BayCEER Workshop 2019
October 10, 2019
NW III, University of Bayreuth
Changes in carbon and nitrogen availability cause contrasting microbial mechanisms of soil organic matter priming in a temperate forest
2 Chair of Ecosystem Functioning and Services, Institute of Ecology, Leuphana University of Lüneburg, 21335 Lüneburg, Germany;
3 College of Agronomy and Biotechnology, Chinese Agricultural University, 100193 Beijing, China;
4 Department of Soil Science of Temperate Ecosystems, University of Göttingen, 37077 Göttingen, Germany;
5 Key Laboratory of Ecosystem Network Observation and Modelling, Institute of Geographic Sciences and Natural Resources Research, CAS, 100101 Beijing, China;
6 Department of Soil Ecology, Helmholtz Centre for Environmental Research – UFZ, Halle (Saale), Germany;
7 Department of Agricultural Soil Science, University of Göttingen, 37077 Göttingen, Germany;
8 Department of Agroecology, BayCEER, University of Bayreuth, 95447 Bayreuth, Germany;
O 2.3 in Stable isotopes in environmental research - bridging disciplines, organisms and processes
10.10.2019, 15:00-15:15, H36, NW III
Increasing inputs of anthropogenic nitrogen (N) and plant-mediated carbon (C) to soil alter soil organic matter (SOM) turnover via priming effects (PE). However, the interactive effect of C and N availability on PE, particularly field validation and relevance of microbial mechanisms are still inconclusive. To fill this gap, we conducted in situ 13C- and 15N- labeling experiment in a temperate forest. We hypothesized that soil N availability controlled the PE response to C addition in which either 1) microorganisms decompose SOM for N and caused higher PE at low N availability (“microbial N mining”), or 2) the better microbial growth under the combined C and N supply cause higher SOM mineralization (“stoichiometric decomposition”).
We found that adding organic C, mineral N and their combination increased native SOM decomposition, causing positive PE via microbial activation. However, distinct mechanisms underlying the PE were observed depending on the availability of C relative to N. Under the prevalent low N availability, labile C input enhanced the synthesis of extracellular enzymes to mine for unavailable nutrients for fueling microbial growth and simultaneously increased SOC and N mineralization (real PE). Further, PE intensity increased with the extent of microbial N limitation and decreased with increasing available N, confirming the presence of microbial N-mining on the PE in this forest ecosystem. Contrary to our hypothesis, the PE for soils with N addition is explained by mechanisms other than stoichiometric decomposition such as accelerated microbial turnover, i.e. apparent PE, and co-metabolism of SOM. And it was coupled to apparent N mineralization via pool substitution. Our study suggests that the N-regulated PE response to C addition is determined by microbial adaptations to the C and nutrient constraints in soil through adjustments in the predominant microbial groups and microbial physiologic functioning (microbial metabolic efficiency and enzymes synthesis).
Keywords: priming effect, microbial activation, microbial turnover, nitrogen mining, extracellular enzyme, temperate forest
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