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Field Trip to the Tropical Forests
of Costa 

In the Ecosystem Ecology Group, we are interested in understanding the contribution of moss-cyanobacteria associations to nitrogen budgets in pristine ecosystems. A lot of research has been conducted in boreal forests and arctic tundra, but less attention has been given to tropical ecosystems.

So we went to Costa Rica to shed some light on the role of moss-cyanobacteria associations in contributing to N availability to cloud forests

and páramo ecosystems 


We hope to bring insights on how these associations may be affected by climate change.

Two locations were chosen for our field experiments; we collected samples in Chirripó National Park, one of the most diverse preserved areas in the country, and in Cloudbridge, a private nature reserve that focus on research and conservation projects, respectively.


Established in 1975, the Chirripó National Park is one of the most diverse spots of Costa Rica. With an area of over 500 km², it hosts environments ranging from tropical rainforests and cloud forests to alpine ecosystems.

The Chirripó trail spans 20 km, starting at an altitude of 1500 km above sea level and going up to the highest mountain top in Costa Rica, Cerro Chirripó, at 3800 m. At 3400 m of altitude, the Crestones Basecamp provides a safe resting spot for visitors and researchers. The temperature in Chirripó is much lower than in the rest of the country, averaging 4-18 °C.


Cloud forests are located in tropical ecosystems that are characterized by a constant cloud cover that tends to  maintain a high humidity level compared to other ecosystems. This contributes to the high diversity rates and is very favorable to organisms living there, including non-vascular plants like mosses. Along the Chirripó mountain, we selected six representative sites along an elevation gradient in which we collected the most dominant mosses and measured the N fixation rates. We will be investigating the bacterial community associated to those. Abiotic factors can influence these associations, so to better understand the ecosystem we have also installed climatic sensors and are looking into N deposition and soil properties


Mosses are non-vascular plants that rely on atmospheric deposition for retrieving nutrients. Several mosses maintain associations with cyanobacteria, which fix atmospheric nitrogen and make it available for the mosses and potentially to the rest of ecosystem as well. These associations are an important source of new N into northern ecosystems. Costa Rica probably has the largest diversity of mosses in Central America, with hundreds of moss species described. We found several interesting mosses along the way that we have collected and are now being analyzed in Copenhagen.


Mosses are associated with cyanobacteria, which fix atmospheric nitrogen. These associations have a large contribution to N balance in boreal forests, but their contribution to tropical forests is mostly unknown. We are evaluating the N fixation rates of the samples we collected in Chirripó to figure out how important they are to N pool in cloud forests and páramos in Costa Rica and how they might be potentially affected by climate change.


Microscope image under UV light of a tropical moss (Thuidium sp.) with filamentous cyanobacteria sitting on the moss leaves in bright red.

Cerro Ventisqueros


Cerro Ventisqueros is the second highest peak in Costa Rica, standing at 3812 m of altitude above sea level. From the top, both the Atlantic and Pacific oceans can be seen on a clear day. It is dominated by an alpine tundra-like ecosystem called páramo, which is similar in many ways to the Arctic tundra.


The Cloudbrige Nature Reserve is a private park located next to the Chirripó National Park that was founded in 2002. Currently, it has a range of approximately 28 hectares and serves as a corridor for several animal species.

We are performing this incredible work in collaboration with Prof. Andrea Vincent, from the University of Costa Rica, in San José, who is also investigating biogeochemical processes, nutrient cycling and the effects of climate change in the Chirripó National Park.

Thanks to Lina Avila Clasen, Danillo Alvarenga, Yinliu Wang & Kathrin Rousk for letting us come along on their amazing field trip.

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