Natural recolonisation is considered to be the most ecologically sound approach to the establishment of habitats such as woodlands, grasslands, ponds and riparian vegetation.
The creation of a woodland, grassland or pond habitat using this method is dependent on a source of seed from an adjacent similar habitat.
When selecting this approach, it is important to be aware that the establishment of the habitat will take a lot longer than habitats which are established through planting or seeding. The length of time varies depending on the habitat type and the proximity of the site to the donor habitat which will provide the seed source. Seeds will arrive into the recipient site either by wind (anemochory) or by animals (zoochory) such as birds and small mammals.
The soil type should be similar in nature to that of the intended habitat type (i.e. should be the same as the donor habitat). Sites should be located adjacent to or as close as possible to the donor habitat (i.e. the source of seeds or propagules).
Sometimes suitable soil needs to be brought into a site to ensure compatibility for natural recolonisation. Checking and monitoring for non-native species is important when considering the importation of soil to a site.
The process of natural recolonisation can be assisted by planting. For example, when establishing an Oak-ash-hazel woodland (WN2), oak and ash whips of local or Irish provenance may be planted in a site to establish the woodland canopy. The understorey and ground flora species will gradually colonise the site over time, especially if adjacent to a WN2 woodland. If the site is immediately adjacent to WN2 woodland natural regeneration can be accelerated during ‘mast’ years by ‘scarifying’ (shallow ploughing with a harrow) the topsoil prior to seed fall to provide a good seed bed for the resultant seed. This applies to the development of any native woodland type.
In addition, soil can be brought in from a donor habitat which contains the seed bank of the habitat which you want to recreate. This often occurs where a proposed development may disturb a habitat, and as part of the landscape mitigation plan the soil from the habitat must be stripped prior to commencement of construction and utilised elsewhere to establish a compensatory habitat. The seed bank contained within the soil will speed up the natural recolonisation process.
Sods or ‘plugs’ from a donor site can also be utilised to complement planting. This approach requires the lifting of small sections of sod from a donor habitat ensuring that the sod contains both the plant and root stock and transporting it to the intended site where it is planted into the ground. This process provides a source of seed and a source of live plant material, which can grow and spread across the site. When considering this approach it is important to remember that the sods will need attention during storage and transportation to ensure that they do not dry out and may also need watering when they are placed in the ground.