• A non-native annual grass from Eurasia

• Dispersed widely throughout the western U.S., where it is

extremely invasive (Knapp, 1996).

• Few studies have examined the plant’s ability to invade natural

systems in the east

• We are studying the species in Duck Harbor, which is located in

Wellfleet, Cape Cod; more specifically, we are studying B.

tectorum found between the foredune and the bluff at Duck

Harbor

Bromus tectorum

To what extent do B. tectorum seeds tend to disperse?

Are there certain types of vegetation that may contribute to B. tectorum’s survival and thriving?

At what rate can the B. tectorum population grow annually?

The Potential for Invasion of Bromus tectorum In Cape Cod’s Dune System:

• B. tectorum seeds tend to disperse locally (< 1 m.), and there is a greater chance

of establishment if the seeds experience a slight disturbance, such as raking, in

order to settle just below the surface of the sand.

• Between 2012 and 2013, the count of B. tectorum seeds doubled on average

(spikelet lambda ranges from 1.18 to 2.71) and the number of individuals

increased six fold on average (plant lambda ranges from 2.09 to 21.0).

• Bromus Tectorum tends to grow in vegetation communities that lie at the interface

of both dune and heath communities, despite the fact that B. tectorum appears

not to thrive in either system individually.

• B. tectorum is capable of rapid population growth in eastern coastal systems.

• Certain plant communities (interface between dune and heath) may be most

susceptible to invasion and/or serve as indicators of B. tectorum presence.

• A moderate level of disturbance appears to promote B. tectorum populations in

natural systems.

We hope to expand our research sites in order to better understand the Bromus

tectorum invasion as a whole.

• Which additional factors allow the species to thrive?

• Are these conditions present in the species’ habitats in the west?

• Which additional factors determine an area’s invasibility?

Results:

Implications

Future Research

Acknowledgements:

Thank you to Professor Alden Griffith, Tania Ahmed, my

parents, Wellesley College, the Priscilla C. Patton

Endowment Fund, and Cape Cod National Seashore!

At what rate can the B. tectorum population grow

annually?

Mean

Population

Growth (λ)

Between

2012 and 2013

Bromus

Individuals

6.09

(2.09-21.0)

Total

Spikelets

1.97

(1.18-2.71)

Fig. 6: The map to the left pinpoints the exact locations of the four demography

plots within Cape Cod’s Duck Harbor.

Conclusions: Both the number of B. tectorum individuals and spikelets

increased (sometimes substantially) over the course of a year.

Surveying seeds and spikelets over the course of a year allowed us to

measure the doubling on average of B. tectorum seed production and

the average six fold increase of individuals.

Take Home Points:

(Population growth (λ) is the geometric mean with the minimum and maximum values in parentheses.)

Shivani Kuckreja ‘16, Tania Ahmed ‘16, and Professor Alden Griffith, Environmental Studies, Wellesley College

Fig. 1: This figure depicts the number of B. tectorum

seedlings that emerged (out of 100 seeds) in April of

2013. This experiment contains four conditions: a

seedling can either be in a barrier/undisturbed

environment, an open/undisturbed environment, a

barrier/disturbed environment, or an open/disturbed

environment.

Conclusions: As the statistics indicate, the barrier

treatment does not have a significant effect on B.

tectorum’s seedling establishment. However, seedlings

in the disturbed environment have the best

establishment rate of all of the conditions.

To what extent do B. tectorum seeds tend to

disperse?

B. tectorum seeds tend to disperse locally (no effect of barrier), and

there is a greater chance of establishment if the seeds experience a

slight disturbance, such as raking, in order to settle just below the

surface of the sand.

Take Home Points

Fig. 2: This figure depicts the mean total

number of spikelets produced per plot in June of

2013.

Conclusions: As the statistics indicate, the

barrier treatment does not have a significant

effect on B. tectorum’s mean spikelet

production. However, B. tectorum in the

disturbed environment has the greatest spikelet

production of all of the conditions.

Effect of disturbance:

p=0.003

Dispersal barriers: NS

Disturbance and

dispersal barriers: NS

Effect of disturbance:

p=0.021

Dispersal barriers: NS

Disturbance and

dispersal barriers: NS

Fig. 3: The leftmost map depicts the population of

B. tectorum within the plots and along the three

transects that we set up in Cape Cod’s Duck

Harbor. The three panels following the map depict

the % plot cover of Ammophila breviligulata,

Artemisia campestris, and Hudsonia tomentosa,

respectively.

Conclusions: B. tectorum tends to grow in the

same plots as both Ammophila breviligulata and

Artemisia campestris, but tends to remain absent

from plots with Hudsonia tomentosa.

Are there certain types of vegetation that may contribute to B.

tectorum’s survival and thriving?

B. tectorum tends to grow in vegetation communities that lie at the interface of both dune and heath

communities, despite the fact that the species appears not to thrive in either system individually.

Fig. 5: These six graphs depict the % cover of

the six plants that seem to have the most

potential association with B. tectorum, based on

overall patterns we observed within the plots at

Cape Cod’s Duck Harbor. (Fig. 3)

The lines represent logistic regression fits.

Conclusions: The % plot cover of A.

breviligulata positively correlates with the

presence of B. tectorum, as does the % plot

cover of A. campestris. The % plot cover of H.

tomentosa, however, negatively correlates with

the presence of B. tectorum.

Take Home Points

Fig. 4: This figure depicts the similarity and dissimilarity

among plant communities within plots along the three

transects. Circles that are closer to each other are most

similar in both the species they contain and the overall

plot cover. The size of the circle represents the number of

B. tectorum spikelets found within a plot. (The larger the

circle, the more spikelets found in the plot.)

Conclusions: There are many large circles within a close

proximity of each other which indicates that B. tectorum

presence is associated with specific plant communities.

References

A. Knapp, Paul. “Cheatgrass (Bromus tectorum L) dominance in the Great Basin Dessert: History,

persistence, and influences to human activities.” Global Environmental Change 6.1 (1996): 37-52.

Duck Harbor

Research Site

April 2013 Seedlings

Ap

ril L

og

See

dlin

gs (

± 1

SE)

June 2013 Spikelets

Ju

ne

Lo

g S

pik

ele

ts (

± 1

SE

)

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