Lina Aoyama: Root diversity in grasslands buffers biomass production under drought

Lina Aoyama: Root diversity in grasslands buffers biomass production under drought

In this post, Lina Aoyama, a PhD student at the University of Oregon, discusses their research “Functional diversity buffers biomass production across variable rainfall conditions through different processes above- versus below-ground“, which has been shortlisted for Functional Ecology’s 2023 Haldane Prize for Early Career Researchers.

About the paper

Water is a strong driver of plant productivity, and which plant species are there and how many of them determine how plant communities respond to fluctuating rainfall patterns. Functional traits are morphological, physiological, or phenological characteristics that are relevant to the response of individuals to the environment. Ecologists have been using functional traits to understand how community-level functional diversity can predict ecosystem functions like plant productivity. Aboveground traits are easy to measure, so we have some understanding of the functional diversity-biomass relationships aboveground. On the other hand, we know little about functional diversity-biomass relationships belowground, let alone in variable water conditions.

My collaborators, Caitlin White, Lauren Hallett, and Katie Suding, collected plant productivity data from their rainfall manipulation experiments in California. When Ashley Shaw, who was a postdoctoral fellow in the Hallett Lab at the time, and I started analyzing the field-collected plant productivity data with existing greenhouse trait data in fall of 2018, we actually didn’t find any strong patterns between functional diversity and biomass across rainfall or seeding treatments that we were looking for. We knew there was a gap in the data, especially belowground traits of some forb species, but we put a pin on this project for three years. In fall of 2021, we decided to collect the missing data for this study when the need to collect greenhouse trait data for other projects in the lab arose.

Greenhouse trait data collection with Ashley Shaw and Eliza Hernández at the University of Oregon (Credit: Lina Aoyama)

Annual grasses grew no problem in the greenhouse, but we had some trouble either germinating or keeping seedlings alive until the benchmark harvest time for some forb species. By scarifying the seeds before sowing and adjusting the watering levels, we had better success, and we were able to get a better representation of forbs in the trait dataset. While our hands were pruned from washing delicate roots, we enjoyed seeing the diversity of root structures across species.

Tedious root washing is not too bad when you do it with friends (Credit: Lina Aoyama)

From this effort, we found that aboveground biomass is driven by a few dominant species in the community, while belowground biomass is not driven by a particular group of species in the community. Interestingly, biomass was largely unaffected by the timing of drought, but we found shifts in community-wide functional traits in response to watering treatments. We would have missed this sensitivity of functional diversity-biomass relationships to changes in water resources if we had not captured the whole suite of functional traits present in the plant community. The management implication of this paper is that seeding diverse seed mixes with high functional diversity could buffer restoration efforts from seasonal drought.

Future direction of this research is measuring how much the changes in community-wide functional diversity is coming from shuffling of plant species within the community or phenotypic plasticity (the ability of individuals to express different phenotypes when grown in different environments). We have yet to understand which species and functional traits are more or less plastic than others. Quantifying this variation in phenotypic plasticity could improve our predictions for plant community responses to changing climate.

About the author

I have always loved spending time outdoors. Attending the School for Field Studies in Tanzania during my sophomore year of college sparked my interest in ecology. Upon returning, I knocked on ecology labs that provided field-based research experiences for undergraduate students. My first research experience was working as a summer research assistant for a project investigating the habitat use of grizzly bears in a provincial park of Alberta, Canada. This was my first time driving a truck so big that I had to climb up to sit in the driver’s seat, learning how to use a hand-held radio, and hiking up mountains with GPS units. My mentor at the time trusted me with much and empowered me to believe that I, too, could become an ecologist like her. Now, when I bring my students to fieldwork, I remind myself that these early experiences in the field are crucial to shaping their careers in science.

My first field research experience in Alberta, Canada (Credit: Lina Aoyama)

As I am currently finishing my dissertation as a PhD student at the University of Oregon, I have been pondering what gives me joy in science. I enjoy doing science, not only because it takes me to beautiful places, but because I meet people who are passionate about making a difference in the world. I think it is really beautiful when people from different disciplines, backgrounds, and values come together to work on solving an environmental problem. For example, I work in the western United States where wildfires, combined with climate change and invasive species, are threatening ecosystem functioning and biodiversity of rangelands. And I have been encouraged to see how much collaboration there is among ranchers, natural resource managers, scientists, and policy makers to tackle the wildfire challenge. I hope to continue working in places where I will be rubbing shoulders with people with different ways of thinking and closing the gap between science and practice.

Collecting seeds in the sagebrush steppe of Great Basin at the start of my PhD (Credit: Lina Aoyama)
Leave a comment

Send a Comment

Your email address will not be published. Required fields are marked *