Some tree species can be established in the field directly from seed. Direct seeding involves:
- collecting seeds from native trees in the target forest ecosystem and if necessary storing them until sowing;
- sowing them in the restoration site at the optimal time of year for seed germination;
- manipulating field conditions to maximise germination.
Advantages of direct seedling:
- Inexpensive because there are no nursery and planting costs
- Transporting seeds to the site is obviously easier and cheaper than trucking in seedlings
- Trees that are established usually have better root development and grow faster than nursery-raised saplings because their roots are not constrained within a container.
- Implemented in combination with accelerated natural regeneration and conventional tree planting, direct seeding can be used to increase both the density and species richness of regenerants.
In addition to establishing framework tree species, direct seeding can be used with the maximum diversity method or to establish ‘nurse tree’ plantations, but it does not work with all tree species.
Potential obstacles to direct seeding
In nature, a very low percentage of dispersed tree seeds germinate and even fewer seedlings survive to become mature trees. The biggest threats to sown seeds and seedlings are:
- Desiccation
- Seed predation, particularly by ants and rodents
- Competition from herbaceous weeds
Burying can also reduce seed predation by making the seeds more difficult to find. Pre-sowing seed treatments that accelerate germination can reduce the time available for seed predators to find the seeds. Once germination commences, the nutritional value of seeds and their attractiveness to predators decline rapidly. But treatments that break the seed coat and expose the cotyledons sometimes increase the risk of desiccation or make seeds more attractive to ants. It could also be worth exploring the possibility of using chemicals to repel seed predators. Any carnivores that prey on rodents (e.g. raptors or wild cats) should be regarded as valuable assets on ANR sites. Preventing the hunting of such animals can help to control rodent populations and reduce seed predation.
Seedlings that germinate from seeds are tiny compared with planted, nursery-raised saplings, so weeding around the seedlings is especially important and it must be carried out with extra care. Such meticulous weeding can greatly increase the cost of direct seeding.
Directions for performing direct seeding are in "How to Plant a Forest" pages 58 to 62. For a broad discussion of the technique, please read "Restoring Tropical Forests: a practical guide" starting on page 140. For really detailed advice on direct seeding, click on the publications tab at the top of the page to access our research papers on the subject. Finally if you are considering using the technique, please send us details of your restoration site and we can probably recommend species suitable for direct seeding for your project.
1: Selecting suitable tree species for direct seeding to restore forest ecosystems in northern Thailand
ABSTRACT: To upscale restoration of tropical forest ecosystems, direct seeding—sowing seeds directly into the ground—is potentially more cost-effective than tree planting. However, its success is...
2: Developing Techniques for Direct-seeding for Forest Restoration in Northern Thailand
ABSTRACT: Forest restoration by direct seeding is potentially more cost-effective than tree-planting, especially for upscaling restoration of tropical forest ecosystems. Unfortunately, its success...
3: Differential seed removal, germination and seedling growth as determinants of species suitability for forest restoration by direct seeding – A case study from northern Thailand
ABSTRACT: Direct seeding is potentially a more cost-effective alternative to conventional tree planting for restoring tropical forest ecosystems. However, seed loss, due to removal and damage by...
4: Aerial robotics and forest management and seeding
ABSTRACT: Dronecoria is a reforestation project that uses customized DIY drones to disperse seeds (“dronechory”) in clay balls. Unlike traditional aerial seeding techniques, which often depend on...
5: A trait-based approach for selecting tree species for aerial seeding
ABSTRACT: We review recent ecological research on functional traits that can aid selection of tree species for restoration by aerial seeding. A major barrier in selecting species for restoration...
6: Smart seed for automated forest restoration.
ABSTRACT: Aerial seeding may be an effective way to restore forest ecosystems on inaccessible or remote sites; it has been used for almost 80 years in agriculture and now is a widespread practice...
7: Developing aerial seeding by UAVs: lessons from direct seeding
ABSTRACT: Direct seeding means sowing the seeds of forest tree species directly into the substrate of restoration sites. It is cheaper than conventional tree planting, but seed predation is high...
8: Seed storage behaviour of native forest tree species of northern Thailand
ABSTRACT: Storage of native forest tree seeds is essential for the development of seed-based forest restoration methods, such as direct or aerial seeding and for increasing representation of...
9: Sowing time and direct seeding success of native tree species for restoring tropical forest ecosystems in northern Thailand
ABSTRACT: Direct seeding (sowing seeds directly into ground) is potentially a cost-effective method of forest restoration that could replace or complement conventional tree planting, under certain...
10: Seed and Seedling Predation of Five Framework Tree Species in a Degraded Forest Area of Ban Nong Hoi, Mae Rim District, Chiang Mai Province
ABSTRACT: One limitation of forest restoration by direct seeding is seed and seedling predation by natural enemies. Natural enemies include both vertebrate and invertebrates. This study was set up...