Native plant recovery in seeded and non-seeded plots following exotic Fennel

(Foeniculum vulgare) control on east Santa Cruz Island – ten years post treatment.

Channel Islands National Park

Clark Cowan, Biological Technician, Channel Islands National Park

Paula Power, Ecologist, Channel Islands National Park James R. Roperts, Channel Islands National Park

Thomas Stanley

Locator map of SCI and park

2007 Condition: Fennel dominates vegetation at Scorpion and Smugglers Project Goal: Treat all fennel east of Montanon Ridge Control fennel so that native plants recover and are the dominant vegetation at Scorpion and Smugglers.

Challenge: Treat every fennel plant on East Santa Cruz Island – 213 acres

Del Norte Trail Infested with fennel Some natives

1. CUT fennel stalks

2. BUNDLE fennel stalks

3. BURN fennel stalks

4. TREAT every fennel plant with Garlon 4 Ultra

MONITORING PLOTS SCORPION and SMUGGLERS

*10 - 1 m2 paired plots

*TREATMENT: Seeded

*CONTROL: Unseeded *Collect data each spring 2009 – 2012, 2018

5. Monitor success of treatment

Eriogonum grande var grande Eriogonum arborescens

Artemisia californica Coreopsis gigantea

0

5

10

15

20

25

30

35

40

45

2008 2009 2010 2011 2012

Year

Smugglers Seeded

Smugglers Unseeded

Scorpion Seeded

Scorpion Unseeded

Number of fennel seedlings in monitoring plots

Bare ground

23%

Litter 43%

Natives 9%

Exotics 25%

Scorpion Seeded-%cover n=10

Bare ground

9%

Litter 2%

Natives 29%

Exotics 60%

2008

2012 2008

Scorpion Seeded-%cover n=10 2018

16% Bare

ground

24% Litter

53% Native

s

7% Exotics

Bare ground

21%

Litter 37%

Natives 23%

Exotics 19%

Bare ground

9% Litter

1%

Natives 40%

Exotics 50%

Scorpion Unseeded - %cover n=10

2008 2012

Scorpion Unseeded - %cover n=10 2018

21% Bare

ground

40% Litter

22% Natives

17% Exotics

Bare ground

1% Litter 37%

Natives 1%

Exotics 61%

Smugglers Seeded -%cover n=10

Bare ground

2%

Litter 1%

Natives 40%

Exotics 57%

2008 2012

Smugglers Seeded -%cover n=10 2018

18% Bare

ground

13% Litter

52% Natives

17% Exotics

Bare ground

1%

Litter 34%

Natives 1%

Exotics 64%

Smugglers Unseeded -%cover n=10

Bare ground

1%

Litter 1%

Natives 0%

Exotics 98%

2008 2012

7% Bare ground

59% Litter

0% Natives

35% Exotics

Smugglers Unseeded -%cover n=10 2018

SO WHAT? As vegetation expanded in the absence of fennel, fewer fennel seeds germinated. Fennel seeds are likely lurking in the soil waiting for disturbance at which point they readily germinate. At Scorpion native plants will dominate the vegetation. At Smugglers exotic grasses dominate when fennel was removed and without seeding the exotics will continue to dominate; however, Coreopsis and Island buckwheat can successfully establish with additional seeding. Fennel can be controlled Treat in spring after rosette forms Use 1% Garlon 4 Ultra on rosettes in spring Use 2% Garlon 4 Ultra later when bolting begins Treat plants and seedlings each year for 10 years Fennel seeds germinated after disturbance.

Acknowledgements

NRPP – project funding Jim Roberts – fennel slayer

extraordinaire Volunteers

Santa Monica Trails Council Randy Nelson Lulis Cuevas

2008

2012

2008

2012

2008

2012