soil microbes
In October 2013, researchers switched on heating cables buried in a conifer forest in California's Sierra Nevada. Three round plots, each three meters across, have run 4 °C warmer than unheated plots beside them ever since, from the surface down to about a meter.
It is a small, controlled stand-in for a warmer climate, built so the effect of heat could be measured against ground left alone.
Sourced · Karaoz et al., Nature Communications, Oct 13, 2026
The microbes in those plots face two differences at once: how deep they live, and how warm the soil is.
Over seven and a half years, the team sampled heated and unheated plots down to 90 cm and sequenced all the DNA in each sample, rebuilding more than 2,300 distinct microbial genomes from it. The question was which difference reshapes the community more.
Sourced · Karaoz et al., 2026
Near the surface, the microbes carry more genes for handling methanol, a small molecule with a single carbon atom.
Plants release methanol as they build and loosen pectin, the material that glues their cell walls together. The authors link the surface pattern to that supply from roots and fallen needles.
Sourced · Karaoz et al., 2026
Between 30 and 50 cm, the community changes faster than anywhere else in the profile.
The authors tie this to steep changes at that depth in roots, in the chemistry of the soil's organic matter, and in oxygen.
Sourced · Karaoz et al., 2026
Deeper down, the genes shift toward other fuel: carbon monoxide, nitrogen pulled from the air, and fermentation that ends in alcohols.
The team also measured proteins, which show what microbes were actually making when sampled in 2018. Among the most abundant sugar-processing enzymes in deep soil were sialidases. A sialidase clips a sugar called sialic acid off a glycoprotein, a molecule built from protein and sugar. Glycoproteins are common in the remains of dead microbes and fungi, and the authors read this as deep microbes feeding on that dead material.
Sourced · Karaoz et al., 2026
Set side by side, the two differences are far apart. Depth accounted for about 33% of the variation in which microbes were present from one sample to the next. Four degrees of heat accounted for 2.3%, roughly fourteen times less.
Look across the two columns, then down either one.
Sourced · Karaoz et al., 2026, Fig. 2
Heat still did things. The heated plots release 30 to 37% more carbon dioxide each year, and their subsoils have lost carbon.
The gap between heated and unheated communities shrank between 3.5 and 7.5 years of warming. Meanwhile specific abilities shifted: more stress-tolerance and nutrient-uptake genes near the surface, and more carbon monoxide and single-carbon processing between 10 and 60 cm. Warming changed what these microbes do more than which microbes live there.
Sourced · Hicks Pries et al., Science, 2017; Soong et al., Science Advances, 2021; Karaoz et al., 2026
This is one forest with three pairs of plots, and the protein measurements come from a single year. Genes show what a microbe could do; proteins show what it was doing on the day it was sampled.
Most ecosystem models do not represent how soil microbes differ with depth, the authors note. To follow the experiment as it continues, search for the Blodgett Forest whole-soil warming experiment.
Sourced · Karaoz et al., 2026