Mosses and other epiphytic organisms like lichens and algae cover large parts of trees and shrubs in the Amazon rainforest. At ATTO, they are practically everywhere we look. We know from studies in other regions of the world that they are important for carbon uptake through photosynthesis, climate processes, and nutrient cycling. But very little research on this has been done on this in tropical rainforest settings. Now Nina Löbs for MPI-C and her colleagues are working to change that.
Two important characteristics of mosses are that
- they are only active when it’s wet, which is why they are so abundant in the rainforest
- they cannot regulate the water content by themselves. Instead, they depend on water from rain or dew.
Mosses are able to survive long dry periods in a dried out inactive state, like bears in hibernation. But as soon as it rains they are activated again and perform respiration or photosynthesis, for example.
To understand the impact of tropical mosses on local, regional, and even global biogeochemical processes we need to learn more about this dependency on water. Therefore, Nina and her team analyzed the water content, temperature and light conditions of mosses at the forest floor and at different heights in the canopy in the Amazon rainforest.
The habitat matters
They found that mosses close to the forest floor react very reliably to rain events and increase their own water content. But for mosses within the canopy, it’s not as simple as that. It appears that the dense foliage might offer a lot of shading from the rain. Instead, the data suggest that air humidity and dew are the more important water source for them. When they have enough water to wake up from their hibernation, light availability becomes most important to determine how productive they are in their photosynthetic activity. This determines if they take up more carbon from the atmosphere than they release due to respiration.
Surprisingly enough, the mosses close to the forest floor still survive under extremely low light intensities.
This study is a first step to investigate the potential role of tropical mosses in carbon cycling and other biogeochemical cycles. The next step will now be to measure CO2 and other trace gas exchange rates of the mosses with the air around them. This is especially crucial in the face of climate change and deforestation, which leads to more severe and longer droughts. This might limit the productivity of mosses in the future.
Löbs et al. published the study “Microclimatic conditions and water content fluctuations experienced by epiphytic bryophytes in an Amazonian rain forest” Open Access in the journal Biogeosciences.
Nora Zannoni and her colleagues measured BVOC emissions at the ATTO tall tower in several heights. Specifically, they looked at one particular BVOC called α-pinene. They found that chiral BOVs at ATTO are neither equally abundant nor is the ratio of the two forms constant over time, season, or height. Surprisingly, they also discovered that termites might be a previously unknown source for BVOCs.
Fungal spore emissions are an important contributor to biogenic aerosols, but we have yet to understand under what conditions fungi release their spores. Nina Löbs and co-authors developed a new technique to measure emissions from single organisms and tested this out at ATTO and with controlled lab experiments. They published their results in the Open Access Journal Atmospheric Measurement Techniques.
In a new study, Nathan Gonçalves and co-authors now wanted to find out if extreme climate events such as droughts influence leaf flushing, and thereby the average leaf age and photosynthetic capacity of the forest, and if is it possible to monitor more subtle changes associated with extreme events (compared to season changes) with satellites?
Pfannerstill et al. compared VOC emissions at ATTO between a normal year and one characterized by a strong El Nino with severe droughts in the Amazon. The did not find large differences, except in the time of day that the plants release the VOCs. They published their results in the journal Frontiers in Forest and Global Change.