Covering pine-seeds immediately after seeding: effects on seedling emergence and on mortality through seed-predation

Direct seeding of Pinus sylvestris (L.) is a regeneration method of increasing popularity due to its comparatively low cost and potential for mechanisation. There is, however, a concern that seed losses to predators may jeopardise some seeding operations and means of reducing losses are therefore sought. In a study in northern Sweden, we studied the effect of covering seeds with a thin layer of the substrate on which the seeds were sown immediately after seeding. This lowered seed-predation from 9.1 to 2.9% and total seed losses from 64 to 45%. More seeds, 40% compared to 27%, failed to germinate when covered. At the end of the first growing season, 15.4% of the initially covered seeds were present as live seedlings compared to 9.2% of the seeds in the uncovered control treatment. However, although the trend remained the same, this effect was no longer significant after the first winter. The seedlings from the covered seeds were significantly larger, even after the second growing season. A complementary laboratory experiment showed that bank-voles, Clethrionomys glareolus, consumed significantly more seeds on the soil surface compared to covered seeds, but that they could find covered seeds with relative ease. We conclude that covering seeds immediately after seeding is a cost-effective way to reduce seed-predation and increase seedling emergence. (C) 2002 Elsevier Science B.V. All rights reserved.