Ecological Impacts of Invasive
Species After Fire
Noxious Weeds Response
to Fire
2005
2005
2007
2007
INTRODUCTION
METHODS
This project looks at how plant communities, specifically bluebunch
wheatgrass and Idaho fescue respond to fire. It was established to
analyze the changes in bunchgrass ground and aerial cover values
and also the cover of indicator species. Between 2001 & 2003 over
28,000 acres burned on the Wallowa Whitman National Forest. In
August 2005, The Tryon Complex fire burned a total of 42,431 acres.
Approximately 70% of these acres were of low to moderate burn
severity leaving exposed surfaces, enhanced nutrient and increased
light resulting in a flush of weed rosettes. This led to further
monitoring & evaluating the ecological impacts of invasive plants
after fire.
Current Vegetation Survey (CVS) plots and weed monitoring plots
were established within Hells Canyon National Recreation Area
(HCNRA). Monitoring plots were established in known weed
infestations to supplement CVS plots and add to invasive plant data
since weeds were not listed as indicator species within the CVS plots.
Data is collected within a 37ft circle. Percent cover is measured using
Daubenmire classification of selected plant categories. A full species
list is generated from each circle as well as determining the apparent
trend of the target species (invasive plants) based on current and past
monitoring. Given the particular vegetation types, the site condition is
also noted during the monitoring process.
TIMELINE
2005
Idaho Fescue Plant Community
Bluebunch Plant Community
2005
% Cover
Pre-Fire
CVS PLOTS
2006
Pre-Fire
2005
2006
2007
Ba
lsa
m
ro
ot
Lo
m
at
Id
iu
ah
m
o
Fe
sc
ue
P
en
st
em
on
B
lu
eb
un
ch
Sk
ul
lc
ap
Ch
ea
tg
ra
ss
Lu
pi
ne
Plant Species
Bluebunch & Fescue Ground Cover
60
50
40
30
20
10
0
2000
2005
2006
en
ts
Fescue appears to
be more resilient in
low severity fires.
2007
tle
th
is
This graph portrays the more aggressive weed
species found throughout HCNRA that are
monitored twice a year, starting after the Tryon
Fire. In 2005, during the first plot reading the
ground was still black from the fire, creating
favorable growing conditions. The 2006 plot
reading showed consistent weed populations
and stunted bunchgrass performance. The
2007 reading shows weed decline, post
treatment, and an increase in native grasses.
The pictures below were taken at the same yellow starthistle patch at the same location for three consecutive years. This
series of pictures show how favorable fire can make a yellow starthistle (a prolific annual seed producer) site by removing
above ground vegetation. The 2006 picture shows almost solid yellow star rosettes. The 2007 picture shows how weed
treatment is promoting native vegetation without the competition of weeds. This is native bunchgrass coming back and
continuing to fill in voids and helping to crowd out new yellow star plants. Other weeds that possess a deep taproot are
less affected by low or medium intensity burns and recovery is often slower.
2006
h
Weed Type
Type of Cover
2005
Sc
ot
c
Sk
el
e
to
nw
ee
d
50
45
40
35
30
25
20
15
10
5
0
Sh
ru
b
Ro
ck
Fr
ag
m
s
So
il
Ba
re
O
rg
an
ic
Cr
yp
to
ga
m
at
te
r
2007
M
Line Intercept Frequency
Plant Species
Fo
rb
s
B
40
35
30
25
20
15
10
5
0
m
ro
ot
St
.J
oh
Id
ns
ah
o
Fe
sc
ue
Sa
nd
be
rg
Bl
s
ue
bu
nc
Ca
h
n.
Th
is
tle
Ch
ea
tg
ra
ss
2007
al
sa
% Cover
30
25
20
15
10
5
0
Plant species selected are
indicators of each
grassland community.
Fall reading of
plots showing weed
decline and an
increase in native
grasses.
2006
Kn
ot
we
ed
Fall reading of monitoring
plots. Weeds within
monitoring plots treated.
Sep-07
ee
d
May-07
le
Sep-06
Kn
ap
w
CVS monitoring plots established
in known weed infestations
within the fire perimeter and
initial reading performed.
Weed Population Changes
St
ar
th
ist
May-06
MONITORING PLOTS
Weed Percentage
Oct-05
Third year reading of monitoring
plots show a decline in all weed
populations regardless of
weed type.
To
ad
fla
x
Aug-05
RESULTS & DISCUSSION
Plots are revisited and
monitored showing a slight
decline in bunchgrasses
from the initial reading.
Weed monitoring plots
established.
Lu
pi
ne
The Tryon Complex
Fire burns 42,431
acres in Hells
Canyon National
Recreation Area
(HCNRA).
2007
Leigh Dawson, lddawson@fs.fed.us, Wallowa Whitman National Forest