A team of international scientists lead by Jennifer Firn and James McGree and that includes MU plant ecologist Lauren Sullivan calls into question the efficacy of using single traits as “biological barometers” of the effects of certain global change factors on ecosystem function. The concept that morphological traits, such as specific leaf area (SLA), can serve as a measure of ecosystem response to perturbation is not uncommon. The problem is a lack of data showing these traits to be functional predictors of ecosystem change at a global scale.

The research, published in Nature Ecology and Evolution, found that SLA, one of the key traits currently used in assessing ecosystem function, did not show a consistent response to nutrient addition or alterations to herbivore communities, contrary to existing ecological theory and expectations from physiological ecology. The researchers found instead that leaf nitrogen and phosphorus content showed a stronger and more predictable response to nutrient additions than SLA, even controlling for climatic and various soil factors. These changes in leaf nutrient content were due, in part, to both alterations to species composition and species-level trait variation in response to treatments. The findings, which are based on data collected from 27 grasslands sites in four countries as part of a globally replicated experiment called the Nutrient Network, demonstrate the importance of variation among different study locations and cautions about the use of SLA to explain large-scale patterns in response to anthropogenic change.

According to Sullivan, who assisted with data collection and analysis at one of the sites, “Grasslands are extremely dynamic systems, and we need to be careful making predictions about how they will change without experiments at the correct scale. Our new study shows the need to examine several traits, in addition to SLA, if we want to understand how they respond to nutrient changes.”

For more about this study, see “BEHIND THE PAPER: Operating instructions for using leaf traits as barometers”