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

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.

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

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  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 credit:Timo Veijola

  5. And after…. Photo credit:Timo Veijola

  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)

  9. 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

  10. Hurricane Disturbance • How does hurricane disturbance alter the biotic and abiotic environment?

  11. Light levels (at 1 m above ground) • Significantly higher light levels after the hurricane • Sharp drop within 3 yrs due to canopy closure

  12. Seedling density • Higher seedling densities for several years post-hurricane (m-2)

  13. 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?

  14. Seedling survival as a function of: • Abiotic factors • Light • Soil • (5 soils types) • Topography • (topo category & % slope)

  15. 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

  16. Generalized linear mixed effects model Logit(S)= TIME + LOG(HEIGHT) + LIGHT + LIGHT2 + SLOPE+TOPO+SOILTYPE CONS + HETS + CONBA + HETBA+ LIGHT:CONS + LIGHT:HETS + LIGHT:CONBA + LIGHT:HETBA +SPECIES + PLOT FIXED EFFECTS RANDOMEFFECTS

  17. ‘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

  18. RESULTS TIME log (HT) CONS HETS CONBA HETBA LIGHT LIGHT2 CONS x LIGHT HETS x LIGHT CONBA x LIGHT HETBA x LIGHT Coefficient estimates

  19. Effect of Light

  20. Effect of Conspecific Seedling Neighbors

  21. 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?

  22. Effects in each census interval

  23. Effects in each census interval

  24. Effects in each census interval

  25. Acknowledgements Maria Uriarte Jill Thompson Jess Zimmerman Nick Brokaw IngeJonckheere LFDP technicians & volunteers

  26. QUESTIONS? Email: lsc2125@columbia.edu

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