Characterizing spatio-temporal patterns of soil carbon pools at field scale

Research Area:
Soil Science, Geochemistry

In the 1st phase of TR32 we established the use of mid-infrared spectroscopy for reliably estimating the spatial patterns of different soil C pools (particulate organic matter (POM) of different size, black carbon (BC), mineral bound carbon) and basic soil properties (contents of clay, pedogenic oxides, lime etc.) at field scale. We found that the spatial heterogeneity of BC and mineral-bound soil organic matter fractions at our test site Selhausen follow a deterministic pattern that could likely be attributed to C-saturation processes.

During the 2nd phase we elucidated the underlying processes governing the dynamics of faster cycling C pools for both, arable- (Selhausen) and grassland (Rollesbroich) ecosystems. Our ultimate goal was the prediction of actual soil respiration in the field from measurable soil properties. For this purpose we monitored the temporal dynamics of SOC and POM at the bare soil test-site in Selhausen and combined it with lab based soil incubations.

A neighboring natural abundance labeling experiment allowed us to quantify the effects of freshly incorporated plant debris and to monitor its fate among the different C-pools. The C dynamics under grassland were investigated for a small catchment in the National-Park Eifel (Rollesbroich). Here, special emphasis was put on the explanatory power of different soil types and its effect on soil respiration. The development of a cheap and field-compliant method for the measurement of in situ soil respiration allowed extrapolating the results from lab-based soil incubations.

In the 3rd phase we focus on the temperature sensitivity of soil respiration (Q10). Within the Community Land Model (CLM), the temperature sensitivity is implemented as a fixed Q10 - an approach which is debated controversially as Q10 values were found to be highly variable.

We test the hypothesis that land use, soil unit, and texture are the primary factors regulating the spatial heterogeneity of Q10 values. Therefore, we sample representative environmental soil classes (that represent each a unique combination of land use, soil unit and texture) from all over the Rur catchment.

Further information of the role of fresh plant litter for C-dynamics and Q10 will be deduced from long-term bare fallow-, and natural abundance labelling experiments. Soil respiration at different temperatures is measured with our RESPICOND system. The ultimate goal is the implementation of variable and soil-specific Q10 values into CLM to improve the estimation of heterotrophic soil respiration.

Cooperation partner:
n/a