Woodlands - Fall 2017 - 8




Vast swaths of Pennsylvania
forests were clear-cut circa 1900
and regrowth has largely been from
local native plant communities, but a
team of researchers in Penn State's
College of Agricultural Sciences
has found that invasive, non-native
plants are making significant inroads
with unconventional natural gas
The spread of invasive nonnative plants could have long-term
negative consequences for the forest
ecosystem in a region where the
ubiquitous woods provide timbering
revenue, wildlife habitat and
ecotourism, warns team member
David Mortensen, professor of weed
and applied plant ecology.
In recent years, he and other
researchers at the University have
been tracking the ecological impact
of hundreds of well pads, access
roads and pipelines built to extract
gas from the Marcellus shale.
"Studies have shown that when
invasive plants such as Microstegium
vimineum (Japanese stiltgrass) move
into an area, it changes the plant
community, and native plants tend to
decline," Mortensen says. "Soon we
will see a ripple effect in the forest
ecosystem that will affect organisms
that depend on the native plants.
Ultimately, economic factors such
as timber harvests may be affected,
and wildlife and bird communities
likely will change."
This most recent Penn State study
documents that non-native plants
are rapidly invading Pennsylvania's
northern forests and establishes
a link between new invasions and

8 WOODLAND * Fall 2017

shale gas development activity. In
findings published in the Journal
of Environmental Management,
researchers show a direct correlation
between the extent of non-native
plant invasion and distinct aspects of
shale gas development.
To investigate, researchers
conducted invasive plant surveys
on and around 127 Marcellus
shale gas well pads and adjacent
access roads in seven state forest
districts in the Allegheny National
Forest. Study sites were distributed
across the Allegheny High Plateau,
which is dominated by mixed-oak
and Northern hardwood forests;
the Pittsburgh Plateau; and the
Ridge and Valley regions of central
Pennsylvania, dominated by mixedoak forests.
Sixty-one percent of pads had at
least one invasive, non-native plant
species, and 19 percent of those had
three or more species. Reed canary
grass, spotted knapweed, creeping
thistle, Japanese stiltgrass and
crown vetch were the most common
invasives found.
The study provides striking
evidence that invasive plant
presence on well pads is correlated
with the length of time since pad
construction; the number of wells
drilled per pad; invasive plant
abundance on adjacent well pad
access roads; and the density of
roads in the area of the pad prior
to construction. Using field data
from the 127 well pads, researchers
created a model to evaluate direct
and indirect relationships between
mechanisms and conditions that

could account for invasive plant
Surrounding plant communities
were also surveyed on a randomly
selected set of 32 well pads in the
study. Non-native plant cover was
greater on the disturbed well pad
edges than in the surrounding plant
Researchers found evidence that
invasive plants were introduced in
gravel delivered to build pads and
roads, and in mud on the tires and
undercarriages of trucks traveling
those roads, noted lead researcher
Kathryn Barlow, a doctoral degree
candidate in ecology. She pointed
out that previous Penn State
research demonstrated Japanese
stiltgrass seeds were moved by
road-grading equipment on gravel
roads in forests.
"Given the fact that, on average,
1,235 one-way truck trips delivering
fracturing fluid and proppant
are required to complete an
unconventional well, the potential to
transport invasive plant propagules
is significant," she says. Propagules
are parts of a plant that can generate
a new plant, such as seeds, spores
and roots.
"Material and equipment used for
road construction and maintenance
can play an important dispersal
role. Road development can
create pathways for invasive plant
establishment and spread," Barlow
Non-native plant invasion into
forests can lead to the demise of
native plants in surprising ways,
Mortensen pointed out, referring to a


Table of Contents for the Digital Edition of Woodlands - Fall 2017

Tools and Resources
Forests and Families
A Legacy to Keep
From Forests to Fermentation
Feathering a Forested Nest
Woodlands - Fall 2017 - intro
Woodlands - Fall 2017 - cover1
Woodlands - Fall 2017 - cover2
Woodlands - Fall 2017 - 3
Woodlands - Fall 2017 - Overstory
Woodlands - Fall 2017 - 5
Woodlands - Fall 2017 - 6
Woodlands - Fall 2017 - 7
Woodlands - Fall 2017 - 8
Woodlands - Fall 2017 - 9
Woodlands - Fall 2017 - 10
Woodlands - Fall 2017 - 11
Woodlands - Fall 2017 - 12
Woodlands - Fall 2017 - 13
Woodlands - Fall 2017 - 14
Woodlands - Fall 2017 - 15
Woodlands - Fall 2017 - 16
Woodlands - Fall 2017 - 17
Woodlands - Fall 2017 - Tools and Resources
Woodlands - Fall 2017 - 19
Woodlands - Fall 2017 - Forests and Families
Woodlands - Fall 2017 - 21
Woodlands - Fall 2017 - 22
Woodlands - Fall 2017 - 23
Woodlands - Fall 2017 - A Legacy to Keep
Woodlands - Fall 2017 - 25
Woodlands - Fall 2017 - 26
Woodlands - Fall 2017 - 27
Woodlands - Fall 2017 - 28
Woodlands - Fall 2017 - 29
Woodlands - Fall 2017 - From Forests to Fermentation
Woodlands - Fall 2017 - 31
Woodlands - Fall 2017 - 32
Woodlands - Fall 2017 - 33
Woodlands - Fall 2017 - Feathering a Forested Nest
Woodlands - Fall 2017 - 35
Woodlands - Fall 2017 - 36
Woodlands - Fall 2017 - 37
Woodlands - Fall 2017 - 38
Woodlands - Fall 2017 - cover3
Woodlands - Fall 2017 - cover4