Ellen Welti: Better with a grain of salt. Sodium addition increases leaf herbivory and fungal damage in grasslands

Ellen Welti shares her experience doing her latest research ‘Sodium addition increases leaf herbivory and fungal damage across four grasslands’, the implications of Sodium fertilization for agriculture and her secret cat taming skills.

About the paper

Ellen setting up a transect for the plots
Ellen setting up a transect for the plots

In this paper, we test how elevated sodium in plants would affect how much herbivorous insects and leaf fungal pathogens consume. This study followed previous research from our group which found insects are attracted to sodium fertilization and are likely using plant tissue as a source of dietary sodium. We wanted to know what the consequences would be of more insects around- would the insects also eat more plants? We predicted that—just like we love salted potato chips—salty leaves may be more delicious to wild plant consumers.

The plots at Selman Living Lab in western Oklahoma (photo by the author)

To test this idea, we set up large sodium addition plots across four grasslands in the central US Great Plains. Every month during the summer, we travelled to the four grasslands to add salt to the plots and measure plant growth and chemistry, and damage to plant leaves by insects and fungal pathogens. We measured the amount of leaf tissue eaten on sodium addition plots in comparison to plots which we had not added sodium (controls). Both insect herbivores and fungal pathogens caused greater damage to plants in the sodium addition plots than in the control plots. This is the first paper of a sodium fertilization experiment in a natural ecosystem to look at leaf herbivory rates. The implications of this research are broad. The amount of available sodium on land is increasing in many places—through salting of winter roads, use of increasingly saline irrigation water, and more sodium deposition due to rising sea levels—all increasing our need to understand how sodium affects ecological communities. This work suggests a saltier world favours herbivores, at the expense of plants.

About the research

clipping plant biomass at the Niobrara Prairie Reserve in northern Nebraska
Clipping plant biomass at the Niobrara Prairie Reserve in northern Nebraska

Do you remember that time you sat down to eat dinner and realized you forgot to add salt while cooking? Our research suggests that insect herbivores and even leaf fungal pathogens share our love for a sprinkle of salt with a meal! Sodium is an essential element for all animal life, but not plants. This means animals which primarily depend on plants for food—like grasshoppers and elephants—can be left looking for that extra pinch of salt.

A monarch caterpillar in a plot at Konza Prairie (NE Kansas)

While most plants do not require sodium, they will absorb it passively from their environment. Our results indicate that increased sodium availability will be costly for plants. However, more work is needed on how elevated sodium will reshape food webs over the long-term. For example, if more sodium supports a larger insect herbivore population, will this lead to more predators, like spiders in the next year? Alternatively, in a recent lab experiment, we found that grasshoppers fed more sodium-rich diets jumped further than those fed sodium poor diets. This may suggest that sodium-stocked herbivores are more fit, allowing them to better escape predation.

About the author

A Melanoplus bivittatus grasshopper on a thistle at Konza Prairie
A Melanoplus bivittatus grasshopper on a thistle at Konza Prairie

I am currently working with the Senckenberg Institute in Gelnhausen, Germany on how and why functional traits of invertebrate communities are changing over the long-term. My favourite project I have worked on was a long-term study of changes in the grasshopper community at Konza Prairie, a tallgrass prairie in Kansas, USA. Researchers at Konza have been sampling the grasshopper community since before I was born! I have been involved with this grasshopper monitoring since my time as an undergraduate and am still working with this incredible long-term dataset. Most recently, in 2020 me and my colleagues published a paper showing grasshoppers are declining due to declining plant nutritional quality, likely as a consequence of elevated atmospheric CO2.

the plots at Niobrara Prairie Reserve
The plots at Niobrara Prairie Reserve

The best thing about being an ecologist is that there are so many questions to work on- I never worry about being scooped! On the other hand, it can be depressing to thing about all the negative anthropogenic effects on ecosystems. As the field of ecology moves towards more large-scale and synthesis studies, I would encourage my fellow ecologists to take advantage of local knowledge of study systems by conversing and working with data collectors, field ecologists, and other local experts. One pattern I have noticed in younger ecologists is a tendency to try and complete research planning before going out in the field. As a field ecologist, my experience is you often have to go out in and fail a couple times before you can work out the practical details, so my advice is to go try it out! And of course, the most important advice is to know your research question and design your research with your question in mind at every step.

Personally, I was attracted to ecology all my life. I loved insects and digging in the dirt from an early age and just never grew out of it! In my free time I enjoy water colouring, being outside, and telling my cat that he is a good cat.

Read the article in full here.

2 thoughts on “Ellen Welti: Better with a grain of salt. Sodium addition increases leaf herbivory and fungal damage in grasslands

  1. What a beautiful love story about Ecology. I consider myself fortunate to have stumbled across this little piece of masterful journalism. Keep up the good work, please.

    Like

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