Soil microbes capture more carbon when warm, far less when dry
Su Y, Fan L, Chen Z, Tang X, Wang J
Soil Health
The alpine meadows grazing animals depend on are running a carbon-nitrogen trade-off underground that swings hard with weather, meaning a dry summer can undo what a warm one built up in the soil's hidden carbon bank.
In high-altitude grassland soil, tiny microbes called nitrifiers pull nitrogen from urea (like the kind livestock leave behind) and use some of that energy to trap carbon dioxide from the air, turning it into their own cells. Scientists found that warming makes these microbes grab up to 2.5 times more CO2, but drought cuts that capture by as much as 91%. The catch: the same microbes also release nitrous oxide, a greenhouse gas so potent that the tiny bit of carbon they capture barely offsets it.
Key Findings
Warming increased microbial CO2 fixation rates to 1.48-2.58 times the level seen at 15°C under moist conditions
Drought reduced CO2 fixation by 59-91%, and captured carbon offset only 1.3-12.1% of associated N2O emissions (as CO2 equivalents)
Ammonia-oxidizing archaea showed the strongest carbon uptake under combined warming and drought and were the most connected group in microbial co-occurrence networks
chevron_right Technical Summary
Alpine grassland soils use microbial nitrogen processing to lock away small amounts of CO2, but this natural carbon capture is highly vulnerable to climate swings: warming boosts it while drought nearly shuts it down, and the process barely dents the potent greenhouse gas it releases as a byproduct.
Abstract Preview
Original paper
Nitrification Couples Microbial CO2 Fixation to Warming and Drought Responses in Alpine Grassland Soils.
Microbial CO2 fixation in alpine grassland soils is highly sensitive to warming and drought. Nitrogen inputs from grazing may stimulate autotrophic nitrifiers, including ammonia-oxidizing archaea (...
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