Abstract/Summary

During the 21st century, global mean temperature is expected to rise by 1.5°C to 5.7°C (1). Climate change has already resulted in an overall decrease in the number of cold days and nights, and an increase in the number of warm days and hot nights, across most land areas globally (2). Our changing climate will influence soil ecosystems because soils have a complex interaction with the atmosphere through carbon, nitrogen, and hydrological cycles (3). Soil is the largest terrestrial carbon pool (4–6), but it also provides a habitat for diverse and complex communities of organisms (7). Soil represents a huge potential source of volatile carbon and a potential sink for additional carbon. Soil can therefore buffer CO2 losses into the atmosphere, depending on the balance between photosynthesis, autotrophic respiration, and heterotrophic respiration (2, 8). This balance exerts major controls on the biogeochemical interactions between land and atmosphere leading to the exchange of greenhouse gases like CO2, CH4 and N2O (2), the emissions of which could cause positive feedbacks that warm our climate system (9, 10). While the response of autotrophic respiration to changing climates is relatively well understood, predicting changes to the soil carbon sink due to climate change has been a major source of uncertainty in projections. Although it is known that increasing temperature can stimulate microbial degradation of soil organic carbon and increase the atmospheric concentration of CO2 (10–12), the magnitude of this positive feedback is unclear.