Náttúrufræðingurinn

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Náttúrufræðingurinn - 1981, Qupperneq 29

Náttúrufræðingurinn - 1981, Qupperneq 29
TAFLA III Tilraun til flokkunar tegunda og tegundahópa — Classificalion of species by response lo fertilizalion I Kornsúra ( Polygonum viviparum) Músareyra og vegarfi (Cerastium alpinum; C. caespitosum) II Stinnastör (Carex Bigelowii) Ljónslappi (■•1 lchemilla alpina) Krossmaðra (■Galium boreaie) Gulmaðra (Galium verum) Fjalldrapi (Betula Nana) Elftingar (Equisetum) III Vallhæra (Luzula multiflora) Axhæra (Luzula spicala) Hrafnaklukka (Cardamine nymanii) Hvítmaðra (Calium pumilum) gjöf að draga úr fjölbreytni gróður- lendis, og hefur það líka komið fram hér á undan. Þegar allt er dregið saman, eru það fyrst og fremst tegundir grasaættar, sem nýta sér áburðinn. Aörar tegundir geta oröið á undan við að nýla áburð i lítið grónu landi, en þær láta síðan undan grösum vegna hæfni þeirra siðarnefndu til að lifa í þéttum sverði. ÞAKKARORÐ Eyþór Einarsson grasafræðingur las handrit greinarinnar yfir og gaf mörg góð ráð og leiðbeiningar. Við kunnum honum bestu þakkir fyrir. SUMMARY Effects of fertilization on rangeland vegetation in Iceland by Jónatan Hermannsson, Andre's Arnalds and Ingvi Þorsteinsson Agncultural Research Institute, Keldnaholt, Reykjavík. Extensive fertilizer trials on native range- lands were initiated in 1966 by the Agricul- IV V Móasef Holtasóley (Juncus (Dryas tnfrdus) octopelala) Þursaskegg Blóöberg (Kobresia (Thymus myosuroides) arcticus) Fífur (Eriophorum) Sauðamergur I .ainbagras (Loiseleuria procumbens) (Silene acaulis) Krækilyng Hrjóstagras (Empetrum (Thalictrum nigrum) alpinum) Fléttur Bláberjalyng (Lichenes) (Vaccimum uliginosum) Grávíðir og loðvíðir (,Salix caUicarpa; S. lanata) Grasvíðir (Salix herbacea) Mosar (Bryophyta) tural Research Institute of Iceland. The trials were conducted both on the lowlands and highlands on 34 sites with varying vegetative covers and growth conditions. The effects of fertilizations on botanical compositions are reported (1) on total canopy cover, (2) on number of species, and (3) on individual species. Fertilizer levels of 50 — 85 kg N and 29 —38 kg P per hectare changed most dryland plant communities to almost pure grasslands in 2 — 3 years with over 80% canopy cover of grasses in most cases. The residual effects of two years of fertili- zation are discussed, on most sites the vege- tation gradually changed to the initials composition. The rate of the retrogression depends on growth conditions and vegeta- tion types of the sites. Some of the dwarf shrubs, especially Empetrwn nigrurn and Loiseleuria procumbens had difficulties in re- establishing themselves. 107
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