Leaf litter has slower decomposition rate in warm temperatures than previously thought

The time it takes for a leaf to decompose might be the key to understanding how temperature affects ecosystems, according to Kansas State University ecologists. 

Using leaf litter data in streams from 1,025 publications, a team of international stream ecologists, including Kansas State University's Walter Dodds, university distinguished professor, and Lydia Zeglin, assistant professor, both in the Division of Biology, found average leaf litter decomposition rates are less than half of what the metabolic theory of ecology would predict. The research, which measured how sensitive leaf litter is to increases in temperature, is published in Global Change Biology. 

"The theory of how organisms respond to temperature says organisms will move at a faster rate at higher temperatures," Dodds said. "That relationship for single organisms — whether it's a lizard or bacterium — has a certain rate of increase with warmer temperatures. According to our study, the rate of decomposition will still happen faster with a rise in temperature, just not as fast as we expected."

The team evaluated data from publications that measured leaf litter in streams and rivers and determined that leaf litter breakdown rates may increase 5-21 percent if the average water temperature warms about 1-4 degrees Celsius. This finding is counter to the metabolic theory estimates of a 10-45 percent increase with the same increase in temperature. 

Dodds said understanding the relationships among temperature, leaf decomposition and running water can help ecologists better predict how the carbon cycle will react with future climate adjustments. Since plant materials store a lot of the world's carbon, and streams and rivers help transport plant material around the world, leaf litter decomposition in streams can be a big contributor to atmospheric carbon.

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Image credit: Walter Dodds.