Temperature sensitivity of soil respiration changes with long-term warming and cooling of grassland soils – a question of carbon stability?

Larissa Schierling1, Johanna Pausch1, Khatab Abdalla1, Yue Sun1, Max Schuchardt2, Anke Jentsch2, Eva Lehndorff3, Nele Meyer3
1 Department of Agroecology, BayCEER, University of Bayreuth, Bayreuth, Germany
2 Department of Disturbance Ecology, BayCEER, University of Bayreuth, Bayreuth, Germany
3 Department of Soil Ecology, BayCEER, University of Bayreuth, Bayreuth, Germany

P 5.6 in Open Poster Session

Climate change is one of the biggest challenges in future years. It is altering ecosystems in almost every ecozone. Higher average temperatures and changing precipitation patterns are influencing the carbon storage and CO2-release from soils to the atmosphere. Especially grasslands play a crucial role for carbon cycling because they are important carbon sinks. Further, particularly alpine, and subalpine ecosystems are expected to be mostly affected by climate change. For an analysis how soils react to higher temperatures a reciprocal translocation experiment of grassland soils from an alpine site (Furka), subalpine site (Stubai), and colline site (Bayreuth) was done. Therefore, soil samples were translocated upslope and downslope along an elevation gradient of 2,090 m to expose soils to warmer and colder conditions. For all study sites a climatic control was reburied at site of origin. Here, we aimed at investigating whether long-term warming or cooling affects the temperature sensitivity of soil respiration. We hypothesized that warming increases the proportion of stable C in soil (e.g. aggregation), thereby also increasing the temperature sensitivity (Q10) of soil respiration. To test these hypotheses, soil properties like C/N-ratio, pH, soil respiration, microbial biomass, and aggregate size distribution were investigated and Q10 was measured. Especially the long-term warming of alpine grasslands had a great impact and showed decreasing Q10 values, respiration rates, microbial biomass and C/N-ratios. Both, long-term warming and cooling of subalpine grassland soils, showed often conversely trends. This indicates that especially for alpine grassland soils global warming will decrease the temperature sensitivity of soils, the carbon stabilisation and carbon release in the atmosphere through soil respiration.

Keywords: temperature sensitivity, carbon stability, aggregate size distribution, grassland soils, reciprocal translocation