Topsoil translocation: One step from the tip
Transcript of Topsoil translocation: One step from the tip
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Topsoil TranslocationOne step from the tip
a wasted resource
or …from bitumen to
bush in a few steps…
Mark Walters Teacher - NSI Ryde TAFE
Let me start with a question
“How do you revegetate this degraded environment?”
A severely degraded environment, • Poor abiotics (bitumen, gravel, no natural soils)• Poor biotics (no native species or resilience, no beneficial
soil micro-organisms, abundant in weeds and weedy resilience)
• Will planting do???
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What is topsoil translocation?
“…moving seed-rich topsoil from good bushland to be developed (Donor) to a degraded site (Recipient)…”
• Builders send topsoil to landfills at great expense, or it is composted to provide landscaping topsoil.
• We are wasting a resource - the seed stored in the topsoil;• 89% of Sydney native species store seed in topsoil.• 80 – 90% of those seed are in top 5cm of the soil.
• Poorly used & understood in New South Wales, but used in Europe and Western Australia.
How is it done?
Fig 3: Recipient site readyFig 2: Topsoil strippingFig 1: Donor Site –Slash understorey & tree lopping
Fig 6: Plants in topsoil Fig 4: Topsoil layingFig 5: 18 months later
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So a possible answer is this…..
8 years later
What are the benefits? • As a Planning Tool
– Conserve biodiversity– Practical conservation of some ecological attributes– Planning tool of last resort “ as a condition of consent ”– Planning tool of last resort …as a condition of consent…
• As a Site Rehabilitation tool– Better ecological outcomes than traditional revegetation
• Greater species diversity• Topsoil’s abiotic & biotic features - optimum mix for reveg• Overcomes many limiting thresholds in revegetation (biotic & abiotic)
– Cheaper rehabilitation method.• ‘Set and forget’ approach – minimal weeding• Cost burden on developer as a condition of consent
General Question: Does the method work in Sydney’s sandstone areas?
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THE CASE STUDY: JJ Hills, Terrey Hills: Warringah Council
In Duffys Forest Vegetation Community a translocation opportunity presented itselfpp y p– an Endangered Ecological Community TSC Act 1995– 16% left, highly fragmented, confined to ridges
The Development site (Donor site) could not be saved– Already failed a Flora and Fauna (7 part test) & Species Impact
Statement (SIS)
A Council Consent Condition required the translocation of A Council Consent Condition required the translocation of the seed rich topsoil to a revegetation site– Developer pays and an opportunity to study the results
General Question: Does the method work in Sydney’s sandstone areas?
Study Sites• Terrey Hills – Sydney Northern BeachesDonor Site - Duffys Forest Vegetation
Recipient site - Former landfill site
Reference sites (REF) Reference sites (REF) -• 6 sites in 3 Age Classes• 19, 60 & 120 months since
fire
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Fast, Cheaper $$$
Costs $$$ vs. Plant outcomes
We asked 5 Questions - Questions 1 to 3
Slow, high $$$ Vs.
Q1. Does Leaf litter location have an effect?
On-top vs. Mixed-inSeparated with later top-dressing Non-separation at stripping
Q2. Do plants need a subsoil beneath the topsoil?
Subsoil-present vs Subsoil-absentSubsoil present vs. Subsoil absent
Q3. Are post-translocation germination stimuli needed?
Burnt vs. Smoke-products vs. Disturbance
Translocation vs Reference sites
Five Questions – Questions 4 & 5Two questions at study end, did the process
create a ‘natural’ outcome?
Translocation vs. Reference sites
Q4. Are vegetation structure and cover similar?
- Structure stratum - Ground cover - litter layer types
Q5. Are the ant communities similar?RESULTS NOT REPORTED
Ants are regarded as useful bioindicators for a variety of disturbances
e.g. Mining, Fire regime, Differing land use, Habitat disturbance
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Recipient Site JJ Hills - Plots Established
24 Experimental lots created (each plot 4-5 m x 10 m)
Factorial TreatmentsGermination - Burning vs. Smoke product vs.
Disturbance alone • 8 plots each
Leaf litter - mixed-in & ontop• 12 plots each
S b il P Ab tSubsoil – Present vs. Absent• 12 plots each
Q1 – 3: Leaf litter, Subsoil & germination treatments
SAMPLED: 5th, 19th, 40th and 60th months
Translocation Sites only
QUADRATS : Species and stem densities in 1m x 1m quadrats (2 quadrats per plot = 48 quadrats).
Figure 1: 60 months of growth note large number of Gum trees recruiting to site
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Sampling Q4: Vegetation Structure
Timing: 60th month
Translocation vs. Reference Sites
Cover in stratum>2m x 2m quadrats % cover estimated by eye for;
>Canopy >Midstorey
>Ground >litter type and depth>Translocation n =48; Ref sites n =96
Foliage Cover upto 2m in 20cmFoliage Cover upto 2m in 20cm increments
>2m Levy Pole - no. of live/dead contacts in each 10 x 20cm pole graduation.
>Pole Placements >Translocation n =96; Ref sites n =192
Q1: Results - Leaf Litter location Native Species Weed Species
Native spp. for On-top & Mixedfollowed same trajectory
Native spp 4 – 10 x more than weed
Vs
Native spp. 4 – 10 x more than weed
* p<0.01, other results not sig.
*
Native stems for On-top & Mixedf ll d t j tfollowed same trajectory
Native stems >> than weeds
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Q2: Results -Subsoil Present or AbsentNative Species
S i Ri h / 2
Weed Species
Native spp. for treatments follow same trajectory
Native spp 6–10 x >> weeds
Vs
Species Richness / m2 Native spp. 6–10 x >> weeds
Native stems for treatments
No significant results
follow same trajectory,
Natives stems >> weeds
Q3: Results -Germination treatmentsNative Species
S i Ri h / 2
Weed SpeciesTreatments converge at 40+ months
Native species 5 to 12 times more than weed sp. (Particularly burnt)
Vs
Species Richness / m2
N ti t 5 t 100 ti (Di t
Stem density converge at 40+ months
Native stems 5 to 100 times (Dist & Burnt) more than weed stems
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Translocation vs. Reference Sites - MDS Plots Q4 Levy Pole Results I: Veg Structure – MDS Plot
Translocated plots most similar to
same or older age class REFsitesclass REFsites
All Data were arcsine transformed; 30 repeats; Numbers = months; Contour lines shows single linkage Bray-Curtis similarity)
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3
4
pth
(cm
)
Leaf Litter depth (inc. SE bars) show 60 month translocated sites
= younger REF19 months
Translocation vs. Reference Sites - Graphs
Q4 Results: Litter Depth (cm)
0
1
2
t s e 9 0 0
Litte
r dep
y g
Bur
nt
Smok
ePr
oduc
t s
Dis
turb
ance
REF
19
REF
60
REF
120
Translocation Site Reference Sites
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Q4: Levy Pole in reference sites – ‘bush’
Q4: Levy Pole Results - translocation
Dense
Disturbance & Smoke treatments more similar
age class up high
Hollow under layer
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Conclusion – The General answerThe process worked resulting in;
1. High biodiversity outcomes• 35 - 70 seedlings/sqm ., • 6 - 12 species /sqm.,• 46 native species >> 42 spp. recorded on donor site!• Another site had 70+spp. vs. 106spp. before
Study shows cheaper options work;• No leaf litter separation or Subsoil required• Germination treatments converged after 40 months
Future study areasFuture study areas• Plant canopy species after translocation, or • Bring in donor canopy brush to the site• Use Burning, if weed invasion risk at recipient site • Burn donor site before removal?• Spread thinner topsoil depth permitting more area coverage?• No topsoil, Leaf litter alone?
Problems Managing a translocation
• Consent Conditions & Specifications not clear• Builder delivered subsoil, believing the topsoil is “rubbish”
• Council’s DA conditions translocation, but Construction Certificate ,CC, needed only AFTER veg clearance >> inappropriate clearance and damaged soils and plants
• Site clearance and then not translocating
• Not using experienced specialists• Excavation contractors / miners to do the work and mixing
t il i t b il dil ti db ktopsoil into subsoil – diluting seedbank
• Stockpiling topsoil• Seedbank killed by stockpiling – composting (recently
stockpiles measured at 50oC. midwinter)
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Same photopoint Top: Completed site Bottom : 8 years later
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Some References– Auld, T. and M. Tozer (1995). "Patterns in Emergence of Acacia and Grevillea Seedlings
after Fire." Proceedings of the Linnean Society of New South Wales 115: 5-15.– Grant, C. D., D. T. Bell, et al. (1996). "Implications of seedling emergence to site restoration
following bauxite mining in Western Australia " Restoration ecology 4(2): p146-154following bauxite mining in Western Australia. Restoration ecology 4(2): p146 154.
– Koch, J. M., S. C. Ward, et al. (1996). "Effects of bauxite mine restorations on topsoil seed reserves in the jarrah forest of Western Australia." Restoration Ecology 4(4): p368-376.
– Good, J. E. G., H. L. Wallace, et al. (1999). "Translocation of Herb-Rich Grassland from a Site in Wales Prior to Opencast Coal Extraction." Restoration Ecology 7(4): 336-347.
– Pywell, R. F., N. R. Webb, et al. (1995). "Comparison of techniques for restoring heathland on abandoned farmland." Journal of Applied Ecology 32(2): 400-411.
– Rokich, D. P., K. W. Dixon, et al. (2000). "Topsoil Handling and Storage Effects on W dl d R i i W A li " R i E l 8(2) 196 208Woodland Restoration in Western Australia." Restoration Ecology 8(2): 196-208.
– Vecrin, M. P. and S. Muller (2003). "Top-soil translocation as a technique in the re-creation of species-rich meadows." Applied Vegetation Science 6: 271-278.
– Ward, S. C., J. M. Koch, et al. (1996). "The effect of timing of rehabilitation procedures on the establishment of a jarrah forest after bauxite mining." Restoration ecology 4(1): p19-24.
– Ward, S. C., J. M. Koch, et al. (1997). "Ecological aspects of soil seed banks in relation to bauxite mining, I: unmined jarrah forest." Australian journal of ecology 22(2): p169-.