A year-long study of three Madrid parks found that soil moisture, not heat, drives carbon dioxide emissions from Mediterranean urban soils. Researchers monitored soil respiration at 36 points across different plant communities. Emissions rose with temperature only up to about 18.4 C, then fell as soils dried out. The standard Q10 model, which assumes emissions keep climbing with temperature, did not fit the data. The authors propose a new model that links warming to moisture loss. Above the temperature breakpoint, soil moisture and recent rainfall were the strongest predictors of CO2 release. The study also found an urban signature: compacted soils blunt the usual rewetting pulse after rain. That means city parks may not behave like natural Mediterranean ecosystems, and urban carbon inventories based on temperature alone could overestimate summer soil emissions. For park managers, the takeaway is practical. Reducing soil compaction, adding organic amendments, improving infiltration, and watering based on soil moisture could help retain carbon. The full study is published in the journal SOIL with DOI 10.5194/soil-12-915-2026.
