Náttúrufræðingurinn

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Náttúrufræðingurinn - 2009, Qupperneq 52

Náttúrufræðingurinn - 2009, Qupperneq 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 Joeckel, R.M. & Diffendal, R.F. 2004. Geomorphic and environmental 1. change around a large aging reservoir: Lake C.W. McConaughy, Western Nebraska, USA. The Geological Socitey of America 10. 69−90. Olga Kolbrún Vilmundardóttir, Borgþór Magnússon, Guðrún Gísladóttir 2. & Þröstur Þorsteinsson (í prentun). Shoreline erosion and aeolian deposi- tion along a recently formed hydro-electric reservoir, Blöndulón, Iceland. Geomorphology (2009), doi: 10.1016/j.geomorph.2009.08.012. Bird, E. 2000. Coastal geomorphology. An introduction. Wiley, Chiches-3. ter. 322 bls. Martinez, M.L., Psuty, N.P. & Lubke, R.A. 2004. A perspective on coastal 4. dunes. Í: Coastal dunes, ecology and conservation. Ecological studies 171 (ritstj. Martinez, M.L. & Psuty, N.P.). Springer, Berlin. Bls. 3–10. Sigurður Greipsson & Davy, A.J. 1994. 5. Leymus arenarius. Characteristics and uses of a dune-building grass. Icelandic Agricultural Science 8. 41–50. Maun, M.A. 1998. Adaptions of plants to burial in coastal sand dunes. 6. Canadian Journal of Botany 76. 713–738. Owen, N.W., Kent, M. & Dale, M.P. 2004. Plant species and community 7. responses to sand burial on the machair of the Outer Hebrides, Scotland. Journal of Vegetation Science 15. 669–678. Skidmore, E.L. & van Donk, S.J. 2003. Soil erosion and conservation. Í: 8. Handbook of processes and modelling in the soil-plant system (ritstj. Benbi, D.W. & Neider, R.). Haworth Press, New York. Bls. 227−259. Ólafur Arnalds 1989. Sandur – sandfok. Í: Græðum Ísland, árbók Land-9. græðslunnar VI (ritstj. Úlfur Björnsson & Andrés Arnalds). Bls. 69–82. Ólafur Arnalds, Elín Fjóla Þórarinsdóttir, Sigmar Metúsalemsson, Ásgeir 10. Jónsson, Einar Grétarsson & Arnór Árnason 1997. Jarðvegsrof á Íslandi. Landgræðsla ríkisins og Rannsóknastofnun landbúnaðarins. 157 bls. Fanney Ósk Gísladóttir, Ólafur Arnalds & Guðrún Gísladóttir 2005. The 11. effect of landscape and retreating glaciers on wind erosion in south Ice- land. Land Degradation & Development 16. 177–187. Okin, G.S., Murray, B. & Schlesinger, W.H. 2001. Degradation of sandy 12. arid shrubland environments: observations, process modelling, and management implications. Journal of Arid Environments 47. 123–144. Guttormur Sigbjarnarson 1969. Áfok og uppblástur. Þættir úr gróður-13. sögu Haukadalsheiðar. Náttúrufræðingurinn 39. 68–118. Sigurður Þórarinsson 1971. Damage caused by tephra fall in some big 14. Icelandic eruptions and its relation to the thickness of tephra layers. Reprinted from the Acta of the 1st International Scientific Congress on the Volcano of Thera. Held in Greece 156th–23rd of September 1969. Okin, G.S., Gillette, D.A. & Herrick, J.E. 2006. Multi-scale controls on and 15. consequences of aeolian processes in landscape change in arid and semi- arid environments. Journal of Arid Environments 65. 253–275. Dugmore, A.J., Guðrún Gísladóttir, Simpson, I.A. & Newton, A. 2009. 16. Conceptual models of 1200 years of Icelandic soil erosion reconstructed using tephrochronology. Journal of the North Atlantic 2. 1−18. Guðrún Gísladóttir, Egill Erlendsson & Lal, R. (í prentun). Erosional 17. effects on terrestrial resources over the last millennium in Reykjanes, southwest Iceland. Quaternary Research. 78 3-4 LOKA.indd 136 11/3/09 8:33:32 AM
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