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![Page 1: Effects of watering, mulch, and fabric on tree survival Results from controlled experiments at King County Restoration Sites Josh Latterell, Laura Hartema,](https://reader035.fdocuments.in/reader035/viewer/2022062715/56649da05503460f94a8bdd6/html5/thumbnails/1.jpg)
Effects of watering, mulch, and fabric on tree survival
Results from controlled experiments at King County Restoration Sites
Josh Latterell, Laura Hartema, and Kate AkyuzWater and Land Resources Division
![Page 2: Effects of watering, mulch, and fabric on tree survival Results from controlled experiments at King County Restoration Sites Josh Latterell, Laura Hartema,](https://reader035.fdocuments.in/reader035/viewer/2022062715/56649da05503460f94a8bdd6/html5/thumbnails/2.jpg)
Why bother studying plants?
Oct 2005
Aug 2009
Ecological function, pervasive, potentially expensive, highly visible, high variable
![Page 3: Effects of watering, mulch, and fabric on tree survival Results from controlled experiments at King County Restoration Sites Josh Latterell, Laura Hartema,](https://reader035.fdocuments.in/reader035/viewer/2022062715/56649da05503460f94a8bdd6/html5/thumbnails/3.jpg)
The Goal
• To develop evidence-based guidelines for re-establishing native forests on restoration sites, based on clearly specified treatments shown to be effective in controlled research with a delineated population
– Best establishment methods?• Planting vs. natural?
– Most cost-effective maintenance techniques?• Watering, fabric, mulch,
weeding?
– How do these vary with site conditions?• High vs. low?
– How do these vary between wet vs. dry years?
![Page 4: Effects of watering, mulch, and fabric on tree survival Results from controlled experiments at King County Restoration Sites Josh Latterell, Laura Hartema,](https://reader035.fdocuments.in/reader035/viewer/2022062715/56649da05503460f94a8bdd6/html5/thumbnails/4.jpg)
Study #1 & 2 - PAUTZKE
August 2012
![Page 5: Effects of watering, mulch, and fabric on tree survival Results from controlled experiments at King County Restoration Sites Josh Latterell, Laura Hartema,](https://reader035.fdocuments.in/reader035/viewer/2022062715/56649da05503460f94a8bdd6/html5/thumbnails/5.jpg)
November 2009
• Study 1 (2010-2012)– Does watering improve the survival of cottonwood
stakes (with fabric)?
![Page 6: Effects of watering, mulch, and fabric on tree survival Results from controlled experiments at King County Restoration Sites Josh Latterell, Laura Hartema,](https://reader035.fdocuments.in/reader035/viewer/2022062715/56649da05503460f94a8bdd6/html5/thumbnails/6.jpg)
Study Design
Details• 20 plots (10 x 10 m)
– 10 wet– 10 dry
• Spatially randomized• 721 cottonwood stakes
– Avg. 36 per plot– fabric
• 165 cedar– Avg 8 per plot– fabric
• Treatment randomly assigned at plot level
• Watered 3 times in 2010– 15 July – 30 Aug
Layout
2010 photo
![Page 7: Effects of watering, mulch, and fabric on tree survival Results from controlled experiments at King County Restoration Sites Josh Latterell, Laura Hartema,](https://reader035.fdocuments.in/reader035/viewer/2022062715/56649da05503460f94a8bdd6/html5/thumbnails/7.jpg)
Results
97% 98% 93%98% 95% 93%0%
50%
100%
Year 0 Year 1 Year 2
Surv
ival
rate
of c
otton
woo
d liv
esta
kes
(+
/-95
%CI
)
WET
DRY
![Page 8: Effects of watering, mulch, and fabric on tree survival Results from controlled experiments at King County Restoration Sites Josh Latterell, Laura Hartema,](https://reader035.fdocuments.in/reader035/viewer/2022062715/56649da05503460f94a8bdd6/html5/thumbnails/8.jpg)
Pautzke SE - Study #2
1. How does fabric and mulch affect survival, relative to no treatment?• No irrigation
2. Does the effect differ between species?– Red alder (more sensitive to drought?)– Cottonwood livestakes
![Page 9: Effects of watering, mulch, and fabric on tree survival Results from controlled experiments at King County Restoration Sites Josh Latterell, Laura Hartema,](https://reader035.fdocuments.in/reader035/viewer/2022062715/56649da05503460f94a8bdd6/html5/thumbnails/9.jpg)
Study Design
Details• 30 plots (7.6 x 7.6 m)
– 15 alder• 5 mulch• 5 fabric• 5 nothing
– 15 cottonwood
• 650 trees– 25 plants per plot
• Treatment randomly assigned at plot level
• Not watered
Layout• Cottonwood live stakes
• Potted 1-gal red alder
f n m f f mm n n f m f n m n
n n f mmm f f n f m n f n m
![Page 10: Effects of watering, mulch, and fabric on tree survival Results from controlled experiments at King County Restoration Sites Josh Latterell, Laura Hartema,](https://reader035.fdocuments.in/reader035/viewer/2022062715/56649da05503460f94a8bdd6/html5/thumbnails/10.jpg)
65%
40%
73%
96%91%
86%
0%
50%
100%
fabric mulch none fabric mulch none
Red alder Cottonwood
Ave
rage
pre
-sum
mer
surv
ival
rate
+/
-95%
con
fiden
ce in
terv
al
2011 to May 2012
“Be very careful if you use mulches around trees and shrubs! Voles are often encouraged by a nice, loose mulch.”-WSU extension website
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85% 83% 84%90% 89%
95%
0%
50%
100%
fabric mulch none fabric mulch none
Red alder Cottonwood
Ave
rage
sum
mer
surv
ival
rate
+/
-95%
con
fiden
ce in
terv
al
Summer survival Sept 2012(after 45 days of no rain)
![Page 12: Effects of watering, mulch, and fabric on tree survival Results from controlled experiments at King County Restoration Sites Josh Latterell, Laura Hartema,](https://reader035.fdocuments.in/reader035/viewer/2022062715/56649da05503460f94a8bdd6/html5/thumbnails/12.jpg)
23%
39%
30%
5% 11% 3%0%
50%
100%
fabric mulch none fabric mulch none
Red alder Cottonwood
Ave
rage
Per
cent
age
of su
rviv
ing
stem
s w
ith
vole
dam
ange
+/
-95%
con
fiden
ce in
terv
al
Vole damage on surviving stems 2012
![Page 13: Effects of watering, mulch, and fabric on tree survival Results from controlled experiments at King County Restoration Sites Josh Latterell, Laura Hartema,](https://reader035.fdocuments.in/reader035/viewer/2022062715/56649da05503460f94a8bdd6/html5/thumbnails/13.jpg)
Cost:Benefit AnalysisSpecies Plant +
InstallationTreatment Install &
removalSubtotal per plant
Subtotal per acre
1-gal potted red alder
$11.25
None $0 $11.25 $20,000
Mulch $1.81 $13.06 $23,000
Fabric $4.09 $15.34 $27,000
8’ Cottonwood live stake
$9.82
None $0 $9.82 $17,000
Mulch $1.81 $11.63 $20,000
Fabric $4.09 $13.91 $24,000
•Adding fabric to the entire site (3.3 acres) would have unnecessarily added a cost of roughly $23,000.
![Page 14: Effects of watering, mulch, and fabric on tree survival Results from controlled experiments at King County Restoration Sites Josh Latterell, Laura Hartema,](https://reader035.fdocuments.in/reader035/viewer/2022062715/56649da05503460f94a8bdd6/html5/thumbnails/14.jpg)
Rainbow Bend
Aug 2012
![Page 15: Effects of watering, mulch, and fabric on tree survival Results from controlled experiments at King County Restoration Sites Josh Latterell, Laura Hartema,](https://reader035.fdocuments.in/reader035/viewer/2022062715/56649da05503460f94a8bdd6/html5/thumbnails/15.jpg)
Study design
Details Layout• 24 paired plots (4 x 16 m)
– 12 wet– 12 dry
• Spatially randomized• 960 cottonwood stakes
– Avg. 77 per plot (49-109)
• Randomly assigned treatment at plot level
• Watered 3 times in 2011– 2 gallons each plant
![Page 16: Effects of watering, mulch, and fabric on tree survival Results from controlled experiments at King County Restoration Sites Josh Latterell, Laura Hartema,](https://reader035.fdocuments.in/reader035/viewer/2022062715/56649da05503460f94a8bdd6/html5/thumbnails/16.jpg)
Results of paired t-tests
Year 1 (p = .117) Year 2 (p=0.062; +8%)
SURV
IVAL
SURV
IVAL
DRY PLOTS WET PLOTS DRY PLOTS WET PLOTS96%93% 91%83%
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Rainbow Bend Cost : Benefit Results
• Cost to irrigate 15,000 stakes 3 times over 1 summer– At $1-3 each = $15,000-$45,000
• If we assume 8% more would have died without irrigation…– 1,200 stakes were ‘rescued’– $15-45,000/1,200 stakes = $12.50-37.50/stake
• Cost:benefit comparison– $12.50 - $37 to irrigate vs. $10 to replace– Irrigation more expensive than replacement
• Performance standards would likely have been met with no watering at all (replacement not necessary)
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Something else is going on…
![Page 19: Effects of watering, mulch, and fabric on tree survival Results from controlled experiments at King County Restoration Sites Josh Latterell, Laura Hartema,](https://reader035.fdocuments.in/reader035/viewer/2022062715/56649da05503460f94a8bdd6/html5/thumbnails/19.jpg)
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Influence of soil texture
0%
50%
100%
Year 1 Year 2
Surv
ival
of C
otton
woo
d liv
esta
kes
(+/-
95%
CI)
Year
Rainbow Bend Watering Experiment
sand
loamy sand
sandy loam
silty loam
loam
Highest survival in loam, but not evident until 2nd year
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Influence of soil conditions
Effect of soil depth on survival Effect of soil depth on moisture
0%
50%
100%
0 20 40 60 80
2-yr
surv
ival
rate
of c
otton
woo
d liv
esta
kes
Depth of fine-textured soils (cm)
WET
DRYy = 0.4367x + 38.414
r² = 0.54
0
50
100
0 20 40 60 80
Soil
moi
stur
e (%
; Sep
t 252
012)
Soil depth (cm)
Survival is consistently high in deep soils – which have more moisture.Perhaps moisture is limiting, but we watered too little to have effect!
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Summary
![Page 23: Effects of watering, mulch, and fabric on tree survival Results from controlled experiments at King County Restoration Sites Josh Latterell, Laura Hartema,](https://reader035.fdocuments.in/reader035/viewer/2022062715/56649da05503460f94a8bdd6/html5/thumbnails/23.jpg)
Effects of watering• On high, sunny sites with good soils
(Pautzke)– Did not affect survival of cottonwood
livestakes– Was not necessary to achieve >80%
oversummer survival of alder or cottonwood
• On a low, sunny site, with shallow soils (Rainbow Bend)– Marginally increased survival, but cost
more than replacement
• Preliminary recommendation:– Don’t assume watering is necessary– Map soil texture and depth to guide
the planting plan
![Page 24: Effects of watering, mulch, and fabric on tree survival Results from controlled experiments at King County Restoration Sites Josh Latterell, Laura Hartema,](https://reader035.fdocuments.in/reader035/viewer/2022062715/56649da05503460f94a8bdd6/html5/thumbnails/24.jpg)
Effects of wood mulch (hog fuel rings)
• On a high, sunny site with good soils (Pautzke SE)– No positive effect on
survival– Negative effect on red alder,
probably by attracting voles
• Preliminary recommendation: – Do pre-planting survey to
estimate severity of vole damage and avoid mulch where voles are abundant
– Developed by WSU
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Effects of fabric• On a high, sunny site with good
soils– Did not affect survival of red
alder or cottonwood livestakes
• Recommendation: More testing needed, use with caution. Fabric has high costs, uncertain benefits at this point.
• Next steps – – Testing effects in reed
canarygrass now…stay tuned!
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Your mileage may vary
• Narrow scope of inference (don’t be hasty!)– Only cottonwood stakes and alder– Representative of wetter than normal springs,
followed by mostly drier than normal summers*
• Need more sites, years, and species!!
Season Average 2010 2011 2012
Spring 13.4” 128% 149% 141%Summer 5.7” 112% 54% 60%
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Three years after planting