They selected similar forest types, hardwood deciduous forests, to focus on major differences in climate across the regional gradient. (The average annual temperature in southern New England is about 11 degrees Celsius cooler than Florida.) Within each of the five sub-regions they placed the wood blocks in different types of terrain to evaluate the effects of local versus regional factors as controls on decomposition.
"Most people would try to make sure everything was as standard as possible," said Mark A. Bradford, an assistant professor of terrestrial ecosystem ecology at the Yale School of Forestry & Environmental Studies (F&ES) and lead author of the study. "We said, 'Well, let's generate as much variation as possible.' So we put some blocks on south-facing slopes, where they would be warmer in the summer, and others on north-facing slopes where it's colder. We put some on top of ridges and others next to streams where it was wetter."
After 13 months, they measured how much wood had been lost, whether to the consumption of fungi growing on the wood or to termites consuming the wood.
According to their analysis, local-scale factors explained about three quarters of the variation in wood decomposition, while climate explained only about one quarter, contrary to the expectation that climate should be the predominant control.
"We're reaching the wrong conclusion about the major controls on decomposition because of the way we've traditionally collected and looked at our data," Bradford said. "That in turn will weaken the effectiveness of climate prediction."
The team's recommendation: collect more data at local sites and improve our understanding of how local conditions affect the organisms that drive decomposition, because the
|Contact: Zenaida Gonzalez Kotala|
University of Central Florida