Persistence and turnover of soil organic carbon in global drylands
- Hui Wang
- Fernando T. Maestre
- Nan Lu
- Guang Zhao
- Yangjian Zhang
- Sergio Asensio
- De Shorn E. Bramble
- Weiliang Chen
- Michaela A. Dippold
- David J. Eldridge
- Juan J. Gaitán
- Miguel García-Gómez
- Beatriz Gozalo
- Nicolas Gross
- Emilio Guirado
- Yoann Le Bagousse-Pinguet
- Jaime Martínez-Valderrama
- Betty J. Mendoza
- Victoria Ochoa
- César Plaza
- Hugo Saiz
- Marion Schrumpf
- Carlos A. Sierra
- Andrés Tangarife-Escobar
- Enrique Valencia
- Sophie F. von Fromm
- Cong Wang
- Kai Wang
- Yunqiang Wang
- Sönke Zaehle
- Bojie Fu
- Susan Trumbore
- Jianbei Huang
2026-04-22
Reliable predictions of dryland carbon fluxes require understanding the persistence and turnover of soil organic carbon (SOC). We measure radiocarbon to quantify the age of SOC and CO 2 released from soil respiration at 97 dryland sites across six continents. Here we show that bulk SOC contains little C fixed in the past 60 years, while respired CO 2 originates from both bomb-derived recent C and millennia-old C, challenging the idea that old C is chemically or physically protected. Radiocarbon suggests mean ages of ~2100 years for bulk SOC and ~520 years for respired CO 2 , the latter far older than machine-learning (<50 years) or Earth system models predict. Aridity, net primary productivity, and SOC content are dominant predictors for radiocarbon signatures, with abrupt shifts to older C beyond an aridity threshold of ~0.87. Our findings underscore the need to incorporate the vulnerability of older carbon into models and land management strategies.