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After the fire: What vadose zone science can tell us

June 8, 2026
This illustration shows interactions among burn severity, soil profile features, water repellency formation, and hydrological response after fires. It is being republished from Stewart et al. (2025):  https://doi.org/10.1002/vzj2.70030.
This illustration shows interactions among burn severity, soil profile features, water repellency formation, and hydrological response after fires. It is being republished from Stewart et al. (2025): https://doi.org/10.1002/vzj2.70030.

The effect of fires on soils is a hot topic of research, particularly among those who study what’s known as “the vadose zone.” The vadose zone is the portion of the Earth’s surface that extends from the land surface to the water table. It contains soil, minerals, nutrients, rocks, air, water, roots, organic matter, microorganisms, and animal life and is critical to life on Earth, regulating water, plant growth, and the movement of nutrients and contaminants. Fire alters the vadose zone, changing infiltration, storage, and flow pathways and can make soil water-repellent, reducing absorption and increasing runoff.

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Ryan Stewart using thermal imaging to understand how critical vadose zone properties affect plant heat stress. Photo courtesy of Georg Leitinger.
June 17, 2026

The science of the in-between: Why the vadose zone matters

What happens just underneath the Earth’s surface is responsible for our agricultural systems, regulates our climate, and supports our infrastructure. A multistate group of soil scientists recently published a Vadose Zone Journal review that outlines key areas of research happening in this unsaturated zone. Knowledge gaps turn into research opportunities as the scientists review what we know—and don’t know—about how soil moisture, the hydrologic cycle, emerging soil contaminants, and more.

Check out the short video below summarizing the main points of this article and next month's companion article