Summary (from the scientific paper: Willoughby et al., 2004a)
The history of direct sowing as a method of creating woodlands stretches back to the Middle Ages. We have recently initiated new research into direct seeding as a result of renewed commercial interest in the technique for lowland afforestation in the UK. Two commercially established sites were monitored, and three replicated field trials were set up.
It is concluded that commercial direct seeding practices involving sowing high quantities of tree seed (>100,000 seeds per hectare) with an agricultural cover crop, but no protection or weed control, were failing to establish new woodlands as reliably as might be expected if planting.
Replicated experiments on reclaimed and ex-agricultural land showed the clear potential for the use of direct sown Quercus petraea (oak) as an alternative to planting, but the cost of purchasing acorns may make its use as a pure sown crop impractical. Pinus sylvestris (Scots pine) was less successful.
Direct seeding of Fraxinus excelsior (ash) and Acer pseudoplatanus (sycamore) may have more potential, since they are fast growing pioneer species and the seed is relatively cheap, but initial experiments suggest more work is required on sowing date and weed control.
These experiments confirmed the value of protection and weeding when using direct sowing as a method of lowland afforestation, and showed no benefits from establishing cover crops or relying on naturally occurring vegetation to protect seedlings from browsing mammals. Further research into vegetation management, sowing dates, the fate of tree seed and alternative species is recommended.
- Direct seeding has a number of potential advantages over conventional tree planting for new woodlands, e.g. more rapid establishment, using less pesticides, more naturalistic, at cheaper cost.
- Direct seeding has potential for establishing links between fragmented ancient semi natural woodland, and for large scale woodlands. However, the process is more exacting and the outcome less reliable than planting.
- The technique is worth considering for new broadleaved woodland establishment on good quality lowland sites with lighter textured soils, where mechanised access is possible, providing ash, oak or sycamore form a dominant part of the species mix. Seed must be appropriately pretreated to overcome dormancy, and seedlings protected from browsing mammals and weeds. Agricultural cover crops are not recommended.
- Direct seeding is not recommended for any tree species on restock sites where seed eating mammals are abundant, or on heavy textured soils subject to winter waterlogging.
- Detailed practical recommendations have been issued in a new Forestry Commission Practice Guide (Willoughby et al., 2004b).
Willoughby, I., Jinks, R.L., Gosling, P.G. and Kerr, G. (2004a). Factors affecting the success of direct seeding for lowland afforestation in the UK. Forestry 77 (5), 467-482.
Willoughby, I., Jinks, R.L., Gosling, P.G. and Kerr, G. (2004b). Creating new broadleaved woodlands by direct seeding. Forestry Commission Practice Guide 16. Forestry Commission, Edinburgh.
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