Simulating climate change in situ in a tropical rainforest understorey using active air warming and CO2 addition

Background: Future climate-change effects on plant growth are most effectively studied using microclimate-manipulation experiments, the design of which has seen much advance in recent years. For tropical forests, however, such experiments are particularly hard to install and have hence not been widely used. We present a system of active heating and CO2 fertilisation for use in tropical forest understoreys, where passive heating is not possible. The system was run for two years to study climate-change effects on epiphytic bryophytes, but is also deemed suitable to study other understorey plants.

Methods: Warm-air and CO2 addition were applied in 1.6-m tall, 1.2-m diameter hexagonal open-top chambers and the microclimate in the chambers compared to outside air. Warming was regulated with a feedback system while CO2 addition was fixed.

Results: The setup successfully heated the air by 2.8K and increased CO2 by 250 ppm, on average, with +3K and +300 ppm as the targets. Variation was h...