Project Description
Innovation in Conservation Symposium – May 10, 2024 – Ryde TAFE
Topsoil translocation- 25 years- What’s been learnt?
Mark Walters – Soil Translocation Specialist
Topsoil from development sites is usually headed for the tip and, although it’s distressing to see bush being cleared, the silver lining can be found in saving the seed-rich topsoil. Mark will be sharing how using translocated topsoil seed banks is an effective restoration method.
The project involved a team from Northern Beaches Council in Sydney, pushing the idea forward and people from National Parks got involved. This process is good, but it needs governance, and it needs recognition.
The first picture on the video shows sites that have been rehabilitated and shows how the site started and what the site looks like about two years later.
Planning
The first question to ask is how do you revegetate this kind of degraded environment? The land we identifies is owned by National Parks. Council was looking for a suitable site to translocate to. We ended up translocating topsoil and remediating the site.
The second thing is that once you have done the remediation, how do you measure restoration success. This is an industry wide question.
Using The Sera Guidelines.
https://www.seraustralasia.com/standards/home.html
https://www.seraustralasia.com/standards/NationalStandards2_2.pdf
Principle 4 states that full recovery is what you are aiming for. With topsoil translocation and the right site, results should be be good. The translocation sites have become self – replicating. Two of these sites have gone through fire – one eight years ago and one four years ago They have regenerated well, which is a test of restoration success.
SERA Attributes 5-star Full Recovery
The SERA wheel is a good way of looking at a site holistically and to work out where your opportunities are and where your limitations. You can download the SERA wheel from the SERA website.
Four of the six attributes.
The physical conditions. Look at the chemical and physical substrate of soils. If it looks similar to the reference community, you have succeeded. You are stealing that soil from a site and moving into another place The physical structure of the soil gets disturbed but the texture, the chemical properties and the nutrient status are retained.
Species composition. All the sites used had high levels of species diversity because we took the soil from a different site with the seed bank within it.
Structural diversity. Most of the sites did not have issues with structural diversity. Look at canopy, mid and ground layers. The big thing to focus on is getting soil with your ground layer and the shrub layer. Canopy often can be planted later or is naturally recruited from outside. Particularly if you are planting or revegetating and translocating to a disturbed area within a greater, healthier remnant.
Look at the structural diversity such as all your age classes and the structural layers. Initially because you are translocating, you will not have all the structural layers, but over time it will sort itself out. Trees take longer to appear and establish. But they will.
Ecosystem function – the acid test for any kind of community. Will that community become a self-replicating, sustaining, and resilient community that can resist external threats.
What is topsoil transportation?
It is where seed rich topsoil is moved from one site to another. You prepare a donor site and you prepare a recipient site. Donor sites have generally been given permission to be cleared as part of a development consent. The soil containing the seed bank can be relocated somewhere else.
For sandstone vegetation areas about 89 % of our species in those kinds of environments have some kind of seed bank that is stored in the soil, either ephemerally or persistently. Most of that seed bank is in the top five centimetres. If you can strip that layer of seed rich soil and relocate it somewhere else, you have an instant kind of starter kit for a whole revegetation process. This has been done in WA and Europe but not so common in New South Wales.
How is it done?
This is best seen in the video.
Identify a donor site and prepare it. There may need to be initial weed clearing and moving species that may be problematic later
Identify the area to translocate to and then start stripping down the donor site. The first thing you remove is the trees and maybe brush cutting or slashing the ground layer. Then take off a hundred millimetres of topsoil with an excavator. This ensuring you capture the entire seedbank and that any rhizomes come along as well. It is good to have a bush regenerator supervising the machinery who can identify what layer to scrape.
For the recipient site, there might be a need for some weed control.
Move the layers from the donor site. Start reconstructing the recipient site layer by layer.
Three case studies (best seen in the video presentation)
The recipient sites are
- 1999, JJ Hills, Terry Hills, Northern Beaches Council – a trial. Data was recorded the whole way through.
- 2000 Mona Vale Road North
- 2008 Moona Vale Road South
Managing a Translocation
- Do not forget about the other things that a translocation can deliver. That includes things like logs and debris that you can drag along from one site to another. Bring all the other material too.
- The edges of the site are important eg where adjacent land has weeds you will need to ensure these are controlled to prevent weeds moving into the translocation area. You have always got to be on top of your edge issues.
- Where subsoil is not loose enough, try to get a looser subsoil for drainage, so it does not shift towards a wet environment.
- Use people who know what they are doing.
- Do not stockpile your soil, as this is composting and will decompose organic matter and kill the seed bank.
References
References are listed on the video.
Presenter
Mark is a distinguished teacher at Ryde Tafe and has spent 23 years teaching certifications in conservation ecosystem management and has also made a mark in the private sector as an ecologist and a bush regeneration officer.