25, was deter-
mined for each meso-plot. The same
method was used to classify the vegetation
into plant communities (Fosaa, 2004).
At 600 m a.s.l., the vegetation was sam-
pled in 2000, used grazed plots, and again
in 2005 used as enclosed plots. At 70 m
a.s.l., the vegetation was samplcd both in-
side and outside the enclosure in 2006.
Thus the method for selecting vegetation
plots in the grazed vegetation was different
for the two altitudes. The vegetation cover
and the length of the tallest graminoid
were measured for each mesoplot.
For the mycorrhizal samples, three
small soil cores with Agrostis capillaris
were sampled randomly from grazed plots
(outside the fence), and from the enclosure
(inside the fence). In 2002, samples were
taken from both low and high altitude, a
total of 36 samples, but in 2003 only at
high altitude, a total of 18 samples.
Percent root length colonisation
The root clearing was a modified proce-
dure after Grace and Stribley (1991),
Koske and Gemma (1989) and Walker and
Vestberg (1994). The staining procedure
followed Vierheilig et al. (1998). Coloni-
sation was measured following McGonigle
et al. (1990). In addition to mycorrhizal
structures, an estimate of whether the plant
root at the intersection point was coarse or
fme was recorded (percent fine roots,
%FR). A typical fíne root was between 0.1
and 0.15 mm diameter, but a diameter up
to 0.20 mm could be considered as a fíne
root if the stele was poorly developed.
Statistics
The composition of plant species in grazed
and ungrazed vegetation plots was com-
pared at 70 m a.s.l. and at 600 m a.s.l. by
comparing richness of plant species and
abundances of plant species. All plant
species recorded were assigned to six life-
forms, which are herbs, graminoids,
sedges, woody, mosses, and lichens and
compared with a one way ANOVA. The
vegetation cover and the length of the
longest graminoid leaf in grazed and un-
grazed plots at 70 m a.s.l. and at 600 m
a.s.l was also compared with a one way
ANOVA. Species richness was calculated
by summing up the number of species in
each plot.
Statistics for fíne roots and mycorrhiza
were computed using univariate GLM in
SPSS 11.01 for Mac.
Results
After four years, changes were seen in the
vegetation. The mean increase in vegeta-
tion cover at the alpine site (600 m a.s.l.)
was 14% and the mean length of the high-
est grass leaf increased 25%, from 4.4 to
5.5 cm (Fig. 1).
At thc lowland site (70 m a.s.l.), the dif-