This article was downloaded by: [Riege, Dennis A. 30 November 2009 Access details: Access Details: [subscription number 917246612] Publisher Taylor...
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PLEASE SCROLL DOWN FOR ARTICLE This article was downloaded by: [Riege,DennisA.] On: 30November2009 Access details: AccessDetails:[subscriptionnumber917246612] Publisher Taylor&Francis Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37- 41 Mortimer Street, London W1T 3JH, UK Scandinavian Journal of Forest Research Publication details, including instructions for authors and subscription information: Facilitation of afforestation by Lupinusnootkatensis and by black plastic mulch in south-west Iceland Dennis A. Riege a ; Adalsteinn Sigurgeirsson b a University of Maryland University College, USA b Icelandic Forest Research, Reykjavík, Iceland First published on: 30 November 2009 To cite this Article Riege, Dennis A. and Sigurgeirsson, Adalsteinn(2009) 'Facilitation of afforestation by Lupinus nootkatensis and by black plastic mulch in south-west Iceland', Scandinavian Journal of Forest Research, 24: 5, 384 — 393, First published on: 30 November 2009 (iFirst) To link to this Article: DOI: 10.1080/02827580903117404 URL: Full terms and conditions of use: This article may be used for research, teaching and private study purposes. Any substantial or systematic reproduction, re-distribution, re-selling, loan or sub-licensing, systematic supply or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material.
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ORIGINAL ARTICLE Facilitation of afforestation by Lupinus nootkatensis and by black plastic mulch in south-west Iceland DENNIS A. RIEGE 1 & ADALSTEINN SIGURGEIRSSON 2 1 University of Maryland University College, PSC 482, Box 178, FPO AP 96362, USA, and 2 Icelandic Forest Research, Mo ´gilsa ´, IS-116 Reykjavı´k, Iceland Abstract Afforestation has proven difficult in south-west Iceland in a region of degraded soils and high winds. Experiments at Keflavik International Airport began in 2002 to examine whether Nootka lupine (lupin; Lupinus nootkatensis ) or black plastic mulch facilitates establishment of Sitka spruce ( Picea sitchensis ), Hooker willow ( Salix hookeriana ) or downy birch ( Betula pubescens ) by ameliorating microsite conditions. By 2008, both lupine and black plastic mulch facilitated growth of all species at most plots. However, survival of spruce and birch seedlings decreased where dense lupine was accompanied by dense grass (but not in dense lupine alone). This indirect mechanism (nurse plant stimulation of competitor species) differs from prior models of shifts in balance from facilitation to competition under the stress-gradient hypothesis. Hooker willow performed best in both lupine and plastic mulch. However, in areas without dense grass, Sitka spruce continued successful growth and has potential for longer term afforestation. Planting seedlings into shallow excavations in lupine improved growth of willow and birch but not spruce. For afforestation in south-west Iceland, it is recommended that a mix of tree seedlings be transplanted directly into young lupine stands with sparse grass cover, with shelterbelts of seedlings planted into black plastic mulch along the stand edges. Keywords: Betula pubescens , competition, Nootka lupine, Picea sitchensis , Salix hookeriana , stress-gradient hypothesis. Introduction One plant species may have both facilitative and inhibitory effects on another species, depending on densities and circumstances (Callaway & Walker, 1997; Holmgren et al., 1997). Callaway and Walker (1997) proposed a model that stated that facilitative effects will increase under conditions of abiotic stress and will decrease in a natural succession as stress diminishes over time. Subsequent studies generally support this stress-gradient hypothesis (Go ´mez- Aparicio et al., 2004; Lortie & Callaway, 2005; Michalet, 2005; Veblen, 2008). In Iceland, Arado ´ttir (2004) found that Nootka lupine (lupin; Lupinus nootkatensis ) had competitive as well as facilitative effects on tree seedling establishment of native downy birch ( Betula pubescens ) and that the compe- titive effects increased as lupine cover expanded. In the present study, experiments were initiated at Keflavik International Airport, Iceland in 2002 to exploit a window of opportunity to plant tree seedlings in young lupine ± grass meadows. The timing allowed for examination of whether lupine facilitation might be superseded by competition as lupine density increased, in accord with the stress- gradient hypothesis. Iceland faces a formidable set of difficulties compared with other countries practicing afforesta- tion (O ´ skarsson & Sigurgeirsson, 2001). The climate is windy with low temperatures during the growing season. Soils are cold, wet and deficient in nitrogen. Frost heaving is common. Icelandic soils are of volcanic origin and most are andisols (Arnalds et al., 1995). Because of the volcanic origin and fine textures, the soils are highly susceptible to wind erosion. Human activity since the settlement of Iceland 1100 years ago has resulted in soil erosion and desertification of large areas (Magnu ´sson, 1997). The Sudurnes peninsula, protruding into the Atlantic Ocean, is an area of strong winds that has lost much of its original topsoil. The winds, Correspondence: D. A. Riege, University of Maryland University College, PSC 482, Box 178, FPO AP 96362, USA. E-mail: [email protected] Scandinavian Journal of Forest Research , 2009; 24: 384 ± 393 (Received 21 October 2008; accepted 11 June 2009) ISSN 0282-7581 print/ISSN 1651-1891 online # 2009 Taylor & Francis DOI: 10.1080/02827580903117404 Downloaded By: [Riege, Dennis A.] At: 14:19 30 November 2009
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