Náttúrufræðingurinn - 2009, Side 52

Náttúrufræðingurinn
136
útbreiðslu. Þó er um endurtekna
áfoksatburði að ræða og gróður
hefur sums staðar eyðst. Nýju áfoks-
geirarnir eru litlir í samanburði við
þá áfoksgeira sem eytt hafa gróðri
og jarðvegi á heiðunum í gegnum
aldirnar. Samt sem áður teljum við
mikilvægt að fylgjast með áfoki og
framvindu á þessum svæðum og
grípa inn í gerist þess þörf.
Lokaorð
Rannsókn okkar á gróðurframvindu
í áfoksgeira í Sandvík við Blöndulón
hefur þann annmarka að hér var
aðeins um eitt lítið og afmarkað
svæði að ræða. Æskilegt hefði verið
að kanna fleiri áfokssvæði við lónið,
hafa fleiri endurtekningar og mis-
munandi áburðarskammta. Aðstæð-
ur og umfang verkefnisins leyfðu
það þó ekki. Það er mat okkar að
í rannsókninni hafi fengist góðar
vísbendingar um skammtímaáhrif
sandfoks á mólendisgróður og við-
nám hans við því. Jafnframt hver
áhrif áburðargjöf hefur á gróðurinn.
Rannsóknarsvæðið í Sandvík var
tegundaríkt og nokkuð dæmigert
fyrir mólendi við lónið og víðar um
heiðar. Ekki er ástæða til að ætla
annað en að viðbrögð tegunda við
aðstæðum hafi verið lík því sem
annars staðar hefði verið. Við teljum
því að draga megi víðtækari álykt-
anir af niðurstöðum.
Summary
Effect of sand burial on alpine
heathland vegetation at
Blöndulón Reservoir, Iceland
Aeolian depositions have a negative ef-
fect on vegetation and can lead to a vast
devastation of vegetation and soil cover.
Since the enlargement of the Blöndulón
Reservoir in 1996 small aeolian deposits
have repeatedly formed on vegetated
land where sand is transported with dry
winds from the lakebed. The most ex-
tensive deposits formed in 2000 and
2005 during low reservoir water levels.
The aim of this research was to investi-
gate the effect of sand thickness on veg-
etation cover, species richness and com-
position in aeolian deposits formed in
2000 at an inlet on the northern shores of
the reservoir. Vegetation and sand thick-
ness was measured on four transects,
with 40 sampling plots in total, in 2003
and 2007. Fertilizer was applied annu-
ally on two of the transects from 2004.
Sand thickness was greatest close to the
shore but diminished with distance in-
land. Thick sand accumulated in depres-
sions and Betula nana bushes. Thickness
increased on sampling plots between
measuring periods due to repeated dep-
osition. The principal variance in vege-
tation cover was mainly related to sand
thickness but also to the fertilizer appli-
cation. Species richness and total cover
decreased with increased thickness of
sand. Mosses and lichens were eliminat-
ed at 2.5−5 cm sand thickness, most
herbal species, dwarf shrubs, rushes
and sedges disappeared at 5−10 cm
thickness whereas shrubs and grasses
sustained or increased their cover in the
thick sand. Very few species survived 10
cm thick deposits, which determined
the critical sand depth for the heathland
vegetation in the area. In fertilized sam-
pling plots the total cover increased re-
gardless of sand thickness and the
number of species increased slightly.
Grasses dominated the cover, especially
Festuca richardsonii. Fertilizer treatment
enhanced the vegetation and it may be
used to prevent further vegetation dete-
rioration in deposition areas.
Þakkir
Rannsókn þessi er hluti af verkefninu „Grunnvatn, gróður og strandmyndun
við Blöndulón“, sem unnið var af Náttúrufræðistofnun Íslands fyrir
Landsvirkjun. Verkefnið var jafnframt meistaranámsverkefni Olgu K.
Vilmundardóttur í landfræði við Líf- og umhverfisvísindadeild Háskóla
Íslands og var styrkt af Rannsóknarnámssjóði Rannís. Þeim starfsmönnum
Náttúrufræðistofnunar sem komu að rannsókninni, Hugrúnu Gunnars-
dóttur og Victori Helgasyni á Landsvirkjun, Guðmundi Stefánssyni og starfs-
mönnum í Blöndustöð kunnum við bestu þakkir fyrir aðstoðina.
Heim ild ir
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