Shrubs and invasive mammals on retired crown land
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Shrubs and Invasive Mammals on Retired Crown Land. Andrea Byrom Richard Clayton, Roger Pech, Amy Whitehead. Crown land reform. More than half a million hectares may be used primarily for conservation by 2015 Biodiversity protection Soil protection Water conservation Landscape values

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Shrubs and Invasive Mammals on Retired Crown Land

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Shrubs and invasive mammals on retired crown land

Shrubs and Invasive Mammalson Retired Crown Land

Andrea Byrom

Richard Clayton, Roger Pech, Amy Whitehead


Crown land reform

Crown land reform

More than half a million hectares may be used primarily for conservation by 2015

  • Biodiversity protection

  • Soil protection

  • Water conservation

  • Landscape values

  • Carbon sequestration


Special habitats

  • Strong tendency for woody succession

Special habitats

  • Shrublands

  • Cushionfield

  • Herbfields

  • Grasslands

  • Tussocklands

  • Wetlands

  • Inland sand dunes

  • Saline habitat

  • Forest


Shrubs and invasive mammals on retired crown land

19% New Zealand’s land area

53,000 km2

83% cleared

3% protected

~50% NZ’sthreatened flora


A sequence of large scale biological impacts

A sequence of large-scale biological impacts

  • Kiore(1000 yr bp)

  • Burning(800 yr bp)

  • Burning and livestock grazing(150 yr bp)

  • Rabbits(150 yr bp)

  • Ferrets, stoats, weasels, (cats)(130 yr bp)

  • Exotic pastures and fertiliser(130 yr bp)

  • Hares, hedgehogs, mice, rats, possums, goats

  • Broom, briar, gorse, hawthorn

  • Cropping, viticulture, horticulture, dairying, forestry

  • Housing subdivisions


Shrubs and invasive mammals on retired crown land

Native biological diversity


Common management approaches

Common managementapproaches

  • Land retirement► changes in grazing, fertiliser, and burning (‘tenure review’)

  • Weed control

  • Rabbit control

  • Predator control to conserve native biodiversity


Public perceptions

Public perceptions

“The Department of Conservation is priding itself on the return of a huge section of Mesopotamia Station into its fold… how does it intend to manage .. land taken under the tenure review process?”

“.. the loss of any [wilding] pine is a loss to New Zealand’s ability to store CO2 .. millions of wilding pines are helping to stop climate change.”

Letters to The Press, 2008

“.. money that could be spent on fencing is spent instead trying to control the weeds that spring from seeds blown from DOC land…

Christine Fernyhough, ‘The Road to Castle Hill’, 2007


Former pastoral lease land

Former pastoral lease land

  • Successional plant communities

  • How to manage weeds and pests?

  • How to mitigate threats to biodiversity?

  • Potential for these systems to accumulate carbon


Focus on major changes

Focus on major changes

  • Grazing ceases when land retired to Crown

  • Removal of livestock can start successional change in plant communities

  • Grazing removal = ‘experimental manipulation’

  • Paired sites close to fencelines have similar physical characteristics


Grazing removal study aims

‘Grazing removal’ studyAims

  • Measure changes in weed and pest animal abundance

  • Measure changes in indigenous biodiversity

  • Provide in-depth understanding of ecosystem responses

  • Point to what to do next(research & management)


Hypotheses

Hypotheses

Removal of grazing will:

  • Influence shrub growth rates

    • Faster growth on ungrazed sites

  • Alter shrub recruitment processes

    • Release seedlings from grazing pressure

    • Increase competition from grasses

  • Increase plant species richness

  • Provide habitat for invasive mammals

    Manuka and matagouri

    (native shrubs)


Sites chosen

Sites chosen

  • Land retired from grazing in last 30 years

  • Well-maintained fence separated DOC land from grazed land

  • Paired grazed and ungrazed plots on each side of fence (n=8)

  • All located in Canterbury high country


Methods

Methods

  • Shrub measurements: volume, height, age (growth rings), stem diameter, weight(n = 10-30 shrubs/site)

  • Index surveys of invasive mammals

  • Plant richness (site and quadrat scales)


Results matagouri

F3

C2

• Grazed

+Ungrazed

B1

C1

Ln (stem diameter at 8 cm)

B2

Ln (plant age)

Results: matagouri

  • Grazing did not affect allometric relationships (e.g. age/diameter)

  • Similar results for plant weight, volume and height

C2 = P Williams data


Results manuka

1.0

0.8

0.6

Cumulative number of shrubs

0.4

0.2

Grazed

Ungrazed

0.0

0

5

10

15

20

25

30

Age (years)

Results: manuka

  • Significant effect of grazing on shrub volume, weight, & stem diameter

  • Evidence of a pulse in recruitment on ungrazed sites ~10-20 yr ago


Shrubs and invasive mammals on retired crown land

Results: native plant richness

20

15

10

Native vegetation richness

5

0

P = 0.015

Grazed

Ungrazed


Shrubs and invasive mammals on retired crown land

Results: pest animal responses

1.0

1.0

F1

F3

Rabbit

Hedgehog

B1

M1

F3

Rat

M2

B2

M2

NMDS axis 2

0.0

NMDS axis 2

0.0

Wallaby

B2

Non metric multidimensional scaling ordination (NMDS) & analysis of dissimilarity (ANODIS)

F1

B1

Hare

Possum

F2

C

M1

Mouse

F2

C

-1.0

-1.0

-1.0

0.0

1.0

2.0

-1.0

0.0

1.0

2.0

NMDS axis 1

NMDS axis 1

Grazed

Ungrazed

ANODIS: P<0.001


Crown land reform summary

Crown Land Reform: summary

► Release from grazing

► Shrub succession

  • Grazing effects on shrub dynamics & growth vary depending on species

  • Higher richness of native plants in ungrazed areas

  • Different guilds of invasive mammals associated with grazed vs. ungrazed areas

  • All have implications for ‘successional trajectories’


Management recommendations for retired crown land

Management recommendationsFor retired Crown land

  • Embrace complexity

    • take a broad ‘ecosystem’ view(surprises always around the corner)

  • General rules don’t always apply

  • Evidence-based science can support management programmes

  • Think long-term(high country is changing, but changing slowly)

  • Invest in monitoring


Thanks to

Thanks to

  • Foundation for Research, Science & Technology (funding)

  • DOC (logistic support)

  • Susan Walker, James Reardon, Susan Timmins, Liz Rayner & Peter Williams (discussions and reviews)


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