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Contact: Kirsten Bosnak, Kansas Biological Survey & Center for Ecological Research, 785-864-6267, [email protected]
KU study shows that species-diverse systems like prairies have built-in protection
LAWRENCE — Six years into a study on the effect of plant pathogens in grasslands, University of Kansas researchers have the data to show that species diversity — a hallmark of native prairies — works as a protective shield: It drives growth and sustains the health of species-diverse ecosystems over time, functioning somewhat like an immune system.
The research findings, just published in the Proceedings of the National Academy of Sciences (PNAS), have implications for management of native grassland, rangeland and agricultural lands. The results support regenerative agricultural approaches that strengthen the soil biome long-term, such as intercropping, rotation of different cover crops and encouraging a variety of native perennials (prairie strips) along field margins.
The study emphasized the interaction of changing precipitation and the loss of species diversity.
“We want to understand how far-reaching precipitation changes, along with declines in the number of plant species, work together to affect above-ground ecosystems — their productivity, specifically,” said Jim Bever, who leads the research team. “It’s a big, global question that we’re addressing right here at the KU Field Station in a highly controlled, sustained experiment.”
Bever is a KU Foundation Distinguished Professor of Ecology and Evolutionary Biology and a senior scientist at the Kansas Biological Survey & Center for Ecological Research. The experimental site, known as the Rainfall and Diversity Experiment, covers 10 acres at the KU Field Station north of Lawrence.
All nine study authors were from KU: faculty, postdoctoral researchers, laboratory researchers or graduate students (several early-career researchers now have gone on to doctoral programs, or to postdoctoral or faculty positions at other institutions). The lead author of the new paper is Laura Podzikowski, now a KU postdoctoral researcher, who conducted research leading to the paper for her KU dissertation.
The researchers say that the findings make the strongest case yet that species diversity is directly connected to disease resistance — and that the benefits of that resistance, which strengthens diversity, are long-term.
Over the course of several years, a couple of dozen researchers, including students, have spent time under the research site’s “rainout shelters.” A key activity: counting and weighing plant species in individual plots, which is standard field ecology work. Over time, with varying levels of initial plant diversity and exposure to differing amounts of water, the changes in species makeup became evident.
The study found that plant productivity benefits (on a large scale, things such as carbon storage and food for wildlife) increase with more precipitation. Of course, wetness also drives the growth of plant pathogens. But species-rich systems like native grasslands have built-in protection against this disease pressure. That’s because most pathogens target specific hosts, and where many plant species grow together, their differing levels of resistance dilute the effect of the pathogens.
In the study, this pathogen dilution drove overyielding, which refers to how total biomass produced in a mixed-species plant community is more than what’s expected for a single species, as in a monoculture.
Another factor also drove overyielding: resource partitioning, in which different species use resources differently in the same site, as the researchers had expected.
For decades, ecologists have seen that overyielding occurs in diverse plant communities and that this happens in systems across the world and under vastly differing environmental conditions. The question is why.
“Our research shows two important things,” Podzikowski, lead author, said. “First, multiple factors contribute to increased productivity where there is plant biodiversity, and that might explain why the phenomenon occurs in so many different environments. Second, where the effect of pathogens is diluted, this amplifies the benefits of biodiversity, and this is more important in wetter environments, which encourage pathogens.
“What this suggests is that the loss of biodiversity might have the greatest effect on plant productivity in wetter climates. That might explain why biodiversity loss has differing effects on plant productivity in different climates.”
The research continues at the KU Field Station site. Two National Science Foundation grants supported the study:
A $1.7 million grant, beginning in 2018, through the NSF Dimensions of Biodiversity program.
A $3 million grant, beginning in 2021 as part of a cluster of studies focused on the restoration of native prairie and agricultural ecosystems and based at the Donald Danforth Plant Science Center in St. Louis.
The study has been central to two KU dissertations by students in the lab headed by Bever and by Peggy Schultz of the Biological Survey and the KU Environmental Studies Program.
Podzikowski, who graduated in 2023, focused on ecosystem consequences of plant diversity, including an exploration of the effects of altered precipitation. Haley Burrill, who graduated 2024, focused on the role of plant pathogens in plant community dynamics and mediation of coexistence; Burrill now is a postdoctoral researcher at the University of Oregon and an affiliate researcher at the Kansas Biological Survey.
The Kansas Biological Survey & Center for Ecological Research, a KU designated research center, houses a diverse group of ecological research and remote sensing/GIS programs on KU’s West Campus in Takeru Higuchi Hall, the Smissman Laboratories building and the West District Greenhouse. The research center also manages the 3,200-acre KU Field Station, a site for study in the sciences, arts, humanities and professional programs.
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