Soil seed banks of woodland, heathland, grassland, mire and montane communities, Cairngorm Mountains, Scotland

Abstract

The size and species composition of soil seed banks were assessed at 111 altitudinally diverse sites in the Cairngorm Mountains. Mean densities of germinable seeds varied from 83 000 m⁻² in Scots pine (Pinus sylvestris L.) woodland at 230–490 m to 200 m⁻² in moss (Racomitrium lanuginosum (Hedw.) Brid.) heath at 1000–1120 m. Seed banks were dominated by Calluna vulgaris (L.) Hull, not only wherever it was prominent in the vegetation, but also at some sites with less than 5% cover of parent plants in the ground vegetation. Many species conspicuous in the vegetation were under-represented in or absent from the seed bank and surface vegetation generally was more species rich than was the underlying seed bank, especially in high montane communities. Multiple regression was used to examine the relationship between the density of buried Calluna seeds and the abundance of parent plants in the vegetation, site altitude and the organic matter content of the soil. The model fitted to woodland communities accounted for 95% of the variation in seed density. The heathland model was less predictive but still explained 52% of the variation in seed bank size. In mire communities there was no relationship, collective or individual, between buried seed density and the measured environmental variables, possibly due to variations in the duration and frequency of waterlogging at these sites. The potential role of seed banks for initiating the recolonisation of disturbed ground is discussed. Densities of buried seeds at most Calluna-dominant sites were probably sufficient to generate successful recolonisation but the prospects for recovery were poor at other sites, particularly in graminaceous communities at 800 m or higher.