Climate change could have negative effects on stream and forest ecosystems

Science Daily: A rare April freeze in 2007 provided researchers at the Department of Energy's Oak Ridge National Laboratory with further evidence that climate change could have negative effects on stream and forest ecosystems.

As warm weather arrives sooner in many parts of the nation, forest plants and trees on the banks flourish, shading the stream from sunlight and causing an overall decrease in productivity in the late spring and summer. A new research paper describes how a small change in canopy cover can dramatically impact a stream.

"The study implies that the algal productivity pulse in the stream that drives the ecosystem during the spring months could be shortened with climate change if leaf-out continues to occur earlier each year," said ORNL researcher Patrick Mulholland, author of the paper. "The stream no longer gets that period of peak productivity in spring because the leaves are shading the stream when the sun angle is relatively high."

For this particular study, an Arctic air mass sent temperatures to below 28 degrees Fahrenheit for several nights in succession, freezing many of the newly emerged leaves and leaving the stream exposed to higher than normal levels of sunlight over the next several months.

This early April freeze resulted in positive effects for a well-studied East Tennessee stream and reiterated the importance of sunlight on the growth of algae, bacteria, snails and other organisms in forest streams…..

The Falling Water River near the Burgess Falls Dam at Burgess Falls State Park near Cookeville, Tennessee, shot by Brian Stansberry, Wikimedia Commons, under the terms of the GNU Free Documentation License, Version 1.2