Viable seeds in deposits of the former lakes Kvismaren and Hornborgasjön, Sweden

Abstract

The viable seed content in sediments from two shallow lowland lakes, Lake Kvismaren and Lake Hornborgasjön in south Sweden, was investigated and compared. The number of seeds per species and their depth distribution (0–50 cm) in the sediment were examined through germination trials in a greenhouse. Samples of sediments were given either an exposed moist treatment (Kvismaren and Hornborgasjön) or a submerged treatment (Hornborgasjön). The species composition of viable seeds differed considerably between the two lakes. The sediments in Kvismaren were dominated by Alisma plantago-aquatica L. and Carex spp. and in Hornborgasjön by Carex acuta L., other Carex spp. and Juncus spp. From the two samples sites in Kvismaren, 481 000 seeds m −2 and 248 000 seeds m −2 germinated. In Hornborgasjön an average of 48 300 seeds m −2 germinated. Exposed moist treatments resulted in the germination of 30 species. Submerging the sediment samples gave only 23. Depth distributions of seeds in the sediments differed strikingly between the lakes. Large numbers of seeds were found in a distinct horizon ∼ 25 cm below the sediment surface in Kvismaren. This horizon is interpreted as being the remains of an earlier vegetation stage. In Hornborgasjön the greatest number of seeds was found near the sediment surface.