What do tractors have to do with ecological restoration?

 Ross Carter Brown is a postgraduate student who wrote this article as part of his Euroleague for Life Sciences course work at Lincoln University. This is his second article for EcoLincNZ.

V-blade seeder. Image from Treesforlife.

Typically, when you hear the word “tractor” things like potatoes and McCain’s TV ads come to mind. You wouldn’t normally associate tractors with ecological restoration. However, these work horses of the agricultural industry have been busy in places like the USA and Australia in large-scale ecological restoration projects. They are used for both the direct seeding of woody plants and herbaceous species.  Traditionally, the main activity in restoration projects is the control of weeds and the hand planting of nursery grown stock to re-establish a native plant community.

The main problem with hand planting to re-establish plant communities is that it’s costly, very labour intensive, and usually only practical for relatively small restoration projects. Even if a majority of the planting is carried out by volunteers, you still have to buy the plants and the materials for protecting them once they’re in the ground. If you are paying contractors to do the planting then you are looking at whole lot more money. The cost of direct seeding can be as low as 35% of the hand planting cost . However, there are a number of things you need to consider before electing to use direct seeding in your restoration project.

Factors to be considered include:

  • Can I source enough viable seed of our selected species? Being able to source large quantities of viable seed is the main barrier to implanting direct seeding on a large scale
  • Can the restoration site be accessed by heavy machinery? Some restoration sites may be too steep or difficult to use seed drills or spreaders
  • Can I control weeds and pasture grass adequately and long enough to allow the establishment of seedlings? Normally blanket spraying of herbicide and ploughing is required for site preparation to give sustained weed suppression
  • Is my site wet enough? Sustained moisture levels are needed to ensure good germination and establishment rates. You may want to consider irrigation for dryer sites if there is water nearby.
Whakaipo Bay Community Planting Day
Whakaipo Bay Community Planting Day

Greening Australia has been running a program called “Whole of Paddock Restoration” for a number of years which involves the revegitation of degraded pastoral land. The revegetation involves retiring the degraded land from grazing which is then followed by direct seeding. Once the trees and shrubs are established, the land is brought back into production. The revegetation results in improved pasture and shade for stock whilst providing habitat for native species. Despite the successes of both direct seeding and traditional restoration plants we still need to be mindful of the overall goal.

Restoration projects tend to focus largely on the establishment of a native plant communities through the planting of nursery stock. Direct seeding is simply a cheaper way of doing this. Establishing a plant community of pioneer species does not constitute successful restoration of an ecosystem, or even after succession to a more developed plant community. There are other ecosystem attributes to be considered which can be summarised as:

  1. Composition: species present and their relative abundances including plants, invertebrates, birds, lizards, fungi etc.
  2. Structure: the vertical arrangement of plants and soil components (both living and dead)
  3. Pattern: horizontal arrangement of ecosystem components
  4. Function: ecosystem processes such as water, energy, and nutrient transfers/inputs/outputs
  5. Resilience: recovery from disturbance and successional processes.
4x4 Towed-Disc-seeder
4×4 Towed-Disc-seeder: Towed disc seeder. Image from Treesforlife.

As you can see direct seeding has huge potential for large scale restoration or to bring ‘life’ back into our agricultural land. The technique does have its limitations, so it’s important that we match the correct method with the site. We also need to be aware that restoring plant communities, as important as it is, is just one piece off a large puzzle.

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