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. Photo credit: Timo Veijola Before….

5. Photo credit: Timo Veijola And after….

6. 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

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)

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 (m -2 ) Higher seedling densities for several years post-hurricane

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 + LIGHT 2 + SLOPE+TOPO+SOILTYPE CONS + HETS + CONBA + HETBA+ LIGHT:CONS + LIGHT:HETS + LIGHT:CONBA + LIGHT:HETBA +SPECIES + PLOT FIXED EFFECTS RANDOM EFFECTS

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. TIME log (HT) CONS HETS CONBA HETBA LIGHT LIGHT 2 CONS x LIGHT HETS x LIGHT CONBA x LIGHT HETBA x LIGHT Coefficient estimates 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 2000-022002-042004-072007-08 LIGHT+000 CON Seedlings0--+ HET Seedlings0000 CON BA---- HET BA+000

24. Effects in each census interval 2000-022002-042004-072007-08 LIGHT+000 CON Seedlings0--+ HET Seedlings0000 CON BA---- HET BA+000

25. Effects in each census interval 2000-022002-042004-072007-08 LIGHT+000 CON Seedlings0--+ HET Seedlings0000 CON BA---- HET BA+000

26. Maria Uriarte Jill Thompson Jess Zimmerman Nick Brokaw Inge Jonckheere LFDP technicians & volunteers Acknowledgements

27. Email: lsc2125@columbia.edu QUESTIONS?