The whole region was uplifted from below sea level after the last glaciation; the land at higher levels consists of moraine click here soil, whereas clay deposits dominate lower land areas. The topography within the region is relatively flat and the highest altitude above sea level on any of the eskers is 75 m. Fig. 1 Positions of the thirteen study sites in Uppsala County in east-central Sweden.

Names of numbered sites are listed in Table 1 The 13 study sites were all sand pits that had either been abandoned or had low levels of disturbance from mining activity (Fig. 1; Table 1). They were selected using records collected from the County Administration of Uppsala, i.e., their database (133 pits) and older inventory learn more maps (291 pits). The sources had partly overlapping records and many of the older pits have become overgrown. The criteria for selecting pits were that they should (1) represent a range of patch sizes (area 200–180,000 m2), (2) mainly consist of bare ground (40–95%), and (3) include sand and gravel material in various proportions.

The sites also needed to be isolated from each other by discrete habitat (minimum distance between sites was 225 m). The surrounding landscape (edge habitat) consisted of forest, open areas or a mixture of both. In this paper, the term ‘sand pit’ is used as a generic term for both sand and gravel pits. Table 1 Study sites in east-central Sweden (Fig. 1) and their characteristics as measures by six variables Study site Total area (m2) Area of bare ground (m2) Proportion of sand material (%) Vegetation cover (%) Tree cover (%) Edge habitat (1/0.5/0)a Interleukin-2 receptor 1 Vånsjöbro V 200 160 0 20 5 0.5 2 Vånsjöbro Ö 1,500 1,350 100 10 0 1 3 Lugnet 2,000 1,600 65 20 10 1 4 Nyboda 2,050 1,230 15 40 10 1 5 Vallsgärde

2,300 920 50 60 20 0 6 Mehedeby 3,600 3,240 100 10 20 1 7 Östanås 5,000 4,500 15 10 15 1 8 Aspnäs 6,600 3,300 100 50 30 0.5 9 Nyåker 7,000 6,650 100 5 40 0 10 Vappeby 50,000 45,000 5 10 15 0 11 Svedjan 74,000 70,300 5 5 65 1 12 check details Korsbacken 95,000 90,250 70 5 5 0.5 13 Skommarbo 180,000 171,000 5 5 5 1 aRefers to the amount of forest surrounding the sand pit; 1—surrounded by forest, 0.5—surrounded partly by forest and partly by open area, 0—surrounded by open area Environmental variables Six variables were measured at each study site (Table 1). The total area of the sites was defined as the original area of the pit, excluding edge areas of intruding neighbouring habitats. This area was calculated by a GIS program using GPS measurements taken along the site borders, except for two of the largest sites, for which areas were calculated from aerial photographs. Results obtained with the two methods were compared for the other sites, and were strongly correlated. Due to the topological shape of the pits, the area measurements are not the actual surface areas, however, the difference between actual area and the area calculated using our methodology has been shown to be negligible (see Triantis et al.