P6 Soil incubations for model validation data sets and experiments to quantify the anaerobic soil volume fraction [funded by DFG]

Project staff:

Dr. Balázs Grosz
PD Dr. Carsten Müller
PD Dr. Reinhard Well


Robust denitrification data suitable to validate N2 fluxes in denitrification models are scarce due to previous methodical limitations and the extreme spatio-temporal heterogeneity of denitrification. The anaerobic soil volume fraction (ansvf), a major control of denitrification, is known to depend on the spatial distributions of gas diffusivity and respiration. However, estimating ansvf has been hampered in the past by the difficulty to quantify its controls. Today, new and improved methods are available to fill those gaps. These aspects will be tackled in four parts:


1. We will use new and improved stable isotope approaches to provide denitrification data sets comprising as much detail on activity and regulation as possible as a basis to validate existing and calibrate new denitrification models that are applied and/or developed by DASIM subprojects (P7, P8, PC).


2. Incubations with increasing soil volumes under standardized conditions will be conducted to determine the minimum elementary volume of denitrification as a basis for upscaling.


3. In cooperation with P1 and P8, we will employ spatial gas diffusivity measurement and modeling as well as denitrification measurements at defined O2 status to obtain independent estimates of the ansvf. These will be cross-validated and the most promising approach will be used to calibrate ansvf in the new denitrification models (P8).


4. We will test to which extent the measurement of µ-scale distribution of denitrification and its controls is feasible using NanoSIMS and whether it is a suitable tool to further investigate µ-scale heterogeneity in phase 2 of DASIM. This test includes the measurement of organic matter distribution within selected soil aggregates and a new 15N tracer approach to locate nitrate consumption in aggregates.


Publications and poster presentations: