We have been carrying out a series of investigations aimed at helping to define sites and situations where direct seeding, as a method for woodland creation and regeneration, is more likely to succeed.
What affects the success of direct seeding?
A former arable field direct-sown with a range of lowland trees and shrubs
Although, it has not been extensively practiced in Britain, direct seeding has several potential advantages over conventional planting or natural regeneration. Successful direct seeding depends on the:
- Quality of seed
- Quantity of seed sown
- Site selection
- Soil preparation.
Recent work has shown that the technique can be successfully used for creating new woodland on reclaimed or former-agricultural land, but it has not been successful at woodland sites (Willoughby et al. 2004).
Seed germination and seedling establishment are precarious stages in the life cycle of plants (Harper 1977). A range of factors can kill seeds and seedlings and these usually vary from place-to-place and year-to-year; this makes predicting outcomes difficult and contributes to the potential unreliability of direct seeding. These factors include:
- Soil condition and temperature
- Predation - in woodlands one of the main limiting factors is seed predation by seed-eating animals.
Even in new planting situations recommended sowing rates are very high, typically 100 000 to 200 000 seeds to hectare, in an attempt to overcome early losses.
The need to sow at relatively high rates reduces the economic advantage that direct seed seedling might have over conventional planting, and may preclude inclusion of more expensive seed in direct seeding mixtures.
If sowing rates are to be reduced, reliability increased, and the technique extended to other situations, then it is important to find out more about the causes of losses and explore ways of overcoming potential limiting factors.
For further information contact:
Alice Holt Lodge
Surrey GU10 4LH
Tel: 01420 22255