Spanning the continental divide, near the border of Panama and Costa Rica, is the cloudiest place in Central America: the Fortuna Hydrological Reserve, a tropical highland forest with almost as many tree species as the entire United States. New species and important new information about carbon storage from this tiny area—19,500 hectares/75 square miles—of nearly-intact wilderness continue to surprise researchers from the Smithsonian Tropical Research Institute, who have been studying Fortuna’s vegetation, soils, insects, microbes and amphibians for several decades.

STRI research associate Jim Dalling, an ecologist at the University of Illinois-Urbana Champaign, has explored Fortuna’s montane forest for 25 years. In an effort to understand how environmental factors determine the distribution of plant species in tropical mountains, he measured the growth rates of over 30 thousand trees across a variety of soil conditions.

“There are 891 tree species, which is 30 percent of the species in all of Panama,” Dalling said, during a recent STRI webinar. “Throughout the USA there are 950 species of trees. This diversity is due to extreme variation in climate. The mix of lowland and highland species generates more diversity.”

At higher elevations and cooler temperatures, tree communities have different survival strategies than in the lowlands. Understanding this is crucial to determining how montane forests are responding to climate change: as clouds form at higher elevations, warming temperatures may already be contributing to species migrations.

Fortuna’s forests have been an important training ground for students from the University of Panama and UNACHI (Autonomous University of Chiriquí) in Western Panama, through field courses, fellowships and internships. Over a dozen research projects have been developed in these montane forests by local undergraduate, master’s and doctoral students under Dalling’s mentorship.

Among the new species still waiting to be discovered in Fortuna are an abundance of fungi. Several of them have been recently described by Adriana Corrales, a former STRI fellow who conducted research in Dalling’s laboratory.

“There are a lot of undescribed species of fungi globally, and particularly in tropical forests that have been traditionally understudied,” said Corrales, now a faculty member in the Department of Biology at Universidad del Rosario in Colombia. “We expect the montane forests of Panama to host a high diversity of fungi that are unknown to science.”

In a paper published last year in Frontiers in Microbiology, she documented seven species of the genus Laccaria from Fortuna. Three of them were new: Laccaria dallingii sp. nov., L. nitrophila sp. nov., and L. fortunensis sp. nov., all mycorrhizal fungi: they live in plant roots and help them absorb nutrients. Most of them were found in the roots of tree species in the walnut family, Oreomunnea mexicana, which is abundant in the hydrological reserve.

Since 2013, only three new Laccaria species have been described in the neotropics, out of 22 new species described worldwide. And only about 75 species of Laccaria are known, so Corrales’ research has advanced the knowledge of Laccaria diversity in the world and in Central America, in particular. She also explores how mycorrhizal fungi may have diversified after the formation of the Isthmus of Panama, in a new study published in Mycologia.

Another surprise discovery was made by Cecilia Prada, a former doctoral student of Dalling’s. She found that Fortuna’s forests store two to three times more carbon than previously calculated based on LiDAR technology, which is done by overflying an area and measuring tree biomass by bouncing a laser light off the forest below.

Prada’s estimates, which included carbon in soils, decaying wood and living trees, show that Fortuna’s forests store up to 10 million tons of carbon. This is three times the amount of carbon that Panama’s air conditioning units, cars and deforestation release into the atmosphere each year, clearly demonstrating the potential of cloud forests to offset the emissions that cause global warming.

Due to the pandemic, the STRI Field Station in Fortuna remains closed to visiting scientists, but researchers are eagerly waiting to continue to explore this unique habitat.