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Biotic and Abiotic Drivers of Seedling Survival in a Hurricane-Impacted Forest. Liza S. Comita Columbia University. Tropical cyclone tracks from 1985 to 2005. Photo credit: Larsen & Torres-Sanchez, USGS. Before…. Photo credit: Timo Veijola. And after…. Photo credit: Timo Veijola. - PowerPoint PPT Presentation
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Biotic and Abiotic Drivers of Seedling Survival in a Hurricane-Impacted Forest
Liza S. ComitaColumbia University
Tropical cyclone tracks from 1985 to 2005
Photo credit: Larsen & Torres-Sanchez, USGS
Photo credit:Timo Veijola
Before….
Photo credit:Timo Veijola
And after….
Hurricane Damage
• Abiotic environment– Open up forest canopy ->
increased understory light levels & more heterogeneity
• Biotic environment– Increased light levels-> increased
seedling densities -> density-dependent mortality
Hurricane Disturbance
• How does hurricane disturbance alter the biotic and abiotic environment?
• Which biotic and abiotic factors determine patterns of seedling survival in the understory?
• Does the importance of these factors change as the forest recovers?
Luquillo Experimental Forest, Puerto Rico
•16 ha Forest Dynamics Plot
•138 tree and shrub species•Aseasonal, hurricane-impacted forest (Hugo 1989, Georges 1998)
0 50 100 150 200 250 300
010
020
030
040
050
0
Meters east
Met
ers
north
Seedling census• 2 x 1 m seedling plots• 150 est. in 2000• 63 added in 2004• Tree, shrub, palm
seedlings ≥10 cm tall • Tagged, measured,
identified to species in 2000, 02, 04, 07, 08
• Hemispherical photos taken over each plot to quantify light levels
Hurricane Disturbance
• How does hurricane disturbance alter the biotic and abiotic environment?
Light levels (at 1 m above ground)
1999 2002 2004 2007
Year
Mea
n %
tran
smis
sion
010
2030
4050
60 •Significantly higher light levels after the hurricane•Sharp drop within 3 yrs due to canopy closure
Seedling density
2000 2002 2004 2007 2008
Year
See
dlin
g de
nsity
810
1214
1618
20(m
-2) •Higher seedling densities for
several years post-hurricane
Hurricane Disturbance
• How does hurricane disturbance alter the biotic and abiotic environment?
• Which biotic and abiotic factors determine patterns of seedling survival in the understory?
• Does the importance of these factors change as the forest recovers?
Seedling survival as a function of:• Abiotic factors
– Light– Soil
• (5 soils types)
– Topography • (topo category & % slope)
0 50 100 150 200 250 300
010
020
030
040
050
0
Meters east
Met
ers
north
Seedling survival as a function of:• Biotic neighborhood
– Density of • conspecific seedlings • heterospecific seedlings• conspecific tree BA• heterospecific tree BA
• Abiotic x Biotic interactions– Light x Neighbors
Generalized linear mixed effects model
Logit(S)= TIME + LOG(HEIGHT) + LIGHT + LIGHT2 + SLOPE+TOPO+SOILTYPECONS + HETS + CONBA + HETBA+LIGHT:CONS + LIGHT:HETS +LIGHT:CONBA + LIGHT:HETBA
+SPECIES + PLOT
FIXED EFFECTS
RANDOMEFFECTS
‘lme4’ package
• lmer() function• Binomial errors (survival 0/1)• Standardized predictors
– Divide by mean and subtract 1 sd– Makes it easy to directly compare effects for
variables that are measured on different scales
TIME
log (HT)
CONS
HETS
CONBA
HETBA
LIGHT
LIGHT2
CONS x LIGHT
HETS x LIGHT
CONBA x LIGHT
HETBA x LIGHT
Coefficient estimates-0.6 -0.2 0.2 0.6
12
34
56
78
910
1112
All species
-0.5 0.0 0.5 1.0
Shade tolerant
-0.5 0.0 0.5
Intermediate
-0.5 0.0 0.5 1.0
Light demandingRESULTS
Effect of Light
0.0 0.2 0.4 0.6 0.8
0.35
0.40
0.45
0.50
0.55
0.60
Percent transmission
Pro
babi
lity
of s
urvi
val
Effect of Conspecific Seedling Neighbors
0 20 40 60 80 100 120
0.42
0.44
0.46
0.48
0.50
0.52
0.54
Conspecific seedling neighbors
Pro
babi
lity
of s
urvi
val
Light level:
High (trans = 0.50)Mean (trans = 0.21) Low (trans = 0.10)
Hurricane Disturbance
• How does hurricane disturbance alter the biotic and abiotic environment?
• Which biotic and abiotic factors determine patterns of seedling survival in the understory?
• Does the importance of these factors change as the forest recovers?
Effects in each census interval
2000-02 2002-04 2004-07 2007-08LIGHT + 0 0 0CON Seedlings 0 - - +HET Seedlings 0 0 0 0CON BA - - - -HET BA + 0 0 0
Effects in each census interval
2000-02 2002-04 2004-07 2007-08LIGHT + 0 0 0CON Seedlings 0 - - +HET Seedlings 0 0 0 0CON BA - - - -HET BA + 0 0 0
Effects in each census interval
2000-02 2002-04 2004-07 2007-08LIGHT + 0 0 0CON Seedlings 0 - - +HET Seedlings 0 0 0 0CON BA - - - -HET BA + 0 0 0
Maria Uriarte Jill ThompsonJess Zimmerman Nick BrokawInge JonckheereLFDP technicians & volunteers
Acknowledgements
Email: [email protected]
QUESTIONS?