Íslenskar landbúnaðarrannsóknir - 01.09.1980, Side 101

GRÓÐURSKILYRÐI, GRÓÐURFAR, UPPSKERA 99
The production of plant communities
Most of the measurements of the annual
yield of range plant communities in Ice-
land has been done by clipping. In the last
years a double-sampling method (a combi-
nation of clipping and estimates) has been
successfully applied.
Table 2 shows the average production
of the main plant communities in the peri-
od 1962— 1978, mosses and lichens not
included. As could be expected the
average production is considerably great-
er below the 400 meters elevation than it is
above. The production of the ground veg-
etation of woodlands is about 70 per cent
higher than the production of other com-
munities averaged together. This is an
indication of the reduction in the pro-
ductivity of the rangelands that followed
the destruction of the woodlands.
The moss heaths which are the most
extensive plant communities in the Ice-
landic highlands are by far the least pro-
ductive.
The plant preference of sheep
Studies on the plant preference ofsheep in
HEIMILDIR - REFERENCES:
Ingvi Porsteinsson og Gunnar Olafsson, 1965. Plöntuval
sauðfjár og meltanleiki beitarplanta. Freyr
10-11.
Ingvi Porsteinsson og Gunnar Olafsson, 1965. Efnamagn
og meltanleiki nokkurra úthagaplanta. Rit
Landbúnaðardeildar, A-flokkur, 17. 36 bls.
Ingvi Porsteinsson og Gunnar Ólafsson, 1967. Fjárbeit í
skóglendi og úthaga. Ársrit Skógræktarfélags
íslands. 6-14.
Ingvi Porsteinsson og Gunnar Ölafsson, 1969. Efnainni-
hald og meltanleiki nokkurra úthagaplanta II.
Islenzkar Landbúnaðarrannsóknir 1: 45—63.
Iceland using esophageal fistulated
sheep were started in 1964. These studies
have been carried out on many of the most
common plant communities, both on de-
teriorated and climax vegetation, on fer-
tilized and unfertilized rangelands and on
cultivated pastures in all seasons of the
year. An example of the results is shown in
fig. 1.
As can be expected, the botanical com-
position of the diet on open range varies
with plant communities and the variety of
plants available to the sheep. The general
tendency is, however, that from the be-
ginning ofplant growth in spring until the
end of the growing season herbs, many
grasses, different forbs and sedges, con-
stitute the major part of the diet. From
then on and until the start ofplant growth
the next spring, the diet consists mainly of
leaves and twigs of woody plants.
The most common range plant species
are graded into three classes according to
their palability during the growing sea-
son.
The main reasons for the different
palatability of plants are briefly discussed.
Ingvi Porsteinsson, Arnþór Garðarsson, Gunnar
Ólafsson og Gylfi M. Guðbergsson, 1970. Islensku
hreindýrin og sumarlönd þeirra. Náttúrufræð-
ingurinn 40: 145-70.
Sturla Friðriksson, 1960. íslenzku hreindýrin, Nátt-
úrufræðingurinn 30.1: 1—7.
Sven Skjenneberg, Lars Slagsvold, 1968. Reindriften:
52-76. Universitetsforiaget Oslo / Bergen /
Tromsö.