• CUBE - Computational Systems Biology

  • DOME - Microbial Ecology

  • TER - Terrestrial Ecosystem Research

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Latest publications

Full 15N tracer accounting to revisit major assumptions of 15N isotope pool dilution approaches for gross nitrogen mineralization

Braun J, Mooshammer M, Wanek W, Prommer J, Walker TWN, Rütting T, Richter A
2018 - Soil Biology and Biochemistry, 117: 16-26

Mineral-Associated Soil Carbon is Resistant to Drought but Sensitive to Legumes and Microbial Biomass in an Australian Grassland

Drought is predicted to increase in many areas of the world with consequences for soil carbon (C) dynamics. Plant litter, root exudates and microbial biomass can be used as C substrates to form organo-mineral complexes. Drought effects on plants and microbes could potentially compromise these relative stable soil C pools, by reducing plant C inputs and/or microbial activity. We conducted a 2-year drought experiment using rainout shelters in a semi-natural grassland. We measured aboveground biomass and C and nitrogen (N) in particulate organic matter (Pom), the organo-mineral fraction (Omin), and microbial biomass within the first 15 cm of soil. Aboveground plant biomass was reduced by 50% under drought in both years, but only the dominant C4 grasses were significantly affected. Soil C pools were not affected by drought, but were significantly higher in the relatively wet second year compared to the first year. Omin-C was positively related to microbial C during the first year, and positively related to clay and silt content in the second year. Increases in Omin-C in the second year were explained by increases in legume biomass and its effect on Pom-N and microbial biomass N (MBN) through structural equation modeling. In conclusion, soil C pools were unaffected by the drought treatment. Drought resistant legumes enhanced formation of organo-mineral complexes through increasing Pom-N and MBN. Our findings also indicate the importance of microbes for the formation of Omin-C as long as soil minerals have not reached their maximum capacity to bind with C (that is, saturation).

Canarini A, Mariotte P, Ingram L, Merchant A, Dijkstra FA
2017 - Ecosystems, 1-15

Soil carbon loss regulated by drought intensity and available substrate: A meta-analysis

Drought is one of the most important climate change factors, but its effects on ecosystems are little
understood. While known to influence soil carbon (C) cycling, it remains unresolved if altered rainfall
patterns induced by climate change will stimulate positive feedbacks of CO2 into the atmosphere. Using a
meta-analysis frame-work including 1495 observations from 60 studies encompassing a variety of
ecosystems and soil types, we investigated drought effects on respiration rates, cumulative respiration
during drying-rewetting cycles, metabolic quotient (qCO2), dissolved organic C (DOC), microbial biomass
and fungi to bacteria (F:B) ratios from laboratory and field experiments. We show that C-rich soils (>2%
organic carbon) increase CO2 release into the atmosphere after intense droughts, but that C-poor soils
show a net decline in C losses. We explain this self-reinforcing mechanism of climate change in C-rich
soils by: (i) high substrate availability that magnify bursts of CO2 release after drought events and (ii) a
shift in microbial community with increased loss of C per unit of biomass. These findings shed light on
important responses of soil CO2 emissions to drought, which could either offset or facilitate positive
feedbacks to global warming. Our results should be considered in global climate models, as even small
changes in soil CO2 emission have large repercussions for global warming.

Canarini A, Kiær LP, Dijkstra FA
2017 - Soil Biology and Biochemistry, 112: 90-99