EGU2020-11341, updated on 12 Jun 2020
https://doi.org/10.5194/egusphere-egu2020-11341
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Does long-term soil warming affect microbial element limitation? A test by short-term assays of microbial growth responses to labile C, N and P additions

Chupei Shi1, Carolina Urbina Malo1, Ye Tian1, Shasha Zhang1, Marilena Heitger1, Steve Kwatcho Kengdo3, Werner Borken3, Jakob Heinzle2, Andreas Schindlbacher2, and Wolfgang Wanek1
Chupei Shi et al.
  • 1Department of Microbiology and Ecosystem Science, Center of Microbiology and Environmental Systems Science, University of Vienna, Vienna, Austria
  • 2Federal Research and Training Centre for Forests, Natural Hazards and Landscape, Vienna, Austria
  • 3Department of Soil Ecology, Bayreuth Center of Ecology and Environmental Research (BAYCEER), University of Bayreuth, Germany

Human activities have caused global warming by 0.95 °C since the industrial revolution, and average temperatures in Austria have risen by almost 2 °C since 1880. Increased global mean temperatures have been reported to accelerate carbon (C) cycling, but also to promote nitrogen (N) and phosphorus (P) dynamics in terrestrial ecosystems. However, the extent of warming-induced increases in soil C, N and P processes can differ, causing an eventual uncoupling of biogeochemical C, N and P cycles, and leading to altered elemental imbalances between available plant and soil resources and soil microbial communities. The altered dynamics in soil C and nutrient availability caused by increased soil temperature could shift the growth-limiting element for soil microorganisms, with strong repercussions on the decomposition, mineralization and sequestration of organic C and nutrients. The latter relates to the conservative cycling of limiting elements while elements in excess are mineralized and released at greater rates by microbial communities.

Despite the many laboratory and in situ studies investigating factors that limit soil microbial activity, most of them explored nutrient addition effects on soil respiration or soil enzyme activities. A critical assessment, however, clearly indicated the inappropriateness of these measures to deduce growth-limiting nutrients for soil microbes. Similar to studies of plant nutrient limitation, unequivocal assessment of soil microbial element limitation can only be derived from the response of microbial growth to element amendments. To our knowledge this has not been performed on soils undergoing long-term soil warming.

In this study, we therefore investigated the effect of long-term soil warming on microbial nutrient limitation based on microbial growth measurements in a temperate calcareous forest soil. Soil samples were taken from two soil depths (0-10, 10-20 cm) in both control and heated plots in the Achenkirch soil warming project (>15 yrs soil warming by + 4 °C). Soil samples were pre-incubated at their corresponding field temperature after sieving and removal of visible roots. The soils were amended with different combinations of glucose-C, inorganic/organic N and inorganic/organic P in a full factorial design, the nutrients being dissolved in 18O-water. After 24 hours of incubation, microbial growth was measured based on the 18O incorporation into genomic DNA. Nutrient (co)limitation was determined by comparing microbial growth responses upon C and nutrient additions relative to unamended controls. Basal respiration was also measured based on the increase in headspace CO2, allowing to estimate microbial C use efficiency (CUE). The fate of C and nutrient amendments was finally traced by measurements of inorganic and organic extractable and microbial biomass C, N and P. This study will thereby provide key insights into potential shifts in limiting nutrients for microbial growth under long-term soil warming, and into concomitant effects on soil C and nutrient cycles.

How to cite: Shi, C., Malo, C. U., Tian, Y., Zhang, S., Heitger, M., Kengdo, S. K., Borken, W., Heinzle, J., Schindlbacher, A., and Wanek, W.: Does long-term soil warming affect microbial element limitation? A test by short-term assays of microbial growth responses to labile C, N and P additions, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11341, https://doi.org/10.5194/egusphere-egu2020-11341, 2020

Comments on the presentation

AC: Author Comment | CC: Community Comment | Report abuse

Presentation version 1 – uploaded on 06 May 2020
  • CC1: Comment on EGU2020-11341, Grace Pold, 07 May 2020

    Nice work!

    I was wondering whether you measured the CNP ratio of microbial biomass to see if there was evidence of nutrient limitation in that too? Or enzyme activity? In other words, do your results lead to different conclusions than "classic" methods?

    I am also interested in the what looks to be a decrease in growth with inorganic N addition in the topsoil. How do you interpret this? Does there seem to be some kind of inorganic N toxicity evident in the respiration, or are microbes perhaps accumulating biomass without undergoing DNA growth?

    Thank you!