When plant ecologists are out for a walk, they see a puzzle. For almost 100 years, they’ve been trying to understand what governs the presence and abundance of a plant species in a community.
For example, why does cheatgrass blanket a landscape, while grand collomia is rare?
Andrew Kulmatiski, an assistant professor of ecology at Utah State University, has identified a potentially important process associated with the abundance of plant species on the sagebrush landscape.
"Farmers have known for thousands of years about plant-soil feedbacks, basically the idea is as a plant grows it accumulates pathogens and symbionts in the soil and that can change subsequent plant growth," Kulmatiski said. "Just in the past 10 or 20 years ecologists have started to think about how plants change soils, and how that affects how plants grow, which plants coexist, and how productive plants are."
This study was performed in the sagebrush steppe using both native and invasive grasses and flowers. The most common species in the sagebrush steppe, like balsamroot and bluebunch wheatgrass, associated with beneficial bacteria and fungi. They also tended to live longer. The rarest species, like grand collomia, interacted with harmful bacteria or fungi and had short lifespans. Invasive species like cheatgrass also tended to have short lifespans, but interacted with beneficial microbes.
Weedy plants’ associations with symbiotic bacteria and fungi could cause them to be successful invaders, and could explain why they are so common in the sagebrush steppe.
"Plants that live a long time and become abundant on the landscape benefit from an ability to increase the abundance of symbionts in the soil like mycorrhizae and growth-promoting bacteria," Kulmatiski said.
Kulmatiski hoped that in the future, plant growth-promoting bacteria and fungi can be isolated in the laboratory. The cultured microbes could then be applied to plants to help desirable plants grow.
Kulmatiski’s research can be found in the December 2017 issue of the Journal of Ecology, under the title Live long and prosper: plant–soil feedback, lifespan, and landscape abundance covary.