DeepEarthShape - Biogeochemistry: Microbial element cycling as a driver of soil formation

 

Investigator Names and Contact Info:

• Marie Spohn (Soil Ecology). Swedish University of Agricultural Sciences, Sweden

 

Chilean Collaborators Involved:

• Felipe A. Aburto (Pedology, Biogeochemistry). Facultad de Ciencias Forestales, Universidad de Concepción, Chile

 

 

 

Postdoc:

Understanding soil microbial activity effects on soil formation in the terrestrial subsurface along a climate gradient in Chile.

• Andrea Scheibe. University of Bayreuth, Germany

supervisor: Dr. habil. M. Spohn

 

MSc:

Microbial processes along a climate gradient and their dependency on the soil water content.

• Isabell Zeißig. University of Bayreuth, Germany

supervisor: Dr. habil. M. Spohn

 

 

 

 

Project summary:

It is not known in detail how microbial activity in soils affects soil formation in different soil depths and under different climatic conditions. The overarching aim of the project proposed here is therefore to study how microbial cycling of C, N, P and Si affects soil formation. For this purpose, we will, first, study microbial biomass, microbial respiration, and the age of total organic C and respired C in soil and saprolite along a climate gradient in the Costal Cordillera of Chile. Second, we aim at quantifying non-symbiotic N₂ fixation along the climate gradient, and at understanding the factors that limit N₂ fixation, microbial respiration and silicate weathering. We will test the hypotheses (i) that microbial respiration in the saprolite that advances weathering is fueled by young organic matter, (ii) that CO₂ concentrations in saprolite are positively correlated with the net primary production, and that (iii) N₂ fixation is strongly limited by water availability along the climate gradient in the Costal Cordillera of Chile. In order to test these hypotheses, we will quantify microbial biomass in 10 m deep saprolite cores taken from four study sites along the climate gradient, and we will quantify the age of total organic C and respired C based on radiocarbon dating. Furthermore, we will quantify N₂ fixation in incubations with ¹⁵N-N₂. Finally, we will synthesize and model the results on biogenic weathering and microbial C, N, P, and Si cycling along the climate gradient in the Costal Cordillera that have been collected during the first and second phase of the priority program. The main value of the project will be that it relates microbial cycling of C, N, P and Si to the formation of soils.