Long-Term Effects of Reclamation Treatments on Plant Succession in Iceland Jarngerdur Gretarsdottir, 1,2,5 Asa L. Aradottir, 1 Vigdis Vandvik, 3 Einar Heegaard, 3 and H. J. B. Birks 3,4 Abstract The long-term effects (2045 years) of reclamation treat- ments on plant succession are examined at two localities in Iceland that were fertilized and seeded from 1954 to 1979 with perennial grasses or annual grasses, or left untreated. The areas that underwent reclamation treatments had significantly higher total plant cover (7100%) than the untreated control plots (<5%), and floristic composition was usually significantly different between treated and untreated plots. Dwarf-shrubs (Calluna vulgaris and Empetrum nigrum), bryophytes, biological soil crust, grasses, and shrubs characterized the vegetation in the treated plots, but low-growing herbs that have negligible effects on the environment, such as Cardaminopsis petraea and Minuartia rubella, and grasses characterized the control plots. The seeded grass species had declined (<10%, the perennials) or disappeared (the annuals) but acted as nurse species that facilitated the colonization of native plants. It seems that by seeding, some factors that limit plant colonization were overcome. Soil nutrients, vegetation cover, litter, and biological soil crust were greater in the treated areas than the control plots. This may have enhanced colonization through an increase in soil stability and fertility, increased availability of safe microsites, increased moisture, and the capture of wind-blown seeds. This study demonstrates the importance of looking at the long-term effects of reclama- tion treatments to understand their impact on vegetation succession. Key words: erosion, grass seeding, Iceland, natural colon- ization, nurse species, ordination, reclamation, restoration, shrubs, succession. Introduction Iceland is an example of a fragile northern ecosystem where anthropogenic activities in conjunction with highly erodible volcanic soils and a harsh climate have combined to cause extensive vegetational degradation and soil erosion since set- tlement in AD 874 (Arnalds 1987; Hallsdottir 1987). The combination of severe erosion and a cold, moist climate is unique in the world (Aradottir & Arnalds 2001). It has been estimated that the vegetated land area around the time of settlement was about 5060% (Thorsteinsson et al. 1971; Haraldsson & Olafsdottir 2003). Recent satellite images (National Land Survey of Iceland 1993) show that only 14% of the country has a continuous vegetation cover and 13% is fairly well vegetated, but vegetation cover is poor on 23% of the country and near-barren deserts cover about 3545% (Arnalds & Kimble 2001). Vegetation cover on the eroded areas is usually less than 5%, there is still active erosion (Arnalds et al. 1987, 2001), and the rate of natural plant succes- sion is very slow (Gunnlaugsdottir 1985). The vast areas of degraded land and the very slow natural recovery demand effective reclamation methods based on ecological principles. An organized battle against soil erosion started about a century ago in Iceland, and broad-scale revegetation of land began about a half century ago (Runolfsson 1987). One of the most common revegetation methods involved fertilizing and seeding grasses (Festuca rubra and Poa pratensis). The short-term effects of these reclamation treatments have been studied in detail by Gunnlaugsdottir (1982, 1985). There is, however, limited documentation of the long-term effects of the reclamation treatments on natural colonization and vegetation succession. Some key questions are: Do the seeded grass species persist or dis- appear? Is the establishment of native species inhibited or facilitated by the seeded grass species? Unfortunately, no systematic time-series of the treatments exists, but infor- mation gained by investigating treatments of different type and age is of potential value. Understanding the processes of succession is the basis for directing vegetation change along desired trajectories during reclamation of degraded land (Bradshaw 1987a; Cargill & Chapin 1987; Whisenant 1999; Walker & del Moral 2003). In this study we attempt to ameliorate this lack of knowledge by investigating the vegetation on several reclamation treatments initiated for different purposes 2045 years ago, in two different regions of Iceland. Our approach is to use these areas as ad hoc experiments and evaluate the long-term effects of the reclamation treatments on revegetation and succession. Vegetation 1 Soil Conservation Service of Iceland, Gunnarsholt, 851 Hella, Iceland. 2 Present address: Agricultural Research Institute (RALA), Keldnaholt, 112 Reykjavik, Iceland. 3 Botanical Institute, University of Bergen, Alle ´gaten 41, N-5007 Bergen, Norway. 4 Environmental Change Research Centre, University College London, 26 Bedford Way, London WC1H OAP, United Kingdom. 5 Address correspondence to J. Gretarsdottir, email jarngerdur@rala.is Ó 2004 Society for Ecological Restoration International 268 Restoration Ecology Vol. 12 No. 2, pp. 268278 JUNE 2004