Climate-warmed leaves change ecosystems: Study

Rising soil temperatures significantly affect autumn leaves and in the process our food supply chain and appearance and biochemical makeup of the lakes these leaves fall into, finds a new study.

This is one of the first studies to rigorously explore climate warming's impact on "ecological subsidies," or the exchange of nutrients and organisms between ecosystems.

"Our findings could have profound consequences for conceptualizing how climate warming impacts linkages between terrestrial and aquatic ecosystems," said Samuel Fey, visiting scholar at the Dartmouth College, Germany and lead author.

For the study, the researchers collected maple leaves during autumn from experimental forest plots where the soil had been warmed or left untouched.

The leaves were left to experimental freshwater enclosures containing plankton food webs consisting of zooplankton, algae and bacteria, thus creating "no leaf", "ambient leaf" and "heated leaf" conditions.

The soil warming caused a two-fold decrease in the leaves' phosphorus concentrations.

The addition of these "warmed" leaves to the ponds decreased the water's phosphorus, dissolved organic carbon and density of bacteria.

The process also improved the water's clarity and caused a three-fold increase in the density of cladoceran zooplankton or water fleas.

Zooplankton provide a crucial source of food to many larger aquatic organisms such as fish.

"Virtually nothing is known about how climate change may alter ecological subsidies," Fey pointed out.

"Our results suggest that changes in soil temperature can have unexpected consequences for lake ecology and that predicting the consequences of climate change will require research across ecosystem boundaries," Fey concluded.

The study appeared online in the journal Oikos.