case study: neighborhood models of the allelopathic effects of an invasive tree species
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FEE Course, January 2013. Case Study: Neighborhood Models of the Allelopathic Effects of an Invasive Tree Species. - PowerPoint PPT PresentationTRANSCRIPT
Case Study:
Neighborhood Models of the Allelopathic Effects of an Invasive Tree
Species
Gómez-Aparicio, L. and C. D. Canham. 2008. Neighborhood analyses of the allelopathic effects of the invasive tree Ailanthus altissima in North American forests. Journal of Ecology 96:447-458.
FEE Course, January 2013
Lorena Gómez-Aparicio(Instituto de Recursos Naturales y
Agrobiología, Sevilla, Spain)
Tree of heaven(Ailanthus altissima)
Introduced from China in 1784
The cast of characters…
Neighborhood Effects of Canopy Trees on Ecosystem Properties
Gómez-Aparicio, L. and C. D. Canham. 2008. Neighborhood models of the effects of invasive tree species on ecosystem processes. Ecol. Monogr. 78:69-86
Distance (m)
Rel
ativ
e ef
fect
of a
30-
cm D
BH
Aila
nthu
s al
tissi
ma
Ca pH
K
NO3- Net nitrification
Mass N
0.00
0.02
0.04
0.06
0.08
0.10
0 5 10 15 20 0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0 5 10 15 20 25
0.00
0.02
0.04
0.06
0.08
0.10
0 5 10 15 20 25 0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0 5 10 15 20 25
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0 5 10 15 20 25 0.00
0.02
0.04
0.06
0.08
0.10
0 5 10 15 20 25
25
Estimated footprint of a 30 cm DBH Tree of Heaven…
Bottom line: Ailanthus increases soil fertility relative to background effects of the native tree species…
Allelopathic effects of Ailanthus
Direct effects of the invasive species on nutrient availability are not the whole story….
Lab studies have isolated an allelopathic exudate from Ailanthus (ailanthone)
Could allelopathy by Ailanthus negate any positive effects of the species on soil N and Ca?
Will the magnitude of the allelopathic effect vary for different species of tree seedlings?
Gómez-Aparicio, L. and C. D. Canham. 2008. Neighborhood analyses of the allelopathic effects of the invasive tree Ailanthus altissima in North American forests. Journal of Ecology 96:447-458.
Basic experimental design
Select 20 locations in each of 3 sites with a range of abundance of A. altissima within the immediate neighborhood (and map the exact locations of those trees relative to the sample locations)
Two quadrats at each location, one with activated carbon mixed into the soil
Plant a seedling of each of three native tree species into each quadrat
Statistical model
Response = sitej* sizel * Ailanthus effect (A)
i
n
ii distanceexpDBHANI
1
max
iANI
ANIt
expA
where t = treatment (activated carbon or control), and can be positive (facilitation) or negative (inhibition).
where DBH and distance are the size and distance to neighboring Ailanthus…
NOTE: separate models were fit using either = 0 or = 2
Alternate Models
Our “null” model: Set Ailanthus effect to 1, and just fit a model for site and plant size effects…
An alternate model: test whether the magnitude of allelopathic effects was site specific:
Response = sitej* sizel
Response = sitej* sizel * Ailanthus effect (A)
max
iANI
ANItj
expA But now, varies as a
function of both treatment and site…
The error term and PDF
Error terms varied depending on the response variable - Survival: logistic regression (more later…)
- Seed emergence: binomial
- Growth: normally distributed, but with variance a power function of the mean
ij2
ijij y ),,y(Ny 2
Note: estimates of for the 3 seedling species were ~ 1.5
Model Comparison (as Hypothesis Tests)
Parameter Estimates
Acer saccharum
0 2 4 6 8 100.0
0.2
0.4
0.6
0.8
1.0
1.2
Acer rubrum
0 2 4 6 8 10
Aila
nthu
s ne
ighb
orho
od in
dex
(ANI
)
0.0
0.2
0.4
0.6
0.8
1.0
1.2
Quercus rubra
Distance (m)
0 2 4 6 8 100.0
0.2
0.4
0.6
0.8
1.0
1.2
Extension growth Extension biomass Leaf biomassLeaf areaRoot biomass
Aila
nthu
s ne
ighb
orho
od in
dex
(AN
I)
Shapes of the effective allelopathic footprint of Ailanthus for the 3 native seedling species
i
n
ii distanceexpDBHANI
1
The implications of alpha (): models with = 0 had the highest likelihood (and lowest AIC). Thus, the density of Ailanthus (stems > 2 cm DBH) was more important than their cumulative biomass…
(a) ACRU - Extension growth
0.0 0.2 0.4 0.6 0.8 1.00.5
1.0
1.5
2.0
2.5
3.0
3.5 (b) ACRU - Extension biomass
0.0 0.2 0.4 0.6 0.8 1.00.5
1.0
1.5
2.0
2.5
3.0
3.5 (c) ACRU - Leaf biomass
0.0 0.2 0.4 0.6 0.8 1.00.5
1.0
1.5
2.0
2.5
3.0
3.5
(d) ACRU - Leaf area
0.0 0.2 0.4 0.6 0.8 1.00.5
1.0
1.5
2.0
2.5
3.0
3.5
(j) QURU - Extension growth
Ailanthus neighborhood index (ANI)
0.0 0.2 0.4 0.6 0.8 1.00.0
0.2
0.4
0.6
0.8
1.0
1.2
(e) ACSA - Extension growth
0.0 0.2 0.4 0.6 0.8 1.0
Nei
ghbo
rhoo
d ef
fect
s m
ultip
lier
( X)
0.0
0.2
0.4
0.6
0.8
1.0
1.2
AC Control
(f) ACSA - Extension biomass
0.0 0.2 0.4 0.6 0.8 1.00.0
0.2
0.4
0.6
0.8
1.0
1.2
(g) ACSA - Root biomass
0.0 0.2 0.4 0.6 0.8 1.00.0
0.5
1.0
1.5
2.0 (i) ACSA - Leaf area
0.0 0.2 0.4 0.6 0.8 1.00.0
0.2
0.4
0.6
0.8
1.0
1.2(h) ACSA - Leaf biomass
0.0 0.2 0.4 0.6 0.8 1.00.0
0.2
0.4
0.6
0.8
1.0
1.2
0.0 0.2 0.4 0.6 0.8 1.00.0
0.2
0.4
0.6
0.8
1.0
1.2 (k) QURU - Extension biomass
Prop
ortio
nate
Cha
nge
allelopathy
without allelopathy
Responses of different native tree species to Ailanthus allelopathy…
Red oak (Quercus rubra)Allelopathy shifts the neighborhood effect from negative to downright nasty…
Solid circles: activated carbon (no allelopathy); Open circles: control
(a) ACRU - Extension growth
0.0 0.2 0.4 0.6 0.8 1.00.5
1.0
1.5
2.0
2.5
3.0
3.5 (b) ACRU - Extension biomass
0.0 0.2 0.4 0.6 0.8 1.00.5
1.0
1.5
2.0
2.5
3.0
3.5 (c) ACRU - Leaf biomass
0.0 0.2 0.4 0.6 0.8 1.00.5
1.0
1.5
2.0
2.5
3.0
3.5
(d) ACRU - Leaf area
0.0 0.2 0.4 0.6 0.8 1.00.5
1.0
1.5
2.0
2.5
3.0
3.5
(j) QURU - Extension growth
Ailanthus neighborhood index (ANI)
0.0 0.2 0.4 0.6 0.8 1.00.0
0.2
0.4
0.6
0.8
1.0
1.2
(e) ACSA - Extension growth
0.0 0.2 0.4 0.6 0.8 1.0
Nei
ghbo
rhoo
d ef
fect
s m
ultip
lier
(X)
0.0
0.2
0.4
0.6
0.8
1.0
1.2
AC Control
(f) ACSA - Extension biomass
0.0 0.2 0.4 0.6 0.8 1.00.0
0.2
0.4
0.6
0.8
1.0
1.2
(g) ACSA - Root biomass
0.0 0.2 0.4 0.6 0.8 1.00.0
0.5
1.0
1.5
2.0 (i) ACSA - Leaf area
0.0 0.2 0.4 0.6 0.8 1.00.0
0.2
0.4
0.6
0.8
1.0
1.2(h) ACSA - Leaf biomass
0.0 0.2 0.4 0.6 0.8 1.00.0
0.2
0.4
0.6
0.8
1.0
1.2
0.0 0.2 0.4 0.6 0.8 1.00.0
0.2
0.4
0.6
0.8
1.0
1.2 (k) QURU - Extension biomass
Prop
orti
onat
e C
hang
e
Ailanthus Neighborhood Index (ANI)
Sugar maple (Acer saccharum)Allelopathy shifts the neighborhood effect from
neutral to negative…
Solid circles: activated carbon (no allelopathy); Open circles: control
allelopathy
without allelopathy
(a) ACRU - Extension growth
0.0 0.2 0.4 0.6 0.8 1.00.5
1.0
1.5
2.0
2.5
3.0
3.5 (b) ACRU - Extension biomass
0.0 0.2 0.4 0.6 0.8 1.00.5
1.0
1.5
2.0
2.5
3.0
3.5 (c) ACRU - Leaf biomass
0.0 0.2 0.4 0.6 0.8 1.00.5
1.0
1.5
2.0
2.5
3.0
3.5
(d) ACRU - Leaf area
0.0 0.2 0.4 0.6 0.8 1.00.5
1.0
1.5
2.0
2.5
3.0
3.5
(j) QURU - Extension growth
Ailanthus neighborhood index (ANI)
0.0 0.2 0.4 0.6 0.8 1.00.0
0.2
0.4
0.6
0.8
1.0
1.2
(e) ACSA - Extension growth
0.0 0.2 0.4 0.6 0.8 1.0
Nei
ghbo
rhoo
d ef
fect
s m
ultip
lier
(X)
0.0
0.2
0.4
0.6
0.8
1.0
1.2
AC Control
(f) ACSA - Extension biomass
0.0 0.2 0.4 0.6 0.8 1.00.0
0.2
0.4
0.6
0.8
1.0
1.2
(g) ACSA - Root biomass
0.0 0.2 0.4 0.6 0.8 1.00.0
0.5
1.0
1.5
2.0 (i) ACSA - Leaf area
0.0 0.2 0.4 0.6 0.8 1.00.0
0.2
0.4
0.6
0.8
1.0
1.2(h) ACSA - Leaf biomass
0.0 0.2 0.4 0.6 0.8 1.00.0
0.2
0.4
0.6
0.8
1.0
1.2
0.0 0.2 0.4 0.6 0.8 1.00.0
0.2
0.4
0.6
0.8
1.0
1.2 (k) QURU - Extension biomass
Prop
ortio
nate
Cha
nge
Ailanthus Neighborhood Index (ANI)
Red maple (Acer rubrum)
Allelopathy shifts the neighborhood effect from strongly positive to neutral…
Without allelopathy
allelopathy
The art of choosing your model(s)
Response = sitej* sizel * Ailanthus effect (A)
i
n
ii distanceexpDBHANI
1
max
iANI
ANIt
expA
where t = treatment (activated carbon or control), and can be positive (facilitation) or negative (inhibition).
where DBH and distance are the size and distance to neighboring Ailanthus…