Effects of manual and mechanical removal of Ammophila arenaria on coastal plant

communities and dune morphology

Monique Silva-Crossman mrs75@humboldt.edu

Coastal Sand Dunes

Modified from Jackson 2011

Audubon

Study Sites

Removal Treatments Manual

Mechanical

California State Parks

California State Parks

Dune Morphology

• UAV • DJI Phantom 4

• Structure for Motion (SfM)/Agisoft

• Analysis included • Built a digital elevation

model (DEM)

• Compared treatment areas’ foredune height with Kruskal-Wallis test (α=0.05)

Ammophila arenaria cover Gold Bluffs Beach

0

1

2

3

4

5

6

7

Before 1 year post-treatment 4 years (May) post-

treatment

4 Years (September)

post-treatment

Mea

n C

over

Cla

ss A

mm

op

hil

a a

ren

ari

a

Time

Control

Mechanical

Manual

a

b

a

a

b c

d de

f

eg g

deg

(75- 100%)

(50-74%)

(25-49%)

(10-24%)

(5-9%)

(1-4%)

(>0-<1%)

(0%)

Shannon’s diversity index Gold Bluffs Beach

Stress: 0.138 PERMANOVA: F=31.88, df= 2, R2= 0.133, p-value=0.005

Gold Bluffs Beach NMDS

Stress: 0.115 PERMANOVA : F= 104.56, df=1, R2 = 0.440, p-value= 0.005

Little River NMDS

Stress: 0.139 PERMANOVA : F= 84.126, df=1, R2 = 0.321, p-value= 0.005

Tolowa Dunes NMDS

Gold Bluffs Beach Little River

Gold Bluffs Beach Little River

Results

• Both removal treatments lowed target species cover

• Native diversity was greater after removal in manual plots

than mechanical

• At both Gold Bluffs Beach and Little River mechanical

removal lowered the foredune

• At Little River the removal area had low dune hummocks

rather than a tall linear foredune

Management Implications

• Restoration goals will determine which removal

treatment to use

• Mechanical removal

• Decreased the cover of A. arenaria

• Price is lower

• Manual removal

• Native diversity is higher

Acknowledgements

• CSU Council on Ocean Affairs, Science

& Technology

• Alison O’Dowd, Erik Jules & David

Gwenzi

• Jim Graham & Jordan Adair

• Michele Forys, Amber Transou, Patrick

Vaughan & the California State Parks.

• Ayla Mills

• Robin Bencie

• Sugarboy Cannon

• Volunteers: Michael Rada, Marcel

Safford, Jacob Smith, Wendy Martinez

Murillo, Alex Magliano & Mark McCuen

Vegetation Monitoring • Monitoring in manual,

mechanical and control plots

• 1 m2 plots cover recorded to closest percentage point • converted to Braun-Blanquet

cover scale to match previous data

• Analysis included • Kruskal-Wallis test (α=0.05)

• Non-metric multidimensional scaling (NMDS) ordination with a PERMANOVA

Gold

Bluffs

Beach

Little River Tolowa Dunes

Mills 2015, Master Thesis

Vegetation Plot Layout

22.9m

18.3 m

13.7 m

9.1 m

4.6 m

18.75 m 12.5 m 6.25 m

Ammophila arenaria cover Little River

0

1

2

3

4

5

6

7

Before 1 year post-

treatment

2 years post-

treatment

8 years(May)

post-treatment

8 years

(September)

post-treatment

Mea

n C

over

Cla

ss A

mm

op

hil

a a

ren

ari

a

Time

Control

Mechanical

a a

a

a

a

b

c c

c

c

(75- 100%)

(50-74%)

(25-49%)

(10-24%)

(5-9%)

(1-4%)

(>0-<1%)

(0%)

Ammophila arenaria cover Tolowa Dunes

0

1

2

3

4

5

6

7

7 years(May) post-treatment 7 years (September) post-treatment

Mea

n C

over

Cla

ss A

mm

op

hil

a a

ren

ari

a

Time

Control

Manual

b b

a a

(75- 100%)

(50-74%)

(25-49%)

(10-24%)

(5-9%)

(1-4%)

(>0-<1%)

(0%)

Shannon’s diversity index Little River

Shannon’s diversity index Tolowa Dunes