Impacts of Bohemian Knotweed on Litter Decomposition, etc.
20
Impacts of Bohemian Knotweed on Litter Decomposition, etc. Shannon Claeson Olympia PNW Research Station USDA Forest Service 14 November 2013
Transcript of Impacts of Bohemian Knotweed on Litter Decomposition, etc.
Impacts of Bohemian Knotweed
on Litter Decomposition, etc.
Shannon Claeson
Olympia PNW Research Station
USDA Forest Service
14 November 2013
• Forms dense monocultures, up to 5m tall,
• Displaces native vegetation,
• Perennial - drops leaves all at once in autumn,
• Reabsorbs nutrients from leaves prior to leaf-fall!
Bohemian Knotweed
Bohemian knotweed (Polygonum x bohemicum)
red alder (Alnus rubra)
black cottonwood (Populus trichocarpa)
Objectives
Aquatic litter processing
Aquatic litter processing
Leaves high in nutrients • more fungal biomass, • more insect shredders, • decompose faster.
Nutrients
(nitrogen,
phosphorus)
Fungi
Invertebrate
detritivores
Leaf decomposition
+
+
+
+ Leaves high in structure • less fungal biomass, • less insect shredders, • decompose slower.
Physical
abrasion
Structure
(fiber, cellulose,
lignin)
-
-
-
-
-
-
Field Experiment - Methods
Single species leaf-packs: • Leaf-pack = 5.0g of senesced, dry leaves • 3 species = alder, cottonwood, or knotweed • 3 streams = Stony, Wildcat, Porter
(Chehalis Basin) • Leaf-packs in water January-March 2011
Field Experiment - Methods
At start (day 0) and after 15, 31, & 56 days Removed 5 leaf-packs/species/stream & measured: • % Fiber, Cellulose, Lignin (day 0 only) • % Carbon, Nitrogen, Phosphorus (each time) • Dry mass (each time) • Fungal biomass (each time) • # Aquatic invertebrates (day 31 only)
Aquatic litter processing
Structure (%FCL)
Nutrients (%CNP) Fungal biomass Change in leaf mass
Insect abundance
Study Streams
StonyPorter
Wildcat
123°0'0"W124°0'0"W
47
°30
'0"N
47
°0'0
"N4
6°3
0'0
"N
Chehalis
Rive
r
WASHINGTON
0 10 20 30 Kilometers
Study reaches
Rivers
Sea water
Forested, 2nd-3rd order, pool-riffle, gravel-cobble, alder & cottonwood, support salmon.
Wildcat Creek
Stony Creek
Porter River
1
2
3
4
5
6
7
8
9
10
deg
rees
Cel
ciu
s
Water Temperature (˚C) - Daily Mean
WildcatStonyPorter
Stream Reaches (50m long)
Wildcat Creek Stony Creek Porter River
Stream Reaches
Wildcat Creek
Stony Creek
Porter River
Parameter Stony Wildcat Porter
pH 7.0 6.9 7.3
Conductivity (µS/cm) 43.5 62.7 45.9
Dissolved Oxygen (mg/L) 12.4 12.1 12.8
NO3/NO2-N (µg/L) 579 627 638
NH4-N (µg/L) 33 11 11
PO4-P (µg/L) 11 15 10
Streams similar!
Senesced Leaf Structure (day 0)
Alder
Cottonwood
Knotweed
Leaf conte
nt
(%)
0
10
20
30
40
50
60
70
80
90
100
a
Species
a a
ab b
b
b c
c
Al
Lignin Cellulose Fiber
Ct Kw Al Ct Kw Al Ct Kw
Bars are mean ± 1 SE
Tukey-Kramer adjusted p<0.05
Senesced Leaf Chemistry
a a
Alder
Cottonwood
Knotweed
Ca
rbo
n:N
itro
ge
n
10
20
30
40
50
60
70
80
90
Ca
rbo
n:P
ho
sp
ho
rus
400
500
600
700
800
900
1000
1100
1200
1300
1400
0 20 30 60 10 40 50 0 20 30 60 10 40 50
a
b
c
a
b
c
a
b b
a
b b
a
b
b
a
a
b
a
a
a
a
Time (days) Time (days)
More nitrogen/phosphorus lowers C:N/C:P ratios.
Points are mean ± 1 SE
Tukey-Kramer adjusted p<0.05
Fungal Biomass (ergosterol)
Fun
gal bio
ma
ss (
mg/g
)
0
10
20
30
40
50
60
70
80
90
Time (days)
0 20 30 60 10 40 50
a b
c
a
b
c
a
a
a
a
ab
b Alder
Cottonwood
Knotweed
Points are mean ± 1 SE
Tukey-Kramer adjusted p<0.05
Aquatic Invertebrates (day 31)
*
Bars are mean ± 1 SE
Tukey-Kramer adjusted p<0.05 *
0
50
100
150
200
250
300Abundance
0
5
10
15
20
25
Taxa Richness
0%
1%
2%
3%
4%
5%
6%
7%
8%
9%
10%Scraper
0%
5%
10%
15%
20%
25%
30%Shredder
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%Collector
0%
1%
2%
3%
4%
5%
6%
7%
8%
9%
10%Predator
Alder
Cottonwood
Knotweed
*
Functional feeding groups:
Invertebrate Community Composition (day 31)
Abundance
%CF
%CG
%SC
%SH Richness
Wildcat
Creek Porter Creek
Stony
Creek
Axis
2 (
r2 =
0.1
9)
Axis 1 (r2 = 0.63)
NMS ordination of 45 leaf-packs with 43 taxa.
Streams differed in abundance, richness, and % FFG’s.
Alder
Cottonwood
Knotweed
Mass remaining %
Mass r
em
ain
ing (
%)
0
20
40
60
80
100
Time (days)
0 20 30 60 10 40 50
a
b
b
a
a
ab
b
a
Alder
Cottonwood
Knotweed
Bars are mean ± 1 SE
Tukey-Kramer adjusted p<0.05
Results Alder leaves:
• More nutrients, less structure
Initially less fungal biomass, developed more over time
• More insect shredders
• Initially decomposed faster
Knotweed leaves:
Less nutrients, more structure
Initially more fungal biomass, developed less over time
Fewer insect shredders
Initially decomposed slower
Cottonwood leaves: in between…
Nutrients
(nitrogen,
phosphorus)
Fungi
Invertebrate
detritivores
Leaf decomposition
+
+
+
+
Physical
abrasion
Structure
(fiber, cellulose,
lignin)
-
-
-
-
-
-
Native vs. Non-native
leaf litter inputs:
Quality
? Quantity
? Timing
Wildcat Creek, Chehalis Basin, WA
Funding & Resources provided by:
• U.S. Fish & Wildlife Service
• U.S. Forest Service
• Dr. Carri LeRoy at The Evergreen State College (TESC)
• Dr. Kevin Kuehn at University of Southern Mississippi (USM)
Special thanks to:
• Jacob Barry (USM)
• Tamara Cowles, Ben Leonard, Steve Scott, Caitlin Reece (TESC)
• Environmental Analysis class 2011 (TESC)
Acknowledgements
