Sifting Through the ‘Noise’
To Assess Health of Tropical Forests

liza comita
Liza Comita
Some of the things that made Liza Comita want to study tropical forests in the first place are the same things that can make it a rather daunting field of research.
 
The array of species, hundreds or more at most sites, almost dizzying in their abundance. Trees and plants so rare that learning even their basic biology is a challenge, let alone understanding how they are faring in the face of human intrusion.
 
And then there is the background “noise” in the forest system, the wide variation of species success from year to year even in the absence of human influence, making it all the more difficult to find, say, the effects of climate change.
 
For Comita, who joins F&ES this semester as Assistant Professor of Tropical Forest Management, they were the kinds of challenges that grabbed her when she conducted her first research in the forests of Costa Rica as a University of Pennsylvania undergraduate. And they’re the questions she has been trying to answer during more than a decade as a researcher and professor.
 
Comita, who comes to F&ES from Ohio State University, researches the regeneration ecology of tropical tree species and how spatial and temporal variations in regeneration dynamics act to maintain forest diversity and shape tropical tree communities. 
 
“I fell in love with this work, trying to understand how ecosystems are structured, and how different species interact, how all these different pieces fit together,” she says. “I was excited by the intellectual challenge of it. And also the fact that you got to do this work while being outside in beautiful places.”
 
The key to answering these complex questions, she says, is collecting large, long-term data sets, year after year.
 
As the climate changes, she says, the major impacts on many forests will be driven not only by temperature changes, but also by shifts in precipitation. Since 2001, she has been collecting her own data — primarily in Panama — to help assess whether this is already happening.
 
In one of her projects, being conducted across the Isthmus of Panama, Comita is part of a research team studying whether different individuals of the same species, but located in different parts of the country, have different sensitivity to drought based on how much rainfall they typically see.
 
“If some individuals are more drought resistant or more drought sensitive based on where they’re growing currently,” she says, “then that would change predictions about whether these species are going to be able to able to survive under predicted climate change.”
 
In a separate, long-term study — which began 13 years ago on a 50-hectare plot leased to the Smithsonian Institute — Comita is exploring seedling recruitment, growth, and plant survival in response to precipitation, among other factors, for more than 350 woody plants.
 
Eventually, she expects this research will reveal insights into which species will do well during wetter years; which ones are most vulnerable to severe dry seasons; which species are recruiting well over time; and which ones appear to be in decline. But she knows it will probably take a while. After 13 years, the answers still aren’t clear-cut. That, she says, is the nature of these large, complex systems.
 
“We’ve found that some species are extremely drought-sensitive, so when there’s an extremely dry season their seedlings have very low survival rates,” she says. “And so what this is suggests is, if you see a drying trend due to climate change, there is a chance you will see these species start to drop off. We haven’t started to see that yet.
 
“Thirteen years seems like a long time in our lifetimes, but it’s not very long in the lifetime of a tropical tree or for a population of trees,” she says. “And that’s one of the major challenges, especially in this changing world: understanding how these changes are going to affect these very large, long-lived organisms.”
– Kevin Dennehy    kevin.dennehy@yale.edu    203 436-4842
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PUBLISHED: August 26, 2014
 

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