The study found that the base rate of organic carbon decomposition in soils across the United States can vary widely, a difference that can matter for climate forecasts because soil holds more carbon than the atmosphere and plants together. Researchers collected samples from 20 sites in the National Ecological Observatory Network (NEON) and incubated them under uniform laboratory conditions for 18 months.
During incubation the team measured carbon dioxide emissions and 26 soil properties to estimate each sample's decay rate and carbon use efficiency. Machine learning identified expected factors such as soil type, pH and nitrogen, and also highlighted fungal abundance plus certain forms of iron and aluminum. These minerals help stabilize mineral-associated organic carbon, a pool that can persist for decades or centuries.
The researchers combined measurements and base-rate estimates to build AI models that reproduced variation across 156 soil samples. They then mapped decay rates and carbon use efficiency across the continental US, finding clear regional differences. The authors say Earth system models should include more geochemical and microbial controls to improve climate projections and guide conservation and carbon market programs.
Difficult words
- decomposition — breakdown of organic material into simpler parts
- base rate — typical speed at which something occurs
- incubation — period when samples are kept in controlled conditions
- decay rate — measure of how fast material breaks down
- carbon use efficiency — proportion of carbon turned into organism biomass
- fungal abundance — amount of fungi living in a soil sample
- mineral-associated organic carbon — organic matter bound to soil minerals
- geochemical — related to chemical processes in soils and rocks
- microbial — relating to very small living organisms like bacteria
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Discussion questions
- How could maps of decay rates across regions help conservation or land managers in your area?
- Why is it important for climate models to include geochemical and microbial controls?
- What simple actions could people or farmers take to help protect soil carbon where you live?
