Ecological Engineering 64 (2014) 255–261 Contents lists available at ScienceDirect Ecological Engineering journa l h om epage: www.elsevier.com/locate/ecoleng To seed or not to seed in alpine restoration: introduced grass species outcompete rather than facilitate native species Dagmar Hagen a,∗ , Tor-Ivar Hansen b , Bente J. Graae b , Knut Rydgren c a Norwegian Institute for Nature Research, P.O. Box 5685 Sluppen, NO-7485 Trondheim, Norway b Department of Biology, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway c Faculty of Science, Sogn og Fjordane University College, P.O. Box 133, NO-6851 Sogndal, Norway a r t i c l e i n f o Article history: Received 24 June 2013 Received in revised form 8 November 2013 Accepted 20 December 2013 Keywords: Festuca rubra F. ovina Arctic and alpine restoration Field experiment Greenhouse experiment Facilitation a b s t r a c t Anthropogenic disturbance in alpine ecosystems is on the increase, and knowledge is needed about restoration methods and their long-term effects in these environments. Sowing seeds from introduced grass species has been a common approach to encourage the growth of new vegetation, but there is disagreement over the long-term effects. Little is known about native alternatives and their ability to promote establishment of native vegetation. We compared vegetation cover, species richness and soil conditions in a long-term field experiment in seeded sites and unseeded reference sites 21 years after seeding with a commercial seed mixture. We also tested germination and establishment of an introduced grass Festuca rubra and its native congener Festuca ovina and their effect on the establishment of the native shrub Betula nana in a greenhouse experiment in different soil types. In the long-term field exper- iment, the introduced Festuca species outcompeted rather than facilitated natural vegetation recovery in the seeded sites. Total vegetation cover was significantly higher in the seeded sites, but native veg- etation cover and species richness were significantly higher in the unseeded sites. In the greenhouse experiment, the native F. ovina showed a tendency to facilitate the seedlings of B. nana in contrast to the introduced F. rubra, which clearly suppressed B. nana seedlings. However, seedlings of the native shrub B. nana performed best when seeded without any of the species that are presumed to be facilitators or nurse species. Suppression by seeded grass was stronger on commercial peat soil compared to fine mineral soil and coarse soil. When seeding is used in restoration efforts, it is important to choose species that do not compete strongly with the natural vegetation. Fertilization and other soil improvements may even favor strong seeded competitors at the expense of native species. Hence the combination of seeding introduced species and improving the soil may delay successful alpine natural vegetation recovery. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Human-caused disturbances from the exploitation of natural resources, infrastructure development, and tourism are increasing in alpine areas, putting ecosystems, species under pressure. The accompanying loss of biodiversity, and habitat fragmentation sug- gest a need for ecological restoration to improve alpine ecosystem recovery (Aradottir and Hagen, 2013; Bullock et al., 2011). Natural recovery after disturbances in alpine, arctic environments is usually a slow process (Harper and Kershaw, 1996; Jorgenson et al., 2010; Rydgren et al., 2013). In these areas, the establishment, growth of plants, soil development all occur under conditions with short growing seasons, low summer and winter temperatures, and strong winds. If the disturbances are severe the mineral soil is exposed ∗ Corresponding author. Tel.: +47 99264856; fax: +47 73801401. E-mail address: dagmar.hagen@nina.no (D. Hagen). resulting in the loss of soil nutrient, and soil seed bank, which in turn creates increasingly deteriorating conditions for vegetation recovery. Assisted revegetation may speed up the restoration process in severely disturbed sites where succession proceeds slowly (Forbes and Jefferies, 1999; Jorgenson et al., 2010). A number of techniques are used for this purpose, based on ecological, monetary, aestheti- cal, logistic, and speed considerations (Aradottir and Hagen, 2013; Comín, 2010; Perrow and Davy, 2002). The main ecological pur- pose of these techniques is to provide the site with conditions that will facilitate further recovery, such as the accumulation of nutri- ents, provision of shade and lee, and protection from herbivores (Callaway et al., 2002). Positive results are particularly likely in alpine habitats, since they are subject to a variety of stresses and disturbances, and the abiotic environment is the primary limitation for plant growth (Brooker and Callaghan, 1998). The use of seeds from introduced grass species, often in combi- nation with fertilizer application, has been commonly used over 0925-8574/$ – see front matter © 2014 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.ecoleng.2013.12.030