The Relationship Between Invasive Earthworms and Japanese ...

The Relationship Between Invasive
Earthworms and Japanese Stiltgrass

(Microstegium vimineum)

By David Friedman

Sleepy Hollow High School

Background

-Glaciation wiped out native
earthworms

-European settling aided
return

-Consume undergrowth and
seedlings

-Open canopy for invasive
plants

-Japanese stilt grass arrived 1919

-Large populations in
northeastern forests

-Significant threat to biodiversity

Importance

-Currently no good way to
eradicate earthworms

-Management focuses on
containment

-A connection between these two
species could help identify areas
prime for invasion

Hypothesis

-Studies have suggested that Japanese Stiltgrass raises
soil acidity, and that earthworms prefer normal to
acidic soil

-More invasive earthworms will be found in areas with
Japanese Stiltgrass

Methods

-18 total sampling areas, 9 with
Stiltgrass, 9 without, in three different
areas
-Mustard solution (pictured) draws
worms to surface of soil
-pH testing in lab done on soil
samples from sites

-Nitrogen levels, phosphorus levels,
soil temperature, and canopy
coverage also measured

Results

-Correlation between Average Number of Worms Found
Stiltgrass presence, and
invasive earthworm 12
population
10

Average Worms Found 8

6

4

2

0 Non-stiltgrass
Stiltgrass

Area

Results

Average pH

6.2

-Soil acidity slightly Average pH 6
higher in areas 5.8
with Japanese 5.6
Stiltgrass 5.4

5.2

5.694 5.628
5 Non-stiltgrass

Stiltgrass

Area

Worms Found Results

Effect of Soil pH on Worm Populations

16
14
12
10

8
6
4
2
0

5 5.2 5.4 5.6 5.8 6 6.2 6.4
pH

-More worms are found in less acidic soil

Results

Effect of Ant Activity on Worm Population

16

14

12

Average Worms Found 10

8
No Stiltgrass
Stiltgrass

6

4

2

0

No Ant Activity Ant Activity

Area

Interpretation

-Invasive earthworms appeared to prefer areas with
Japanese Stiltgrass

-Average pH in Stiltgrass areas similar to that in non-
Stiltgrass areas

-Worm population most likely levels out in soil with
slightly higher pH levels than found in tested soil

-Abundances of ants in soil seemed to deter worms
from occupying the same area

- This could be because of predation, or ant
consumption of worm food sources

Acknowledgements

I would like to thank Hillary Siener and Mike Rubbo.
Also, I would like to thank Oliver, Liv, and Eli.
And Steve.
And everyone else.

And Mom.