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Project Description

Located in the Luquillo Experimental Forest, Puerto Rico

Cox, S.B., Willig, M.R. & Scatena, F.N. Plant and Soil (2002) 247: 189. doi:10.1023/A:1021488313783

We are working in a wet tropical forest that receives on average 3500 mm of rainfall per year and the mean annual temperatures is 23 C. The site is within El Yunque National Forest, which is part of the Luquillo Long-Term Ecological Research Program as well as the Luquillo Critical Zone Observatory.

Experimental site prior to construction

Tana Wood at one of the plots that is being warmed prior to infrastructure installation.
Plots are 4m diameter hexagons (~12m2).  We have three warmed and three control plots (six total).
Supporting Infrastructure of the Experimental Plots
(3 warmed, 3 control)
Warmed plot: Heaters have been installed on crossbars connected to posts at each of the six corners of the hexagonal plot.  
Control plot: Identical infrastructure to the warm plots has been installed, with the exception of the heaters, which were substituted with dummy panels
Other Infrastructure
We have installed a canopy access tower at the site for plant physiological studies, including warming of individual canopy leaves.
An understory weather station will help us understand microclimate dynamics in our study site.

Coordinated Warming of
Canopy, Leaves, and Understory Vegetation 

The canopy access tower enables us to warm individual branches and leaves in the forest canopy. Infrared heaters have been installed above the understory woody vegetation to warm understory vegetation and soils. Together, these methods enable an integrated understanding of canopy and soil responses to warming.
Project Summary

Tropical forests contain ~25% of Earth’s terrestrial biomass and exchange more carbon (C) and energy with the atmosphere than any other biome.  As such, our poor understanding of how tropical forests will respond to projected increased temperatures severely constrains global predictions.  To meet the increasing need for improved understanding of tropical forest responses to global warming, we are implementing field warming experiments in a wet tropical forest in Puerto Rico to evaluate temperature responses of the most influential and biogeochemically-active tissues and organisms: leaves, fine roots, and soil microbes. Specifically, we will be warming understory vegetation and soils with an array of Infrared heaters along with complimentary warming of individual canopy leaves and branches.  Our concentration on both above- and belowground components of the forest will provide an integrated understanding of C storage and flux, which is critical to considerations of how climate effects on tropical forests will feed back to affect future C cycling and climate at the global-scale (Heimann and Reichstein 2008). 

Our specific objectives are two-fold: 
1) Assess the mechanisms behind and effects of warming on C and nutrient cycling and storage in tropical forest soils. 
2) Investigate threshold temperature responses of both canopy and understory tropical tree foliage. 

We expect this work will make significant advances in our understanding of coupled biogeochemical processes in a globally important and poorly understood ecosystem that has strong potential feedbacks to climate. This field warming experiment would be the first of its kind in any tropical forest, and the experimental research would be the first to investigate warming response to tropical processes from coordinated above- and belowground perspectives.  Our focus on the mechanisms regulating temperature responses will allow us to extrapolate results beyond that of a single tropical forest site, leading to wide geographic applicability. This work will additionally provide critical information regarding the vulnerability and adaptation potential of the only tropical forest in the US National Forest System (The Luquillo Experimental Forest inside El Yunque National Forest). 


Warming started on September 28th, 2016 and was paused on September 2017 due to the passage of Hurricanes Irma and María through Puerto Rico; then resumed on September 2018 after reconstruction and adaptation. 

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