Rico Holdo

Challenging the maximum rooting depth paradigm in grasslands and savannas

Author(s): Jesse B. Nippert and Ricardo M. Holdo
Date of Publication: January 2015
Abstract:

For many grassland and savanna ecosystems, water limitation is a key regulator of individual plant, community and ecosystem processes. Maximum rooting depth is commonly used to characterize the susceptibility of plant species to drought. This rests on the assumption that deep-rooted plant species would have a greater total volume of soil water to exploit and should be less susceptible to episodic changes in water availability.
Independent of maximum rooting depth, rooting strategies based on differences in biomass allocation with depth, uptake plasticity in relation to water availability and variation in water transport capability may all influence growth responses and susceptibility to drought. Many examples from grasslands and savannas reflect these rooting strategies among coexisting grass, forb and woody species.
Here, we use a dynamic model of plant water uptake and growth to show how changes in root distribution, functional plasticity and root hydraulic conductivity have the potential to influence aboveground biomass and competitive outcomes, even when maximum rooting depth remains constant. We also show theoretically that shifts in root distribution to surface soils without changes in maximum depth can potentially outweigh the benefits of increased maximum rooting depth.
Combining our current reliance on biogeographic descriptions of maximum rooting depth with insights about other, more subtle aspects of root structure and function are likely to improve our understanding of ecosystem responses to dynamic water limitation.

Citation: Nippert, J. B., Holdo, R. M. (2015), Challenging the maximum rooting depth paradigm in grasslands and savannas. Functional Ecology. doi: 10.1111/1365-2435.12390
Team(s): Plant Team

Plant and Education Teams: Learning Modules with High School Students in Native Prairies and Woodlands

As a part of the Missouri Transect project, MU biologist Ricardo Holdo is studying how drought impacts tallgrass prairie community dynamics. He has partnered with Troy Sadler and Patricia Friedrichsen, MU science education researchers, to integrate aspects of his studies at Tucker Prairie into teaching and learning materials appropriate for high school students. Sadler and Friedrichsen are working with biology teachers and students from Rock Bridge High School to develop and pilot these materials.  The learning module features climate change as a central issue for the students to explore as they develop an understanding of ecosystem dynamics and ecological relationships.

                                                        

175 high school students along with their honors biology teachers and a team of 18 scientists and science educators—including faculty and graduate students—from the University of Missouri explored Tucker Prairie, one of the last remaining tall grass prairie ecosystems in Missouri.  The students engaged in five activities designed to explore different dimensions of the prairie ecosystem. In the field, students 1) explored the role of fire in maintaining prairie ecosystems, 2) documented encroachment of woody plants into the tall grass community, 3) compared the current landscape with historic records, 4) surveyed insect diversity, and 5) examined soil profiles.

Similar student learning projects will be implemented around the state by Missouri Transect researchers and educators.

Tags: ecology, learning modules, high school education, outreach, Tucker Prairie, Rico Holdo, Troy Sadler, Terry Woodford-Thomas