Tropical and Boreal Forest – Atmosphere Interactions: A Review

This review presents how the boreal and the tropical forests affect the atmosphere, its 
chemical composition, its function, and further how that affects the climate and, in 
return, the ecosystems through feedback processes. Observations from key tower sites 
standing out due to their long-term comprehensive observations: The Amazon Tall 
Tower Observatory in Central Amazonia, the Zotino Tall Tower Observatory in Siberia, and 
the Station to Measure Ecosystem-Atmosphere Relations at Hyytiäla in Finland. The review 
is complemented by short-term observations from networks and large experiments.
The review discusses atmospheric chemistry observations, aerosol formation and 
processing, physiochemical aerosol, and cloud condensation nuclei properties and 
finds surprising similarities and important differences in the two ecosystems. The 
aerosol concentrations and chemistry are similar, particularly concerning the main 
chemical components, both dominated by an organic fraction, while the boreal 
ecosystem has generally higher concentrations of inorganics, due to higher influence 
of long-range transported air pollution. The emissions of biogenic volatile organic 
compounds are dominated by isoprene and monoterpene in the tropical and boreal 
regions, respectively, being the main precursors of the organic aerosol fraction.
Observations and modeling studies show that climate change and deforestation 
affect the ecosystems such that the carbon and hydrological cycles in Amazonia are 
changing to carbon neutrality and affect precipitation downwind. In Africa, the tropical 
forests are so far maintaining their carbon sink.
It is urgent to better understand the interaction between these major ecosystems, the 
atmosphere, and climate, which calls for more observation sites, providing long-term 
data on water, carbon, and other biogeochemical cycles. This is essential in finding a 
sustainable balance between forest preservation and reforestation versus a potential 
increase in food production and biofuels, which are critical in maintaining ecosystem 
services and global climate stability. Reducing global warming and deforestation is 
vital for tropical forests.