Biotic and Abiotic Drivers of Seedling Survival in a Hurricane-Impacted Forest

1
Biotic and Abiotic Drivers of Seedling Survival
in a Hurricane-Impacted Forest

• Liza S. Comita
• Columbia University

2
Tropical cyclone tracks from 1985 to 2005
3
Photo credit Larsen Torres-Sanchez, USGS
4
Before.
Photo creditTimo Veijola
5
And after.
Photo creditTimo Veijola
6
Hurricane Damage

• Abiotic environment
• Open up forest canopy -gt increased understory
  light levels more heterogeneity
• Biotic environment
• Increased light levels-gt increased seedling
  densities -gt density-dependent mortality

7
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?

8
Luquillo Experimental Forest, Puerto Rico

• 16 ha Forest Dynamics Plot
• 138 tree and shrub species
• Aseasonal, hurricane-impacted forest (Hugo 1989,
  Georges 1998)

9
(No Transcript)
10
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

11
Hurricane Disturbance

• How does hurricane disturbance alter the biotic
  and abiotic environment?

12
Light levels (at 1 m above ground)

• Significantly higher light levels after the
  hurricane
• Sharp drop within 3 yrs due to canopy closure

13
Seedling density

• Higher seedling densities for several years
  post-hurricane

(m-2)
14
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?

15
Seedling survival as a function of

• Abiotic factors
• Light
• Soil
• (5 soils types)
• Topography
• (topo category slope)

16
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

17
Generalized linear mixed effects model

• Logit(S)
• TIME LOG(HEIGHT)
• LIGHT LIGHT2
• SLOPETOPOSOILTYPE
• CONS HETS CONBA HETBA
• LIGHTCONS LIGHTHETS
• LIGHTCONBA LIGHTHETBA
• SPECIES PLOT

FIXED EFFECTS
RANDOMEFFECTS
18
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

19
RESULTS
20
Effect of Light
21
Effect of Conspecific Seedling Neighbors
22
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?

23
Effects in each census interval
2000-02 2002-04 2004-07 2007-08
LIGHT 0 0 0
CON Seedlings 0 - -
HET Seedlings 0 0 0 0
CON BA - - - -
HET BA 0 0 0
24
Effects in each census interval
2000-02 2002-04 2004-07 2007-08
LIGHT 0 0 0
CON Seedlings 0 - -
HET Seedlings 0 0 0 0
CON BA - - - -
HET BA 0 0 0
25
Effects in each census interval
2000-02 2002-04 2004-07 2007-08
LIGHT 0 0 0
CON Seedlings 0 - -
HET Seedlings 0 0 0 0
CON BA - - - -
HET BA 0 0 0
26
Acknowledgements

• Maria Uriarte
• Jill Thompson
• Jess Zimmerman
• Nick Brokaw
• Inge Jonckheere
• LFDP technicians volunteers

27
QUESTIONS?
Email lsc2125_at_columbia.edu