Fróðskaparrit - 01.01.2007, Page 184

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THE IMPACT OF GRAZING ON MOUNTAIN VEGETATION
AND THE ARBUSCULAR MYCORRHIZAL SYMBIONT
Plant responses
■ Grazing DEnclosure
25
Nardus Potentilla Carex Agrostis Euphrasia
stricta erecta panicea canina off. agg.
Fig. 3. Mean abundance of
plant species witli signifícant
response to grazing, in grazed
and ungrazed plots.
and two at high altitude (Fig. 3). The three
species that changed their abundance sig-
nificantly (p < 0.01) at low altitude were
Nardus stricta, which had the highest
abundance in grazed plots, while more
palatable grasses like Agrostis capillaris
and A. canina had the opposite trend. Herb
species like Potentilla erecta increased
their abundance in ungrazed plots signifi-
cantly (p < 0.01) and the same trend was
seen for Narthecium ossifragum although
these changes were not significant. Carex
panicea had a significantly higher (p <
0.01) abundance in grazed plots.
The two species that changed their
abundance at high altitude were Agrostis
canina, which was found to have signifi-
cantly (p < 0.05) higher abundance in un-
grazed than in grazed plots, and Euphrasia
sp., which had a signifícantly (p < 0.05)
higher abundance in grazed plots. In un-
grazed plots, we found that the abundance
of Deschampsia cespitosa, Bistorta vivip-
ara, and Salix herbacea increased while
the abundance of Festuca rubra increased
in grazed plots.
Most of the plants that had a significant
response to grazing were normally mycor-
rhizal, and fonu symbiosis with arbuscular
mycorrhizal fungi (Table 1). The species
examined for mycorrhiza in this study was
Agrostis capillaris whose mean abundance
was found to be slightly greater in un-
grazed plots. The difference was not sig-
nificant (Fig. 4). The roots were finer in
grazed plots at high altitude than in un-
grazed plots at high altitude, while there
was no signifícant difference in the roots
from low altitude (p < 0.01). The percent
root length colonisation (%RLC) was sig-
nificantly greater in roots from grazed
Agrostis capillaris at high altitude than at