Revegetating Mined Rock: merely gathering moss

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Revegetating Mined Rock merely gathering moss?

• Rowan Buxton Craig Ross
• Landcare Research
• Jill Stanley, Peter Alspach Chris Morgan
  HortResearch

The research was funded by PT FREEPORT INDONESIA
and SOLID ENERGY INTERNATIONAL LIMITED
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Problems with revegetation of some mine sites

• Often harsh environments
• Steep sites up to 37
• Rock substrate is low in organic matter and
  nutrients, high in heavy metal concentration
• Acid rock drainage andpH issues
• Limited topsoil available
• Locally-sourced native species

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Natural revegetation after 50 years
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Revegetation by planting or direct transfer not
suitable on rock slopes
Plantings 7 yr old
Direct transfer
Shortfall of soil for over-tipping onto slopes
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Hydroseeding of native seeds not very successful
in these conditions

• Low germination rates for native seeds
• Seedlings not adapted to harsh environment of
  bare rock surface.

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Why Use Mosses For Revegetation of Mine Rock
Slopes?

• Mosses are successful natural pioneers.
• Some of the first plants to establish on bare
  rock surfaces.
• Tolerant of drying and rewetting cycles.

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Why Use Mosses For Revegetation of Mine Rock
Slopes?

• Begins the soil formation process, increases
  microbial activity, increases organic matter.

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Why Use Mosses For Revegetation of Mine Rock
Slopes?

• Stabilises slopes and increases
  evapotranspiration.

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Why Use Mosses For Revegetation of Mine Rock
Slopes?

• Acts as a nursery for vascular plant
  establishment.

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Why Use Mosses For Revegetation of Mine Rock
Slopes?

• Tolerant of naturally-occurring heavy metals.

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Why Use Mosses For Revegetation of Mine Rock
Slopes?

• Tolerant of low pH.

pH of 2.5
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Why Use Mosses For Revegetation of Mine Rock
Slopes?

• Easily propagated using vegetative fragments.

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Grasberg Mine, Papua

• Largest gold deposit and copper deposit in the
  world 4,000 m a.s.l. 4S of equator

Over 900 ha to revegetate
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Environmental conditionsGrasberg Mine

• Mean max temps 7 to 12C
• Mean min temps 2 to 6C
• Frosts possible throughout the year
• Rain on 80 of days
• Light levels for photosynthesis are low.

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Stockton Opencast Coal Mine, NZ 800-1,000m a.s.l.
Over 550 ha to revegetate
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Environmental conditions Stockton Mine

• Mean monthly temps 4C in winter, 13C in summer
• Rainfall can be over 6m p.a.
• Frosts snow possible for 7 months
• High wind run
• Fog low mist common.

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On-site Evaluation
Mosses, other plants, soil, rock types,
environment, topography
Access, equipment, locally-available resources,
personnel capability.
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Controlled Environment Trials

• Conditions based on 5 yrs Met data at Grasberg
  Mine
• Screening trials enabled a large number of
  treatment combinations to be examined.

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Moss biomass index (area x height)
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Controlled Environment Trials

• The most successful moss species combinations
  differed depending on the rock type.
• The collection site of the moss species
  significantly affected its establishment.
• The trial did not identify whether the difference
  in performance within a species was due to
  genetic variation, the amount and type of
  micro-organisms present at each collection site,
  other soil characteristics or a combination of
  factors.

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Rocktype 3Mildly acid-generating diorite
After 14 months
After 7 months
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Small Plot Trials Grasberg Mine

• Best combinations Moss cover of 12, 1.1 and
  1.7 for limestone, mildly-acid diorite and
  strongly-acid diorite respectively after 16
  months
• Demonstration plots on the acidic diorite rock
  suggested that different ratios of moss and mulch
  or protective cloches could result in moss cover
  of 2-10 within 7 months.

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Small Plot Field TrialsGrasberg Mine
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Small Plot Field Trials Stockton Mine
Control Granite Plots Moss-treated
Granite plots
Difference 6 months after treatment applied. N.B.
Using mixture of mosses, lichens herbs pioneer
seeds.
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Best Treatment Combinations Stockton Mine

• Vegetative cover increased from nil to 22.5 moss
  and 3.5 vascular cover within 18 months

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Small Plot Field Trials Stockton Mine
Webb2 3-yr-old South-facing Sandstone
slope Webb 6C 5-yr-old North facing Sandstone
slope Granite 1-month-old South-facing Granite
veneer slope Treated moss and vascular
fragments/seeds applied Control no treatment
applied
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Small Plot Field Trials Stockton Mine
Webb 2 3-yr-old South-facing Sandstone
slope Webb 6C 5-yr-old North facing Sandstone
slope Granite 1-month-old South-facing Granite
veneer slope Treated moss and vascular
fragments/seeds applied Control no treatment
applied
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Large Scale Trials
Hydroseeding
Dry Application
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Large Scale Trials After 5 months
Hydroseeding Treatment
Control
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Large Scale Trials
Dry Blower Treatment
Control
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Large Scale Trials

• Some sub-plots had 10-20 moss cover and 10-20
  vascular cover.
• This resulted in a total cover of 20-40 in small
  pockets of the rock dump slope.

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Large Scale TrialsMoss cover after 5 months

• 95 confidence limits
• Initial cover

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Large Scale TrialsVascular cover after 5 months

• 95 confidence limits
• Initial cover

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Need to Regenerate Harvested Areas
Grasberg Mine
Bryum after 16 months
Splachnobryum after 16 months
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Need to Regenerate Harvested Areas
Stockton Mine
Campylopus clavatus 7 months after removing moss
for use in revegetation trials
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Moss growth on nursery plot after 5 months
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Future Opportunities

• Methods have potential to be successful on other
  mine sites, roadside cuttings, quarries, stream
  embankments, natural slips and other disturbed
  sites.
• Methods need to be adapted for each site
  selection of suitable species their ratio,
  quantity and other ingredients.
• Potential to complement other rehabilitation
  methods e.g. hand-planting on flatter areas would
  provide seed sources for further succession on
  rock dump slopes.

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Summary of Rationale for this Technique

• Aim is to accelerate the establishment of mosses
  and other pioneer plants and therefore accelerate
  soil formation and natural succession.
• Technique should encourage maximum natural
  biodiversity by creating a range of micro-sites.
• Technique should enable rapid plant establishment
  on steep slopes thus reducing erosion rather than
  accelerating it by disturbance during
  hand-planting.
• Technique is likely to be cost effective and
  easy to execute.

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Using mosses for revegetation of bare surfaces
has potential for success on many mines and other
disturbed sites