Dr Sabine Reinsch1, Prof David Robinson1, Prof Per Ambus2, Claus Beier2, Timo Breure3, Christiana A. Dietzen2, Dr Marie F. Arndal2, Prof Inger K Schmidt2, Associate Prof Klaus S Larsen2, Prof Anders Michelsen2, Fiona Seaton1, Prof Bridget A. Emmett1
1Centre For Ecology & Hydrology, Bangor, United Kingdom, 2University of Copenhagen, Copenhagen, Denmark, 3Rothamsted Research, Harpenden, United Kingdom
Soil carbon stocks are vulnerable to climate change. Climate change modulates the soil physico-chemical environment with direct consequences for microbes and soil carbon stocks. Extreme droughts change the physical soil structure, and change the microbial carbon and nutrient supply. Warming affects the microbial activity and their substrate use.
Here we highlight results from two long-term manipulation change experiments and the effects of drought, warming, and elevated CO₂ on soil carbon stocks. Precipitation (drought) and temperature (warming) were manipulated in an Atlantic heathland on seasonally waterlogged organo-mineral soil in Wales, and in a temperate heathland on dry sandy soil in Denmark. The latter included the increase of atmospheric CO₂concentration in a full factorial design with drought and warming.
The aboveground plant community showed little response to drought or warming at both sites. At the wetter organo-mineral site, drought and warming changed the soil physico-chemical environment for microbes over time. Drought permanently decreased the soil water content, increasing the activity of the soil microbial community, which resulted in soil carbon loss, specifically during winter.
At the drier Danish site, the microbial community composition was largely unaffected by drought or warming. However, the pathway of carbon through the microbial community changed in all climate manipulations. Soil carbon was only accumulated under elevated atmospheric CO₂ concentration, and was unaffected by warming and drought.
We show that responses of the soil microbial community adopt to climate-driven changes in the physico-chemical soil matrix, affecting carbon stocks and maintaining overall ecosystem functionality.