Greenhouse gases surge from desert soils just minutes after rain

Drylands are famous for their silence after long droughts – until the first raindrops hit. Then the ground itself seems to exhale. For decades, scientists assumed those sudden “pulse emissions” of gases came almost entirely from soil microbes jolted awake by water.

New research from Ben-Gurion University of the Negev (BGU) upends that idea. In some desert soils, the very first and strongest bursts can be driven by chemistry alone.

Dead soils release gas

A team led by Dr. Isaac Yagle and Professor Ilya Gelfand at BGU’s Blaustein Institutes for Desert Research compared gas releases from natural desert soils.

The team used identical soils that had been sterilized with high-dose gamma irradiation. The soils – collected near the Dead Sea – were then wetted to mimic a passing shower.

Within minutes, both sets began emitting carbon dioxide (CO₂), nitrous oxide (N₂O), and nitric oxide (NO). Surprisingly, the sterilized soils – essentially stripped of living microbes – released far more nitrogen gases in the first moments after wetting: up to thirteen times more NO and five times more N₂O than the “live” soils.

The finding overturns a longstanding assumption that biology is the sole trigger for post-rain gas surges in drylands. It also helps explain why pulses arrive so quickly. Microbes can react fast, but chemical reactions can ignite almost instantly.

Rain triggers chemical surges

What’s going on inside those first few wet minutes? In arid, alkaline soils that bake under intense sun, reactive nitrogen compounds accumulate during drought – especially nitrite (NO₂⁻).

When water finally arrives, it sparks a burst of purely chemical activity. A process called chemodenitrification, driven by minerals and trace metals, allows nitrite to decompose into NO and N₂O without microbial help.

Water also dissolves carbonates and releases CO₂, creating a non-biological gas pulse that joins the familiar microbial “breath” of soil.

The team’s side-by-side tests make the point clear. Even when soils were sterilized, the earliest emissions surged. And when the researchers compared inorganic nitrogen levels, the first N₂O and NO pulses looked nearly identical in sterilized and live soils – evidence that abiotic chemistry dominates the opening act.

Soil microbes join the act

Still, the chemical start is not the whole story. In live soils, CO₂ rose higher overall because microbes add a steady respiratory contribution.

Over the next hours and days, as bacteria and archaea recover from drought stress, they resume nitrification and denitrification, layering biological processes on top of the chemical foundation.

This gradual handoff creates a two-part performance. Abiotic reactions set the stage in those first wet moments, while microbial activity delivers the longer, steadier second act. For nitrogen gases in particular, though, the curtain-raiser belongs mostly to chemistry.

Why these gases matter

N₂O and NO aren’t just lab curiosities. Nitrous oxide is a powerful, long-lived greenhouse gas and a leading destroyer of stratospheric ozone. Nitric oxide is a building block of ground-level ozone and smog.

In drylands around the world – from the Sahel to the American Southwest – short rain showers are becoming more erratic as climate change reshapes storm patterns. That means more frequent wet–dry cycles and, potentially, more frequent pulses.

Until now, most models that estimate greenhouse gas emissions from soils have treated these bursts as a microbial phenomenon. The new results show that approach can miss a big piece of the puzzle in deserts and semi-deserts.

If chemistry is responsible for a large share of the earliest emissions – especially for N₂O and NO – then ignoring abiotic reactions likely underestimates a region’s contribution to warming and to air pollution episodes following storms.

Curbing desert gas surges

There’s also a management angle. In some dryland soils, high background salinity, alkalinity, and stored nitrogen set the stage for stronger chemical pulses.

Land uses that alter soil nitrogen – think fertilized rangelands, irrigated fallows, or dust inputs – could unintentionally prime bigger emissions after rain.

Recognizing the chemical pathways at play might guide strategies to reduce peaks, for example by limiting nitrogen buildup in vulnerable areas.

Inside desert soil reactions

The study’s design is as important as its conclusions. By sterilizing soils with gamma irradiation  – a method that preserves the physical structure and many chemical traits while eliminating most life – the team could cleanly separate biological from abiotic processes.

Rapid measurements right after wetting captured the fleeting first minutes that field campaigns often miss.

The comparison revealed a mixed picture for CO₂. Biology dominates, but non-biological carbonate reactions can make a meaningful contribution, especially in alkaline desert soils. For N gases, chemistry takes the initial lead, and biology joins later.

It’s a nuanced message: post-rain pulses in drylands aren’t either microbial or chemical – they’re both, but their timing differs. The chemicals sprint; the microbes run the middle distance.

Drylands shape the future

Drylands already cover more than 40 percent of Earth’s land surface, and they’re expanding. As droughts lengthen and rain arrives in shorter, sharper bursts, the conditions that produce pulse emissions will become more common.

Translating the lab results to landscapes will require field tests across different deserts, soil types, and storm intensities. But the core takeaway is ready for prime time: abiotic processes belong in the accounting.

For climate modelers, that means adding fast chemical terms to the equations that predict N₂O and NO releases after rain.

For air-quality forecasters, it means recognizing that even “sterile” soil chemistry can feed ozone formation in the hours after a storm. And for anyone who thinks of deserts as lifeless, it’s a reminder that the ground itself holds a lively chemistry set – one that can shape the air we all share.

The study is published in the journal Scientific Reports.

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