Jennifer Jones: The importance of bark decomposition

Admiring some nearby fungi (photo by Astrid Ferrer)
Admiring some nearby fungi (photo by Astrid Ferrer)

In our latest Insight, Jennifer Jones, a researcher at Michigan State University talks about her recent paper, Habitat‐specific effects of bark on wood decomposition: Influences of fragmentation, nitrogen concentration and microbial community composition, moving from policy to research and what happens when a tree falls in wood (and across your experiment.)

About the paper

What’s your paper about?

We explored the differences between bark and wood decomposition and the impact of bark on the decomposition of underlying wood. To address these questions, we did a bark removal experiment in which we decomposed sticks with bark and without bark on the forest floor and in adjacent streams. Through this experiment, we explored three mechanisms by which bark and wood decomposition could differ: nutrient availability, fragmentation, and microbial communities.

What is the background behind your paper?

River near field site (photo by Jennifer Jones)
River near field site (photo by Jennifer Jones)

Bark is a woody substrate that covers most trees. Despite bark and wood differing in nutrient concentration, density, structure, and function, bark and wood are often treated as one substrate in experiments. However, because bark and wood differ in ways that are known to impact decomposition, separating bark and wood decomposition is an easy and potentially revealing way to 1) reduce unexplained variation in predicting wood decomposition rate, and 2) better understand how substrate composition influences decomposition processes.

What are the key messages of your article?

We found that the main drivers of decomposition differ between bark and wood. Bark is likely more susceptible to fragmentation than wood, while wood decomposition is influenced more by nitrogen concentration than bark. The differences in these drivers have implications for understanding bark and wood decay across habitats. Additionally, we found that bark serves as a protective layer surrounding wood, thus slowing wood decomposition in our study. This finding links the rate of bark decomposition with wood decomposition.

About the research

Why is the paper important?

Bark covers wood all over the planet and can make up a substantial proportion of woody biomass. In this paper, we show that different factors drive bark and wood decomposition and that those different factors likely have consequences for how bark and wood decompose across habitats. We found that fragmentation is more important for bark mass loss than wood mass loss, which makes the difference in mass loss between habitats greater in bark than wood. While fragmentation isn’t the chemical breaking apart of carbon compounds by decomposers, it does break woody substrates into smaller pieces which can influence their later digestibility by decomposers. Additionally, because bark serves as a protective layer surrounding wood and slowing wood decomposition, the faster mass loss of bark in streams could speed the decomposition of underlying wood. Overall, our paper demonstrates the importance of studying bark decomposition as separate from wood decomposition, when understanding ecosystem carbon cycling.

Did you have any problems setting up the experiment or gathering your data?

Tree fall (photo by Jennifer Jones)
Tree fall (photo by Jennifer Jones)

A huge tree fell on the experiment between the first and second collection. It’s not that uncommon in a tropical forest to have a tree fall on your experiment, but this one was huge! The tree fell across one of the stream plots and onto the nearby land plot, so I ended up losing both aquatic and terrestrial wood samples. Fortunately, I still had plenty of samples to publish. I also still use the picture I took of the fallen tree in talks as an example of a large pile of dead wood.

What is the next step in this field going to be?

Currently, there are a growing number of studies exploring bark decay, but there is not a consensus on the drivers of bark decay or a thorough understanding of the effect of bark on underlying wood. Our study further complicates the story of bark decay by showing that bark decay can differ from wood decay in habitat-specific ways. There are a few promising questions that I think are important next steps for understanding bark decomposition: Are the effects of bark on underlying wood diameter-dependent, species-specific, or ecosystem-specific? Are the organisms responsible for bark decomposition the same as those responsible for wood decomposition? Studying these questions about bark and wood decay will be important for understanding carbon cycling in forests around the world.

About the Author

However, as I thought more about how to evaluate environmental policies, I realized that I wanted to know more about the science behind the policies. The summer after my sophomore year, I volunteered in a lab to find out if I could do science.

How did you get involved in ecology?

Experiment setup 1 (photo by Jennifer Jones)

I’ve always loved nature, but through middle school and high school I was not interested in being a scientist of any kind. At the end of my freshman year in college, I declared a double major in Political Science and Environmental Policy, thinking that I could have a career in environmental advocacy and/or policy making. However, as I thought more about how to evaluate environmental policies, I realized that I wanted to know more about the science behind the policies. The summer after my sophomore year, I volunteered in a lab to find out if I could do science. That summer, I learned about mycorrhizae and how awesome fungi are. I also learned about the research process. I realized that organizing and problem solving, two aspects of environmental policy and advocacy I enjoyed, were also critical parts of research. Once I realized that I enjoyed the research process and I could combine research with my love of nature, I never looked back.

What are you currently working on?

I still work on microbial ecology and carbon cycling, but my current research is much different from what I did for my dissertation. As a Postdoc at Kellogg Biological Station, I’m working on soil fungal and bacterial communities in agriculture in the U.S. Midwest. Now I am working on a project to study microbial community responses to drought. By manipulating resource availability, fungal diversity, and growing season drought, I hope to explore how trait trade-offs impact microbial community response to stress. 

What article are you most proud of?

So far, I think it’s this one. This paper was the first paper that I tried to write from my dissertation. The paper you read today looks very different from my first few drafts. I tried and failed to answer many questions with this paper (In retrospect I should have made a few more measurements on my samples). However, with the patient guidance of my advisors, a bit of frustration on my part, and a LOT of time, we finished it. In the end, I feel good about the conclusions that we made with the data that we had. While it wasn’t the paper we expected to write, the conclusions are still pretty darn cool!

Read the paper here or the free plain language summary here.

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