As a biogeochemist, I'm interested in how life has been sustained on Earth deep in its past as well as here and now - and what that means for our search for life on other planets.

Soil nutrient cycling

If we want to know more about how ancient nutrient cycles worked, we need to understand modern processes as best as we can. I have collected over 400 modern soils (from mostly North America) to study spatial and climatic trends in modern B horizons, which are the horizons typically used in paleoclimate or paleoenvironment reconstructions. Improving our understanding of modern nutrient cycles on land is also useful when thinking about how land use and fertility may shift under a changing climate.

In particular, I'm interested in potential relationships between the iron content of soils and regional climates/seasons, and how biological soil crusts (symbiotic desert communities of microbes, moss, and fungi) cycle phosphorus, an essential nutrient that's typically biolimiting in terrestrial ecosystems.

PAPER: Dzombak & Sheldon (2020), Soil Systems 73(4)

DATA: on Mendeley Data

Modern soils with a range of iron oxides make a red and yellow rainbow!

Terrestrial early Earth

Thick mosses cover a recent volcanic landscape in Iceland. This scene stretches for miles and miles, making it easy to imagine a misty, primordial landscape!

The same nutrients that are important in terrestrial systems today were important two and a half billion years ago, too. I'm interested in constraining what these nutrients were doing - specifically, phosphorus and iron (and how they relate to the all-important carbon cycle). I'm also interested in how weathering has changed over time, delivering different amounts of nutrients to the oceans. Knowing how essential nutrients behaved is critical for reconstructing past oxygen levels and understanding the conditions in which early life evolved.

Speaking of early life...

By studying the chemistry of fossil soils (paleosols), we can look for signs of terrestrial life in the rock record - life that probably looked a lot like the biological soil crusts I also study. They leave chemical traces, called 'biosignatures,' in the soil, and this is what I look for in paleosols. These same terrestrial communities likely contributed oxygen; the question now is, how much?

Paleoclimate & paleoenvironments

We can also use these paleosols to reconstruct past climates and environments. Since soils form at the intersection of the biosphere, atmosphere, and the solid Earth, they provide a unique opportunity for us to understand what was happening right at Earth's surface. Using their chemistry, we can estimate how hot it was, how much it rained, what plants were growing in the soil, and even how much carbon dioxide and oxygen were in the atmosphere when they formed.

My research using paleosols focuses on two aspects: reconstructing climate change during key times in Earth's history (e.g., mass extinctions and greenhouse periods), and statistical analyses of paleosol geochemistry to explore their heterogeneity and constrain paleosol-based proxies.

This type of reconstruction is of interest beyond academia - constraining how climate changed in the past is critical for understanding how the climate (and ecosystems) might change in the future. For example, my work using Eocene paleosols from the Faroe Islands well help us understand how high-latitude regions respond to greenhouse warming, like our planet is undergoing today.

PAPER: Stable terrestrial climate and environment in India across the K-Pg

The Little Grand Canyon in the San Rafael Swell area (near Green River, UT) is a great example of ancient terrestrial landscapes - check out the dark red, oxidized horizons! Those are ancient soils (paleosols).

Gender and race in science communication

In addition to my 'pure' science, I'm interested in the intersection of gender, race, and academic identities in the context of science communication. Who does science communication, and why? How do visible identities of communicators affect perceived support networks of people either in or considering joining STEM? Is mass media coverage of science unintentionally biased?

These are questions I'm passionate about seeking answers to. I've begun to follow this path during my graduate work, but I look forward to continuing this line of research as I move through my career.

Future avenues of work

With my background in modern soils, paleosols, and nutrient cycling, the next step I want to take is in modeling global biogeochemical cycles using constraints from the rock record - paleosol compositions - and modern soil, sub-glacial, and riverine outputs. Several commonly-used biogeochemical models exist, but I would like to better integrate data and models for more robust conclusions about global biogeochemical cycling through Earth's past.

Feel free to contact me!