Climate Change and Tropical Ecosystems
Effective beginning 5/30/2025
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Tropical forests take in and store more carbon dioxide than any other biome around the world, but climate change may pose a threat to this invaluable service. The International Institute of Tropical forestry, along with Scientists from various governmental agencies and universities are working together to measure the potential impacts of climate change- particularly temperature increase on soil structure, carbon cycling, and plant physiology.
Among the many research initiatives of the institute, here are a few that advance our understanding of Climate change and tropical ecosystems:
The TRACE experiment consists of using infrared heat to warm the soil and plants of the understory, as well as individual leaves and branches in the forest canopy.
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, limited 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 in combination with hurricane disturbance. 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).
LUQ serves as a platform for long-term ecology research and education in Puerto Rico’s Luquillo Mountains, and collaborates with many academic institutions, government agencies, and other entities. Major research sites include El Verde Field Station, Sabana Field Research Station, Bisley Experimental Watersheds, and Pico del Este. In addition to research activities, LUQ can also provide information, facilitate communication, and assist with permitting processes for individuals interested in conducting research and educational activities in the Luquillo Experimental Forest.
The goal of Luquillo Long Term Ecological Research Program (LUQ) is to understand how forest and stream ecosystems, and the services that they support, are changing in Puerto Rico, thereby providing guidance for management of change in the tropics. We focus on understanding the key role of disturbance in determining ecosystem functions, processes, and their services. In the first phases of LUQ (1988–2006), degrees and mechanisms of resistance and resilience were studied, especially after the passage of hurricanes. This background led to more recent work on response to human disturbance and climate change, both likely to cause long-term, directional change in ecosystems and services.
To read more about the Luquillo Long Term Ecological Research visit their page: https://luquillo.lter.network/
There are a series of plots along the elevation gradient from the coast to the top of the Luquillo Mountains in northeastern Puerto Rico, which intersect with a variety of montane, and coastal and lowland forest types with distinct composition and structure.
Montane forest types:
Dwarf (Photo A below), Colorado, Tabonuco, Sierra palm, Mahogany plantations.
Coastal and lowland forest types:
Lowland moist secondary, Subtropical dry, Pterocarpus swamp and riparian, Laguncularia racemosa - white mangrove, and Avicennia germinans - black mangrove .
The plots are periodically monitored for soil properties and plant species composition, microclimate, rainfall chemistry, tree growth, litterfall, and woody debris. These data facilitate both comparisons between forest plots and analyses of temporal variation in ecosystem properties within individual plots.
Tropical ecosystems across the globe are highly sensitive to climate, and individual regions are able to support their diversity of species because of their variability of climate across elevation. Forest Service researchers studied patterns of trends in local climatic conditions along a tropical elevation gradient in an ecologically sensitive area of northeastern Puerto Rico. They examined precipitation and temperature records collected over twenty years at twenty sites, ranging from sea level in the coastal zone of the San Juan Metropolitan area up to 1000 m at the top of the Luquillo Experimental Forest. An analysis of the driest and wettest months of the rainfall seasons revealed that the driest months are getting slightly wetter over time, while no trend was perceived for the wettest months. Precipitation also appears to increase faster at higher elevations. As for temperature, the daily minimum was observed to increase slightly, and the daily maximum decreased, suggesting that the range of temperatures along the elevation gradient is narrowing. Unlike with precipitation, the pace of temperature change did not vary with elevation position. These results emphasize that differing patterns of climate change across tropical elevation gradients should be explored in order to understand the effects of future climate scenarios on biological life.