Analyses led by the University of Michigan can help land managers and conservationists help nature prepare for a warmer future
Study: A few key species drive community thermophilization under experimental warming (DOI: 10.1073/pnas.2533434123)
A new analysis of experimental data led by the University of Michigan has unveiled insights into why and how plant communities are changing their makeup to survive in warmer temperatures.
Thanks to field studies of plant communities in nature, scientists had previously established that plant species that prefer warmth are becoming more abundant, while those that prefer cooler temperatures are waning. Although researchers strongly suspected that this phenomenon, known as thermophilization, was driven by warming temperatures, their observations alone couldn't rule out other factors.
With data from six long-term experiments that controlled for other variables, the new study has confirmed that the warming global climate is the cause of thermophilization. And the analysis also provided a more surprising finding: A small number of species dominated the shifting temperature preference for an entire community.
The research was supported, in part, by federal funding from the U.S. National Science Foundation.
"You might have a community that's composed of tens of different species, but what we're finding is that it's really just a handful that are responsible for driving the changes in the community temperature profile," said Kara Dobson, lead author of the new report published in the Proceedings of the National Academy of Sciences. Dobson is a postdoctoral research fellow with the Institute for Global Change Biology at the U-M School for Environment and Sustainability, or SEAS.
"We think this information will be very relevant for land managers and conservationists, especially looking into the future if they want to preempt climate change," she said.
For example, land managers and conservationists could steer plant communities to feature more warm-loving species to potentially make entire communities more resilient. There is a wrinkle, though, in that the species that have an outsized community impact are different in different settings. Dobson and colleagues also found no shared traits or ancestry across species that could predict which would be the driver of a community's response.
"This thermophilization is occurring in a very specific way for each specific site that we looked at," Dobson said.
The team's study included data from six experimental sites in Minnesota, Oklahoma, Wyoming and California, representing a diversity of ecosystems, said Kai Zhu, a corresponding author of the study and associate professor with SEAS. Each experiment ran for at least seven years. To understand a given species' contribution to thermophilization, the team relied on a value known as the community temperature index, or CTI.
Technically, this characterizes what's known as a plant community's thermal niche. More abstractly, imagine asking each plant species in a given habitat what its preferred temperature would be. Taking an average of those answers that are weighed according to the abundance of each species would yield the CTI. Zhu, Dobson and their colleagues could then track how CTIs changed as the experiments raised the temperature in a community.
"The first question is, 'Does CTI go up with warming?' The answer is yes, and it's a strikingly consistent result. The next question is what you might call attribution: Which species are contributing and how much?" Zhu said. "What we found is that not everyone has an equal share-only a handful of species make the greatest contributions."
Although which species would be the most influential didn't become clear until after the warming started, the research did find that those few species remained in control as warming increased.
"To some extent, this makes managing for climate change a little more convenient," Zhu said. "It means you don't have to give every species in an ecosystem the same amount of attention. You can zoom in on the species that really drive change in the community."
Co-authors from U-M included doctoral student Jiali Zhu, postdoctoral fellow Yiluan Song and Peter Reich, a SEAS professor and director of the Institute for Global Change Biology. Collaborators from the University of Wisconsin, University of Minnesota and Utah State University also contributed to the research. Additional funding for the project was provided by Schmidt Sciences.
