Drylands: The Dark Horse of Carbon Cycling

Brooke Osborne is an assistant professor in the Department of Environment and Society at Utah State University’s Moab campus. Brooke is an expert in biogeochemistry and global change ecology. She is fascinated by how ecosystems respond to and shape our changing world and motivated to provide useful and timely information to land managers and policymakers to support healthier ecosystems. She and her lab are especially interested in drylands of the western U.S. and how intensifying and overlapping pressure from grazing, drought, and atmospheric deposition impact how and where soil carbon is stored in arid systems. 

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Drylands, not Wastelands Webinar

Science Moab talks with ecologist Brooke Osborne about the fascinating world of biogeochemistry and dryland science. Brooke is an assistant professor in the Department of Environment and Society at Utah State University’s Moab campus.  We discuss Brooke’s ongoing research into soil carbon storage and sequestration, particularly in the context of grazing practices and land management. 

ScienceMoab: Drylands cover approximately 40% of the Earth’s surface, and they are inhabited by almost a third of the human population. some of your research focuses on the biogeochemical cycling within dry lands.  Can you explain what is meant by this?

Osborne: Biogeochemistry offers this really powerful approach to understanding how ecosystems work, how they may change in the future as a result of human actions. So we look at pools and we look at fluxes. And when I say pools, where and how something is stored, a resource, carbon, water, whatever it might be. And the flux would be the processes that move that element or resource in between pools, 

There’s a lot of things about Drylands that make their biogeochemical cycles really unique. it’s hard to pull from the literature in other ecosystems like a temperate forest or a tropical forest, and to apply that to drylands. They just don’t work that way. First of all, they have really low resource availability. We all know Drylands have low water availability. Sure, that’s true. They also have low carbon availability, nitrogen, phosphorus, and other essential nutrients.  So, it’s hard to generalize about what is limiting things like plant growth or the health and functioning of soils.

In addition to that low resource availability, drylands are really different through space and time. So by space, it’s hard to map patterns of growth, because what’s happening beneath that shrub, what’s happening beneath the bio crust, and what’s in the bare soil is totally different. It’s almost like their own little micro ecosystems.

Drylands are also weird through time. They’re really sensitive to change.  In our annual variability, do we get monsoons or not? That also really impacts what happens in a given year. 

ScienceMoab: Things are getting drier, things are getting hotter. Why are dry lands more susceptible to this warming and drying?

Osborne: Drylands have low resource availability and there’s a lot of heterogeneity. Those things in combination make Drylands more susceptible. When you don’t have a lot of water or a lot of plant cover and your nutrients are limited, you’re sensitive to change.  you can really get rocked by a wet year or a dry year or even changes in land use practices like grazing or oil and gas pad development. Those things are enough to tip conditions over an edge that would create new conditions and processes and functions for an ecosystem.

ScienceMoab:  More recently, your research has focused on the role of carbon stored in dryland ecosystems.  What ideas or questions are you asking?

Osborne: Drylands are the dark horse in these global carbon cycles, and a lot of the carbon is actually beneath our feet in the soil.  Drylands store about 38% of soil carbon on earth.

But if you ask a bio geochemist, where is it? Is it in the shallow soil? Is it deep? What form is it in? Not all soil carbon is created equal. Some cycles quickly. Some stays in the ground for centuries or millennia. How is it changing? We don’t know. Those are fundamental questions, and we do not have those answers.

My work has become very focused on characterizing where and how soil carbon is stored in drylands as well as improving our ability to predict how that’s going to change in the future by trying to ramp up the representation of drylands in the development and implementation of models for predicting and for making decisions.

Soil carbon is a key component of soil health and our ability to grow food, to graze cattle, and to maintain healthy air and water quality.  It also is a key factor in climate.   We talked about what a big player dryland carbon cycling is, and soil carbon storage is no exception to that.  Soil carbon is beginning to play a major role in rural economies through carbon markets and trying to manage carbon with grazing.

We can make decisions that impact how much organic carbon is in our soil and how it functions and how long it’s there through things like grazing practices, rotational grazing, rest periods, things like erosion control or biochar.   We have tools to manage soil carbon, like the resource that it really is.

ScienceMoab: What studies do you hope to see advancing in the next five to 10 years in the arena of dryland science? 

So one of the things I’m really excited about with this project is plugging our data into a new model that’s coming out of a lab at Colorado State University led by Dr. Francesca Cofo, where they are stimulating plant soil, carbon and nitrogen cycling dynamics. These models are pretty sophisticated.  We plug them into the global models. We make projections.  We put them in the international panel climate change graphs. How good are they at representing Drylands?

We want to make sure our predictions about what’s going to happen at the global scale are accurate when it comes to drylands, which again, are such big players at that scale as well.