Degradation of SOM in cultivated peat soils, why is there no stabilization?

Dr Mariet Hefting1, Dr Joost  Keuskamp1,2, Prof Dr George  Kowalchuk1

1Ecology and Biodiversity, Institute of Environmental Biology,  Utrecht University, Utrecht, The Netherlands, 2BIONT Research , Utrecht, The Netherlands

Drainage of peatlands for cultivation leads to oxidation of organic material and subsequent soil subsidence and increased carbon emissions. Development of counteracting or mitigating strategies for these negative effects require improved understanding of oxidation dynamics in drained peatlands. While initial dynamics are well-known, it is less clear what happens after peat has been transformed to secondary organic compounds through initial oxygen exposure.

It is often assumed that drainage leads to a short peak in CO₂ emissions, our experiments however show that these high emission rates are maintained throughout the entire conversion of organic peat to its inorganic constituents, indicating that no organic matter stabilization takes place during peat decomposition. This high degradation rate of degraded peat samples deviates from the general pattern of organic matter dynamics where decay rates reduce with degradation. The apparent lack of SOM stabilization in peat soils can be explained with two scientifically interesting concepts: 1) the turnover of microbial biomass is low in peat soils, increasing the proportion of maintenance respiration and decreasing the relative production of secondary compounds and 2) the absence of mineral material organo-mineral complexation. Understanding these differences in SOM dynamics between peat soils and mineral soils can result in a crucial guideline for peat oxidation reduction and assessment of peat oxidation risks.

Biography: Mariet Hefting is an associate professor in soil ecology at Utrecht University the Netherlands. Mariet received a Master of Science degree in soil science at Wageningen University and a PhD degree at Utrecht University on Nitrogen transformation in riparian buffer zones.  She has general as well as specific expertise on the interactions between plants and soil in the context of cycles of carbon and nitrogen and the response of soil ecosystems to multiple global change drivers. She is a strong empirical scientist with a thorough knowledge on quantitative research methods both in the field and laboratory. She has worked in a wide range of scientific consortia on the topic of decomposition, peat degradation and greenhouse gas emissions both in national and international (EU-funded) projects. She has a good publication record with 54 scientific papers and a H index of 25. Besides research Mariet Hefting is an inspiring PhD and MSc supervisor and academic teacher.

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