Investigating the fate of direct-sown seeds of birch, rowan, Scots pine and Sitka spruce on an upland clearfell site in North Wales
News from Forest Research: December 2008
Newly emerged Scots pine seedlings with threads still attached to the seed coats
Last winter, as part of a wider investigation into the potential for direct seeding in the uplands, Forest Research began to investigate the fate of direct-sown seeds of birch, rowan, Scots pine and Sitka spruce on an upland clearfell site at Clocaenog, North Wales. The aim was to identify the key factors limiting seedling establishment in order to help judge the viability of direct seeding for woodland regeneration, and to devise practical ways to improve the success rate.
Seeds were placed in the same environment as direct-sown seeds, with each one tagged to mark its location; they were then recovered some months later to determine what proportions had germinated, died or been removed. The biggest challenge was the small size of the seeds, which made tagging them difficult, but a technique used for larger, broadleaved seeds was adapted, which involves gluing a fine fishing line to each seed and tethering the other end to a stake.
It was expected that the test site would not sustain many seed-eating small mammals in winter, so environmental conditions would be the main factors affecting seedling establishment. Nevertheless, some rodent-proof exclosures were included to determine the extent of loss to predators. It soon became clear that for most species this was a key issue because nearly all tagged seeds placed outside the exclosures were rapidly removed. Inside the exclosures, however, over 90% of seeds were recovered, demonstrating the resilience of our tagging technique. Losses of birch seeds were high in all treatments, due to premature seed detachment; the technique has now been refined for birch and better results are expected this winter.
For further information please contact Richard Jinks at richard.jinks@forestry.gsi.gov.uk
See also studies on the fate of direct sown tree and shrub seeds
