Day and night are not equal when it comes to warming, Shiqiang Wan of the Chinese Academy of Sciences’ Institute of Botany reminded the audience today.
Since 2005 Wan has been part of a team looking at how ecosystems change in Inner Mongolia, along the gradient that runs from meadow to typical (grassy) to desert steppe. They’ve set up big experimental plots (right) that alter precipitation, temperature, and other inputs, then see what happens. The idea is to simulate how climatic change might affect various ecosystem responses.
Among many questions they tackled a fairly thorny one: what difference it makes whether warming occurs during the night or during the day. Many computer models, Wan told the meeting, rely on a 24-hour average to sum up the expected effects of warming. His team, however, split out these factors, warming some of their plots during the day only, some during the night only, and some during a 24-hour cycle.
The differences were fairly dramatic, his team reports in a paper in press in Biogeosciences. Plots warmed only during the night turned from being a net carbon source to a net carbon sink; the extra warming at night stimulated leaf respiration rates, which meant they sucked down more carbon than before.
The take-home message? It might sound familiar: climate change could affect the world’s ecosystems in unpredictable and currently little-understood ways.