Heavy precipitation speeds carbon exchange in tropics

New research by the University of Montana and its partner institutions gives insight into how forests globally will respond to long-term climate change. Cory Cleveland, a UM professor of terrestrial ecosystem ecology, said that previous research in the wet tropics - where much of global forest productivity occurs - indicates that the increased rainfall that may occur with climate change would cause declines in plant growth.

However, their new work suggests that climate-change driven increases in rainfall in warm, wet forests are likely to cause increased plant growth. Plant-growth declines are still expected in cooler forests with increased precipitation.

The research was published April 17 in Ecology Letters. The article, "Temperature and rainfall interact to control carbon cycling in tropical forests," is online.

"Our work is based on real measurements of trees, not from computer models, and therefore may offer the most realistic picture of how much forests grow now, and how they may respond to changing temperature and climate," Cleveland said. "The biggest takeaway is that understanding variations in both rainfall and temperature is important for predicting how climate, as well as climate change, affect tree growth."

He said the research has important implications for climate change. It shows changes in rainfall and temperature in the future likely will affect both plant growth, which removes carbon dioxide from the atmosphere, and organic matter decomposition, which pumps carbon dioxide into the atmosphere.

"If increases in productivity in the tropics outpace increases in decomposition, then greater plant growth in the future will continue to provide an important climate benefit by slowing the rate of global climate change," Cleveland said. "But much more work is needed to resolve the effects of other factors, like soil fertility, on ecosystem carbon exchange and its overall effects on atmospheric CO2 concentrations."

He said the research reinforces the importance of conserving tropical rainforests, where more than 1/3 of global plant production occurs.