Natalie Oram: how prepared are legumes for climate change?

In our latest post, Natalie Oram recalls her work at the Wageningen University ‘Plant traits of grass and legume species for flood resilience and N2O mitigation’, highlights the importance of diverse plant strategies to cope with flood and suggests there is a limit for how much ABBA a person can listen to.

It’s raining, it’s pouring

Climate change is increasing the frequency and severity of extreme weather events, such as floods. This poses a threat to ecosystems, including managed grasslands. Flooding can reduce the growth and survival of grassland plant species and can drastically increase nitrous oxide (N2O) emissions, a greenhouse gas ~300 times stronger than CO2. The key question of our study was, ‘Can we increase the resilience of managed grasslands to these flood events, while also mitigating their N2O emissions?’

We decided that the first step to answering this question would be to determine how a variety of different grassland plant species cope with flooding, and how they mediate flood-induced N2O emissions. One thing that may underlie how a plant deals with flooding is its traits. Groups of plant traits can be used to describe a plant’s general strategy for growth and survival, varying from slow growing plants that produce durable leaves and roots, to plants that opt for faster growth and nutrient uptake while producing cheaper tissues.

We choose 8 grass and 4 legume species that differ in their traits and strategies and grew them (in monocultures) in a greenhouse experiment. Each species was exposed to either control or temporarily flooded conditions. We use aboveground biomass directly after the flood, and after a recovery period to measure a plant species’ resistance and recovery, and measured various traits related to growth and survival, as well as N2O emissions. This meant spending a lot of time at the Unifarm Wageningen greenhouse – a great place to be, with a great group of people! Yan Sun included part of the measurements we took in this study for her MSc thesis, and we were joined by many of our colleagues from the Soil Biology Group and the Unifarm for busy periods of the practical work: harvesting, measuring traits, and of course (the crowd-pleaser) root washing.

Before the words hit the page there are a lot of busy days in the greenhouse. With a great group of people (and chocolate and nice music) it is a lot of fun. Perhaps a bit too much ABBA while root washing (hearing the first chords of Mamma Mia still gives me root washing flashbacks).

When it was all said and done, we found that by using plant’s traits (in control conditions) we could predict how a plant species resisted and recovered from flooding. Slower-growing grass species with a conservative strategy better resisted flooding, while faster-growing grass species with an acquisitive strategy recovered better. In other words, grasses with more durable tissues were more flood-tolerant, with a smaller productivity decline during the flood, while faster growing grass species had higher recovery after the flood. Plant traits were less closely related to legumes’ response to flooding. Legumes were generally less flood tolerant than grasses during the flood but recovered faster. Plant species that had higher resistance and recovery also mitigated flood-induced N2O emissions.

Trifolium fragiferum, Lolium perenne, Lotus corniculatus, and Festuca arundinacea in flooded conditions (top) and their leaf and root morphology (bottom)

Plant traits as a tool to design more flood-resilient grasslands?

By understanding the relationships between plant traits and flood resilience, we can select plant species to grow in mixtures that can best tolerate flooding. For example, sowing conservative grasses that better resist flooding together with acquisitive grasses and legumes that recover better. This could create a grassland that could both resist and recover well from a flood, while mitigating flood-induced N2O emissions during both the flood and post-flood drying periods. The next step is to use the information we gained in the greenhouse experiment to create more flood-resilient mixtures. Increasing plant species richness, or combining specific plant species, in managed grasslands has been shown to increase productivity and reduce nitrogen losses. Mixtures also show higher stability, i.e. perturbations have a smaller effect on their productivity, compared to monocultures. This project will continue by testing how specific plant species combinations (based on their resource acquisition strategies) can tolerate flooding and mitigate flood induced N2O emissions in the field.

About the author

I am an ecologist interested in how grasslands cope with climate change, in terms of plant and microbial community resilience and cascading effects on nutrient and carbon cycling. I am interested in the effects of changing rainfall patterns on grasslands, what underlies these effects, and how we can use this information to increase grassland resilience to more frequent and severe floods and droughts.

Left – making a 13CO2 pulse labelling chamber (photo: Akira Yoshikawa) and right – enjoying a race in the Bernina mountains (photo: Laura Gantenbein).

I conducted this research together with a great group of people while I was a postdoc at the Soil Biology Group, Wageningen University & Research. Currently, I am Research Leaders 2025 Marie Skłodowska Curie fellow at the Functional Ecology Group, University of Innsbruck and the Soil Environmental Microbiology Group, Teagasc. Along with my supervisors, colleagues, and students, I am studying how drought intensity affects plant-soil interactions and ecosystem carbon cycling, and how soil drought legacies affect plant and microbial resilience to subsequent drought. I want to find out if soil remembers a drought, and if this memory affects ecosystem responses to future droughts.

In my spare time, I enjoy hiking and exploring the local nature, running, and baking.

Read the article in full here.

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